Question

a) Sketch the circuit diagram of an instrument used for measuring electrical insulation resistance.

b) Describe the circuit diagram sketched, explaining how it operates when measuring electrical insulation resistance.

b) On the instrument sketched for testing insulation resistance in electrical circuits, it's trade name a meggar, a permanent magnet provides a magnetic field for a pivoted core which is wound with two coils.

A needle or pointer is pivoted at the centre of the two sets of coils and moves as they do.

The two coils are wound at right angles to each other and connected in such a way that one measures Voltage, while the other current.

The needle deflection is a result of the opposing effects of the two Coils, which gives a reading of electrical insulation resistance.

A hand driven generator gives a test

Voltage to operate the instrument.

Test probes are used to measure resistance at desired points.