Mechanical Electrometer

Mechanical electrometer (electrostatic voltmeter) is a device that measures electrical charge or potential difference. The measurement is done by using the forces in an electrostatic field. A metal plate is connected to a solid metal rod and a rotary metal needle. If the metal plate is electrically charged, the charge is distributed on to the surface of the rod and the needle. Depending on the quantity of the charge, the rotary needle is then forced away from the solid rod by the repulsive force of the like electric charges. The level of the mechanical displacement of the needle from the vertical rod shows the measurement of the charge thanks to the scale with units in kilovolts (kV).