Reading Amps with 100 mV meter

Discussion in 'General Electronics Chat' started by Gregfox, Mar 19, 2013.

  1. Gregfox

    Thread Starter Member

    Jul 23, 2011
    14
    1
    Hello all,
    Does anyone know how I can read up to 2 amps on a millivolt panel meter that has a DC limit of 0-100 mA? I'm connecting the panel meter across a 1 ohm resistor to read current up to 2 Amp.
    Thanks!
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,439
    3,360
    If the meter reads 100mV fullscale you need a 50mΩ shunt resistor.
     
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  3. crutschow

    Expert

    Mar 14, 2008
    13,001
    3,229
    It's simple Ohm's Law. R = V/I thus R = 100mV / 2A = 50mΩ as MrChips stated.

    You can buy an accurate resistive shunt designed for that purpose or, if you don't need high accuracy, you can use a short piece of small gauge wire to generate that resistance. A wire gauge resistance table will allow you to determine the required length for a given wire gauge.
     
  4. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Either I can't read, or it would take a truckload of fine wire to equal a 50 megohm resistor... :D D'oh !!! :p or is it Duh !!!
     
    Last edited: Mar 22, 2013
  5. jmoffat

    Member

    Jul 18, 2012
    42
    1
    100 mv / 2 A = 50 milli ohms! Lower case m is for milli. 50 megohms certainly would be many pounds of fine wire.
     
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