2. Tutorial: Mechanic - electrician Topic: Electric measurement the 2nd. year Measurement of non-electrical quantities 1 Prepared by: Ing. Jiří Smílek Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3.  Types of non-electrical quantities measured weight flow pressure Pressure - the pressure difference Velocity of fluid temperature

4.  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.

5.  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. ΔR - change in electrical resistance R 0 - nominal resistance of the strain gauge K - characteristic coefficient of the sensor e - relative elongation e = Δl/l, Δl - change in the length of the sensor l - length of the sensor ΔRΔR

6.  Strain gauge semiconductor Used material: Semiconductor strain gauges are formed by diffusion of impurities into a thin layer (15μm) 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

7.  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

8.  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.

9.  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 ◦

10.  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…………… …………… …………….

11.  Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.  Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.  Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnosthttp://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnost  Učebnice Elektrická měření – Ing. Pavel Vylegala, SŠE Ostrava, 2006  Učebnice Elektrické měření – SNTL, 1981