Constant Current Source for Instrument Calibration

Abstract

Two current sources which give a constant current over a wide range of applied voltage have been built for use in calibrating electrometers having input resistors in the 10⁺¹⁰ to 10⁺¹² Ω range. The sources consist of sealed parallel plate ionization chambers having one electrode coated with ²⁴¹Am. Calibrations using the rate of charge method spaced over a period of 1 year define the respective current output of the sources as (6.943±0.003)×10⁻¹¹ and (4.263±0.004)×10⁻¹² A.