Lab Report Temperature Transmitter (2)

7/25/2019 Lab Report Temperature Transmitter (2)

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Design of Temperature Transmitter

1. Abstract:

To measure temperature we have many devices like RTD,

thermocouples etc. but in order to use that measured temperature we have to send

the control signals to the controller which are electrical in nature so we have to

convert the measured temperature into respective voltage or current whichever is

required according to the application. So we here the design the temperature

transmitter which converts the given temperature range into voltage or current.

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2. List of Figures

S.no Name Page No

!" #$ Pin Diagram #

% Signal "onditioning "ircuit &

' Plot o( )utput current versus Temperature %

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PRELAB QUET!"#

1. $%at is a transmitter& 'o( )oes it )iffers from ot%er )e*ices&

Ans:*n electronic device that generates and ampli(ies a carrier wave, modulates

it with meaning(ul signal derived (rom speechor other sources, and radiates the

resulting signal (rom an antenna. The transmitter converts the real world signal,

such as (low, speed, position, level, temperature, humidity, pressure, etc., into

the control signal necessary to regulate the (low o( current. !t acts like a variable

resistor with respect to its input signal and is the key to the $+%&m* signal

transmission system.

Transmitters are current output devices. !( it is a two wire transmitter it isused to receive power and transmit an output signal. They (requently vary

between $+%&m*. They do not su((er (rom degradation o( signal output with

distance irrespective o( line distance. So they are used (or long distance

transmission. !n usual devices electrical resistance o( the connecting cable can

cause signi(icant error. The current loop in the transmitter is mostly insensitive

to noise.

2. $%at is a 2+ (ire, -+(ire an) +(ire transmitter&

Ans : %+wire transmitters are used to convert various process signals

representing (low, speed, position, level, temperature, pressure, strain, p, etc.,

to $+%&m* D" (or the purpose o( transmitting the signal over some distance

with little or no loss o( signal. * two - wire transmitter is energied by the loop

current. %+wire transmitter relies on loop power (rom the receiving device,

usually %$ /D", to operate the transmitter inter(ace, to tranduce, characterie,and send the signal back to the receiving device.

The advantage o( % wire systems is hal( the wire runs are required. The

disadvantage is relatively low impedance capability that may limit the type and

number o( devices you can drive with the signal as well as distance that

the signal can be transmitted be(ore circuit loading occurs.

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'+wire transmitter is energied by a supply voltage at the transmitter. The

transmitter sources the loop current. Transmitter common is connected to the

receiver common. The only advantage o( '+wire technology is that higher ohmic

loads are possible, i.e., the current loop can also be operated on a measuring

instrument o( relatively high input impedance

$+wire transmitter, or sel(+powered, can be %$ /D" or line powered 0requires

e1ternal power supply2. $+wire transmitter is energied by the e1ternal power

supply at the transmitter. The transmitter sources the loop current to a (loating

receiver load.The advantage o( $ wire systems is higher signal side impedance, so

better loading and signal transmission distance characteristics. The disadvantage,

more wire.

-. Differentiate con*entiona/ an) smart transmitters&

"onventional transmitters can handle analog signals only where the smart

transmitters can handle digital signals also. !n conventional $+%&m* transmitter

only in(ormation regarding the process variable is measured is sent while smart

transmitters can sent metadata. Smart transmitter contain microprocessor as

integral unit within the device .These devices have built+in diagnostic capability

and greater accuracy. They are less sub3ected to the e((ect o( temperature and

humidity .

. $%0 it is preferre) to transmit signa/s in t%e form of current t%an

*o/tage&

Ans : The current loop is very less sensitive to electrical noise, which make them

ideal (or long distance transmission. The impedance o( current loop is very less

compared to the high impedance o( the voltage loop.

"urrent signals are pre(erred to voltage signals because they are inherently

more immune to noise, and the $m* ero o((set helps (urther with signal integrity.

4hile maintaining a per(ect & m* signal would be nearly impossible in the

presence o( noise, it is possible to 5bury5 the noise in the $m* o((set signal and

represent the minimum value cleanly. /oltage signals are also used, but they are

usually con(ined to relatively noise+(ree areas like control panels or laboratory

environments.

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The inherent disadvantage o( using voltage to transmit signals in an

industrial environment is voltage drops over long cable lengths due to wire

resistance. 6y using current signals and low impedance data acquisition devices,

industrial applications bene(it (rom better noise immunity and longer transmission

cable lengths.

. $%at is t%e ro/e of a uni*ersa/ ca/ibrator in an in)ustr0&

Ans : 7niversal calibrator can be used to calibrate any instrument in the

industry .7niversal calibrator is a hand held, battery operated tool (or measuring

electrical parameters. !t has all the (eatures o( a digital multimeter 0besides the

(eature o( RTD and Thermocouple2, it could also output signals o( direct voltage,

current, resistance, temperature and (requency as well

!t can be used to8

"alibrations o( instruments

"ommissioning o( (ield instruments

Repair 9 :aintenance o( (ield instrument

7se as millimeter with limited (acilities

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. Eperiment Description

Aim:

To design a signal conditioning (or a temperature transmitter, that has output

range $+%&m* (or a temperature range o(c

o;&

toc

o'&&

.

3omponents Re4uire):

. 6read board

%. D" Power Supply

'. !c#$

$. Resistors

;. 6"P


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The *merican Aundamental !nterval isc

o@&&'>%.&

, based on using a purer grade o(

platinum than the Buropean standard. The signal conditioning circuit consists o( a

4heatstone bridge with RTD as one o( its resistors. Thus the change in temperature is

converted to change in resistance value o( RTD and thus the corresponding voltage change

0&+$v2 (or the given range o( temperature. The di((erence in voltage (rom the bridge is

ampli(ied by the di((erential ampli(ier and the inverting ampli(ier, the summer adds up v

in order to obtain the desired range 0+;v2 corresponding to the given temperature range.

Ainally /+! converter converts the voltage into the current signal o( range 0$+%&m*2.

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Fig 2 : IC 741 Pin

Diagram


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Design Proce)ure:

Aor PT&&RTD we know have && )hms at ero degree centigrade. 4e know

that

CD TRR oT +=

*tc

o;&

=+= #;.;#C;&&&'?;.&D&&;&R

*tc

o'&&

=+= ;.%;C'&&&&'?;.&D&&%;&R

Eet bridge resistancesvVRRR

in;,


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Aor summer==== kRRRR $'&

, gainF

Proce)ure:

. /eri(y and check working o( components, opamps.

%. Set up the circuit as shown in the bread board.

'. Airst balance the bridge as per the RTD minimum corresponding to the

minimum temperature (orm the range selected.

$. /eri(y the RTD value as per design and note the voltage output o( each stage.

;. Ne1t (ind the current output and note down the readings.


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Tabu/ation:

Temperature Resistance RTD 5o/tage6*7 3urrent6mA7

co

;& #;.;# $

10

3

:SignalConditioning

Circui


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co

#& $;.& ;.#' .>; #.?

co

%& ?;.?& %.< '.# $.?

co

%#& >;.%&' $.$ #.& .%

co'&& ;.%; $.> >.>

8rap%:

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Resu/t: The signal conditioning circuit (or temperature transmitter that allows a

transmission range o(c

o;&

toc

o'&&

is designed.

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Fig 4 : Plot of Current versus

Temperature

Lab Report Temperature Transmitter (2)

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