electrometer n 1: meter to measure electrostatic voltage differences; draws no current from the source
Electrometer \E`lec*trom"e*ter\, n. [Electro- + -meter: cf. F. ['e]lectrom[`e]tre.] (Physics) An instrument for measuring the quantity or intensity of electricity; also, sometimes, and less properly, applied to an instrument which indicates the presence of electricity (usually called an electroscope). [1913 Webster] {Balance electrometer}. See under {Balance}. Electro-metric