Impedance Magnitude Measurement from a Resistive Bridge

It is shown that the familiar resistive bridge can be used to measure the magnitude of an unknown impedance. In order for this conclusion to hold, the bridge must have equal ratio arms. The measured voltage is then a minimum when the variable resistance in the bridge is equal to the magnitude of the unknown resistance. The sensitivity, however, decreases as the reactive component of the unknown impedance increases. The analytical tools used are well within the reach of the sophomore student in electrical engineering.