[SOLVED] Megohmmeter to measure Insulation Resistance

[ParkerMike]

Measuring the Insulation Resistance of cables or wiring

When or what circuits do you want to measure the Insulation Resistance?

What else can you use to measure the Megohmmeter?

I know you can measure resistance with a Megohmmeter while the power or voltage is supplied to a circuit.

A Megohmmeter can be use to test Relays while power is turned on. If you tried to do this with a DVM meter it will damage your DVM meter.

 

[js]

you can apply lower voltage and measure very low current with this:
https://www.eevblog.com/projects/ucurrent/

 

[chuckey]

"
I know you can measure resistance with a Megohmmeter while the power or voltage is supplied to a circuit. ". I have never seen this. Mixing live power circuits and insulation tester is extremely dangerous. Megohmeters ("Meggers") are often used to test power kit (motors, transformers etc) which are suspected of becoming damp. They always use a high voltage >500V. This is to ensure that any faulty insulation is capable of use at the mains voltage. Using a low voltage DVM will not achieve this.
Frank

 

[FvM]

I have never seen this.

Me neither. A resistance measurement with a Megohmeter, which usually puts 2 V across the device under test, will reveal some faults like permanent shorts or leakage resistance, but not test for high voltage strength. Dedicated insulation testers with built-in voltage source are available to perform the measurement safely. E.g. https://www.farnell.com/datasheets/88037.pdf

 

[KlausST]

Hi,

for the first sight it may not be a good idea to measure the insulation resistance of a live system.

But it is often done with isolated safety power grids like in a hospital, but it´s indeed more called "insulation measurement" than "megohmmeter".
And it measures not across the mains connections, but mains to earth or to case...

Klaus