ELECTROMETER

"A voltmeter with very large input resistance. A typical modern voltmeter has an input resistance of around ten million ohms, an electrometer can have ten million times more. Electrometers are used to measure the electromotive force of electrochemical cells that can be easily polarized by current. The voltmeter always draws a small current, the magnitude depends on the ratio of the resistance of the cell and the voltmeter. High resistance cells (e.g., one containing a glass electrode, must be measured with an electrometer. "