Shunts are standardized to deliver either 50 millivolts or 100 millivolts at their full rated current,
although there are times when other millivolt ratings are desired or other physical sizes or
configurations are more suitable for an application.
Since the shunt is a resistor which operates in a varying ambient temperature environment and generates heat whenever current flows through it, we must design the shunt resistance portion with a special metal alloy which has, essentially, a constant resistance value through its operating range. In addition to using a precision resistance alloy with a negligible temperature coefficient of resistance, the alloy must have a low resistivity in order to keep the self-heating to a minimum, and it must also have a low thermal E.M.F. against copper. A special shunt manganin alloy meets all these criteria, therefore, all our shunts are designed using this special alloy.