Megohmmeter

Acceptable insulator resistance values are typically 1 to 10 megohms, depending on the standards referenced.

If the resistance to be measured is small, high current flow through the deflecting coil and the resulting torque sets the pointer to zero.

For the intermediate value of resistance, depending upon the torque production, the pointer is set at a point between zero and infinity.

Control and deflecting coil has a current limiting resistor connected in series so as to protect the external circuit in case of damages caused due to very low resistance.

The scale of the voltmeter is calibrated in ohms (kilo-ohms or megohms, as the case may be).