Jump to content

As of July 17, 2015, the LabJack forums here at forums.labjack.com are shut down. New registrations, topics, and replies are disabled. All forums are in a read-only state for archive purposes.

Please visit our current forums at labjack.com/forums to view and make new posts. To post on the current forums, use your labjack.com login account. Your old LabJack forums login credentials have been retired. There are no longer separate logins for labjack.com and LabJack forums.


High Voltage (3kV) Probe?

  • Please log in to reply
1 reply to this topic

#1 Cache

  • Members
  • 1 posts

Posted 30 January 2013 - 01:40 PM

I have a LabJack U3-HV that I'd like to use to measure a dc voltage as high as +/-3kV. Originally I was just going to use a voltage divider but the more I read about source impedance, buffering, etc. the more I'm thinking I need something a little more complex. Can anyone recommend a circuit or product to accomplish this?

#2 LabJack Support

LabJack Support
  • Admin
  • 8677 posts

Posted 30 January 2013 - 03:16 PM

The first concern would be safety ... to prevent damage to yourself and the equipment involved such as the U3 and computer. I suggest you only proceed if you have the proper expertise, and at least get a USB isolator to hopefully protect your computer if something goes wrong:


As for source impedance, how much load can your source drive? If it can drive 10 megaohms, I would go ahead and use a voltage divider like that.

Then since impedance is so high, you do then need a buffer between the divider and the U3. Consider using the LJTick-Divider. Figure 3 of the LJTD datasheet shows how the LJTD-UNI10V ships:


You could replace R1-R3 with suitable resistors, and then add external series resistors. I suggest enough external series resistance to bring the voltage down to <100V before it gets to R1.

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users