Errors in Moving Iron Instruments
There are two types of error which occur in moving iron
instruments. They are
1. Errors with both A.C and D.C work:
(a)
Hysteresis
error
(b)
Stray
magnetic field error.
(c)
Temperature
error.
(d)
Friction
error.
2. Errors with A.C work only:
(a)
Frequency
error.
(b)
Error
due to reactance of the instrument coil.
(c)
Error
due to eddy current.
(d)
Error
due to waveform.
(A)
Hysteresis error is serious type of error in MI instruments when used on D.C circuits.
The effect of this error is that the readings are higher when current increases
than when it decreases.