Coulometer

Coulometer in A. Horsfield,
"The Faraday and Its Significance in Determining the Fundamental Constants"

A coulometer is a device to determine electric charges. The term comes from the unit of charge, the coulomb. There can be two goals in measuring charge:

• Coulometers can be devices that are used to determine an amount of substance by measuring the charges. The devices do a quantitative analysis. This method is called coulometry, and related coulometers are either devices used for a coulometry or instruments that perform a coulometry in an automatic way. For details, see coulometry.
• Coulometers can be used to determine electric quantities in the direct current circuit, namely the total charge or a constant current. These devices invented by Michael Faraday were used frequently in the 19th century and in the first half of the 20th century. In the past, the coulometers of that type were named voltameters. For details, e.g. the different types used, see voltameter.