PolySwitch for an Ampermeter?

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#1
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Hi,

Yesterday, I blew out the fuse in my multimeters ampermeter part. I don't have any left, and all of the specialized electronics shops are closed :-( . Can I use a PolySwitch fuse instead of a traditional one? Are there any problems that could arise?

Thanks,

David

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Polyswitches do have an amount of resistance - most likely more than a fuse.

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Don't do it. For principle, as well as for practical reasons.

A fuse is a safety device. One never ever plays with, alters, or manipulates a safety device. Never.

For practical reasons, as kartman already mentioned, polyfuses have a certain resistance. And after they trip and reset it takes a while until they are back to their original resistance. Your meter reading will not be correct. Also, polyfuses do not completely cut off the current when tripped.

If you need to measure current with that multimeter use a small resistor (small in resistance, large in wattage) in series in the circuit, and a voltmeter in parallel with the resistor. The rest is Ohm's law.

Oh, and did I mention one does not mess with a safety device?

Stealing Proteus doesn't make you an engineer.

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Thanks for the advice. Good idea with the small resistor arnold! I'll poke around my supplies.

Thanks guys!

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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A personal note:

I remember that I lost a meter right on
christmas many years ago (when I was nearly a kid).
All shops closed and no possibility to go on.

Be very very careful when all shops are closed !

Martin

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Hey David,

I shouldn't admit this but, I have wrapped cartridge fuses in tin foil and reinserted them in a pinch but, wholeheartedly recommend against it:-))

Everything was fine and in my case the amperages were in milli-amps and I forgot to change the meter leads before taking the reading :oops:

John

Just some guy

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One last thing. Instrument fuses are designed to blow VERY fast to protect the meter. An ordinary low amp fuse would work temporarily if you are careful.

Rick

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... and furthermore, if you attempt to measure mains voltage while accidentally having the "10 A" configuration (been there) an 'instrument fuse' will blow without sustaining a welder's arc in the innards of your expensive multimeter.

Happy new year!

Andreas

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alenze: Heh, once a guy asked me about "How much current is there in a 230V plug?" I almost couldn't resist to tell him to measure it.

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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The fuses in the better meters also have the capability to break a realy high instanteaneous cuurent of up to 10000 A. This is important if one works close to the mains fuse pannels or high current installations.
I remember a small 25 W-230V light bulb burned with the outlet close to the mains fuses cabinett. It triped 3 different sizes fuses (AFAIR 16A, 32A ? and 100 A) burned the wired on the wall, and the glass broke into pieces with some of them having copper evaorated on them. The 16 A fuse used here would not give a good pretection for a meter.

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Quote:
Final exams are coming and I'm doomed
Good luck!

Andreas