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I have a simple digital multimeter in which a fast tube fuse, rated at 0.1A and 250V is soldered directly to the plate.

Now, recently this fuse blowed and I have to replace it. Because I don't want to mess with soldering every time a fuse is blown (and there is no place for a fuse holder), I was thinking about replacing the tube fuse with the polymer fuse rated at 0.1A and 60V (RXEF010). Is this reasonable?

There are two possible concerns:

  • Will a polymer fuse break the circuit as fast as a tube fuse?
  • Is there a large ohmic difference between two fuses? Voltage and current ratings suggest that the polymer fuse has four times smaller resistance, which should be advantageous.

Anyone has any idea about these issues?

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  • \$\begingroup\$ No! That's a recepie for an electric fire. \$\endgroup\$ – winny Jan 13 '18 at 17:31
  • \$\begingroup\$ @winny Could you elaborate on your answer? \$\endgroup\$ – Pygmalion Jan 13 '18 at 17:50
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I think it's reasonable IF you never touch anything above 60V with it (and certainly not AC current), AND you don't mind damaging it AND you will be the only person using it. IMO that's many conditions and it's better replacing it with the exact same part. If you can't, consider that repair temporary.

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You should always replace safety devices with the exact type and rating.

The RXEF010 can interrupt 60VAC at 40A max fault current. A ceramic fast blow fuse can interrupt 250VAC at 1500A maximum fault current.

If you make the same error in using your meter again, and the fault current or voltage exceeds the ratings of the protective device you could be injured, there could be damage to property, and your meter quite likely will be damaged beyond economical repair.

When you exceed the maximum fault current/voltage the protective device is not guaranteed to open.

You should not be blowing fuses in your meter regularly. It's better to learn from this and not repeat the conditions that caused the fuse to blow. There are other bad things that could happen- especially with cheap meters- that the fuse will not protect you from. See also my answer here.

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  • 1
    \$\begingroup\$ Thanks for the reply. What I am using here is a tiny cheap multimeter, which I don't think is appropriate for high voltages and currents anyway - I only use it for electronics. But I agree that fuse blow incidents should be fairly rare. It is first such incident in several years, due to the fact I forgot to turn the knob when I changed from current to voltage measurements... \$\endgroup\$ – Pygmalion Jan 13 '18 at 18:10

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