Easy 1 to 100 High Voltage DC Probe

Each resistor is minimum 2 watts and coated in epoxy to avoid arching. Designed for a voltmeter with an internal impedance of 1M ohm (most low budget meters are 1M ohm, more expensive meters often use 10M ohm). Resistors in the series must match internal resistance of meter. Use of multiple resistors distributes power and prevents thermal breakdown. The 100Kohm resistor can be any resistor below the impedance of your meter, but at least 10%. The 100Kohm resistor is technically optional but will protect the meter in the event of a component failure or current overload, it does however cause a deviance from accuracy (in this example 1% - thus 50Kv reads as 495v). Most cheaper voltmeters like the $3 one on eBay have a maximum voltage of 600v (which is a fine meter if you replace the cheap probes that come with it). This circuit should probably be used at 30Kv or less. Although this design will also work with AC and pulsed DC, frequency can affect accuracy.

published 5 years ago