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High Voltage (3kV) Probe?


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#1 Cache

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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

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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:

http://microcontroll...roducts_id=3769

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:

http://labjack.com/s...vider/datasheet

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.


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