Transcript of Tutorial: Mechanic - electrician Topic: Electric measurement the 2nd. year Measurement of...
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- Tutorial: Mechanic - electrician Topic: Electric measurement
the 2nd. year Measurement of non-electrical quantities 1 Prepared
by: Ing. Ji Smlek Projekt Anglicky v odbornch pedmtech,
CZ.1.07/1.3.09/04.0002 je spolufinancovn Evropskm socilnm fondem a
sttnm rozpotem esk republiky.
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- Types of non-electrical quantities measured weight flow
pressure Pressure - the pressure difference Velocity of fluid
temperature
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- Weight measurement gauges Method of measurement: using strain
gauges resistance - metal or semiconductor The principle of the
strain gauge: is a resistive sensor in the form of tapes or wires
Principle of measurement: is the deformation measurements of
supporting structures under static or dynamic stress when
stretching the strain gauge it increases its resistance, because as
it expands, its length and its cross section decrease.
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- Metal strain gauges Used material: constantan (60% Cu a 40% Ni)
or stainless alloys (80% Cr a 20%Ni). The basic parameter of the
strain gauge: coefficient k expresses the ratio between the
relative change in resistance and the relative change in length. R
- change in electrical resistance R 0 - nominal resistance of the
strain gauge K - characteristic coefficient of the sensor e -
relative elongation e = l/l, l - change in the length of the sensor
l - length of the sensor RR
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- Strain gauge semiconductor Used material: Semiconductor strain
gauges are formed by diffusion of impurities into a thin layer
(15m) of pure silicon. Principle of operation: Deformation of the
resistors changes significantly the carrier mobility charge and
hence conductivity. This phenomenon is called a piezoresistive
effect. Features: small size sensitivity up to 60 times greater
than that of metal strain gauges, strong temperature
dependence
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- Measurement of flow Types of flow: The volumetric flow rate Q v
- the volume of fluid that passes through the pipeline per unit
time (e.g. m 3.s -1 ) Mass flow rate Qm - the weight of fluid which
flows through the pipeline per unit time (e.g. g.s -1 ) Flowed
volume - the volume or mass of fluid passed through a particular
place pipe for some time (eg gas meters or water meters) Methods
for measuring flow Measurement of pressure difference before and
after the primary element flow Measurement of flow velocity of
fluid Measurement of volume flow Measurement of mass flow
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- Measurement of pressure difference before and after the primary
element flow Types of throttle bodies iris nozzle Venturi tube
Types of speed probes Pitot tube - thin tube rotated estuary in an
upstream direction of fluid. Prandtl tube - spherical and
cylindrical probe, Types of flowmeters Variable area flowmeter -
vertical conical measuring tube that extends upward freely moving
to float turbines flowmeter - freely rotating rotor blades
electromagnetic (inductive) flowmeter - principle of Faraday's law
of electromagnetic induction - moving wire induces an electrical
voltage. ultrasonic flowmeter - Doppler principle frequency
received ultrasound waves different from the frequency waves
sent.
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- Name the non-electrical quantities that can be measured Name
the types of throttle bodies Name the kinds of speed sensors Name
the types of flowmeters
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- Fill in the missing words : . Q v - the volume of fluid that
passes through the pipeline per unit time (e.g. m 3.s -1 )
ultrasonic flowmeter - Doppler principle .. received ultrasound
different from .
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- Muk, J. Management ve vzdlvn dosplch. Praha: EUROLEX BOHEMIA,
2000. ISBN 80-7361-269-7. Operan program Vzdlvn pro
konkurenceschopnost, ESF 2007 2013. Dostupn na:
http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-
konkurenceschopnosthttp://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-
konkurenceschopnost Uebnice Elektrick men Ing. Pavel Vylegala, SE
Ostrava, 2006 Uebnice Elektrick men SNTL, 1981