I babbitt Any of the white alloys composed princi­

l" pally of lead or tin that are used extensively to make linings for sliding bearings. I B babble The composite sig­

pressure t? an intermediate value, usually� 10-2 to 10-:> psia. Also known as "ore pump."�

backing ring A ring of steel or other material placed behind the welding groove when joining tubes or pipes by welding so as to confine the weld metal.

nal caused by cross talk among a large number of

interfering channels. backbone 1. The trunk media of a multime­~ dia local area network (LAN) that is sepa­:

I J rated into sections by bridges, routers, or

gateways. 2. A high-speed high-performance network that links other networks together.

backbone network Traditionally, a transmis­sion facility designed to interconnect low­speed distribution channels or clusters of dispersed user devices. It is currently defined as a high-speed line or series of con­nections that form the major pathway within a given network.

backdrive To use an external test driver to electrically force a logic device's output to a specified state that is independent of its input state.

back face The machined surface on the side of a through-bolted flange, opposite the gas­ket face, that is provided for nut seating. [ANSI! ISA-75.05.01-2000]

backflush The injection of a fluid against the process flow manner in order to remove line fluid or obstructions. [ISA-67.02.01-1999; S67.1O]

background 1. In a computer's graphic dis­play, the field that information is displayed upon for contrast. [ISA-5.5-1985] [Meas] 2. In radiation counting, a low-level signal that is caused by radiation from sources other than the source of radiation being measured. [Comp]3. A computer environment in which low-priority programs are executed.

background discrimination The capacity of a measuring instrument or detection circuit to distinguish an input signal from electronic noise or other background signals.

background noise Undesired signals or other stimuli that are always present in a trans­ducer output or electronic circuit, regardless of whether a desired signal or stimulus is also present.

background program A program of the low­est urgency that may therefore be preempted by a program of higher urgency and priority. Contrast to foreground program.

backing pump In a vacuum system that uses two pumps, the pump that discharges directly to the atmosphere. It reduces system

backing strip A piece of metal, asbestos, or other nonflammable material placed behind a joint before welding to enhance the quality of the weld.

backlash r. In·-proc~ss. instrumentation, a rel­ative movement tnat"occurs between inter­acting me~hanical parts, caused by loose­ness, when motion is reversed. [ANSI!ISA­51.1-1979 (R1993)] 2. In a mechanical linkage or gear train, the amount by which the driv­ing shaft must rotate, when reversing direc­tion, just to take up the looseness in the linkage or gear train before it begins to trans­mit motion in the reverse direction. 3. The difference in actual values of a controlled variable when a co~trol dial is.bi~tighno an indicated position from opposite rotati.onal directions.

back pressure The absolute pressure level, expressed in pascals, as measured four pipe-diameters downstream from the turbine flowmeter under operating conditions. [ISA-RP31.1-1977]

back seat A seating surface in the bonnet that mates with the closure member or valve stem in the extreme open position so as to provide pressure isolation of the stem seal. [ANSI! ISA-75.05.01-2000]

backplane A wiring board, usually con­structed as a printed circuit, that is used to provide required connections between logiC, memory, and input/output modules. A backplane is usually located in the back of a rack that has sockets into which specific boards fit so they can be interconnected.

backscattered electron imaging (BEl) A method for producing scanning electron microscope images by detecting electrons that are reflected back out of a sample after they collide with surface atoms. Backscat­tered electron imaging is used to detect sub­surface cracking, contamination, and inclusions.

backscattering The scattering of light in the opposite direction it was originally traveling In.

backtracking A technique for synchronizing mixed-signal simulation systems in which an analog simulator is made to back up to a pre­vious point in time in order to process a sig­nal originating in the digital simulator.

39�

I backup / balanced (to ground)�

backup 1. Equipment used to complete an operation in the event that the primary equipment fails. 2. A copy of a computer file made so as to protect against destruction or loss of the original.

backup copy In data processing, a copy of data or of a program that can be used if the original copy is lost or destroyed.

backward compatible Designs that provide compatibility with earlier versions. Often referred to as reverse compatible.

BACnet Building Automation and Control network. An object-oriented model of the standard automation system network sup­ported by ASHRAE to serve as a high-speed, low-cost network for commercial building services, but not designed for industrial pro­cess control.

bad break In the typographical composition of screen displays and printing, starting or ending a page (or ending a paragraph) with a single word, or "widow."

baffle A plate or vane, either plain or perfo­rated, that is used to regulate or direct the flow of fluid.

baffle-nozzle amplifier A device for convert­ing mechanical motion into a pneumatic sig­nal. It consists of a supply tube that ends in a small nozzle and a moveable baffle plate that is attached to a mechanical arm. The length of the supply tube is restricted to a short dis­tance before the nozzle, so that as the baffle plate moves closer to the nozzle opening, the pressure rises in the section of the supply tube between the restriction and the nozzle. The arm motion and nozzle clearance are small-on the order of 0.2 mm or less. A baf­fle-nozzle amplifier serves as the primary detector in almost all pneumatic transmitters and controllers. Often referred to as a "flap­per-nozzle amplifier" because the baffle plate is mounted on a pivoting arm.

baffle plate A tray or partition, either solid or perforated, that is positioned in the flow path through a process vessel so as to cause the process stream (a) to flow in a certain direc­tion, (b) to reverse its direction of flow, or (c) to slow its velocity.

baffle-type collector A device in gas paths that utilizes baffles arranged in such a way that dust particles are deflected out of the gas stream.

bag filter A device that contains one or more cloth bags that serve to recover particles from the dust-laden gas or air blown through it.

bag-type collector A filter consisting of a cloth-filtering medium taking the form of a cylindrical bag.

bakeout The process of heating the surfaces of a vacuum system during evacuation in order to degas them and to promote their progress toward of a stable final vacuum level.

balance 1. Generically, a state of static or dynamic equilibrium. Such equilibrium is static when, for example, forces on a body counteract each other exactly. It is dynamic when materiar flowing into and out of a pipeline or process has reached steady state, and there is no discernible rate of change in the process variables. 2. An instrument for making precise measurements of mass or weight. 3. A condition in which the rotation centerline between bearings coincides with the line that defines the center of mass distri­bution.

HOPPER

BALANCE� WEIGHT�

LIP GATE

0­RELAY

Simple Beam Balmlcc

balanced bridge A Wheatstone bridge circuit that, when in a quiescent state, has an output voltage of zero. A balanced bridge can be used to measure changes in resistance in such applications as RTDs, strain gauges, and so on.

balanced draft A system of furnace pressure control in which the inlet air flow or the out­let flue gas flow is controlled in order to maintain the furnace pressure at a fixed value (typically slightly below atmospheric).

INLET VANE INLET VANE

CONTROL CONTROL

AIR

o PR=HEATER

FORCED DRAFT FAN

REDUCED DRAFT FAN

balanced (to ground) See ullbalanced (to ground).

40�

I oalancea tnm I bandwidth

..-Of··.·

balanced trim A control valve trim that is ,~;

designed to minimize the net static and dynamic fluid flow forces, from fluid pres­sure, that are acting on the trim. [ANSI/ISA­t 75.05.01-2000]

.i' balance weight A mass that is positioned on the balance arms of a weighing device so they can be brought to a predetermined (null position) for all conditions of use.

balancing A procedure for adjusting the mass distribution of a rotor by adding or removing weight so as to achieve less vibra­tion amplitude at rotational speed.

ball A spherically shaped closure member. [ANSI/ ISA-75.05.01-2000]

ball, full A closure component that has a complete spherical surface that includes a flow passage.

ball, segmented A closure component that is a segment of a spherical surface which may have one edge contoured to yield a desired flow characteristic.

ball bearing A type of antifriction bearing in which the load is borne by a series of hard spherical elements (balls) that are held in place between inner and outer retaining rings (races).

ball burnishing 1. Producing a smooth, dimensionally precise hole by forcing a slightly oversize tungsten-carbide ball through a slightly undersize hole at high speed. 2. A method of producing a lustrous finish on small parts by tumbling them in a wood-lined barrel with burnishing soap, water, and hardened steel balls.

ball bushing A variation of ball bearing that permits axial motion of a shaft instead of rotating motion.

ball check valve A valve that permits flow in one direction only by lifting a spring-loaded ball off its seat when a pressure differential acts in that direction and by forcing the ball more tightly against the seat when a pressure differential acts in the opposite flow direc­tion.

ball-float liquid-level meter A device that consists of a hollow or low-density float attached by a linkage to a pointer. The float rises and falls with the level of liquid in a tank, while the pointer indicates the position of the float on a scale outside the tank

balloon 1. The circular symbol used to denote and identify the purpose of an instru­ment or function. It may contain a tag num­ber. 2. Synonym for "bubble." See also bubble.

ballot box In the typographical composition of screen displays and printing, an open,

41

square bullet, usually intended to receive a check mark. See also check box.

ball sizing See ball burnishing. ball-type viscometer An apparatus for deter­

mining viscosity, especially of high-viscosity oils and other fluids. The time required for a ball to fall through liquid confined in a tube is measured.

Balun Balanced/unbalanced. In the IBM cabling system, Balun refers to an imped­ance-matching device that is used to connect balanced tWisteq:Rair cabling with unbaV' . anced coaxial cables..

ball valve A valve that has a rotary motion clo­sure member consisting of a full ball or a seg­mented ball. [ANSI/ISA-75.05.01-2000]

band 1. The gamut or range of frequencies. 2. The frequency spectrum between two defined limits. 3. Frequencies that are within two definite limits and are used for different purposes. 4. A group of channels; See chan­nel. 5. A group of recording tt~s on a com­puter magnetic d'isk or drum.

band brake A device for stopping or slowing rotational motion by increasing the tension in a flexible band so it tightens around a drum that is attached to the rotating member.

band-elimination filter A wave filter that has a single attenuation band whose critical and cutoff frequencies are finite, nonzero val­ues.

band gap In semiconductors, the range of energies between the conduction band and the valence band in which no free electrons or holes are allowed. See conduction band and also valence band.

band pass filter In digital signal processing (DSP), a filter that passes signals in a certain range of frequencies and attenuates signals above and below that range.

Band S gauge Brown and Sharp gauge; See American Wiring Gallge (AWG).

band spectrum A spectral distribution of light or other complex wave in which the wave components can be separated into a series of discrete bands of wavelengths. See also continuous spectrum.

band splitter A multiplexer that is designed to split available bandwidth into indepen­dent, narrower-band subchannels, each of which is suitable for transmitting data at a fraction of the total channel's data rate.

bandwidth 1. The difference, expressed in hertz, between the two boundaries of a fre­quency range. 2. A group of consecutive fre­quencies, constituting a band, that exists between limits of stated frequency attenua­tion. A band is normally defined as being

•••:;11' IlI"IIlZSX!lD"·-lII&IlI------.......·,.,..·--.*' "'.-- -,_.- _._- -----­

I bang-bang control/baseband

more than 3.0 decibels greater than the mean attenuation across the band. 3. A group of consecutive frequencies, constituting a band, that exists between limits of a stated fre­quency delay. 4. The range of frequencies that can be transmitted in an electronic system. 5. A symmetrical region around the set point in which proportional control occurs.

bang-bang control The same as two-position control.

bank switching A method for equipping a computer with greater memory by giving the same address to added memory chips.

bar One atmosphere. bar code A pattern of narrow and wide bars

that can be scanned and interpreted into alpha and numeric characters.

bar-code scanner A type of optical scanner developed to read the 12-character Universal Product Code for identifying items.

bare-board tester A system that tests unpop­ulated printed circuit boards for trace defects.

