Puzzled about DC Clamp meter reading

Discussion in 'General Electronics Chat' started by bhvm, Aug 13, 2014.

  1. bhvm

    Thread Starter Active Member

    Jul 16, 2009
    53
    2
    Dear friends,
    I brought myself a Highend AC & DC "hall effect" Clamp meter that claims to measure Amps, Duty cycle and HZ via Clamp.

    My main reason for the investment is my New off grid solar setup. The solar setup has 4 batteries in PARALLEL for a total of 400AH storage at 12v. I wanted to know How many amps is my solar unit generating and how much is it being distributed to each battery. I also would like to know how many each battery "contributes" during a discharge use.

    I can put the Clamp meter into DC Amps and see some amps on the display. sometimes I see amps Marked with a "-" Sign as well.

    I am confused if the amps I see are charging amps or discharging amps. I can get a positive or negative reading depending on the orientation of the meter itself which aggravates the confusion!
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    the + and _ are determined by the direction of current flow, if you turn the clamp over, it will change. if you mark the clamp on one side, and always have that side toward the load, it shouldnt change except with charge and discharge.
     
  3. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    Amp clamps are typically marked with an arrow on the inductive pickup which indicates the direction of current flow. If you are still unsure, clamp it on the large cable coming off the B+ post on your car and get a positive reading when it is running. The direction will be from alternator to battery.
     
  4. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    The only way to tell the amp capacity is to check it with a load on it. Increasing the load will tell you what the max available current is.
     
  5. bhvm

    Thread Starter Active Member

    Jul 16, 2009
    53
    2
    Thats the major comfusion I see. Even if I am holding the meter with display facing to me, sometimes the wires are routed up to down or Down to up. This causes mess!
    Yes! My Clamp meter has a "+" sign on top (the side with display).
    I loved your car idea. I will try it soon.

    I am wanting to understand the - and + amps.

    Please me explain me below-
    1)Which post shall i take reading? I've heard I should measure the Negative terminal as electrons flow out out negative end, right?
    2) What do '-' amps as a reading on meter mean? (At negative terminal)
    What do + amps mean?
    3) Any tips to increase the accuracy of my readings?
     
  6. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    1) You can take your readings from either post as long as you know what you are reading. If you go from the positive post, using the conventional theory, most meters will want you to place the arrow toward the positive post when you are taking your reading. On the negative post, it would point away from the negative post. You can tell because the reading will be a positive reading.
    2) If you are reading (-) amps, it simply means you have the pickup hooked up in the wrong orientation. It is the meter reading positive or negative, not electrons running backwards. Voltmeters and ammeters are polarity sensitive because they have current running through them. Ohmmeters are not because you are working with a dead circuit.
    3) In order to increase the accuracy of your readings, you can:
    a) Buy a more expensive and accurate meter
    b) Buy an accurate ammeter that you actually hook into the circuit. It must be placed in series with the circuit so that it can measure the full circuit current value.
     
    bhvm likes this.
  7. bhvm

    Thread Starter Active Member

    Jul 16, 2009
    53
    2
    Here is how the meter looks.
    There is + mark on the display side.
    Would someone be kind enough to draw up a rough visual how the wire should pass and which way the battery should be?

    Thanks all for your time.
     
  8. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    Try this:
    Hope it helps.
     
  9. bhvm

    Thread Starter Active Member

    Jul 16, 2009
    53
    2
    Great!
    where should be the battery be? negative side or Positive side?
    Assuming I measure on Negative terminal.
     
  10. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    How about this?
     
  11. bhvm

    Thread Starter Active Member

    Jul 16, 2009
    53
    2
    Wow! That means the Positive side of meter shall be pointing towards the load?

    Thousand thanks dear!!
     
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