Do ammeters use electricity?

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ayurtdweller
ayurtdweller Registered Users Posts: 26 ✭✭
in Off Grid Solar & Battery Systems #1
I would like to add an analog ammeter to my installation buy I am worried about losing efficiency. Do these type of ammeters have a draw? Thanks much!
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    edited November 2016 #2
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    Any instrument will use some energy from the process it's taking a measurement from.
    They do use a tiny amout of power.
    Shunt type cause a 25 to 100 milli volt voltage drop red by a volt meter that displays amps.
    Then you have current transformer type where a current transformer makes an AC signal any where from 25 to 100 mv to make the gauge read.
    Current transformer type only work with AC. Shunt type can be AC or DC.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    As Oil Pan says--There is a little bit of loss... For a worst case example:

    P = V*I = 0.1 volt max drop on shunt * 12 volt battery bank = 12 Watt loss
    100 amps * 12 volts = 1,200 Watts
    12 watts / 1,200 Watts = 0.01 = 1% loss

    Typical losses are:
    • 1% loss for shunt
    • 1-3% loss for wiring
    • 5% loss for solar charge controller
    • 10-15% loss for AC inverter
    • 10-20% loss for AC battery charger
    • 10-20% loss for flooded cell lead acid battery (AGM is 2% to 10% loss, NiFe/NiCad/NiMH ~ 20-35% loss)
    • ~20% loss for solar panel (off of "manufacturer's STD ratings)
    • ~50% loss for fuel->electricity (very efficient power plant)
    • ~65-80%+ loss for fuel->electricity for typical home genset
    1% loss does not look so bad compared to everything else... :'(

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #4
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    A 100mv shunt at full amperage on a 12v system is about a 1% loss.
    I would use an amp meter.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • 706jim
    706jim Solar Expert Posts: 515 ✭✭✭✭
    #5
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    My Trace charge controller has a digital ammeter. if it is displaying 13 amps, the analog meter ahead of the Trace will show about 15 amps.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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