Barkometer scale A specific-gravity scale used primarily in the tanning industry, in which the specific gravity of a water solution is determined from the following formula:

sp gr=1.000 ± O.OOln where n is degrees Barkometer. On this scale, water has a specific gravity of zero Barkome­ter.

bam A unit of nuclear cross section in which the probability of a specific nuclear interac­tion, such as neutron capture, is expressed as an apparent area. In this context, one bam

2equals 10_28 m •

barometer An absolute pressure gauge for determining atmospheric pressure. If it is a recording instrument, it is known as a "barograph."

barometric hypsometry The method of determining elevation above some arbitrary reference plane (usually sea level) through the use of mercury or aneroid barometers.

barometric pressure Atmospheric pressure as determined by a barometer, usually expressed in inches of mercury.

barometry The study of atmospheric pres­sure measurement. In particular, the science of determining and correcting errors in baro­metric instrument readings.

barostat A device for maintaining constant pressure within a chamber.

barothermograph An instrument for auto­matically recording both atmospheric tem­perature and pressure.

barothermohygrograph An instrument for automatically recording atmospheric pres­

sure, temperature, and humidity on the same chart.

barrel A unit of volume. For petroleum, a bar­rel equals 9,702 cubic inches. For fruits, vege­tables, other dry commodities, and some liquids, a different standard barrel is used.

barrel finishing The craft of producing a lus­trous surface finish on metal parts by tum­bling them in bulk in a barrel that is partly filled with an abrasive slurry. Similar pro­cesses ar.e used for cleaning and electroplat­inftmu involve'det,ergent solutions or electrolytes instead of an abrasive slurry.

barrier 1. A part that provides protection against direct contact from any usual direc­tion of access. Note: Enclosures and barriers may provide protection against the spread of fire. [ANSI/ISA-82.02.01-1999 (lEC 1010-1 Mod)] 2. A physical entity that limits the cur­rent and voltage into a hazardous area in order to satisfy intrinsic safety requirements. [ANIS/ISA-50.02, part 2 - 1992]

barrier, intrinsic safety See intrinsic safety barrier.

barrier shield A wall or enclosure that is made of a material designed to absorb ioniz­ing radiation. It shields the operator from an area where radioactive material is being used or processed by remote-control equipment.

base 1. The physical foundation or support upon which a machine or instrument rests. 2. For a number system, the number whose powers determine place value. 3. A chemical substance that hydrolyzes to yield OR ions. 4. A reference value. 5. A number that is mul­tiplied by itself as many times as indicated by an exponent. 6. See radix nllmber.

base address 1. A number that appears as an address in a computer instruction but serves as the base, index, or initial or starting point for subsequent addresses to be modified. Synonymous with "presumptive address" and "reference address." 2. A number used in symbolic coding in conjunction with a rel­ative address; an address used as the basis for computing the value of some other rela­tive address.

baseband 1. A single channel-signaling tech­nique in which the digital signal is encoded and impressed on the physical medium. 2. The frequencies starting at or near DC. 3. Communications signals whose bandwidth is approximately equal to the highest fre­quency transmitted. This contrasts with modulated signals (RF), where the frequen­cies transmitted (approximately the carrier frequency) are much higher than the band­width.

42

baseband modems / batch

baseband modems See limited distance munications on an HI fieldbus segment. See

I , modems.

BASEEFA British Approvals Service for Elec­trical Equipment in Flammable Atmo­spheres. British certification and testing laboratory responsible for testing the equip­ment of different vendors to some common standard. (Subsumed within EECS in 1987.)

baseline 1. Generally, a reference set of data against which operating data or test results are comparea to determine such characteris­tics as operating efficiency or system degrada­tion over time. 2. In navigation, the geodesic line between two stations that are operating in conjunction with each other. 3. In the typo­graphical composition of screen displays and printing, the imaginary line on which the bases of characters sit.

baseline spectrum A vibration spectrum cap­tured from a machine when it is presumed to be in good running condition. Subsequent spectrums captured from this machine are compared to this baseline when looking for changes.

base load The term applied to that portion of a station or boiler load that is practically con­

1!

Hl Field Device. basic element A single component or sub­

system that performs one necessary and dis­tinct function in a measurement sequence. To be considered a basic element, the compo­nent must perform one and only one of the smallest steps into which the measuring sequence can be conveniently divided.

basic frequency In a waveform that is made up of severp~..rompoI}ents of different fre­quencies, bask frequency is the single com­ponent that has the largest amplitude or has

I

\. IiI

IIi

iI ~ !

stant for long periods. ! base metal 1. The metallic element that is

present in greatest proportion in an alloy. 2. The type of metal to be welded, brazed, cut, or soldered. 3. In the welded joint, metal that was not melted during welding. 4. Any metal that will oxidize in air or that will form metallic ions in an aqueous solution. Con­trast with "noble metal." 5. Metal to which a plated, sprayed, or conversion coating is applied. Also known as "basis metal."

base number A synonym for "radix num­ber." See radix number.

BASIC Beginners' All-purpose Symbolic Instruction Code; A widely used computer language for personal computers. Developed at Dartmouth to teach students program­ming, BASIC features array and string manipulation and is widely used for educa­tional and business applications because it is J

some other characteristic that makes it the principal component of the composite wave.

basic input-output system (BIOS) That part of a computer operating system that handles input and output.

basic insulation Insulation that poses the risk of electric shock if it fails. Note: Basic insulation may also serve functional pur­poses. [ANSI/ISA-82.02.01-1999 (IEC 1010-1 Mod)]

basic process control system 1. The control equipment that is installed to perform the normal regulatory functions for the pro­cess-for example, PID control and sequen­tial control. [ANSI/ISA-91.01-1995]2. A system that responds to input signals from the equipment under control and / or from an operator and generates output signals that cause the equipment under control to oper­ate in the desired manner. Some examples include control of an exothermic reaction, anti-surge control of a compressor, and fuell air controls in fired heaters. Also referred to as process control system. [ANSI/ISA-84.01­1996]

basic recipe A generic, transportable process recipe that consists of header information, equipment requirements. formula, and pro­cedure.

basis weight For paper and certain other sheet products, the weight per unit area.

bat file A file name ending in .bat that con­tains a list of the commands most often used

ILrI

easily understood and appropriate for solv­ing small problems.

basic control Control that is dedicated to establishing and maintaining a specific state of equipment or specific process condition. Note: Basic control may include regulatory control, interlocking, monitoring, exception handling, and discrete or sequential control. [ANSI/ISA-88.01-1995]

basic device A basic device is any device that does not have the capacity to control com­

to initiate a computer program. batch 1. The material that is being produced

or that has been produced by a single execu­tion of a batch process. 2. An entity that rep­resents the production of a material at any point in the process. Note: Batch means both the material made by and during the process and also the production of that material. Batch, in other words, is used as an abstract contraction of the words "the production of a batch." [ANSI/ISA-88.01-1995] [Comp]3. A group of similar computer transactions

43

II batch control / BBS

joined together for processing as a single unit.

batch control Control activities and control functions that provide a means to process finite quantities of input materials by subject­ing them to an ordered set of processing activities over a finite period of time using one or more pieces of equipment. [ANSI/ ISA-88.01-1995]

butch manufacturing A technique for manufacturing parts or finished goods in groups, lots, or batches in which each part or finished product in the batch is identical.

batch process A process that leads to the pro­duction of finite quantities of material by subjecting quantities of input materials to an ordered set of processing activities over a finite time using one or more pieces of equip­ment. [ANSI/ISA-88.01-1995]

batch processing [Camp] 1. The technique of executing a set of programs such that each is completed before the next program of the set is started. 2. Loosely, the execution of pro­grams serially. 3. In data processing, a tech­nique in which data are accumulated and processed in batches, as compared with interactive processing. See interactive process­ing. [Proc]4. A production operation that does not operate continuously but must be stopped for loading and unloading after pro­cessing a quantity of material or a limited number of items.

batch schedule A list of batches to be pro­duced in a specific process cell. Note: The batch schedule typically contains such infor­mation as what is to be produced, how much is to be produced, when or in what order the batches are to be produced, and what equip­ment is to be used. [ANSI/ISA-88.01-1995]

bathochrome An agent or chemical group that causes the absorption band of a solution to shift to lower frequencies.

bathometer An instrument for measuring depth in the ocean or other body of water.

bathyclinograph An instrument for measur­ing vertical ocean currents.

bathyconductograph An instrument for mea­suring the electrical conductivity of seawater as it is towed at various depths behind a moving ship.

bathymetry The application of scientific prin­ciples to the measurement of ocean depths.

bathythermograph An instrument for recording sea temperature versus depth (pressure) as it is towed behind a moving ship. Also known as "bathythermosphere."

battery Two or more cells that are electrically connected and used as a source of energy. [ANSI/ISA-12.16.01-1998 (IEC 79-7 Mod)]

battery capacity The quantity of electricity (electric charge), usually expressed in ampere-hours (Ah), that a fully charged bat­tery can deliver under specified conditions. [ANSI/ISA-12.16.01-1998 (IEC 79-7 Mod)]

battery container An enclosure that enve­lopes or secures the battery. Note: The cover ~s a part of the battery container. [ANSI/ISA­

. 12.16.01-1998 (LEG 79-7 Mod)] baud 1: The measure of the rate at which dig­

ital data are transmitted, in bits per second. 2. A unit of signaling speed that is equal to the number of code elements per second. (This d~finition is applied only to the actual signals on a communication line.) If each sig­nal event represents only one bit condition, baud is the same as bits per second. When each signal event represents something other than the logical state of only one bit, baud is used for data entry only in the simplest of systems. 3. The unit of signal speed that is equal to twice the number of Morse code dots continuously sent per second, clarified by rate, bit and capacity, and channel.

baudot code A three-part teletype code con­sisting of a start pulse (always a space), five data pulses, and a stop pulse (1.42 times the length of the other pulses) for each character transmitted. Various combinations of data pulses are used to designate letters of the alphabet, the numerals 0 to 9, and certain standard symbols.

baud rate Any of the standard transmission rates for sending or receiving binary coded data. The standard rates are generally between 50 and 19,200 bauds.

Baume scale Either of two specific-gravity scales devised by French chemist Antoine Baume in 1768 and often used to express the specific gravity of acids, syrups, and other liquids. For light liquids, the scale is deter­mined from the formula: °Be = (l40/sp. gr.) -130 For heavy liquids it is determined from: °Be = 145 - (145/sp. gr.) 60°F is the standard temperature used.

Bauschinger effect The phenomenon wherein the plastic deformation of a metal raises its tensile yield strength but decreases its compressive yield strength.

BBS Bulletin board service; general access provided for users of computers connected to a phone line and provided by a group for the general exchange of messages, illustra­tions, software, etc. A BBS can be commercial

44

I BCC/BEDO

(paid subscribers), volunteer, or perhaps pro­ beam divergence The increase in beam diam­vided by product vendors for use by their eter that results from the increase in distance customers. from a laser's exit aperture. Divergence,

BCC Block check character; the result of the expressed in milliradians, is measured at transmission of a verification algorithm accumulated over a transmission block, nor­

J mally added to the end, such as CRe LRC. J

:{

I',! BCD Binary-coded decimal; method to " express individual decimal digits in four-bit

binary notation. (1 =0001; 2 =0010; 23 =0010 0011). .

BCD, buffered Buffered binary-coded deci­mal; a binary-coded decimal output that has output drivers in order to increase line-drive capability.

BCD, parallel Parallel binary-coded deci­mal; a digital data output format wherein every decimal digit is represented by binary signals on four lines and all digits are pre­sented in parallel. The total number of lines is four times the number of decimal digits.

BCD, serial Serial binary-coded decimal; a digital data output format wherein every decimal digit is presented by binary signals on four lines and up to five decimal digits are presented sequentially. The total number of lines is four data lines plus one strobe line per digit.

