# Measuring high voltage low current using a resistor and measuring the amps

Is it possible to measure a voltage beyond what your multimeter is capable of measuring by measuring the amps providing you know the resistance? Just wondering if the voltage would still harm the meter.

• How high are we talking about? Why not setup a resistive divider? (Also take into account the breakdown voltage of the resistors themselves, in which case you can use many in series). – Wesley Lee Oct 9 '17 at 2:56
• Were talking around 2K VAC. – user1897830 Oct 9 '17 at 3:02
• If you can accept some small error, get a cheap TekPower TP7040 ( amazon.com/dp/B0006GD7NU ) which already does 1000 VAC at $9\frac{\textrm{k}\Omega}{\textrm{V}}$; $9\:\textrm{M}\Omega$ input resistance at the $1000\:\textrm{V}$ setting. Add four $2.2\:\textrm{M}\Omega$ resistors in series into the plastic body of one of your probes. (Four because they usually stand off $200\:\textrm{V}$ each.) You really want them to be $9\:\textrm{M}\Omega$, but the slight added error is probably okay. The meter already has 4% error spec; another few % may be fine. – jonk Oct 9 '17 at 6:12
• Thanks Guys, I think I will just build a voltage divider. – user1897830 Oct 9 '17 at 12:44
• Please don't add "thank you" as an answer. Instead, accept the answer that you found most helpful. - From Review – Ricardo Oct 9 '17 at 14:10

## 2 Answers

Meter specs tend tend to use 250v or 500 V rated parts. Exceeding these ratings by some margin may result is catastrophic failure to other parts when an arc bypasses the part.

There are 10:1 to 1000:1 probes rated to higher specs which must be observe/chosen.

Using high voltage rated resistors you can make a voltage R divider for DC and for AC use high voltage rated capacitors to make a C divider. (not to scale) \$1 rated for 6.1kV simulate this circuit – Schematic created using CircuitLab

If you know the resistance of the meter you can add resistance to increase the voltage range. if the meter has 1M resistance on the 1000v range adding 9 more 1000V rated 1M resistors in series would allow measurement of up-to 10KV, 2kV in would read 200V after the modification. but if you need to be safe, buy a proper high-voltage probe, don't try to build your own.