Wheatstone Bridge: A great trick to unknown resistances in a electric circuit.

Many circuit configurations are used to measure resistance. Today I'll show you the method to find the unknown value of a resistance in a electric circuit.

The Wheatstone Bridge was named in honor of those who described the method, is used to accurately measure mean value resistances, that is, in the range of 1 Ohm to 1000 Ohm. In commercial models of the Wheatstone Bridge, precision of the order of +/-1% is possible. The bridge may be in equilibrium or not: the bridge is considered balanced when the resistor are adjusted so that the current detector (ammeter, galvanometer, multimeter) is measuring a current equal to zero. You can discover the unknown resistance of a resistor through the product and quotient of the known resistors, all that is required is to know the value of the other 3 resistors in order to discover the unknown resistance.

Rx = (R1 * R2)/ Rv

or,

Rx/R2 = R1/Rv

When the bridge is unbalanced, a rheostat can be used to obtain the value of the unknown resistor, it is sufficient to regulate it until the current that the current detector is measuring equal to zero. The rheostat is depicted in the image above as a resistor with an arrow crossing it.

The maximum value that the mounted Wheatstone Bridge can measure is the value of the maximum resistance of the rheostat, because if the unknown resistance is bigger than it is impossible to establish a balance for the bridge. A way to improve the accuracy of the Wheatstone Bridge is removing the measuring instruments inserted in the circuit after the bridge is ready beacause they affect your accuracy.

The Wheatstone Bridge can be applied to measure resistances, pressure, weight and temperature. This type of circuit can be used to determine the mechanical tension. Suppose that Rx is a compressive-sensitive resistor and the other three resistors of known values, the force applied to the variable resistor will be proportional to the resistance value of that resistor. Another application is that, when you have the resistances values knowned you can apply voltage division to discover the total voltage of the battery.

So have you ever made a Wheatstone Bridge in high school or college? Stay safe, maybe someday you need this.