Clamp meter doesn't read same amps in both directions

Discussion in 'General Electronics Chat' started by strantor, Sep 26, 2012.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    I just received a lightly used Fluke 376 Clamp meter with iFlex cable. I tested it out on my toaster oven. I read 9.3A. I then tried it with the iFlex cable and read 8.7A. So I went back and tried it with the regular clamp and got 8.7A. A few times switching back and forth between regular clamp and iFlex cable and I figured out that with the regular clamp, I will read 8.7A or 9.3A depending on which direction I clamp the cable. It's very repeatable. I did it 5 or 6 times in a row...8.7A, flip it over, 9.3A, flip it over again, 8.7A.

    I'm wondering if this is normal; I've never done a test like this on another clamp meter, and for all I know, they all do this. Can anybody confirm/refute this? Anybody have an explanation?
  2. crutschow


    Mar 14, 2008
    It shouldn't make any diffence which direction you clamp it on the wire. I have no explanation for your observed difference. :confused:
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  3. BSomer


    Dec 28, 2011
    I agree that it *shouldn't* make a difference. However, I have experienced the same thing on clamp meters I've used in the past but not all of them.
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  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    Perhaps the CT core needs degaussing.
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  5. lawncegary

    New Member

    Sep 27, 2012
    I have no explanation for your observed difference.[​IMG]
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  6. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
    May be that is why it was "lightly used" and then sold? Maybe time for new batteries or recalibration?
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  8. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    Well I'll try it on another load - a pure resistance, and see what happens. I'll also replace the batteries just for good measure. If it needs cal, then you might see it in the buy/sell section, still "lightly used." (with disclosure, of course)
  9. Wendy


    Mar 24, 2008
    How similar is the hookup for both directions? There will be some mechanical differences in layout. Since you have to clamp only one wire, the other wire will interfere given it generates a similar but opposite field if it is in a tight space.

    In my machine maintenance days I made a 1 foot extenuation cord with the outer insulation stripped off, and the inner insulation intact. This is so I could get a clean grip with clamp meter on one wire, and make sure it was away from the others. It was one of those things in my toolbox I used occasionally.

    My biggest use for a clamp meter was to identify dead heaters, or ones that were failing (much different from their fellows) since in a lot of cases they came in banks. We tended to use a lot of small Firerod brand types, and paralleled them for even heat distribution.
  10. Lundwall_Paul


    Oct 18, 2011
    Fluke will tell you to change batteries then send it out for calibration.
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  11. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    I used it today to check the load on a transformer. It read the same in both directions. The transformer wires were right next to eachother, just as with the toaster oven.