HT probe

I neeed one for 40 Kv but dont want to pay 200.

Anyone know where i can find suitably rated resistors please.

addendum. I want one in 2 days and do not want to wait 10 off ebay.

How about three days?

High voltage resistor

ouch 45 quid :)

Buy two Packs of two = £6. Connect in series = 40kv.

You can use a series of smaller value resistors. Most are rated at break down of 600 for 1/4W as I recall. About 70 resistors would do it in an acrylic tube. What kind of current can your source supply? If you load your source down too much, you might not be measuring anything useful. Dwight

40 Ma @ 5 kv its not a trivial supply.Voltage Output can increase when not under load.

Use the internal resistance of your voltmeter. AFAIK most DMMs have an internal resistance of 10Megohm. Try with a 9volt battery and a 10Megohm series resistor. You should read half the voltage.

If so, 90Megohm in series with the positive lead measures 10x the voltage, and 990Megohm in series measures 100x the voltage. Don't blindly trust resistor's voltage ratings. Use many in series. Use a cheap (throw-away) DMM. Leo..

Think carefully about the source behind the voltage you are measuring. If it's something like a TV or many other consumer electronics, if something goes wrong all you get is a zap and possibly destroy your meter. Just keep your fingers out of it. If it's a power system and something goes wrong you'll get blast of fire which you wouldn't believe. I've seen it twice and both times the room was vacated in about 1 second and the switchgear was pretty much destroyed.


What i want to do (cheaply) is use an arduino with a wifi shield to make the measurements from the other end of the room.

It,s a TWT supply which i suspect is not regulating properly.

It also has a high short circuit current but i'm not sure what.