Accuracy class 0.5 (0.25 USA)

Question

I have a 50 Amp current shunt, Tyco, specified as "Accuracy class: 0.5 (0.25 USA)" What does 0.25 (USA) mean? Is it somehow equivilant to class 0.5 ISO, or does it mean something else? I'm not in the USA or Canada, and our supplier doesn't know either.

Answer 1

The Tyco data sheet says it is made to meet the requirements of MIL-S-61B which is the US Defense Department specification for current shunts. Paragraph 3.5 of that specification states that the voltage drop of the current shunt should be 50 ± 0.3 millivolts when the shunt is carrying its rated current. Since 0.5% of 50 is 0.25, which is close to 0.3, I assume that the 0.5 in the Tyco data sheet mean the shunt accuracy is 0.5% while the reference to 0.25 USA means that the accuracy is equivalent to 0.25 millivolts (slightly better than the US spec).