# COMMUNITY : FORUMS : TECH

## how do you measure HV?

what's the best way to measure High voltage (I think my output is somewhere between 10kv and 50 kv)? Is there a formula for the spark length and humidity (I can measure humidity)? I need to buy an appropriate capacitor for my tesla coil, my initial HV is from an ignition coil.

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FelixSP4 years ago
Maybe a static DC Voltmeter?
http://www.celnav.de/hv/staticvoltmeter.jpg
gmoon8 years ago
Voltage divider? For instance, if the input voltage is 50KV, a 10M and 100K divider would give you an output of about 500V (495.5V).
4 years ago
Are you sure? I got 4950 volts

4 years ago
Yep. special high voltage resistors are used
forgesmith8 years ago
How do I measure HV?

Well if my hand jerks back it's about 5kV, if my arm jumps back and it stings that's about 9kV, if I completely jump backwards and wonder what happened that's at least 15kV, if I get awake slightly singed and find myself up on the roof then...

What? Oh, you want to know how you can measure it! Never mind then.
guyfrom7up (author) 8 years ago
I have an oscilloscope, but how would I use it in this situation? I think a voltage divider would be bad in this situation cause dont resistors fail at a certain voltage
8 years ago
If it's just DC, then a VOM / divider will work fine. You can use a scope, but you'd need a high voltage probe. Which is what? A voltage divider.

It's current that will cause resistor failure. If the scope or VOM is high impedance, where does the current have to go?

Of course, if you're nervous then a VOM is a lot cheaper to replace....
8 years ago
. ROFLMAO. Do GMTA or what? We even used the same page, just at diff URLs!
8 years ago
Oh man, you're right... just a minute or two apart. LOL for sure!
guyfrom7up (author)  gmoon8 years ago
llol anyways the voltage divider didn't work, my multimeter went beserk, flickering random numbers (I think 1900 was displayed a lot), but I don't know...
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