The Keithley Model 414S is a completely solid- state pcioammeter which measures currents over 17 ranges from 10-² to 10-¹⁰ ampere full scale. Accuracy is +2% of full scale on the 10-² to 10-⁸ ampere ranges and +4% of full scale on the 3 x 10-⁹ to 10-¹⁰ ampere ranges. A unique circuit provides complete overload protection for Model 414S without compromising the outstanding features of the MOS FET input. The Picoam-meter will withstand transient overloads up to 1000 volts without damage, and overload recovery is almost instantaneous. The Picoammeter employs matched MOS FET transistors in the input followed by a differential amplifier stage, a transistor driver and a transistor output stage. Negative feedback is used for stability and accuracy. Fast warm-up is an inherent characteristic of the Picoammeter, It can be used almost immediately on its most sensitive range. For maximum stability, however, about 10 minutes warm-up time should be allowed. The time and temperature stability of the 414S Picoammeter is unmatched by any other inexpensive pico-ammeter. The Model 414S will operate for days without requiring rezeroing. Zero drift with time is less than 0.5% of full scale per week. Temperature drift is equally small - a change of 10°C affects the reading less than 0.5% of full scale on the most sensitive range. One volt or 1 milliampere at full-scale deflection on all ranges is provided to drive chart recorders. The 1 milliampere recorder output will drive the Keithley 370 Recorder directly. When potentiometric recorders are used, the output voltage can be conveniently divided by a shunt resistor and adjusted for full scale with the rear panel Calibration potentiometer.