BCD, three-state Three-state binary-coded decimal; an implementation of parallel BCD

I that has 0, 1, and high-impedance output'" states. The high-impedance state is used

when the BCD output is not addressed in parallel connect applications.

BCH Bose-Chandhuri-Hocquendhem; error­checking technique.

BCOMP See buffer complete. BOAT Best demonstrated available technol­

ogy economically achievable in complying to EPA (United States) pollution prevention requirements.

bead 1. A rolled or folded seam along the edge of metal sheet. 2. A projecting band or rim. 3. A drop of precious metal that is pro­duced during cupellation in fire assaying. 4. An elongated seam that is produced by welding in a single pass.

beaded tube end The rounded exposed end of a rolled tube when the tube metal is formed over the sheet in which the tube is rolled.

beam 1. An elongated structural member that carries lateral loads or bending moments. 2. A confined or unidirectional ray of light, sound, electromagnetic radiation, or vibra­tional energy that usually has a relatively small cross section.

specified points across the beam's diameter. beam expander An optical system that

expands a narrow beam to a larger diameter, ideally without changing the divergence of the beam.

beam integrator A devke that integrates the energy in a light beam so it is uniform across the beam's cross' sec"tion:

beam splitter A device that separates a light beam into two beams. Some types affect the polariza tion of the beam.

beam spread The angle of divergence of an acoustic or electromagnetic beam from its central axis as it travels through a material.

bearing 1. A machine part that supports another machine part while the latter under­goes a rotating, slj.d~ng, or oscillating motion. 2. That portion of a beam, truss, or other structural member that rests on the supports. 3. The angle in a horizontal plane between the line of sight to a distant object and some absolute or relative reference direction.

bearing circle· A ring-shaped device that fits over a compass or compass repeater to make it easier to take compass bearings.

beat-frequency oscillator An electrical oscil­lator that generates a frequency that, in turn, is beat against another frequency to generate a third, usually audible frequency. Beat-fre­quency oscillators are generally used in com­munications receivers to provide an audible signal or to reinsert a carrier for the reception of single side-band signals.

beating A pulsating waveform that is some­times produced when two or more periodic quantities of different frequencies combine.

beat note The wave of different frequency that results when two sinusoidal waves whose frequencies differ from each other are supplied to a nonlinear device.

beats 1. Periodic pulsations in amplitude that are created when a wave of one frequency is combined with a wave of a different fre­quency. 2. The alternating rise and fall of vibration amplitude caused by two sources vibrating at close to the same speeds.

bed The part of a machine that has precisely machined ways or bearing surfaces so that it can support and align other parts such as toolholders or dies.

BEDO Burst extended data out; technology for high-speed (66 MHz) bus access to com­puter memory.

45

I� Beer's law / belt conveyor scale

Beer's law The law that relates the absorption coefficient of a material to its molar density.

behavioral modeling Modeling a device or component directly in terms of its underly­ing mathematical equations.

behind the panelLA location that is within an area that (a) contains the instrument panel, (b) contains its associated rack­mounted hardware, or (c) is enclosed within the panel. 2. Behind-the-panel devices ape . not accessible for the operator's normal use. 3. Behind-the-panel devices are not desig- . nated as local or front-of-panel-mounted. [ANSI/ISA-5.1-1984 (RI992)]

bel A dimensionless unit for expressing the ratio of two power levels. The value in bels equals log (P2 /PI), where PI and P2 are the two power levels.

BEL In communication, BEL is a control char­acter used when a need exists for a call to attention. A BEL character may also control alarm or attention devices..

Bell Designa tion for AT&T standards for devices that transmit over telephone lines, such as modems.

Bell 103, 113 [etc.] Codes devised by the Bell system to define modem type and speeds (e.g., Bell 103, Bell 208). They include the fol­lowing: Bell 103 - a 300 bps asynchronous modem with originate or answer; Bell 113-a 300 bps asynchronous modem with originate or answer; Bell 201 - a 2400 bps synchronous modem; Bell 202--an 1800 bps asynchronous modem, full duplex with 4-wire; Bell208-a 4800 bps synchronous modem; Bell 209-a 9600 bps synchronous modem; Bell 212-a 1200 bps asynchronous/ synchronous dial­

bellows expansion joint A type of coupling between two pieces of pipe that uses a flexi­ble metal bellows to prevent leakage while allowing limited linear movement, in order to accommodate, for example, thermal expansion and contraction.

bellows gauge A pressure-measuring device in which variations in internal pressure within a flexible bellows cause an end plate to move against the spring force. The posi­tion of the end pl~.te is directly related to the bellows' "internal pressure. .' .."..~

bellows meter A differential pressure-mea­suring instrument that has a measuring ele­ment of opposed metal bellows whose motion positions the output achlator.

bellows seal 1. A multiconvolution-type ele­ment used as a protective barrier between the instrument and the process fluid. 2. A seal in the shape of a bellows used to prevent air or gas leakage.

bellows sealed valve A valve that utilizes a bellows to replace the conventional packing gland. One end of the bellows is welded to the rising stem; the other is sealed against the valve body.

bellows stem seal A thin-walled, convoluted, flexible component that makes a hermetic seal between the stem and bonnet or body and allows stem motion. [ANSI/ISA­75.05.01-2000]

bellows type valve A fluid-powered device in which the fluid acts upon a flexible, con­voluted member, termed the bellows, in order to provide linear motion to the actua­tor stem. [ANSI/ISA-75.05.01-2000]

bell-type manometer A gauge for measuring up full duplex. differential pressure, which consists essen­ j•

1belled tube end See flared tube end. tially of a cup inverted in a container of liq­Belleville washer See disk spring. uid. Pressure from one source is fed to the bellows 1. A pressure-sensing element of inside of the cup, while pressure from a sec­

generally cylindrical shape whose walls con­ ond source is applied to the exterior of the tain deep convolutions and whose length cup. Pressure difference is indicated by the changes when a pressure differential is position of the cup in relation to the liquid applied. [ISA-37.1-1975 (RI982)]2. An enclosed chamber whose walls are designed pleated or corrugated so its interior volume may be varied, either to alternately draw in and expel a gas or other fluid or to expand and contract in response to variations in internal pressure. 3. A pressure transducer that converts pressure into a nearly linear displacement.

bellows actuator A fluid-powered device in

level. belt conveyor A continuous band of fabric,

rubber, plastic, leather, or metal that moves indefinitely and features a drive, a tail end, and bend terminals; belt idlers; or slider beds for handling bulk materials, packages, or objects placed directly upon the belt. [ISA­RP74.01-1984]

belt conveyor scale A device installed on a belt-conveyor structure that continuously

ji

,Ii

:

f

1

!jjI

which the fluid acts upon a flexible, convo­luted component termed "the bellows". [ANSI/ISA-75.05.01-2000]

weighs the material being conveyed. [ISA­RP74-1984]

46

•

I� ~

belt-speed sensor / beta particle�

Belt Conveyor and Weighbridge Assernbly ·

belt-speed sensor A device that generates a signal as it detects belt speed. [ISA-RP74.01­1984]

belt-speed transmitter A device that trans­mits a belt speed signal to a receiver. [ISA­RP74.01-1984]

bench (optical) A mounting surface for opti­cal components.

bench check A laboratory-type test of an assembly, component, or subassembly to ver­ify its function or to identify a source of mal­function. Bench checks are often done with the unit removed from its housing or system for service or repair. Also kno\vn as "bench test."

benchmark 1. A natural or artificial object that has a specific point marked on it so as to iden­tify a reference location, such as a reference elevation. 2. A fixed point of reference; a standard for comparison; an outstanding example, appropriate for use as a model.

benchmark program A routine used to deter­mine the performance of a computer or soft­ware.

bench set The calibration performed in the shop of the actuator spring range of a control valve, to account for the in-service process forces. [ANSI/ISA-75.0S.01-2000]

bench top equipment Eqllipment that is designed to be used on and supported by a bench, table, stand, and so one, but is neither fixed nor portable, as defined by the follow­ing conditions: (a) It has at least one handle and the weight exceeds 20 kilograms (44 pounds), or (b) It has no handle and the weight exceeds 5 kilograms (11 pounds), or (c) It is not mobile (does not have casters, wheels, rollers, etc., nor is it provided with a cart).

bending� Applying mechanical force or pres­sure to form a metal part by plastic deforma­tion around an axis lying parallel to the metal surface. Bending is commonly llsed to produce anglllar, curved, or flanged parts from sheet metal, rod, or wire.

bend loss Attenuation caused by high-order modes radiating from the side of a fiber. The two common types of bend losses are (a) those occllrring when the fiber is curved Iiaround a restrictive radius of curvature and (b) microbends caused by small distortions of the fiber imposed by externally induced perturbations, such as poor cabling tech­niqlles.

bend pulley Any ptl1ley used to change the direction of travel.of a belt. [ISA-RP74.01­1984]

bend radius The smallest arc in a cable t11at can be made vvithout causing damage.

bend test A ductility test in which a metal specimen is bent through a specified arc around a support of known radius. Bend tests are used primarily to evaluate the inher­ent formability of g}etal sheet, rod, or "vire, or to evaluate the weld quality specific mate­rials prodllce, joint design, and welding tech­nique.

bent tube boiler A water-tube boiler consist­ing of two or more drums connected by tubes, practically all of which are bent near the ends to permit their attachment to the drum shell on radial lines.

Bernoulli coefficient In any stream, if the area is changed, as by a reducer, there is a change in the velocity and a corresponding change in the static pressure, or "head." This pressure change is measured in units of velocity head. The dimensionless coefficient ltsed for this purpose is the Bernoulli coeffi­cient Kg.

BERT/BLERT Bit error rate test/block error rate test; error-checking technique that com­pares received data pattern with known transmitted data pattern to determine the transmission line quality.

bessel The filter characteristic in which phase linearity across the pass band is emphasized rather than amplitude linearity. Also known as constant delay.

best straight line A line midway between, on the one hand, the two parallel straight lines that are closest together and that enclose all output and, on the other, the measurand val­ues on a calibration curve. [ISA-37.1-1975 (R1982)]

best-straight-line linearity An average of the deviation of all calibration points. Also called independent linearity.

beta emitter A radioactive nllclide that disin­tegrates by emitting a beta particle.

beta particle An electron or positron that is emitted from the nuclells of a radioactive nuclide.

47

beta ratio(B) / bimetal thermometer�

beta ratio(B) The ratio of the diameter of a pipeline constriction to the unconstricted pipe diameter.

beta ray A stream of beta particles. beta-ray spectrometer An instrument used to

measure the energy distribution in a stream of beta particles or secondary electrons.

beta test The second stage of testing a new software program. The program is tested by selected "typical" users to discover bugs before releasing it to general sale. Software undergoes beta testing shortly before it is released.

betatron A large particle accelerator that is used to impart energy to a stream of elec­trons by means of magnetic induction.

bevel gear One of a pair of gears whose teeth run parallel to a conical surface so that they can transmit power and motion between two shafts whose axes intersect.

bezel A ring-shaped member surrounding a cover glass, window, cathode-ray tube face, or similar area so as to protect its edges and often to also provide a decorative appear­ance.

Bezier curve A description of a character, sym­bol, or graphic by its outline; used by com­puter drawing programs to define shapes.

