1. A sensitive device for measuring extremely low voltages by means of the forces of attraction and repulsion between charged bodies on plates or wires.
2. An instrument for detecting or determining the magnitude of a potential difference or charge by the electrostatic forces between charged bodies.
3. A fundamental instrument in which potential is measured by the attraction between two oppositely charged disks.
4. An instrument for measuring the quantity or intensity of electricity; also, sometimes, and less properly, applied to an instrument that indicates the presence of electricity; also called an electroscope.
5. An instrument used to determine fluctuations in electrostatic potential difference between charged electrodes due to radiation.

1. An amplifier circuit characterized by low-current drift and input-current offsets, and adequate power and current sensitivities, such that it is capable of measuring extremely low current variations in a circuit.
2. A low-noise amplifier having sufficiently low current drift and other characteristics required for measuring very low currents.

1. A component in an electrometer that has a high input impedance and a low control-electrode conductance, facilitating the measurement of extremely low direct current or voltage.
2. A high-vacuum electron tube having a high input impedance (low control-electrode conductance) to facilitate the measurement of extremely small direct currents or voltages.

A simple instrument for measuring an electrical charge.

A support in an insulating chamber which has a moveable gold leaf attached to it.

Increasing the same charge causes increasing forces of repulsion, which causes additional movements of the gold leaf away from the support.

1. A mechanism for measuring electric current passing through a coil by the deflection of a magnetic needle inside the coil.
2. A device for measuring an electric charge by the movement of a vane suspended on a wire between metal quadrants.

The charge is introduced on the vane and quadrants in such a way that there is a proportional twist to the wire.

An electrometer is a device that uses, as an amplifier, a vacuum tube having a very high input impedance which is the measure of the opposition that an electrical circuit presents to the passage of an electric current when a voltage is applied.