← All revision guidesSEMESTER 3 · DI03000091
6FLASHCARDSElectrical Instrumentation
Measurement errors, indicating instruments and transducers.
Measurement fundamentals
Q1Differentiate accuracy and precision.
Accuracy is closeness to the true value; precision is closeness among repeated readings.
Q2What is loading effect?
The measuring instrument changes the circuit quantity because its impedance is not ideal.
Q3Define sensitivity.
Change in instrument output divided by the corresponding change in measured input.
Instruments and transducers
Q1Why can a PMMC instrument measure only DC directly?
On AC the torque reverses every half-cycle, producing nearly zero average deflection.
Q2What is the function of a current transformer?
It reproduces a reduced, isolated current proportional to a high primary current for metering or protection.
Q3How does an LVDT work?
Core displacement changes the differential voltage of two secondary windings, indicating position and direction.