BFSL Best fit straight line; line midway between two parallel straight lines, enclosing all charted values of measurement. Also known as independent linearity, which allows zero and full-scale values, used to establish the position of a reference line, to be moved to points that minimize the nonlin­earity specification of an instrument, often when zero is generally not zero and full scale will seldom equal the actual or desired full scale of the instrument, such as with pressure devices.

bias 1. An uncertainty component that con­sistently has the same algebraic sign and is expressed as an estimated limit of error. [ISA-RP67.04.02-2000] 2. The departure from a reference value of the average of a set of values. Thus, bias is a measurement of the amount of unbalance of a set of measure­ments or conditions. A biilsed measurement has an average error value that is nonzero. 3. A signal applied to an electronic device to ensure that it operates on a particular portion of its characteristic curve. 4. The average DC voltage or current maintained between a control electrode and the common electrode in a transistor or vacuum tube.

bias current A very low-level DC current generated by a panel meter and superim­posed on the Signal. This current may intro­

duce a measurable offset across a very high source impedance.

bias (tape) The sine wave, typically 10 times the amplitude and 3.5 times the top fre­quency, which is applied to tape recording heads with a signal to eliminate most signal distortion.

bidirectional load cell A column-type strain-gauge load cell with female or male fittings at both ends for attaching load hard­ware. It can be used to measure either ten­siori.·or compre~iO'n loading. Also known as universal load cell.

bidirectional printer An electronic printer capable of printing either forward or back­ward.

bidirectional pulse A wave pulse in which intended deviations from the normally con­stant values occur in two opposing direc­tions.

bilateral tOlerance The amount of allowable variation about a given dimension, usually expressed as plus or minus a specific fraction or decimal.

bilateral transducer A transducer that can transmit signals simultaneously in both directions between two or more termina­tions.

bill of lading A contract or receipt for goods that a carrier agrees to transport from one place to another and to deliver to a desig­nated person or that it assigns for compensa­tion upon the conditions stated in the bill of lading. [ISA-95.00.01-2000]

bill of material A listing of all the subassem­blies, parts, and!or materials that are used in the production of a product. It includes the quantity of each material required to make a product. [ISA-95.00.01-2000]

bill of resources 1. A listing of all resources and at what point in the production process they are needed to produce a product. 2. A listing of the key resources required to manu­facture a product, organized as segments of production. Bills of resources are often used to predict the impact of activity changes in the master production schedule on the sup­ply of resources. [ISA-95.00.01-2000]

bimetal A bonded laminate consisting of two strips of dissimilar metals. The bond is usu­ally a stable metallic bond produced by roll­ing or diffusion bonding. The composite material is used most often as an element for detecting temperature changes by means of differential thermal expansion in the two lay­ers.

bimetal thermometer Temperature-sensing instrument in which two dissimilar metals

48

i

I

I LJllllClalll'- L.ll~.l.l.lI.VJ.J.I.~I.~J. ~J.~J.J.I.~J.I.I. I LJ'.l.llaJ.y U.ll.lL

are bonded together so that the differential expansion of the two metals actuates the pointer, indicating temperature.

bimetallic thermometer element A tempera­ture-sensitive strip of metal (or other config­

i� uration) made by bonding or mechanically joining two dissimilar strips of metal together. Small changes in temperature will cause the composite assembly to distort elas­

1 tically and produce a predictable deflection. 0\ The element is designed to take advantage of.~

the fact that different metals have different� l'·,

coefficients of thermal expansion.�

ROTATING SHAFT

FREE END ATTACHED TO POINTER SHAFT

•"',..1---- FIXED END

Bimetallic Sensor

bin 1. One spectral line in the frequency dis­play of a fast-Fourier transform (FFT) ana­lyzer. The bin can be viewed as a bandpass filter with a bandwidth that is adjusted by

- .� whatever frequency span is selected. 2. In� video development, a place for storing a� piece of video footage.�

binary 1. A term applied to a signal or device that has only tvvo discrete positions or states. When used in its simplest form, as in "binary signal" (as opposed to "analog signal"), the term denotes an "on-off" or "high-low" state, that is, one that does not represent con­tinuously varying quantities. [ANSI-ISA-5.1­1984 (R1992)]2. Pertaining to the characteris­tic or property that involves a selection, choice, or condition in which there are two possibilities. [ISA-RP55.1-1975 (1983)]3. Per­taining to the numeration system that has a radix of two. [ISA-RP55.1-1975 (R1983)]4. A , f ; computer numbering system that uses two

t ,

; ." as its base rather than ten. The binary systemf' uses only aand 1 in its written form. 5. At ' device, such as a computer, that uses only two states or levels to perform its functions,.

binary cell An information-storage element that can assume either of two stable condi­tions and no others.

binary code A code that uses two distinct characters, usually aand 1.

binary-coded decimal (BCD) Describing a decimal notation in which the individual decimal digits are represented by a group of binary bits. For example, in the 8-4-2-1 coded decimal notation each decimal digit is repre­sented by a group of four binary bits. The number twelve is represented as 0001 0010 for 1 and 2, respectively, whereas in binary notation it is represented as 1100. Related to binary. " ' ..

binary counter l.'Acounter that counts according to the binary number system. 2. A counter whose basic counting elements are capable of assuming one of two stable states.

binary digit 1. In binary notation, either of the characters aor 1. 2. Synonymous with bit. 3. See equivalent binary digits.

binary file An electronic term for a file that is not a text file.

binary notation Amethod of numerical representation with two as the base and thus having only two digits, "0" and "1." This notation is easily represented in computing and transmission by two states in frequency, phase, amplitude, voltage, current, and so on.

binary number A number composed of the characters aand I, in which each character represents a power of two. The decimal num­ber 2 is 10; the number 12 is 1100; the number 31 is 11111, and so on.

binary phase-shift keying (BPSK) A digital form of phase modulation in which the out­put phase is modulated betvveen two states.

binary point The radix point in a binary number system. See radix point.

binary scaler A signal-modifying device (scaler) that has a scaling factor of 2.

binary search A dichotomizing search in which the set of items to be searched is divided at each step into two equal, or nearly equal, parts. Also known as "binary chop."

binary synchronous A procedure for con­necting many terminals that share a single link.

binary synchronous communications (BSC) 1. An IBM synchronous communica­tions protocol also referred to as "bisync." 2. A communications procedure that uses spe­cial characters for the control of synchro­nized transmission

binary unit 1. A binary digit. 2. A unit of information content, equal to one binary decision, or the designation of one of two possible and equally likely values or states of anything that is used to store or convey

49�

I binary word / bit duration

information. 3. See check bit and parity bit. 4. Synonymous with bit.

binary word A group of binary digits that have place values in increasing powers of two.

binder 1. In metal founding, a material other than water that is added to foundry sand to make the particles stick together. 2: In pow­der metallurgy, a substance added to the powder to increase the green strength of the compact, or a material (usually with a rela­tively low melting point) added to a powder mixture to bond particles together during sintering that otherwise would not bond into a strong sintered body.

Bingham viscometer A time-of-discharge device for measuring fluid viscosity in which the fluid is discharged through a capillary tube instead of an orifice or nozzle.

bioinstrumentation Instruments that can be attached to humans or animals to record bio­logical parameters, such as pulse rate, breathing rate, or body temperature.

biomedical engineerinp . The application of engineering principles to the solution of medical problems, including the design and fabrication of prostheses, diagnostic instru­mentation, and surgical tools.

biometric To measure using biological tech­niques, typically for security purposes·but also for interfaces for process control involv­ing the recognition or matching of voice, face, fingerprint, iris, retina, and so on.

BIOS Basic input/output system. Com­mands used to tell a CPU how it will com­municate with the rest of the computer. The information that is typically needed when a computer starts up. In some operating sys­tems, that part of program that customizes it to its specific computer.

biphase A method of bit encoding for serial data transmission or recording in which there is a signal transition every bit period.

bipolar meter The ability of a meter to dis­play both positive and negative readings.

bipolar technology Technology that uses two different polarity electrical signals to repre­sent logic states of 1 and O.

bipolar transistor A transistor created by placing a layer of P- or N-type semiconduc­tors between two regions of an opposite type of semiconductor.

BIPS Billion instructions per second (rough measure of processing power).

biquinary code A method of coding decimal digits in which each numeral is coded in two parts-the first being either 0 or 5 and the

second any value from 0 to 4. The digit equals the sum of the two parts.

birefringent element A device that has a refractive index that is different for light­waves of different orthogonal polarizations. Because of this difference, light of the two orthogonal polarizations travels at different speeds and is refracted slightly differently.

Birmingham wire gauge (BWG) A system of standard sizes useqin the United States for brass wire as .well as for strip, ban9s, h09ps, and wire made offerrou5 and nonferrous metals. The decimal equivalent of standard BWG sizes is generally larger than for the same gauge number in both the American wire gauge and U.s. steel wire gauge sys­tems . ..,.

bistable 1. A device that changes state when a preselected signal value is reached. [ISA­RP67.04.02-2000] 2. The capability of assum­.ing either of two stable states, hence of stor­ing one bit of information.

bistable uncertainty (BU) That portion of the channel uncertainty that is due to uncor­rected possible errors associated only with the bistable. [ANSI/ISA-TR67.04.08-1996]

bit 1. An abbreviation of "binary digit." 2. A measure of failure rate that corresponds to 10-8 failures per hour. 3. A single character in a binary number. 4. A single pulse in a group of pulses. 5. A unit of information capacity for a storage device. The capacity in bits is the loga­rithm to the base hvo of the number of possi­ble states of the device. Related to storage capacity. 6. The smallest unit of information that can be recognized by a computer.

bitbus Process control and data acquisition communication by Intel using the seven­layer OSI model, EIA-485 comms, plus SOLC protocol, plus 8044 chip; twisted-pair, multi ­point, up to 28 stations per segment, up to 500 round-trip messages per second.

bit density A measure of the number of bits recorded per unit of length or area.

bit depth In digital graphics, the number of bits used to represent the color of each pixel in an image: a bit depth of 2 = black and white pixels, 4 =16 colors or grays, 8 =256 colors or grays, 16 =65,536 colors, 24 =16.7 million colors, and so on.

bit duration The time it takes for one encoded bit to pass a point on the transmis­sion medium. A relative unit of time mea­surement used to compare delay times, such as propagation delay or access latency, where the data rate of a (typically high-speed) transmission channel may vary.

50

bit error rate (BER) The ratio of bits received in error to bits sent.

bit error ratelblock error rate testing (BERTI BLERT). An error-checking technique that

f compares a received data pattern with ar known transmitted data pattern to determine transmission line quality.

bit error rate tester A system that measures the fraction of bits transmitted incorrectly by

J a digital communication system.

bit fail map A diagnostic report from a mem­ory device test that contains actual failure modes and failure locations through a series of characteristic patterns.

