how do I extend range of ammeter?

Discussion in 'General Electronics Chat' started by BillRush5, Mar 22, 2013.

  1. BillRush5

    Thread Starter New Member

    Jan 13, 2013
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    I have an ammeter that currently reads full scale at 50 uA. I'd like to extend full scale range to read 1.5 mA. How would this be done? Thanks
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,367
    Find out what is the full scale voltage, i.e. the voltage Vfs that takes the meter to full scale at 50μA.

    Calculate the shunt resistor Rs required using Rs = Vfs/1.5mA.

    For example, if Vfs = 150μV

    Rs = 150μV/1.5mA = 100mΩ or 0.1Ω
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,649
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  4. Mike33

    AAC Fanatic!

    Feb 4, 2005
    349
    25
    Watch the power rating of whatever you use for a shunt! (actual high-precision resistors, wire or metal stock) ;)
     
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