Archive for December 9th, 2011

Digital Voltmeter Fuse Gotcha

Measuring some low-value resistances with  one of my DVMs produced weird results: dead shorts around 10 Ω.

Differential diagnosis:

  • Test lead tips clean
  • Wires firmly mounted in probes
  • Banana plugs OK
  • Short banana jumper across jacks reads 10+ Ω

Took the meter apart and what do we see? An ABC ceramic fuse in good old PCB clips:

DVM fuse holder

DVM fuse holder

Spinning the fuse dropped the resistance by a few ohms. Adding a minute drop of DeoxIT to each end, rotating the fuse to scrub it in, and wiping off the excess put the total resistance back around 0.2 Ω where it should be.