J

bit map 1. A table that describes the state of each member of a related set. A bit map is most often used to describe the allocation of storage space; each bit in the table indicates whether a particular block in the storage medium is occupied or free. 2. In computer imaging, the electronic representation of a page or a chosen area of a page or illustra­tion, indicating the position of every possible spot (zero or one). A bit map is pixel-based (typically providing higher resolution on a video screen) rather than object-oriented (typically providing higher resolution on a printer).

bit pattern A combination of n binary digits to represent 2 to the n possible choices. FO'r example, a three-bit pattern represents eight possible combinations.

bit rate 1. The speed at which bits are trans­mitted, usually expressed in bits per second. (Compare with baud). 2. The rate at which binary digits, or the pulses representing them, pass a given point on a communica­tions line or channel (clarified at baud).

bits per second In a serial transmission, the instantaneous bit speed within one character, as transmitted by a machine or a channel. See baud.

bit stream A binary signal without regard to grouping by character.

bit string A string of binary digits in which each bit position is considered an indepen­dent unit.

bit synchronizer A hardware device that establishes a series of clock pulses in syn­chronism with an incoming bit stream and identifies each bit.

blackbody 1. A physical object that absorbs incident radiation, regardless of the spectral character or directional preference of that radiation. A perfect blackbody is most closely approximated by a hollow sphere with a small hole in its wall-the plane of the hole being the blackbody. A perfect black-

bit error rate (BER) / bleeding

body is used as an ideal reference concept in the study of radiant energy. 2. Denotes a per­fectly absorbing object, that is, one for whom none of the incident energy is reflected. It radiates (perfectly) at a rate expressed by the Stefan-Boltzmann Law; the spectral distribu­tion of radiation is expressed by Planck's radiation formula. When a blackbody is in thermal equilibrium, it absorbs and radiates at the same rate.

blackbody temperature. The t~~e tempera­ture of a blackbody source. When used to cal­ibrate a radiation pyrometer, the radiation pyrometer will measure the brightness tem­perature of sources other than the blackbody. To obtain the true temperature of nonblack­bodies using a radiation pyrometer, multiply the brightness temperature by the emissivity of the observed source.

black box A generic term used to describe an unspecified devi"ce that performs a special function or in which known inputs produce known outputs in a fixed relationship.

black-box testing See functional testing. black-bulb thermometer A thermometer

whose sensitive element is covered with lampblack to make it approximate a black body.

blade-type consistency sensor A pneumatic device for determining changes in consis­tency of a flowing non-Newtonian substance such as a slurry. It senses the force required for a shaped blade to shear through the flow­ing stock, and transmits a pneumatic output signal proportional to changes in consis­tency. Its normal operating range is 1.75 to 6.0 percent suspended solids, with a sensitiv­ity of -0.02 percent in many applications.

blank In computer programming, the charac­ter used to represent a space.

blank alarm point See alarm point. blanking Inserting a solid disk at a pipe joint

or union to close off flow during mainte­nance, repair, or testing.

blasting 1. Detonating an explosive. 2. Using abrasive grit, sand, or shot carried in a strong stream of air or other medium to remove soil or scale from a surface.

bleeding 1. Allowing a fluid to drain or escape to the atmosphere through a small valve or cock. Bleeding is used to provide controlled slow reduction of slight overpres­sure, to withdraw a sample for analysis, to drain condensation from compressed air lines, or to reduce the airspace above the liq­uid leve~ in a pressurized tank. 2. Withdraw­ing steam from an intermediate stage of a turbine to heat a process fluid or boiler feed­

51

l

I blend I blocked impedance�

water. 3. Natural separation of liquid from a semisolid mixture-such as oil from a lubri­cating grease or water from freshly poured concrete.

blend 1. To mix ingredients so they are indis­tinguishable from each other in the mixture. 2. To produce a smooth transition between two intersecting surfaces, such as at the edges of a radiused fillet between a shaft and an integral flange or collar.

blind hole A hole in a piece of material that does not completely penetrate to the back surface.

blind nipple A short piece of pipe or tubing, one end of which is closed and sealed.

blind pressure transmitter A pressure trans­mitter that does not have an integral readout device.

blinking A periodic change of the hue, satu­ration, or intensity of a video display unit pixel, character, or graphic symbol. [lSA-5.5­1985]

blip Any erratic signal on a computer screen. blister 1. A small area on the surface of metal

or plastic where gas trapped between layers has forced up a bubble of material from the material underneath. 2. An enclosed macro­scopic cavity in a glaze or other fired ceramic coating. 3. A raised area where a paint, elec­troplate, or other coating has become. detClched from the substrate because gas or moisture has accumulated at the coating­substrate interface.

BLOB Binary large object; in object-oriented programming, a BLOB can contain all kinds of data, such as images, sounds, graphics, programming codes, animations, and the like.

block� 1. A set of things, such as words, charac­ters, or digits, handled as a unit. 2. A collec­tion of contiguous records that are recorded as a unit. The blocks are separated by interblock gaps, and each block may contain one or more records. 3. In data communication, a group of contiguous characters formed for transmis­sion purposes. The groups are separated by interblock characters. 4. A group of physically adjacent words or bytes of a specified size thClt are particular to a device. With respect to I/O, the smallest system-addressable segment on a mass-storage device. 5. A logical processing unit of software thClt comprises an individual, named copy of the block and associated parameters specified by a block type, which persists from one invocation of the block to the next. Note: The values of the data in a block's data structure typically change each

time the block is invoked. [ISA-TR50.02, Part 9-2000]

block, data A set of associated characters or words treated as a unit.

block-and-tackle A hoisting gear consisting of a rope or cable and one or more indepen­dently rotating frictionless pulleys. Also known as "block and falL"

block check character A character, usually transmitted at the end of a block, that is the result of a verification transmission algo­rithm accumulated over all the characteoo in -. a block (e.g., CRe, LRC).

block diagram 1. A graphical representation of the hardware in a computer system. The primary purpose of a block diagram is to indicate the paths along which information or control flows between the various parts of a computer system. It should not be con­fused with the term jlolJxhart. 2. A coarser and less symbolic representation than a flow­chart. 3. A graphical representation of a com­puter program. 4. A simple pictorial repre­sentation of a control system. Block diagrams have two basic symbols, the circle and the function block. The arrows entering and leaving the circle represent the flow of infor­mation, and the head of each arrow has an algebraic sign associated with it, either plus or minus. Block diagrams graphically repre­sent the hardware in a system.

block sequence A welding sequence in which separated lengths of a continuous multiple-pass weld are built up to full cross section before gaps between the segments are filled in. Compare with cascade sequence.

block size The number of voltage measure­ments in a time block of data sampled by a fast Fourier transform (FFT) spectrum ana­lyzer. This number is usually 512 for a 200­line frequency display, 1,024 for a 400-line frequency display, and so on.

block switching A two-level multiplexing technique used in data transmission, whereby one level selects the input channel to be transmitted, and the second level selects the group of first-level input channels to be addressed. The chief advantage of block switching is that it reduces leakage currents from "off" channels that interfere with the data Signals being transmitted. Also known as submultiplexillg.

blocked impedance Of an electromechanical transducer; the electrical impedance at the input terminals when the mechanical system is "blocked," or prevented from moving.

52�

I blow down valve I Hode plot

blow down valve A valve generally used to continuollsly regulate the concentration of solids in the boiler (not a drain valve).

blowback The difference between the pres­sures at which a safety valve opens and closes, usually about 3 percent of the pres­sure at which the valve opens.

blowby Leakage of fluid through the clear­ance between a piston and its cylinder dur­ing operation.

blowdown 1. In a safety valve, the difference between opening and closing pressures. 2. In a steam boiler, the practice of periodically opening valves attached to the bottom of steam drums and \vater drums, during boiler operation, to drain off accumulations of sedi­ment.

CHEMICALS IN FEEDWATER

BOILER CHEMICAL CONCENTRATION STEAM

(CHEMICAL-FREE)

CHEMICALS IN SLOWDOWN SLOWDOWN FLOW =

1/CONCENTRATION RATIO X FEEDWATER FLOW

BIOIudo'lon and Chelnical Balance

blower A fan used to force air under pres­sure.

blowhole A pocket of air or gas trapped dur­ing the solidification of a cast metal.

blow-off valve A specially designed, manu­ally operated valve connected to the boiler for tl1e purpose of reducing the concentration of solids in the boiler or for draining pur­poses.

blowout disk See rupture disk de"vice. bluing Also spelled "blueing." 1. Forming a

bluish oxide film on steel by exposing it to steam, air, or other agents at a suitable tem­perature/ thus giving scale-free surfaces an attractive appearance and improved corro­sion resistance. 2. Heating formed springs after fabrication to improve their properties and reduce resid1lal stress. 3. A thin blue oxide formed on polished metal surfaces when exposeci briefly to air at high tempera­tures.

BMP Bit-mapped format method for saving graphics in electronic memory, used for exchanging data betvveen computers. Also, best management practices, an EPA (United

States) term for a practice that is not standard per se but must be adhered to no matter what or result in perrn.it loss, even if effluent limits are met.

BMS Burner management system; terminol­ogy originating in power generation indus­try.

BNe Bayonet-Neill-Concelman; bayonet­locking connector used on Ethernet 10Base2 thinnet coaxial cabling.

board A flat sheet in which integrated cir­cuits are mounted.. See panel.

board tester A system "that 'tests printed cir­Cllit boards, with or without components.

BOB Break-out box; testing device that per­mits the user to cross and tie leads using jumper wires.

BOD Biochemicaloxygen demand of pollut­ants/ calculated for EPA (United States) regu­lations. Also, bllsiness object document.

Bode diagram In process instrumentation, a plot of the log gain (magnitude ratio) and phase angle values on a log frequency base for a transfer function. [ANSI/ISA-51.1-1979 (1993)]

10 50 100

I I ! _ VBREAK POINT

o 1.0

~ ~,a: 0.5 w I o I :::> CORNER FREQUENCY---.f "...... Z I

"I<..9

<! ~ ~ 0.1 0::: I o I

I " ~ Z 05 I <..9 ~

I I.02

+60 r----.,.-----r--...-~-~-- _

if) UJ

I

'''" ~ a ........~-4----+---'---__+--+------I----J <..9 W o W -60 1-----+--+-~_=:__4--+----+-~

....L <..9 z <! -120 I----+--+------t--+---_+_~ W if)

4:t -·180 '---__...J.--.----L...__---I._-L.-__---L----.J

.1 .5 5 10 50 100

FREQUENCY - CYCLES PER UNIT TIME

Typical Bode Diagranl

Bode plot 1. A graph of transfer function ver­SllS frequency. TIle gain (often in decibels) and phase (in degrees) are plotted against the freqllency on log scale. Also called a "Bode diagram." 2. In vibration analysis, a plot of amplitude versus frequency and phase ver­S115 frequ~ncy with all data points at running speed. The data are admitted through a tracking filter as the machine changes speed.

53

I DUUY I OOloIIleter

body The main pressur.e bounda~y of the valve, which also provIdes the pIpe connect­ing ends and the fluid flow passageway as well as supporting the valve trim. [ANSI/ ISA-7S.0S.01-2000]

body, encapsulated A body \vith all surfaces covered by a continuous surface layer o.f a different material, usually an elastomerIc or polymeric material. ...

body, split A valve body desIgn In whIch trim is secured between two segments of a valve body. .

body, wafer A thin annular sectIon body whose end surfaces are located and clamped between the piping flanges by bolts extend­ing from flange to flange.

body, wafer, lugged A thin annular section body whose end surfaces mount between the pipeline flanges or ~ay be attache?to the end of a pipeline WIthout a~y ad?ItIonal flange or retaining parts, USIng eIther through-bolting and/or tapped hole~.

body, l.veir type A body tha~ has a raIsed con­tour that is contacted by a dIaphragm to shut off fluid flow.

body cavity The internal chamber of the valve body. [ANSI/ISA-75.05.01-2000]

boiler 1. A closed vessel in which water is heated, steam is generated, steam is super­heated, or any combination of these, by th~

application of heat from combustible fuels In a self-contained or attached furnace. [ISA­77.41-1992] A typical boiler control scheme is shown in the illustration accompanying this definition. 2. The entire vessel in which steam or other vapor is generated for use external to itself, including the furnace. This includes the waterwall tubes; the firebox area, including burners and dampers; the convection area, consisting of any super­hea ter, reheater, and / or economizer sections as well as drums, generating tubes, and headers. [ANSI/ISA-77.13.01-1999; ANSI/ ISA-77.42.01-1999; ANSI/ISA-77.44-199S]

boiler drum level A water-tube boiler (not once-through) process variable that is mea­sured and controlled by adding feedwater. Control may be single-element, two-element, or three-element; the control strategy will depend on the user's requir~mentsand the boiler design. Measured varIables may include drum level, steam flow, feedwater flow/ blowdown t1ow, drum pressure, and feedwater pressure.

boiler horsepower The evaporation of 34lh lbs of water per hOllr from a temperature of 212°F into dry saturated steam at the same temperature. Equivalent to 33,475 Btll.

