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Damaged Multimeter probe.

Discussion in 'General Electronics Discussion' started by MattyJ6, Oct 5, 2011.

  1. MattyJ6

    MattyJ6

    2
    0
    Oct 5, 2011
    Hey,
    I'm new here, and slightly new to electronics. Got a new multimeter and made the stupid mistake of having it on current measurement and plugged the probes into a wall outlet. A spark occured and I noticed the negative probe was slightly burnt and there's now a small chip in it. Otherwise the meter works completely fine. Should I get a replacement probe or will it be okay to continue using it?
    Thanks a lot,
    Matt
     
  2. MattyMatt

    MattyMatt

    154
    0
    Mar 24, 2011
    Well, I know from doing that myself by accident once.... that as long as your meter is still okay, the small chip in the probe itself should not make any difference on the measurement, though I will say, it may make it slightly more difficult to get a measurement, depending on how big the chip is.
     
  3. TBennettcc

    TBennettcc

    292
    2
    Dec 4, 2010
    What kind of a chip? Is it a Dorito? >.>

    I think we've all done that at least once, I know I have. You can usually pick up a pair of new probes at RadioShack pretty cheap, although they're the plastic-y-coated ones. One of my elmers (ham radio mentor) wouldn't settle for those, and would always try to get the older cloth-coated ones at hamfests (or was it wrapped?), as he insisted they were better.

    Your preference. I guess the biggest question is, did you learn your lesson the first time, or do you plan on doing it again? No sense in going to get new probes only to do it again. Short answer: aside from the change in contact surface, as long as your meter is fine, it's not really going to matter what the end of the probe looks like, as long as there's a solid electrical connection that you can still use to make measurements. It's not going to change any readings.
     
  4. daddles

    daddles

    443
    3
    Jun 10, 2011
    Yes, many of us have made that mistake. It's easy to do with multimeters that don't have a separate input jack for current measurements. There are two basic types of multimeters: those that use a separate current input jack and those that don't.

    I have both kinds of meters. However, I prefer the separate current input jack like is on my Fluke 83 meter when I'm working around line voltages and measuring current. The meter was designed to make it a bit harder to blow the ammeter's fuses. However, you will virtually always blow the fuse(s) when you connect an ammeter across a voltage source, especially one like a line power outlet that can supply lots of current.

    For convenience, it's quite nice at the bench to be able to switch to current measurement mode and not have to pull a lead out and put it back in to make a quick current measurement. But the downside is that you can have your probes connected to a circuit and turn the rotary selector to or through a current measurement setting and you will likely blow the fuse(s).

    Because of this (and the $5-$10 or more cost of replacement fuses for some meters), I try to make my current measurements with a clamp-on ammeter. There are a variety of them on the market. The one I use the most is a digital model that will resolve to 1 mA and measure up to around 80 A, either AC or DC. My HP 428B is an older vacuum tube analog instrument that will measure from 1 mA to 10 A full scale. I first used them in the 1970's and fell in love with them. It took me 5 years of searching and waiting on ebay, but I got one that looks and works like brand new for $50 delivered -- a steal. That was quite a while ago -- but I'm still gloating. :p
     
  5. MattyJ6

    MattyJ6

    2
    0
    Oct 5, 2011
    Whew. Thanks a lot for the responses. I knew never to measure current parallel to a circuit path but when I got the multimeter I was excited in trying it out and didn't think. So, I guess I'm actually glad it happened (since my meter's okay) because it's much more effective to learn from first hand experience. Again, thanks for all the helpful comments. I'll probably be frequenting here more often since I just started an electronics program in college..
    Matt
     
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