Megger MIT420/2 unstable continuity readings?

[alexcarnes]

Chaps - having problems with a new Megger MIT420/2 insulation/continuity tester 'oscillating' and failing to give stable resistance readings in continuity mode with some motors (although it did it once on a Cal Card!). I don't think it's a duff unit, but anyone else have one and experienced similar? I've got various Flukes to hand which all measure the coil resistance of these motors swiftly and consistently. Following recent experiences with the AVO835 DMM, I'm just gaining the impression that under certain conditions, the autoranging goes haywire (autoranging doesn't seem to be Megger's forte, it's horribly slow on the multimeter). Normally, when it stabilises, the instrument displays the current at which it's measuring the resistance - when it has these mysterious failures, it just displays zero, like it could be hunting for the appropriate current.

Any thoughts?

 

[timhoward]

Have you tried different test leads?

 

[alexcarnes]

Have you tried different test leads?

Yeah it's not the leads. It just looks like the autoranging goes haywire under certain conditions, probably with the test current rattling between a couple of settings. I haven't done a PhD on the manual but it doesn't look like you can set the range manually...

I think I'm right in saying the previous versions of these testers were manual range in continuity mode.