The Keithley Model 615 Digital Electrometer is a fast, accurate and sensitive Electrometer with digital display. It is a versatile, completely solid-state instrument which measures a wide range of dc voltage, current, resistance and charge. The Electrometer's input resistance of greater than 10¹⁴ ohms is the result of extensive instrument development with high input impedance transistors. The Model 615 has all the capabilities of conventional VTVMs, but it can also make many more measurements without circuit loading.