Disappearing fuse wire

Remove the caps, smash it, grind it to dust, and then analyze it in a mass spectrometer.

Or perhaps put a meter on it, and/or just replace it?

t?

I do that too, but it very much depends on the application voltage and available current. Mains fuses can nicely metalize the glass under high fault currents, whereas a similar current at 12V will simply melt the fuse wire. 500mA is a fairly hefty fuse and the wire should be visible or it should have left some indicators.

Neil S.

Ground an end face off, the way the solder dishes on closing and being shiny makes it look like glass, normal open ended glass tube.

Owner had a pack of 10 of these fuses , probably 20 years old. 1 used and soon failed and 2 of the remaining seven were broken cold-wire fashion, ie straight. Looks like they were made with no give and fail just from old age. Where the first filament went to, is still a mystery, my guess is some sort of weird metallurgy, converting to a vapour. No problem at all with the "failed" kit , taking less than 50mA in use

If the fuse came out of a new box maybe it was made faulty?

-- Boris

If the fuse wire was tin, it may have evaporated and then oxidized. Tin oxide is transparent.

Interesting. Has tin been used in fuses? I toured a company that makes fuses for utility companies and they only use silver wire. I asked why and the answer was nothing else is as reliable or ages like silver.

I've been fascinated by cheapo fuses that on the box claim to be "electronically tested", whatever that means for a fuse that was probably made by school children.

It means that they put an ohms meter or continuity tester on it and it read shorted.

shorted? A 10mA fuse (yes they do exist I have some in front of me)can easily measure more than 100 ohm, pro rata for more worldly fuse ratings . Measuring of ohmage probably gives a go/no go for rupture current.