High Voltage Measuring Circuit

Theoretical circuit for measuring output voltages of ballasts and HV transformers. Resolution is 1V/ 10kV. A Voltage divider reduces voltage down to a point where a regular voltmeter (The 1M resistor to represent the input impedance of the DMM) can safely measure a regular voltage. A pot is used to calibrate the circuit. Second branch is a 10v calibrating circuit. Pot is adjusted to get 5v, then this branch is disconnected from the circuit. Power dissipation starts to become extremely important in HV circuits, as you need to make absolutely sure your components can handle the heat. This is why such high-valued resistors are used, and why the trimmer pot is in parallel with a regular resistor (most trimmers only go up to a 1/2 watt). Even then, the circuit still draws around 2.5 watts at its maximum (50kV), so this circuit requires power resistors.

published 10 years ago