A Manganin swap resistance is connected in series with a moving coil ammeter consisting of a milli-ammeter and a suitable shunt in order to.
(a) minimize the effect of temperature variation
(b) obtain large deflecting torque
(c) reduce the size of the meter
(d) minimize the effect of stray magnetic fields
Manganin has a negligible temperature coefficient. Coil is made of copper.
A swamping resistance (R) of manganin having a resistance 20 to 30 times the coil resistance is connected in series.
Since copper forms a small fraction of the series combination, the proportion in which the currents would divide between the meter and the shunt would not change appreciably with the change in temperature.