Repairing a Digital Multimeter?

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somitomi
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Repairing a Digital Multimeter?

Postby somitomi » Mon Nov 27, 2017 2:57 pm UTC

I'm not sure this is the right place to ask, but it's my best bet.
Recently I made the mistake of measuring AC current with a multimeter only capable of measuring DC current (Voltcraft VC130-1). Since then the resistance measuements are all wrong and the diode tester beeps continuously even if I remove the fuse from inside the meter. I'm guessing the current measurement modes are dead too, but I haven't checked that.
I know nothing about the workings of these digital things, so I'm wondering if it is possible to fix this and how hard that might be. Does anyone know what component I might have killed? Do these things have some "fusible" part, that I could replace?
Thanks in advance.
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wumpus
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Re: Repairing a Digital Multimeter?

Postby wumpus » Mon Nov 27, 2017 3:08 pm UTC

somitomi wrote:I'm not sure this is the right place to ask, but it's my best bet.
Recently I made the mistake of measuring AC current with a multimeter only capable of measuring DC current (Voltcraft VC130-1). Since then the resistance measuements are all wrong and the diode tester beeps continuously even if I remove the fuse from inside the meter. I'm guessing the current measurement modes are dead too, but I haven't checked that.
I know nothing about the workings of these digital things, so I'm wondering if it is possible to fix this and how hard that might be. Does anyone know what component I might have killed? Do these things have some "fusible" part, that I could replace?
Thanks in advance.


The first thing to do is open it up and look for a fuse. If it isn't that simple a quick check is to smell each component* (the smell of burnt electronics should be obvious). I'm afraid that modern multimeters are pretty integrated and that it would make more sense to replace the whole thing (presumably when you realize the "voltmeter" chip is bad).

* I learned this trick from my best professor in college. At the time I thought it was hilarious, but considering that thermal failure is a common means to destroy a chip *and* a common means of semiconductors that failed (failure shorted something to ground, so it let the smoke out) that it makes a great "first pass" to determine which parts are bad.

ericgrau
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Re: Repairing a Digital Multimeter?

Postby ericgrau » Sat Dec 09, 2017 12:00 am UTC

First take out your multimeter and... dammit.

Ok but seriously it's a ~$25 multimeter. Unscrew the thing, check the fuse. Hopefully you have a way to check connectivity. If not with a multimeter, then stick it in a quick circuit. If the fuse is fine: drive Uber for 2-4 hours (up to 4 due to costs of gas, repairs and depreciation) and buy another multimeter. There, problem solved in under 4 hours.


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