STEAM

BOILERFEEDW~ Boiler Control

DRUM PRESS

h - ACTUAL WATER LEVEL

H - TAP HEIGHT

P1 - INSTRUMENT PRESSURE-LOWER TAP

P2 • INSTRUMENT PRESSURE-UPPER TAP - H

P h Pc - WATER DENSITY IN REFERENCE c

PL - SATURATED LIQUID STEAM DENSITYt Pv - SATURATED VAPOR STEAM DENSITYI '*Boiler Drum Level Mechanics

boiler water A representative sample of the circulating boiler water after the generated steam has been separated and before the incoming feed water or added chemical becomes mixed with it, thus affecting its composition.

boiling The conversion of a liquid into vapor with the accompanying formation of bub­bles.

boiling out The boiling of a highly alkaline water in boiler pressure parts for the ren10val of oils, greases, and the like.

boiling water reactor (BWR) A nuclear steam supply system in which process steam is generated in the reactor vessel. [IS.LL\-67.03­1982]

boldface In the typographical composition of screen displays and printing, the heavier typeface version of a type family.

bolometer A sensitive infrared detector that operates based on a change in tempe~ature. induced by absorbing infrared radIatIon. It IS

made of two thin, blackened gratings of plat­inum,"one illuminated and the other kept in the dark. The absorption of heat changes the

54�

I bolt / Boolean algebra

-. ----------------------------- ­

electrical resistance, which is detected by comparing the resistances of the two gratings in an electrical circuit.

bolt A threaded fastener that consists of a rod, usually made of metal, that has threads at one end and an integral round, square, or

j hexagonal head at the other end. Short bolts

I usually have threads running the entire length below the head, and longer bolts often have an unthreaded shank between the head

1 and threaded end,I' bolted joint An assembly of two or more I parts held together by a bolt and nut, with or j" without washers, or by a bolt that threadsI into a tapped hole in one of the parts. i bomb calorimeter An apparatus for measur­j ing the quantity of heat released by a chemi­j cal reaction. It consists of a strong-walled " metal container (bomb) immersed in about ~ 2.5 liters of water in an insulated container. A

sample is sealed in the bomb, the bomb immersed, and the sample ignited (or a reac­tion started) by remote control. The heat released is measured by observing the rise in temperature of the water bath.

bond 1. A wire rope that attaches a load to a crane hook. 2. Adhesion between cement or mortar and masonry. 3. In an adhesive­bonded or diffusion-bonded joint, the junc­tion between faying surfaces. 4. In welding, brazing, or soldering, the junction between assembled parts. Where filler metal is used, it

.7 is the junction between fused metal and heat-affected base metal. 5. In grinding wheels and other rigid abrasives, bond is the material that holds abrasive grains together. 6. Material added to molding sand to hold the grains together. 7. The junction between base metal and cladding in a clad metal product.

bondable Designed to be permanently

I,mounted to a surface by means of adhesives.

t [ISA-37.1-1975 (R1982)] ~ bonded Permanently attached over the

length and width of the active element. [ISA-37.1-1975 (R1982)]

bonded liner 1. A liner vulcanized or cemented to the body bore. [ANSI/ISA­75.05.01-2000] 2. In a butterfly valve body, a liner vulcanized or cemented to the body

j bore. J bonded strain gauge A device for measuring t strain. It consists of a fine-wire resistance ele­1 ment, usually in zigzag form, which is

embedded in nonconductive backing mate­rial such as impregnated paper or plastic, which is in turn cemented to the test surface or sensing element.

55

bonded transducer A pressure sensor that uses a bonded strain guage to generate the output signal.

bonding 1. An electrically conductive Con­nection between metallic parts of the equip­ment that needs to be grounded and some other part of the equipment to which a grounding conductor is connected. 2. The permanent joining of metallic parts to form an electrically conductive path that will ensure elect.rical cor:tinuity and the capacity to conduct safely any turrent likely to be imposed. [ISA-12.0tOl-1999]

bone dry A papermaking term used to describe pulp fibers or paper from which all water has been removed. Also known as "oven dry" and "moisture free."

bonnet The portion of the valve that contains the packing box and stem seal and may guide the stem. It provides the principal opening to the body cavity for assembling internal parts or it may be an integral part of the valve body. It may also make it possible to attach the actuator to the valve body. Typi­cal bonnets are bolted, threaded, welded, pressure sealed, o~ integral with the body. [A SI/ISA:75.05.01-2000]

bonnet, seal-welded A bonnet welded to a body so as to provide a zero leakage joint. [A SI/ISA-75.05.01-2000]

bonnet bolting A means of fastening the bonnet to the body. It may consist of studs with nuts for a flanged bonnet joint, studs threaded into the bonnet neck of the body, or bolts through the bonnet flange. [ANSI/ISA­75.05.01-2000]

bonnet gasket A deformable seal between the mating surfaces of the body and bonnet. It may be deformed by bonnet bolting load­ing or energized by fluid pressure within the valve. [ANSI/ISA-7S.0S.01-2000]

bonnetless A gate valve that has packing between the gate and body, such that the gate extends outside the pressure boundary in the open position. [A SI/ ISA-7S.05.01-2000]

bonnetted Agate valve that has a bonnet that encloses the gate within the pressure bound­ary when in the open position. The packing is provided at the stem. [A SI/ISA-75.05.01­2000]

bonnet types Typical bonnets are bolted, threaded, or welded to or integral with the body. [A SI/ISA-7S.0S.01-2000] Other types are extension bonnets and seal welded bonnets.

Boolean Pertaining to logic quantities. Boolean add See OR. Boolean algebra A process of reasoning or a

deductive system of theorems that uses a

I Boolean expression / bottom flange�

symbolic logic and deals with classes, propo­sitions, or on-off circuit elements. To permit mathematical calculation, it employs sym­bols to represent operators such as AND, OR, NOT, EXCEPT, IF, THEN, and so on. Named after George Boole, a famous English mathe­matician.

Boolean expression A quantity expressed as the result of Boolean operations such as and and or, and not upon Boolean variables.

Boolean functions A system of mathematical logic that is often executed in circuits in order to provide digital computations such as OR, AND, NOR, NOT, and so on.

Boolean operator A logic operator whose operands and result are one of two values.

Boolean variable See logical variable. booster A repeater station that amplifies and

retransmits a received signal. booster fan A device for increasing the pres­

sure or flow of a gas. booster relay A volume- or pressure-ampli­

fying pneumatic relay that is used to reduce the time lag in pneumatic circuits by repro­ducing pneumatic signals that have high­volume and/or high-pressure output. [ANSI/ISA-75.05.01-2000]

boot 1. A computer routine in which a few instructions are loaded that then cause the rest of the system to be loaded. 2. To start..ar restart a computer system by causing instructions to be read from a storage device (disk, etc.) into computer's memory. To boot a computer involves loading part of the operating system into the computer's main memory. If the computer is already oper­ating, it is called a "warm boot"; otherwise, it is called a "cold boot."

bootstrap A technique for loading the first few instructions of a routine into storage, then using these instructions to bring in the rest of the routine. This usually involves either entering a few instructions manually or using a special key on the console.

bootstrap loader A routine whose first instruction is sufficient to load the remainder of the routine into memory from an input device. It is normally used to start a complete system of programs.

bore 1. The inner cavity in a pipe or tube. 2. The diameter of the cylinder of a piston-cyl­inder device such as a reciprocating com­pressor, engine or pump, or a hydraulic or pneumatic power cylinder. 3. To penetrate or pierce a workpiece with a rotating cutting tool. 4. To increase the size of an existing hole, generally with a single-point cutting tool, while either the work or the cutting tool

rotates about the central axis of the hole. 5. The inner surface of a gun tube. 6. The cen­tral hole in a laser or other type of tube (a capillary, waveguide, or a hole in a micro-channel plate).

bore Reynolds number A calculated Rey­nolds number, including Rrl using Vbore, Pbore,

llbore' dbore; also Rei = RdB. borescope A straight-tube telescope, incorpo­

rating mirrors or prisms, that is used to visu­ally inspect the inner surfaces of pipes or gun tubes..... '. . .

boresighting 'To a'lign a gun, directional antenna, or other device by optical means or by observing a return signal from a fixed tar­get at a known location, The term is derived from an early military practice of looking down the bore of an artillery piece to obtain an initial line of sight to a target.

boron counter tube A type of radiation counter tube that is used to detect slaw neu­trons, The tube has electrodes that are coated with a borort'cbmpound, and it also may be filled with BF3. A slow neutron is easily absorbed by a BlO nucleus, which results in the emission of an alpha particle.

borosilic~te glass A type of heat-resisting glass that contains at least 5 percent boric acid. Also, business object document.

BOSFET Bipolar metal oxide semiconductor field effect transistor; an optically isolated FET.

boss 1. A localized projection on a valve or actuator surface that can serve various pur­poses, such as for drain connections, auxil­iary connections, a yoke connection, or for other attachments. [ANSI/ISA-75.05.01­2000] 2. A raised portion of metal of small area and limited thickness on flat or curved metal surfaces. 3. A short projecting section of a casting, forging, or molded-plastic part, often cylindrical in shape, and used to strengthen, align, or fasten assembled parts.

bottom contraction The vertical distance from the crest to the floor of the weir box or channel bed.

bottom dead center The position of a piston and its connecting rod when the piston is at the extreme downstroke position.

bottom flange A part that closes a valve body opening opposite the bonnet opening. It may include a guide bushing and/ or serve to allow the reversal of the valve action. In three-way valves, it may provide the lower flow connection and its seat. [ANSI/ISA­75.05.01-2000]

56�

I bound water / branch�

bound water In a moist solid that is to be dried, that portion of the water content that is chemically combined with the solid matter.

boundary lubrication A condition occurring during the sliding contact between two sur­faces when contact pressures are high enough and sliding velocities low enough that hydro­dynamic lubrication is completely absent. Mating surfaces slide across each other on a mliitimolecular layer of lubricant, often with some solid-to-solid surface contact. For liquid lubricants, a bearing-characteristic (Sommer­field) number of 0.01 is considered to be the upper limit of boundary lubrication.

Bourdon tube 1. A pressure-sensing element consisting of a twisted or curved tube of non­circular cross section that tends to be straightened when internal pressure is applied. [ISA-37.1-1975 (R1982)]. 2. A flat­tened tube that is twisted or curved and closed at one end and is used as the pres­sure-sensing element in a mechanical pres­ .. sure gauge or recorder. A process stream pressure is routed to the open end of the tube, and the tube flexes or untwists in rela­tion to the internal pressllre. The change in shape of the tube is used to operate a mechanical pointer or pen positioner. Also known as "Bourdon element" and "Bourdon pressure gauge."

CROSS SECTION o

boustrophedon Literally, writing lines "as the ox plows." Lines that are written (or printed) alternately back and forth, that is, right to left on one, left to right on the next, and so on.

box A flo\vchart symbol. boxcar averager A piece of signal-processing

instrument that averages equally weighted selected portions of repetitive signals to improve signal quality. Sometimes called a

"gated integrator" because it passes or gates portions of the signal, then integrates them.

box header boiler A horizontal boiler of the longitudinal or cross-drum type and consist­ing of a front- and rear-inclined rectangular header that is connected by tubes.

box wrench A closed-end wrench that is designed to fit a single size and shape nut. Different wrench ends are needed for differ­ent nut sizes and shapes. Also ~nown as a "box end wrench." .."

B power ,supply' A·A "ele'ctrical power supply that is connected in the plate circuit of a vac­uum tube electronic device.

Bps, Bls Bytes per second; unit of data transmission ra te.

BPT Best pra~ticable control technology cur­rently available in complying with EPA (United States) pollution prevention require­ments.

