1. A device that detects the presence of minute charges of electricity and determines their sign by means of electrostatic attraction and repulsion.
2. A measuring instrument that detects and measures an electric charge, usually consisting of a rod holding two strips of gold foil that separate when the same charge is applied to each one.
3. An instrument used to detect the presence, sign, and in some configurations the magnitude of an electric charge by the mutual attraction or repulsion of metal foils or pith balls.
4. An instrument for detecting the presence of static electricity and its relative amount, and for determining whether it is positie or negative.
5. An electrostatic instrument for measuring a potential difference or an electric charge with the mechanical force exerted between electrically charged surfaces which detects the intensity of radiation.

In one form, two narrow strips of gold leaf suspended in a glass jar spread apart when charged. The angle between the strips is then related to the charge.

A device consisting of two pieces of thin gold foil, or gold leaf, joined at their upper ends and suspended inside a glass jar.

When an electric charge is applied to the terminal connected to the gold leaves, they spread apart because of the repulsion of the same levels or amounts of charges on them.