Measure microamps current from insulation test

Hi, now I'm working on my insulation test project. This test applies 500V DC through the cables between L and G and then measure the current to calculate the resistance of the cables. I search that the range of the cable is about Megaohms so that the current is in the range of Microamps. So I need to measure this Microamps current and send it to the Arduino to calculate the resistance value by R=500/I. I reckon that I should use the resistor to transform this Microamps current into 0-5 V so that the Arduino can read. I want to know that does this resistor make the cable resistance error because I connect this resistor series with the cable or anyone would recommend me about how to measure this current. Thank you very much

I would use a commercial cable insulation tester.

500V DC is not hobby level, it's pretty deadly.

Have you Googled "megger" and studied how real insulation testers work?

Paul

I guess the problem with testing insulation at 500V is that by the time you find out the insulation was crap, you're flat on your back and or your house is aflame.

This is one of those cases where the response should be "if you have to ask about it you shouldn't be doing it" (which is pretty much what #1 and #2 are getting at?)

Pretty much so, indeed.

The technical part is easier to handle :wink:

Assume a certain (max.) current, then calculate the required resistor for the 5V output. Then subtract that resistance from the calculated total resistance. The ADC input resistance should be below 10k, so that you'll have to add an amplifier as impedance converter.