There is the suggested method of adjusting mA zero on the Dynalyzer II and III high voltage unit. This is to connect a digital volt meter to the BNC output of the HVU, and adjust the one or two mA zero potentiometers for rad and fluoro (Dynalyzer III only) through the hole in the lower front panel of the HVU. The method described below allows the zero drift of the digital display and high voltage unit, as well as residual system noise to be zeroed out all at one time. The method works easily with the Dynalyzer III digital display. Dynalyzer II requires some additional, but easy work.
With your Dynalyzer III digital display set for Auto trigger mode, connect the digital display to the high voltage unit. Try to plug them both in the same power outlet if possible.
Note: The display may read 450 at some time, then zero. This is not a "defect", but an anomaly of Dynalyzer III when data values are at or below zero.
To perform these tests with a Dynalyzer II display, you need an external trigger. This may be as simple as a 1.5 volt battery and momentary switch connected to the rear external trigger input (+ to BNC signal lead). Press the momentary switch to generate and approximately 0.5 second measurement window while adjusting. Of course a TTL pulse generator would also work. Signal level up to +10 volts may be applied to this input.