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Thread: Looking for Ammeter

  1. #1
    SteveRich Guest

    Looking for Ammeter

    I am looking for an inexpensive source for an 0-75 AMP ammeter

    I understand there are 2 types and "shunt" type and a "CT"( current transformer) type. I perfer the CT type either analog or digital but small and cheap is necessary.

    I have a clamp on for testing by I'd like to install one in my car to moitor the operation of my dry cell.

    Thanks, Steve

  2. #2
    Join Date
    Jul 2008
    Posts
    1,174

    Lightbulb

    Quote Originally Posted by SteveRich View Post
    I am looking for an inexpensive source for an 0-75 AMP ammeter

    I understand there are 2 types and "shunt" type and a "CT"( current transformer) type. I perfer the CT type either analog or digital but small and cheap is necessary.

    I have a clamp on for testing by I'd like to install one in my car to moitor the operation of my dry cell.

    Thanks, Steve
    My digital "Ammeter" cost $3.50

    Go to Harbor Freight and but their cheapest multimeter.

    Next, go to Home Depot or Lowes and buy 1 foot of #10 solid copper wire.

    Cut the test probes off the meter and replace them with alligator clips.

    Run the current to your cell through the #10 wire.

    Use the alligator clips to connect to the wire itself 12" apart (not to any other connection point or the reading will be false).

    Turn on your meter to the 200 mV scale.

    Your meter will read current directly.


    IOW If your meter reads 7 mV the current is 7 Amps. +- 3%


    I hope that this helps.

    BoyntonStu

    P.S. If I get the chance, I will upload a photo of my setup.
    I use 2 multimeters, one for Volts and the other for Amps.
    $6.00 is cheap enough for a pair of dedicated digital built-in meters.

  3. #3
    SteveRich Guest

    This is a great idea!

    Thanks,

    This is a terrific idea. As is mentioned I'm looking for 0-75 Amps. I wonder if th "Shunt" of 12 inches of 10 gage wire will handle it(75 amps). Maybe I could find a CT of the right size to do the same thing with a current transformer.

    Steve

  4. #4
    Join Date
    Jul 2008
    Posts
    1,174

    Question

    Quote Originally Posted by SteveRich View Post
    Thanks,

    This is a terrific idea. As is mentioned I'm looking for 0-75 Amps. I wonder if th "Shunt" of 12 inches of 10 gage wire will handle it(75 amps). Maybe I could find a CT of the right size to do the same thing with a current transformer.

    Steve
    Steve,

    #10 wire is very convenient to calibrate because it has a resistance of 0.001 ohm per foot and therefore 0.001 Volt means 1 Amp.

    This is a simple solution to safely increase the shunt capability.

    Use N #10 wires in parallel and measure only one wire; multiply the reading by N.

    BoyntonStu

    PS If you passed 100 Amps through a single #10 wire the power dissipated would be (I^2 x R) 100 x 100 x .001 or only 10 Watts. A little heat, but not much. A night light is typically 7.5 Watts.

    If you have ever seen a 10 Watt resistor, its leads were way smaller than #10 wire.

  5. #5
    IronBear Guest

    Romex cable is a good source

    You mostly find Romex in 12 gauge spec, but if you are lucky you might find some scrap Romex cable that is 10 gauge grade.
    That will cover you cheaply.

  6. #6
    HHO King Guest

    30 Amp Ammeter

    Here's a 0-100 amp digital gauge. http://www.extremehho.com

    I have also used the cheap square ones on ebay and found them to be accurate.

  7. #7
    Join Date
    Aug 2008
    Location
    UK....Devon
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    92
    i think you will find the "CT" as in Current Transformer only works on AC



    Quote Originally Posted by SteveRich View Post
    I am looking for an inexpensive source for an 0-75 AMP ammeter

    I understand there are 2 types and "shunt" type and a "CT"( current transformer) type. I perfer the CT type either analog or digital but small and cheap is necessary.

    I have a clamp on for testing by I'd like to install one in my car to moitor the operation of my dry cell.

    Thanks, Steve

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