what is a current shunt & its use?

Question

what is a current shunt & its use

Answer 1

It is a heavy piece of metal that is used with a current meter. The meter's internal parts are made to take a small current (like .001 Amp and deflect full scale when they detect that. If you want to measure a current that is large like 20 amps you need to make a path for all the current beyond that .001 Amp to bypass the meter. By making the shunt a very low resistance the current is divided up so most goes through the shunt and the tiny remainder feeds the meter.

Answer 2

to make your current meter measures more than it's rating, you can also make your own shunt by the formula:
Rs= Rm/(n-1)
where: Rs= resistance in ohms for shunt
Rm= resistance of meter
n= ratio for stepping up range of meter
Ls=Rs/(Xv)/1000 ft.
where:Ls= lenght of copper wire shunt
Xv/1000= resistivity of copper wire at a certain gage
Ex; #18 awg magnet wire has a resistance of 6.386 ohm/1000 ft.
say you have a 0-1 ma and would like to measure up to 1 amp., meter resistance= 70 ohms.
Compute:
Rs=Rm/(n-1)
0-1ma meter, 1 amp range, 1ma=0.001 amp
n=1 amp/0.001= 1000
Rs=70/(1000-1)=0.070 ohms
for a shunt of #18 awg magnet wire;
Ls= 0.070/6.386/1000=10.96 ft.
you can coil 10.96 ft. of #18 awg and connect it in parallel with your current meter and measure up to 1 amp.
Note:
the thinner the wire, the lesser the lenght.