Representation of Wheatstone Bridge

Description

Wheatstone bridge is commonly used to measure the value of unknown resistance. This type of bridge can be further generalized to measure the unknown resistance, capacitance, and inductance. One detector is required to measure the small value of current flowing in the bridge. A galvanometer (a device to measure a very small amount of current) is generally used as a detector. As a galvanometer is not available in general, hence we have used LEDs to measure the current. The only drawback with the LEDs is that they can not measure very small current values. But for our purpose, it will work well. From the given circuit we can see that four resistances R1, R2, R2, and R4 are connected to form a bridge. LEDs D1 and D2 are connected diagonally to measure the current flowing across them. If the bridge is balanced( if R1*R2 = R3*R4), then no current will flow across D1 or D2. This is the principle of the bridge. Let us connect an unknown resistance R2 to the circuit and connect three known resistances R1, R3, and R4. If the circuit is balanced, then R2 can be calculated by the formula given above.