Insulation resistance

[studentspark]

Just wondering how an insulation resistance tester actually works?

I know how to carry out the test, but just wondering how does the meter calculates the values.


Thanks

 

[Swwils]

Based on ohms law.

Use known DC voltage lower than the voltage for dielectric testing and then measure the current flowing, it is very simple to determine the value of the resistance.

The value of the insulation resistance is very high but not infinite, so by measuring the low current flowing, an IR tester has both a DC voltage generator and a megohmmeter that indicates the insulation resistance value, providing the result.

Most testers also have 2 types of ammeter circuits for different resistance applications - shunt and feedback.