Lost a $400 multimeter to a simple ground loop mistake

Had a $400 Fluke 87V that was reading perfectly for 2 years straight. Then last month I started getting weird voltage spikes on every reading, even on battery test circuits. Turned out I was using a cheap third-party test lead set that had a cracked insulation near the banana plug. It took me 3 days and a blown fuse to realize the before and after difference was just bad leads. Anyone else ever chase a phantom issue only to find out it was your own gear failing you?

2 comments

2 Comments

leo23823h ago

Wait, was it actually the leads or just the fuse? Ive blown fuses in my 87V thinking it was something bigger, and cheap leads can definitely cause issues. But a bad ground loop usually means you had a path to ground through the common jack, not just cracked insulation. If the shield was touching something it shouldn't, that would give you a floating reference and weird readings for sure. I had a similar thing with a fluke 179 where the probe tip was shorting to the barrel, and it took me a week to spot it because the crack was hidden under the strain relief.

rowank6917h ago

I had a DMM once that went crazy and it turned out moisture got inside the rotary switch from sitting in a damp garage.