multimeter drains circuit?

Discussion in 'General Electronics Chat' started by jarwulf, Mar 25, 2014.

  1. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0
    I have my multimeter set to 2 on DC voltage and trying to measure suspected voltage drop from the positive prong of a power jack to a point further along in the positive wire across some junctions in a circuit board. The module I'm measuring is powering on as indicated by an led but does not seem to be getting enough power to perform its function.

    For some reason it seems to shut off the circuit sometimes when I press the probe to the power jack and then comes back on when I take it off. I jiggled around the wires without the multimeter and it didn't seem to shut off then. The voltage is supposed to be around 8-7 volts. The PSU can supply 2 Amps. What could be wrong?
     
  2. pwdixon

    Member

    Oct 11, 2012
    488
    56
    Post a photo of your setup and perhaps a schematic and someone might be able to point at something.
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,809
    1,105
    Depending on what the circuit is, the meter impedance may be such as to modify circuit performance. Instead of measuring between A and B, try measuring between A and ground and between B and ground then subtracting the results.
     
  4. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
    Don't skimp on tools. Buy a nice multimeter. When it comes to my tools, I do not skimp. I buy the best or as close to the best as I can afford.

    I own nothing but Fluke products for that simple reason. Skewed erroneous readings will screw you in the long run. Especially when working with electronics.
     
  5. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    What holes do you have the leads plugged into on the multimeter? If plugged into the holes for measuring current, it can possibly short out the power supply.
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    You'd think it would have blown the meter on first contact.
     
  7. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    All depends upon which hole he plugged in to. Some multimeters have a length of very heavy wire between the AMPS and COMMON holes. Taps on that wire then measure millivolts and indicate AMPS. Remember the old Simpson 260's?
     
    GopherT likes this.
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