Current measurement units with analog or digital displays
A shunt resistor is a low ohm resistor which is used for electricity measurement. The bigger the electricity, which runs through through the shunt, the bigger the potential, which can be determined.
Current measurement units with analog or digital displays are normally implemented by taking the very small potential on a low ohmic shunt. Such normally is 200 mV in digital measuring instruments, or 60 mV in ordinary analog instruments. Circuits with operational amplifiers can also handle smaller potentials on a resistor and therefore can also be used for high precision current sensing.
Shunts are installed in the electric circuit in which the electricity should be determined. The fine potential which occurs on the current resistor is determined with the displaying unit. Because the resistance of transition at the contact points bears the potential to drop, the potential on the power meter shunt is determined by a four point connection (also called Kelvin connection).
The computation of the resistor is determined by Ohm's law. E.g.: If the potential drop over a 300 mOhm shunt is 300 mV, then 1 A of current runs through. If the electricity flowing through the voltmeter is not negligible, it has to be considered in the computation.
In order to calculate large (> 100 A) flows shunts are physically strong, such as as metal band resistor made of Manganin with strong contact points for the measurement circuit and with two smaller contact points for the meter. Further Isotan or Isabelline for resistors are Isotan or Isabelline.
Large shunts are made of many parallel metal bars and can be installed directly between the power rails. A lot of times shunts are directly installed in the measuring instruments (eg multimeter) and are substitutive.
For the measurement of enormous currents (> 50 kA), e.g. of lightning, normally special built, normally coaxial power resistor shunts are used. These permit the measurement of current performance with storage oscilloscopes.
Furthermore, fine shunts for soldering on printed circuit boards are assembled, which also have Kelvin contact points. Furthermore, shunts exist as electrical SMD Resistor or hybrid mounting resistors which normally are installed in BMS Batterymanagement Systems.
Current measurement with high precision resistors like shunts clamed down slightly with the manifestation of current sensors (which additionally offer a potential detachment). Nevertheless shunts are an cheap and accurate approaches of electricity measurement.