Errors in Dynamometer Type Instrument
The main sources of error in a dynamometer type of
instruments are due to
1. Low torque to weight ratio.
2. Frequency
3. Eddy currents
4. External magnetic fields
5. Temperature change
1. Low Torque/Weight Ratio: Since the coils, are air cored,
therefore, magnetic field produced is of small strength. Hence, large number of
turns are to be provided. This results in heavy moving system and therefore,
small torque/weight ratio. Hence frictional losses are large as compared to
other type of instruments.
2. Frequency: The frequency error is due to
(a)
Change
in ration of the operating coils and