Tutorial: Mechanic - electrician Topic: Electric measurement the 2nd. year Measuring devices 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.
Electrical measurements - a task: For electrical measurements we find the size of electrical quantities such as voltage, current, power, resistance, inductance, capacity, frequency, etc. electrical measurements we verify or check properties electrical sources, appliances, telecommunication facilities, electrical grids and lines.
Types of measurement: Measurement – specifies the numeric value of the measured quantity Counting - determines the number of events of the same type Testing – determines whether the sample has the prescribed properties Calibration – determines the deviation from the correct data Adjustment (offset) - offset the MP in order to minimize data which was different from the correct values Calibration - the official procedure for verifying the accuracy
Measuring methods Direct measuring method size of the measured values read directly on the appropriate measuring device Such as voltage, current indirect measuring method from other measured values, we calculate the size of the desired quantities Such as resistance R=U/I, power P=U.I
Measuring methods according to function: deviation size of the measured quantity is determined by the size of the deflection of the measurement devices hands zero measured quantity is subject to settlement (electrical balance), such as measuring bridge
Measuring method according to the nature: substitution an unknown measured element is replaced with the element of known parameters Parallel connection Measured current comparative effects of an unknown element are compared with the effects of an element with known parameters Series connection Measured voltage
Error measuring: Causes of errors according to the cause origin imprecision of the measurement devices imprecision of measuring methods - correctable influence of the environment Observer reading Types of errors according to the manner of occurrence permanent (continuous)- device, the method random – environment, human
Error measuring: Nature of errors - deviations Difference between the measured and actual values Δ m = M - S Distribution Absolute - in units of the measured quantity Relative - expressed in % δ m = Δ m /M. 100 Limit deviation from the nominal value ±%
Write what is the subject of electrical measurement ◦ Name some kinds of measurements ◦ Name the methods of measuring which you know ◦ Name the methods of measuring which you know according to the function ◦ Name the methods of measuring which you know according to the nature ◦
Name the causes of errors ◦ Describe what constitutes an error ◦ Write a formula Name the types of errors ◦ Write a formula ◦ Write a formula ◦ Write a formula
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 Elektrotechnika - Laboratorní cvičení pro bakalářské studium - Doc. Ing. Miloš Hammer, CSc.