13
\$\begingroup\$

I recently bought a cheap multimeter. I played around measuring stuff on simple circuits and I think I managed to damage it as I don't seem to be able to measure current anymore (always get zero amperes, although voltage, resistance, and the rest work just fine). I googled around and found out that it is not uncommon for beginners to blow their multimeter's fuse when trying to measure current the wrong way; I think I've fallen in this category.

Though I would like to confirm, so I took out the fuse from the multimeter. I'm not sure how a damaged fuse should look like, yet it doesn't look broken, it is nice and clear and a very fine wire is visible. It is around 2cm long and on it is written F200mAL250V which I guess means that it is a fast glass 200mA fuse rated for 250V.

Can I use my multimeter to find out if the fuse is broken? What metering mode should I use for this particular fuse and what should I look for?

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Why the downvote? If you find that the question deserves a downvote, please elaborate a bit in a comment; I will try to improve it. As I'm new to the world of electronics I'd like to gain some reputation in this website and use it more often. \$\endgroup\$
    – geo909
    Commented Dec 29, 2012 at 16:47
  • \$\begingroup\$ It's off-topic. See the FAQ. \$\endgroup\$
    – Leon Heller
    Commented Dec 29, 2012 at 19:11
  • 5
    \$\begingroup\$ @LeonHeller How is the proper way to test a defective electronic part off topic? Is repair not apart of design? \$\endgroup\$
    – Passerby
    Commented Dec 29, 2012 at 23:03
  • \$\begingroup\$ @LeonHeller Sorry, I don't understand that either. All the "related" questions that I see on the right column right now seem to be of quite similar nature. Oh well. \$\endgroup\$
    – geo909
    Commented Dec 30, 2012 at 5:13

3 Answers 3

Reset to default
11
\$\begingroup\$

Measure the resistance of the fuse. If it's very low (close to 0 ohms), it's still good. If it's very high (open circuit), it's blown.

A 200 mA fuse should have a very fine wire visible inside the glass. If it's completely clear, the wire is gone (blown).

\$\endgroup\$
6
  • \$\begingroup\$ Thank you. Indeed the fuse must be blown because the multimeter indicates an open circuit. But, there is a very fine wire inside the glass which is visible. Is that a contradiction? \$\endgroup\$
    – geo909
    Commented Dec 29, 2012 at 16:56
  • \$\begingroup\$ I edited the question to include the fact that the fine wire appears \$\endgroup\$
    – geo909
    Commented Dec 29, 2012 at 16:57
  • \$\begingroup\$ No, the wire can be broken near one end, with most of it still visible in the glass. \$\endgroup\$
    – Dave Tweed
    Commented Dec 29, 2012 at 17:21
  • \$\begingroup\$ If it measures open circuit it's broken. You sure the wire is fully intact? media.photobucket.com/image/recent/tbizzle/fuse.jpg \$\endgroup\$
    – NickHalden
    Commented Dec 29, 2012 at 17:21
  • \$\begingroup\$ At least I'm sure that it is not cut in the middle like in the picture, maybe there is something in the very edges that I cannot see. It is a little saturated though (blue-ish to red-ish). \$\endgroup\$
    – geo909
    Commented Dec 29, 2012 at 17:27
0
\$\begingroup\$

You may find there is a second, spare, fuse inside the multimeter. That was the case with a cheap analog multimeter I bought at Radio Shack.

\$\endgroup\$
0
\$\begingroup\$

You can usually use the resistance measurement function to check -- connect the (usually) red ohms measurement wire to the current range input (also usually red) -- no need to connect the black wire.

If it reads < 10 ohm, then the current range (and fuse) is OK; if it reads open, then the fuse is blown.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.