Measuring current shunts

Measuring current shunts Shunt is a device that allows current to flow passing by any part of a circuit. Usually it is a low-Om resistor. Shunts are used, for example, for measuring upper limit of amperemeters in a magnetic electric system. For this purpose you should count necessary shunt resistance using a formula: where R2 is shunt resistance, R1 is amperemeter resistance, l is maximum current that will be correspond to full deflection of needle, l1 is rated maximum current measured with amperemeter without shunt. Depending on shunt resistance copper wire in a coil, metal sheet, normalized (standard) resistor with small resistance deviation allowance can be used as this element but oftener specialized measuring shunts are used. For example, fixed measuring shunts of 75ШИП series with rated voltage drop of 75 mV intended for widening measurement ranges of showing and registering devices for direct current. Shunts are implemented as manganin sheets brazed in caps that made of brass or copper. Caps have screw holes for potential clips (screws) and holes for current-carrying clips (screw bolts). Each shunt has the following mark: type, rated current, accuracy class, product mark of a producer, year of manufacture. Shunts intended for use in tropical climate have besides the above: standard temperature "+27°С" and T3 in shunt type. The main technical characteristics: accuracy class 0,5, voltage drop on potential clips for all shunts under rated current is 75 mV. Shunts are intended for work under environment temperature from -40°С to + 50°С and relative humidity of 95% (under40°С). An average time of service is above 15 years.