What is Megar and structure of the meg ?

What is Megar and  structure of the meg ?

Mega is a type of instrument used to measure the insulation resistance of a conductor.

The structure of the
mega consists of the lower parts of the mega .
1. Hand-operated DC generator
2. Coin coil
3. Pressure coil
4. Pointer or fork
5. Mega scale plate (M omega)
6. Positive edge
6. Negative edge
6. Guard terminal