We have constructed a compact, inexpensive, high‐speed electrometer for use in xerographic voltage measurements. The device consists of a single operational amplifier stage. The type of amplifier is selected to fit the particular experiment. Amplifiers with frequency responses from dc to 100 MHz and input resistances of up to 10+13&OHgr; are available. Measurements on amorphous selenium have shown this type of electrometer to be more versatile than commercially available units.