One of the most common service problems is the maladjustment of the detector high voltage setting. We receive many calls from users who have attempted to trouble-shoot their instrument with a "high Impedance" voltmeter. This usually results with the problem of not being able to adjust the high voltage above 450 V. The reason for this problem is the "high impedance" voltmeter typically has an 11 MΩ output impedance and will overload on resistive loads below 60 MΩ.
To avoid this problem, you should either use a LMI Model 500 Series pulser or an electrostatic voltmeter to measure high voltage. Alternatively, you can acquire a T-1016 HV Divider Box (PN 48-2147) attached to a regular voltmeter.Also, high voltage probes are available such as the Fluke Model 80k-40 high voltage probe. We recommend this probe because it provides a 1000 MΩ input impedance with a 1000:1 division ratio to connect directly to a high impedance (10 MΩ) multimeter. If these alternatives are not possible, secure a 1000 MΩ resistor rated at 2500 V. Connect as follows:
Multiply voltmeter reading by 10,000 for actual high voltage output.