panel amp meter prob?

Discussion in 'General Electronics Chat' started by anode505, May 10, 2009.

  1. anode505

    Thread Starter Member

    Apr 21, 2009
    I'm a bit analog challenged, so bear with me.

    I have 15W of solar panels charging one of them little jumpstart gizmos.
    That works fine and dandy, charges, runs the inverter, etc.

    I wanted to put on a Volt and an amp meter. The amp meter reads WAY high (over 30amps). I got the shunt with it and when that is wired in (in parallel, series also pinned the needle.) it still reads high., about 10-15 amps.

    my Fluke 189, which I trust a LOT more ,and mathematically, is more
    'on' reads in the .2amp range.

    What am I missing? The meters are between the panels and JS gizmo.
  2. Wendy


    Mar 24, 2008
  3. DonQ

    Active Member

    May 6, 2009
    The shunt goes in series, and the amp-meter leads go to both ends of the shunt. You are actually measuring the voltage generated as the current flows through the shunt.

    Not sure what a "jumpstart gizmo" is, but if you actually did put the shunt in parallel, you need to consider yourself lucky that the connection to the batteries have some sort of protection circuits, or isolating diodes, or something. Since the shunt has only a fraction of an ohm resistance, this could have created a really neat show if paralleled across the battery. Please, install it according to the directions.

    The volt-meter leads do go across the circuit, in parallel, i.e. to both ends of the batteries, or both ends of the solar cells. Again, trust the instructions on this.
    Last edited: May 10, 2009
  4. SgtWookie


    Jul 17, 2007
    The key to what both Bill Marsden and DonQ is saying is Ohm's Law, where one permutation of Ohm's Law says:
    I = E/R, or Current = Voltage / Resistance

    In other words, when current flows through a resistance, there will be a voltage "drop" across that resistance.
  5. BillB3857

    AAC Fanatic!

    Feb 28, 2009
    Most Amp Meters that use shunts are actually 50mv meter movements, and the shunts are usually rated in a given number of amps to result in the 50mv drop across the shunt. With the meter in parallel with the shunt, it will give full scale reading for the rated amps of the shunt. Is the shunt you have marked as to what range it is?