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How do you measure high voltages? Standard multimeters only go up to 1000V

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Yanom

Sun Sept 16 2012, 03:12AM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

^ title says it all - what tools do you use to measure high voltages?

Dr. Brownout

Sun Sept 16 2012, 03:44AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

How high of voltage are you talking about? You can use voltage dividers made with custom resistors such as water resistors for extreme voltages. If you are talking output from a tesla coil, I think water resistors would do the job. Although I have not tried it (yet) it sounds feasible.

I have never heard of anyone actually measuring the output, however it does not mean it has not been done. I just have not talked to anyone that has done it.

Yanom

Sun Sept 16 2012, 04:49AM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

I wanted to build a means of generating about 10kv, just for experimenting. I wanted to be able to measure and debug the circuit with a voltmeter

Patrick

Sun Sept 16 2012, 05:00AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Dr. Brownout wrote ...

How high of voltage are you talking about? You can use voltage dividers made with custom resistors such as water resistors for extreme voltages. If you are talking output from a tesla coil, I think water resistors would do the job. Although I have not tried it (yet) it sounds feasible.

I have never heard of anyone actually measuring the output, however it does not mean it has not been done. I just have not talked to anyone that has done it.

Dan McCualey Of eastern voltage research has measured HV from the primary of a tesla coil, Just dont expect alot of explanation from EVR on how (Measuring HV) is done. (I cant find the page on the WayBack Machine either)

Yanom wrote ...

I wanted to build a means of generating about 10kv, just for experimenting. I wanted to be able to measure and debug the circuit with a voltmeter

I have authored more threads on this matter than i can count.... search under my name. High Voltage and project Forums.

The tek probe and mine side by side...
EDIT: here's some:

(HV measurement)

(Pots and HV measurements)

(cap 10,000:1)

(Etching)

(NST HV measurement)

(HV Diode making)

(Mearsuring HV resistor to high accurracy)

(HV resistors, Project)

Antonio

Mon Sept 17 2012, 02:06AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Spark gaps, electrometers, electric field meters, large resistors, etc. I have a discussion here:

Dr. Slack

Mon Sept 17 2012, 07:27AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

If you only want to go to 10kV, and only DC, then there are two very straightforward routes.

a) build a resistive divider
b) buy a secondhand TV HT probe - these are often rated in the 25kV to 50kV region. As applications for repairing CRTs are dwindling, these probes are widely available and very cheap as labs get cleared.

A DIY resistive divider for DC is relatively straightforward. For 10kV, you can buy a suitably rated single resistor in the 100M or Gohm range with a suitable voltage rating, but most amateurs, myself included, will solder dozens of Mohm range resistors in series. This is OK, as long as you respect the voltage rating of the individual resistors. Most 'cooking grade' resistors are only rated in the hundreds of volts range, so you will need a lot in series. Resistors with voltage withstanding in the low kVs are relatively cheap, and radically reduce the number you need to string together. My 12kV divider uses a string of 47Mohm 1.6kV resistors at the sharp end.

If you are going to turn this stick of resistors into a hand-held probe, you need to thin about ruggedisation, and health and safety so that a single point failure doesn't expose you to a shock hazard. My 12kV divider is built into a plastic box with 4mm sockets, which are OK for corona at this low voltage.

When you calculate the bottom resistor value, remember it will be in parallel with the resistance of your meter. 1000:1 is a good ratio to use; it makes the sums easy, and the voltage at your meter benign.

A divider for handling AC well is infinitely more difficult. not a good choice for a first HV instrumentation project.

HV Enthusiast

Mon Sept 17 2012, 01:30PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Here are some high precision AC Voltage Dividers.
This particular one is made by Ross Engineering and has precision of 0.1% over the full bandwidth range AC/DC.

I do have three of these i am selling. They need to be refilled with SF6 however.

Patrick

Mon Sept 17 2012, 08:08PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Does anybody know what a CRT flyback oscillgram looks (or should look) like?
(And i mean in a fully functioning television)

Google images reveals a lot of crap...

EDIT: best thread for you to see how and what is in play for building AC/DC probes.... (note my E-Field simulations)

High voltage probe for O-scope, 2 of 2, ( FABRICATION ).

Tony Matt

Sun Oct 07 2012, 03:22AM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

Antonio:
Congratulations for the nice publications!
And it is very nice remember the earlly men that build up the science to us ...

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