Bragg's law A principle that describes the apparent reflectig~~X-rays (and DeBroglie waves associated with certain particulate beams) from atomic planes in crystals. The maximum reflected intensity occurs along the family of directions that is defined by:

a= arcsin enl/2d where ais the Bragg angle (angle of reflec­tion and of incidence), n is an integer, e is the wavelength of monochromatic radiation reflected from the crystal, and d is the inter­planar spacing of the reflecting parallel planes in the crystal.

brake A machine element for applying fric­tional force to slow or stop relative motion.

brake drum See drum. brake horsepower The mechanical power an

engine develops. It is measured by absorbing the engine's output with a friction brake or dynamometer that is applied to the engine's shaft or flywheel.

brake lining A material with a high coeffi­cient of friction that is used as the principal friction element in a mechanical brake. It usually is made of fabric or molded asbestos and usually can be readily replaced so as to extend the brake's service life and restore braking efficiency.

brake shoe See shoe. Brale A 120

0

conical diamond indenter used in the Rockwell hardness testing of relatively hard metals.

branch [Comp] In computing, anyone of a number of instructiol1 seqllences in a pro­gram to which computer control is passed, depending upon the statlls of one or more variables. The instructions that mechanize this concept are sometimes called branch

57�

I branch circuit / bridged-T network

instructions. However, the terms tran~fer of control and jump are more widely used. Related to conditional transfer.

branch circuit That portion of permanently installed wiring that lies between the final overcurrent protective device and the attach­ment-plug receptacle or outlet, or point of connection to the fixed equipment.

branch instruction An instruction that per­forms a bram::h.

branchpoint A point in a routine where a choice is made of one among of two or more possible paths. See conditional transfer.

brass Any of the many alloys that are based on the binary system copper-zinc. Most brasses contain no more than 40 wt% zinc.

braze welding A joining process similar to brazing but in which the filler metal is not distributed in the joint by capillary action.

brazing A method for joining metals that uses heat and a filler metal whose melting temperature is above 850'F but below the.. of

melting temperature of the base metals. Filler metal is distributed in the joint by capillary action.

breadboard model A prototype or uncased assembly of an instrument or electronic device whose parts are laid out on a flat sur­face and connected together to demonstrate or check its operation.

break [Comp]1. An interruption in computer processing. [Comm] 2. In communications, to interrupt the sending end and take control of the circuit of the receiving end. 3. In digital communications, a signal to another station, usually to interrupt the process of transmis­sion.

break condition In asynchronous transmis­sion, this is a prolonged space condition that often signals a request to terminate computer output. Many asynchronous keyboards are equipped with a break key.

breakdown voltage rating The DC or sinuso­idal AC voltage that can be applied across specified insulated portions of a transducer without causing arcing or conduction above a specified current value across the insulat­ing material. Note: The time duration of application, ambient conditions, and AC fre­quency must be specified.

break point 1. The junction of the extension of two confluent straight-line segments of a plotted curve. Note: In the asymptotic approximation of a log-gain versus log-fre­quency relation in a Bode diagram, the value of the abscissa is called the corner frequency. [ISA-RP51.1-1975]2. A point in a program where an instruction, instruction digit, or

other condition enables a programmer to interrupt the run either by external interven­tion or through a monitor routine.

break-point instruction 1. An instruction that will cause a computer to stop or to trans­fer control, in some standard fashion, to a supervisory routine that can monitor the progress of the interrupted program. 2. An instruction that, if some specified switch is set, will cause the computer to stop or take other special acti9.n.

breaks. Creases or ridges, usually appearing in aged sheet or strip, where the yield point has been locally exce~ded. Depending on the origin of the break they may be termed a

.' \_. "coil break," "cross break," "edge break," or .'.: ."s ticker break."

breeching A duct for transporting the prod-' ucts of combustion between parts of a steam­generating unit or to the stack.

Bremsstrahlung X-rays that have a broad .SF~C,!rum of wavelengths and are formed when a beam of energetic electrons deceler­ates as it penetrates a target. Also known as "white radiation."

Brewster-angle window A window inserted into an optical path at Brewster's angle, that is, the angle at which unpolarized light must be incident upon a nonmetallic surface for the reflected radiation to acquire maximum plane polarization. At Brewster's angle, the reflected plane polarized beam and the refracted beam through the window are both at 90".

bridge [Comm] 1. A network device that interconnects two local area networks (LANs) that use the same logical link control (LLC) but may use different message authen­tication codes (MACs). A bridge requires only OSI (Open Systems Interconnection) Levell and 2 protocols. See gateway and router. [Meas] 2. The strain-to-voltage con­verter in many measurement systems (actu­ally, a Wheatstone bridge).

bridge amplifier A type of amplifier circuit used extensively in instrumentation to pro­vide gains of up to 1,000 at bandwidths up to 50 kHz. It is generally configured as a direct-coupled amplifier constructed of four subamplifiers and suitable fixed resistances.

bridge circuit An electronic network in which an input voltage is applied across two parallel elements and the output voltage-to an indicating device or load-is taken across two intermediate points on the parallel ele­ments.

bridged-T network A T-network that has a fourth branch that is connected in parallel

58

I bridgewall / bronze

'.,;

,".;

with the two series branches of the T, with the fourth branch termination at one input and one output terminal.

bridgewall A wall in a furnace over which the products of combustion pass.

bridging 1. The premature solidification of metal across a mold section before the adja­cent metal solidifies. 2. Welding or mechani­cal jamming of the charge in a downfeed furnace. 3. The forming of an arched cavity in a powder metal compact. 4. The forming of an unintended solder connection between two or more conductors, either a secure con­nection or merely an undesired electrical path without mechanical strength. Also known as "crossed joint" and "solder short."

Briggs pipe thread See American standard pipe thread.

bright dipping Producing a bright surface on metal, such as by immersing it in an acid bath.

brightness A term used in nonquantitative statements to refer to sensations and percep­tions of light. In quantified statements, the term is used to refer to the description of brightness in terms of photometric units. See luminance.

brightness temperature The temperature of any non-blackbody as determined by using an optical pyrometer that is calibrated to give the true temperature of a blackbody. This temperature is always less than the true tem­perature of the non-blackbody.

bright plating Electroplating in order to yield a highly reflective coated surface.

bright switch A solid-state switch that con­sists of two bipolar transistors connected in an inverted configuration to achieve a low offset voltage. Used in only limited applica­tions today.

Brinell test A standard bulk hardness test in which a 10-mm diameter ball is pressed into the surface of a test piece. A hardness num­ber is determined by dividing the applied load in kg by the area of the circular impres­sion in sq mm.

British thermal unit (Btu, BTU) The mean British thermal unit is 1/180 of the heat needed to raise the temperature of lIb of water from 32°F to 21iF at a constant atmo­spheric pressure. It is about equal to the quantit¥ of heat required to raise 1 lb of water 1 F. A Btu is essentially 252 calories.

brittle fracture The separation of solid mate­rial with little or no evidence of macroscopic plastic deformation. It usually occurs by the rapid propagation of cracks and requires less

energy than for ductile fracture of a similar structure.

brittleness The tendency of a material to frac­ture without apparent plastic deformation.

Brix scale A specific-gravity scale used almost exclusively in sugar refining. Degrees Brix represent the weight percentage of pure sucrose in water solution at 17.5'C.

broaching Cutting a finished hole or contour in solid material by axially pulling or push­ing a bar-shaped, t09.thed" tapered cutting tool across a workpi:ece'snrface or through a pilot hole.

broadband A medium based on CATV (com­munity antenna television) technology wherein multiple signals are frequency divi­sion multiplexed. Because of the use of CATV technology, a broadband cable is uni­directional (within any given block of fre­quencies). As a result, two types of broadband systems are in common use: siu­gle cable and dual cable. In a single cable sys­tem, stations transmit and receive on the same cable but at different frequencies. The station transmits on one frequency. The sig­nal travels down the network to the head end, gets translated into a different fre­quency, and is sent back down the network where it is received by all stations. In a dual cable system, the stations transmit and receive at the same frequency but on differ­ent cables. The end of the transmit cable is connected to the beginning of the receive cable, forming a double loop through the plant.

broadband pyrometer See wideband radiation thermometer.

broadband transmission (fiber optic) The transmission of signals that have a large bandwidth, such as video transmissions.

broadcast 1. The simultaneous dissemina­tion of information to one or more stations, in one direction, with no acknowledgment of receipt. 2. A message addressed to all sta­tions connected to a local area network (LAN).

B roll In video development, video footage that is edited over a voice track to illustrate the issues being discussed. See AlB roll.

bronze 1. A copper-rich alloy of copper and tin, with or without small amounts of addi­tional alloying elements. 2. By extension, cer­tain copper-base alloys that contain less tin th"n other elements, such as manganese bronze and leaded tin bronze. Also, certain other copper-base alloys that do not contain tin, such as aluminum bronze, beryllium bronze, and silicon bronze. 3. Trade names

59

brouter / buffered computer

for certain copper-zinc alloys (brasses), such as architectural bronze (Cu-40Zn-3Pb) and commercial bronze (Cu-10Zn).

brouter A device that determines whether data uses a protocol that it can route and bridges data that it cannot route. Performs many of the tasks of bridges and routers without the protocol restrictions of a router. Brouters are expensive, complex, and difficult to install.

browser A software program designed to facilitate navigation along the World Wide Web such as to find informa tion, download files, and print copies.

brush plating An electroplating process in which the surface to be plated is not immersed, but rather rubbed with an elec­trode that contains an absorbent pad or brush that holds (or is fed) a concentrated electrolyte solution or gel.

BSI British Standards Institution; British certification laboratory for testing the equip­ment of different vendors to some common standard. Member of lEe.

BTEX Benzene, toluene, ethyl benzene, and xylene; a consideration in EPA (United States) regulations.

BTF Bend to fit; this comment is the unstated

bubble tight A nonstandard term used to refer to leakage in the seat of a control valve. Refer to ANSl/FCI 70-2 for the specification of seat leakage classifications. [ANSl/ISA­75.05.01-2000]

bubble tube A length of pipe or tubing placed in a vessel at a specified depth to transport a gas that has been injected into the liquid for the purposes of measuring level from hydrostatic back pressure in the tube.

bubbler-type specific-gravity meter See air-bubbler specific-gravity m·eta. .

bubble-type viscometer A device similar to a ball-type viscometer, except that viscosity is determined from the timed rise of a stan­dard-sized bubble through the sample liquid instead of from the timed fall of a ball.

buckle 1. Localized waviness in a metal bar or sheet, usually transverse to the direction of rolling. 2. An indentation in a casting caused by the expansion of molding sand into the cavify: . .

Buckley gauge A device that measures very low gas pressure by sensing the amount of ionization produced by a prescribed electric current.

bucklil1g Producing a lateral bulge, bend, •IIi

1,

•

f

last step of all do-it-yourself instructions. BTG Boiler turbine generator combination;

terminology originated in power generation '. industry.

