Wheatstone bridge
From uCtrl.net
Information
Commonly used method for getting current using resistor based sensors. If the ratio of the two known resistors, R1 and R2, is equal to the ratio of R3 and Rx then the current in the two midpoints is zero. This current can be measured with extreme accuracy, but this requires accurate R1, R2 and R3 resistors. Very small changes in Rx disrupts the balance and are highly detectable.
Rx = (R1/R2) * R3
