Anglicky v odborných předmětech "Support of teaching technical subjects in English “

1. Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“ Tutorial: Mechanic - electrician Topic: Electric measurement the 2nd. year Measurementof non-electricalquantities 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.

2. Measurement of non-electrical quantities • Types of non-electrical quantities measured weight flow pressure Pressure - the pressure differenceVelocity of fluid temperature

3. Measurement of weight • Method of measurement: • using strain gauges • resistance - metal or • semiconductor • Weight measurement gauges 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.

4. Measurement of weight • 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 • R0 - 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 • Metal strain gauges ΔR

5. Measurement of weight • 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 • Strain gauge semiconductor

6. Measurement of flow • Types of flow: • The volumetric flow rate Qv- the volume of fluid that passes through the pipeline per unit time (e.g.m3.s-1) • Mass flow rateQm - 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) • Measurement of flow • 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

7. Measurement of 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. • Measurement of pressure difference before and after the primary element flow

8. Activities for students - questions • 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

9. Activities for students - questions • Fill in the missing words : • ………. …………Qv- the volume of fluid that passes through the pipeline per unit time (e.g. m3.s-1) • ultrasonic flowmeter - Doppler principle – ………….. received ultrasound ……………different from…………… …………… …………….

10. Bibliography • 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-konkurenceschopnost • Učebnice Elektrická měření – Ing. Pavel Vylegala, SŠE Ostrava, 2006 • Učebnice Elektrické měření – SNTL, 1981