# 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
12,646
3,458
If the meter reads 100mV fullscale you need a 50mΩ shunt resistor.

PackratKing likes this.
3. ### crutschow Expert

Mar 14, 2008
13,508
3,385
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
216
Either I can't read, or it would take a truckload of fine wire to equal a 50 megohm resistor... D'oh !!! 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.

PackratKing likes this.