This article will give you some information about current sensor. A sensor which is usually particularized with a variety of mechanical and electrical specifications is called Current shunt resistor. The specifications of the electrical are the indication of the accuracy of the current shunt resistor as a current sensor.
The accurate measurement of this equipment has been claimed by the resistance exactly. The age, temperature and current do not change the resistance. Its resistance to AC current change (inductance) is zero. Precision that calibrated current shunt draw close to the perfect measurement but are very expensive and large.
A device that has low resistance precision used to measure AC or DC electrical currents by the voltage drop then the current produces across the resistance is called Current shunt resistor. This device is also celled as an ammeter shunt. This ammeter is a kind of current sensor.
Some other ammeters use external DC current shunt but still the principal of the measurement is the same. They use the same Ohm's Law:
V= I X R
Ohm's law states that the resistance and the current (I) which are flowing through the resistance produce Voltage (V in Volts) across resistance (R).
Here is an example of the operation of Ohm's law. For instance in a situation where a current resistance has 0.002 Ohms with 25 Amps flowing on it results a voltage (V = I x R) 0.002 x 25 Amps = 0.05 Volts or 50 mV.
Ammeter will measure the voltage drop that across the shunt when you insert this device into a circuit that you want. You can also calculate the current using Ohm's Law by this formula I = V/R. Then, vice versa you can also calculate the ammeter if you know the voltage that is produced across the current shunt, and the voltage.