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Measuring DC amps with a digital multimeter

Discussion in 'General Electronics Discussion' started by krishunt, Nov 10, 2018.

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  1. krishunt

    krishunt

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    0
    Nov 10, 2018
    Please help me understand how to use my digital multimeter to measure amps. There are two scales on my meter for measuring DC amps: 200 mA and 10 A. When I measure a current with the multimeter set to 200 mA, I get about 10 mA, but when I set the scale to 10A, it says 0.10 A. Since there are 1,000 mA in 1 A, why doesn't it say either 10 mA / 0.01 A, or 100 mA / 0.10 A? I don't get it.
     
  2. Minder

    Minder

    3,120
    673
    Apr 24, 2015
    I suspect the 10ma reading is too low for the resolution of the 10amp range.
    That is why you have a Ma range.
    M.
     
    Cannonball likes this.
  3. davenn

    davenn Moderator

    13,883
    1,965
    Sep 5, 2009
    Hi
    Welcome to EP :)


    possibly / probably because the 10A range cannot measure 10mA accurately
    It probably can only read in the minimum of 100mA accuracy .... that would be the obvious answer :)
    hence why it is important to use the correct range for the expected value

    You will also probably find that a high voltage scale will have the same problems reading a very low value voltage


    The 10A range is probably limited to one decimal point value
    as would high voltage ranges



    Dave
     
  4. krishunt

    krishunt

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    0
    Nov 10, 2018
    If that were the case, then it would simply read zero, not fluctuate between 0.10 and 0.11 amps, which is exactly one order of magnitude away from being quite accurate.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,499
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    Jan 21, 2010
    There are a couple of possible reasons.
    1. The first is that you are reading or operating the meter incorrectly .Let's assume that's not the case. However I have been trapped by this in the past where the probes were plugged into the incorrect sockets for the range I selected. Confusingly, one of my meters (at least) will still give readings (wrong ones) in this state.
    2. The next possibility is that it is a problem with burden voltage. If the circuit under test operates at very low voltages, a combination of the current being measured and the resistance across the meter can change the circuit operating conditions. For a simple multimeter, this means the current read on the lower range (which uses a higher resistance shunt) will measure lower current.
    3. Another option is a flat battery. A very cheap multimeter I have starts to read very inaccurately when the battery gets flat. Unfortunately the manufacturer decided to omit a low battery indicator :-(
     
    Last edited: Nov 10, 2018
  6. kellys_eye

    kellys_eye

    4,275
    1,147
    Jun 25, 2010
    My suggestion would be that it's a cheap meter.

    Sadly you can be encouraged to purchase cheap (but useless) meters when there are actually some very good 'cheap' multimeters out there - like the AN8008 for example has had 'rave' reviews for its functionality and practicality.
     
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