A Closed Loop Threshold Calibrator for Pulse Height Discriminators

This paper describes a simple method of inflight calibration of pulse amplitude discriminator thresholds on satellite-borne particle detection experiments. The calibrator uses the discriminator output as a feedback control signal to adjust the average output of a test pulse generator. The test pulse amplitude is stabilized when the discriminator "half-triggers". The average control voltage is a direct measure of the pulse height discriminator threshold. Better than 1% accuracy is obtained over a 50:1 range of discriminator settings. Automatic ranging circuits extend the calibrator dynamic range to 5000:1.