BTL Bridge-tied load; power amplifier tech­nique.

t, bubble 1. The circular symbol used to denote and identify the purpose of an instrument or function. It may contain a tag number. Syn­onym for "balloon." [ANIS/ISA-5.1-1984 (R1992)] 2. A small volume of steam enclosed within a surface film of water from which it was generated. 3. Any small volume of gas or vapor surrounded by liquid. Surface-ten­sion effects tend to make all bubbles spheri­

bow, kink, or wavy condition in a beam, bar, column, plate, or sheet by applying compres­sive loading.

buffer [Comp] 1. In computing, an internal portion of a data processing system that serves as intermediate storage between two storage or data-handling systems with differ­ent access times or formats. The buffer is usually used to connect an input or output device with the main or internal high-speed storage. Clarified by storage buffer. [Eng] 2. In engineering, an isolating component designed to eliminate the reaction of a driven circuit on the circuits driving it, for example, a buffer amplifier. [Sci] 3. See buffer solution.

cal unless they are acted upon by outside buffer circuit An isolating circuit interposed ~. forces. between two circuits to minimize the reac­!I

i .,

bubblegas Any gas that has been selected to tion from output to input. It usually has a bubble from the end of a liquid-immersed, high input impedance and a low output level-measurement tube as a result of the hydrostatic back pressure created in the tube.

bubble memory See magnetic bubble memory. bubble point The temperature at which a liq­

uid mixture begins to boil and evolve vapors. bubble sort A procedure for sorting a set of

items. It begins by sequencing the first and second items, then the second and third, and so on, until the end of the set is reached. It t. then repeats this process until all items are correctly sequenced.

impedance. buffer coating In fiber-optic cable, a layer

such as acrylic polymer applied over fiber cladding for protective purposes.

buffered computer A computing system with a storage device that permits input and output data to be stored temporarily in order to match the slow speeds of input and output devices. Thus, simultaneous input-output and computer operations are possible. A data transmission trap is essential to the effective use of buffering since it obviates the

60

I buffered data channel (BDC) I bUlllpless transfer�

need to test frequently for the availability of a da ta channel.

buffered data channel (BDC) A device tl1at provides high-speed parallel data interfaces into and out of the computer memory.

buffered I/O channel A computer I/O chan­nel that controls the movement of data between an external device and memory, under the control of self-contained registers (i.e., independently of the operating pro­gram). See buffered data channel.

buffer memory A temporary storage device used to compensate for the difference in data rate and data flow of two devices (typically, a computer and printer). Also called spooler.

buffer solution (or buffered solution) In pH terms, a solution that maintains a set pH value regardless of added acids or bases; often used for calibration.

buffer tube In fiber-optic cable, a hard plastic tube for holding one or more fibers.

buffing Producing a very smooth and bright surface by rubbing it with a soft wheel, belt, or cloth that has been impregnated with a fine abrasive such as jeweler's rouge.

bug An error, defect, or malfunction in a computer program.

buildup 1. Excessive electrodeposition on areas of high current density, such as at cor­ners and edges. 2. Small amounts of \vorl<: metal that adhere to the cutting edge of a tool and reduce its cutting efficiency. 3. Deposi­tion of metal by electrodeposition or spray­ing in order to restore the required dimen­sions of worn or undersized machine parts.

bulb In a liquid-filled thermometer, the area at the tip (sensing portion) of a filled system that contains the liquid reservoir and, hence, the largest proportion of the expanding fluid (thus minimizing inaccuracies).

bulb, thermal See therlnal bulb. bulge A local distortion of ouvvard swelling

caused by internal pressure on a tube \vall or boiler shell because of overheating. Also, the similar distortion caused by external pres­sure of a cylindrical furnace when over­heated, provided the distortion is moderate enough to be driven back.

bulk density The mass per unit volume of a bulk material, averaged over a relatively large number of samples.

bulkhead female connector (BFC) The tub­ing to a pipe connector that allows the tube to be joined to a pipe at a bulkhead junction. The tubing connection is on one end, and the female pipe thread is on the other end.

bulkhead male connector (BMC) The tubing to a pipe connector, allowing the tube to be

joineding to a pipe at a bulkhead junction.� The tubing connection is on one end, and the� male pipe thread is on the other end.�

bulkhead union (BU) A tubing connector that allows the joining of two tubes at a bulk­head junction. It has a tubing connection on each end.

bulk memory See secondary storage. bulk modulus An elastic modulus whose

value is determined by dividing hydrostatic stress by the associ~ted volumetric strain (usually complifed"~stl:-efractional change in volume).

bulk storage A hardware device in a com­puter system that supplements computer memory; typically, a magnetic tape or disk.

bulk storage memory Any nonprogrammed large memory, for example, disks, drums, or magnetic tape units.

bullet In the typographical composition of screen displays and printing, a solid dot used as an ornamental character, usually to high­light an important item in the text.

bulletin board service (BBS) A service pro­viding users of computers connected to a phone line with general access to a shared site for the general exchange of messages, illustrations, software, and the like. A BBS can be commercial (paid subscribers), volun­teer/ or perhaps provided by a product ven­dor for use by its customers.

bull gear A bull wheel yvith gear teeth around its periphery.

bull wheel 1. The main vvheel or gear of a machine, llsually the largest and strongest. 2. A cylinder with a rope wound arollnd it for lifting or hauling.

bump A raised or flattened portion of a boiler drumhead or shell formed by fabrica­tion, generally used for nozzle or pipe attach­ments.

t

bumpless transfer The change from a man­ual to automatic mode of control, or vice versa, without changing t11e control signal to the process.

MANUAL A OUTPUT

ADJUSTMENT m o

MAN

~m

AUTO CONTROLLER OUTPUT

ON EACH PROCESSING CYCLE THAT THE CONTROLLER IS IN MANUAL, THE FOLLOWING PROGRAM STEP OCCURS:

INITIALIZE THE OUTPUT VALUE, b, OF THE INTEGRATOR BY:

BUMPLESS TRANSFER

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Buna-N / bushing�

I Buna-N A nitrile synthetic rubber known for

resistance to oils and solvents. bundle (fiber optic) A group of fibers pack­

aged together that collectively transmits light in a coherent bundle. The end fibers are in a fixed relationship to each other and can transmit an image.

bunker C oil Residual fuel oil of high viscos­ity that is commonly used in marine and sta­tionary steam power plants. (No.6 fuel oil.)

buoyancy .The tendency of a fluid to lift any• object submerged in the body of the fluid. The amount of force applied to the body equals the product of the fluid's density and the volume of fluid displaced.

buoyancy displacers The technique for mea­suring liquid level by measuring the buoyant force on a partially immersed volumetric dis­placing device.

buoyancy-type liquid-level detector Any of several designs of level gauge that depend for their operation on the buoyant force act­ing on a float or similar device located inside the tank or vessel.

burden 1. The amount of power consumed in the measuring circuit of an instrument, usu­ally given as the volt-amperes consumed under normal operating conditions. 2. The property of a circuit connected to the second­ary winding of an instrument transformer that determines active and reactive power at the transformer output terminals.

Bureau d'Orientation de la Normalisatin en Informatique The French national stan­dards body for computer-related standards.

burner 1. Any device for producing a flame using liquid or gaseous fuel. 2. A device in the firebox of a fossil-fuel-fired boiler that mixes and directs the flow of fuel and air in order to give rapid and complete combus­tion. 3. A worker who cuts metal using an oxyfuel-gas torch.

burner windbox A plenum chamber around a burner in which an air pressure is main­tained to ensure the proper distribution and discharge of secondary air.

burner windbox pressure The air pressure maintained in the windbox or plenum cham­ber as measured above atmospheric pres­sure.

burn-in The operation of a device, usually under accelerated environmental conditions, to simulate life in the devices' intended application so as to screen out early-life fail­ures.

burnish To polish or make shiny. Specifically, to produce a smooth, lustrous surface finish on metal parts by tumbling them with hard­

ened metal balls or rubbing them with a hard metal pad.

burr 1. A thin, turned-over edge or fin pro­duced by a grinding wheel, cutting tool, or punch. 2. A rotary tool that has teeth similar to those on a hand file.

bursting In data processing, the act of sepa­rating continuous forms into Single sheets.

burst pressure Maximum pressure applied to a device such as a transducer, sensor, or case without cat:.sing)eakage.

burst pressure rating The pressure that may be applied to the.sensing element or the case (as specified) of a transducer without ruptur­ing either the sensing element or trans­ducer's case as specified. Note 1: The minimum number of applications and time duration of each application must be speci­fied. Note 2: In the case of transducers that are intended to measure a property of a pres­surized fluid, the burst pressure is applied to the portiol1.$ubjected to the fluid. [ISA-37.1­1975 (R1982)]

burst proportioning Fast-cycling output from an on-time-proportioning controller used in conjunction with solid-state relay. Burst proportioning is typically used in the control of electric furnaces to prolong the life of heaters by minimizing thermal stress.

bus 1. The trunk and all devices connected to it. [ANSI/ISA-50.02, Part 2-1992]. 2. A group of wires or conductors, considered as a single entity, that interconnect part of a system. 3. In a computer, signal paths such as the address bus, the data bus, and so on. 4. A circuit over which data or power is transmitted, often one that acts as a common connection among a number of locations. Synonymous vvith trunk. 5. A communications path between two switching points. 6. A common connec­tor circuit, usually multiwire, for transferring power, data, timing, and the like between the several modules or units on the bus.

bus arbiter, bus scheduler A device dedi­cated to the task of regulating the fair alloca­tion of bus bandwidth.

bus cycle The transfer of one word or byte between two devices.

bushing 1. A device that supports and/or guides moving parts such as valve stems or shafts. [ANSI/ISA-75.05.01-2000] 2. A removable piece of soft metal or impreg­nated sintered-metal sleeve used as a bearing or guide. 3. An insulating device carrying one or more conductors through the internal or external wall of an enclosure. [ISA­12.00.01-1999 (lEe 60079-0 Mod)]

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I

I butterfly valve / byte�

butterfly valve 1. A valve with a circular body and a rotary motion disk closure mem­ber, pivotally supported by its stem. [ANSI/ ISA-75.05.01-2000]. 2. A valve that consists of a disk inside a valve body, which operates by rotating about an axis in the plane of the disk in order to shut off or regulate flow in a pip­ing system. A similar device used in heating or ventilating ductwork is called a butterfly damper.

"

Shaft

butterfly valve liner types See slip in, locked in, bonded, wrap arollnd, flange retained, elasto­meric energized, pressure energized, and encap­sulated body.

butterfly valve seal types See flexible lip senl, j pressllre energized seal, and metal piston type

seal. i buttering Coating the faces of a weld joint

prior to welding to prevent the cross contam­ination of a weld metal and base metal.

Butterworth The filter characteristic in which constant amplitude across the pass band is the objective. Also known as "constant amplitude (CA)."

butt joint A joint between two members lying approximately in the same plane. In welded joints, the edges may be machined or otherwise prepared to create any of several types of grooves prior to welding.

buttstrap A narrow strip of boiler plate over­lapping the joint of two butted plates. Used for connecting by riveting.

butt weld A weld that joins the edges or ends of two pieces of metal that have similar cross sections, without overlap or offset along the joint line.

BVS Berggewerkschaftliche Versuchsstrecke (Germany). [ANSI/ISA-12.01.01-1999] Ger­man certification and testing laboratory for testing the equipment of different vendors to some common standard

by hand Denotes that an operation does not require the use of a tool, coin, or any other object that may serve as a tool.

bypass A passage for a fluid that permits a portion or all of the fluid to flow around its normal pass flow channel.

bypass capacitor A capacitor connected in parallel with a circuit element to provide an alternative AC current path of relatively low impedance.

bypassing The act of temporarily defeating a safety function in a Safety Instrumented Sys­tem. [ANSI/ISA-84.01-1996]

by-product The incidental or secondary out­put of a chemical production or manufactur­ing process that is obtained in addition to the principal product withJittle or 1)0 additional investment or all6c~tibn of resources.

byte 1. A sequence of adjacent binary digits operated upon as a unit and usually shorter than a word. [ISA-RP55.1-1975 (R1983)] 2. Generally accepted as an eight-bit segment of a computer word. 3. Eight contiguous bits starting on an addressable byte boundary. Bits are numbered from the right, a through 7, with abeing the low-order bit. When inter­preted arithmetically, a byte is a two's com­plement integen~ith8ignificanceincreasing from bits athrough 6. Bit 7 is the sign bit. The value of the signed integer is in the range of ­128 to 127 decimal. When interpreted as an unsigned integer, the significance increases from bits a through 7, and the value of the unsigned integer is in the range a to 255 deci­mal. A byte can be used to store one ASCII character. 4. A collection of eight bits that is capable of representing an alphanumeric or special character.

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