Difference between Megger and Other Measuring Instrument

Difference between Megger and Other Measuring Instrument Points : difference between megger and other measuring instrument When no current flows through the coil of an Instrument like ammeter, voltmeter or wattmeter, the pointer of the instrument rests on zero reading due to tension of the controlling spring. But the system is quite different with a megger. In an insulation testing megger the moving system is mounted on spring-supported jewel bearings and is free to rotate on its axis. Current is led into the coils by flexible conductive ligaments having negligible tension. When the hand-driven generator of the instrument is not operated, i.e. when not current flows through the current coil and the pressure coil of the instrument, the pointer floats over the scale and may remain in any position whatsoever. Therefore, the statement of a person that “the pointer of an insulation testing megger rests on zero reading when not in use is totally wrong.