The Keithley Model 610 Electrometer is an ultra-high impedance voltmeter with full-scale ranges of 0.01, 0.03, 0.10, 0.30, 1.0, 3.0, 10, 30, and 100 volts. Accuracy is within 2% of full scale on all ranges. The maximum input resistance is greater than 10¹⁴ ohms; in addition, the input resistance may be varied in decade steps from one ohm to 10¹¹ ohms by means of the shunt resistors built into the instrument. Thus, the 610 is not only appropriate for lreasurement in high-impedance circuits, but also can be used where a high input impedance would merely introduce unwanted pickup. The 610 may be used as a direct-reading ammeter from 3 amperes to 10⁻¹³ ampere full scale. This 14-decade range is covered in overlapping 3x and 10x scales.