Home >> Science & Nature >> Science

How to Use an Impedance Bridge to Measure Inductance

Electricity is a result of the flow of charged particles through metallic wires. Electrical devices consist of a number of electrical components such as resistors, capacitors and inductors. Resistors impede the flow of electrical current; resistance is measured in ohms. Capacitors store electrical charge; capacitance is measured in farads. Inductors store magnetic energy; inductance is measured in henrys. Resistance and capacitance can be measured using digital multimeters, but the measurement of inductance requires a dedicated electrical circuit such as an impedance bridge.

Things You'll Need

Function generator
100-ohm resistor
Oscilloscope

Instructions

- 1
  Place the inductor in series with the 100-ohm resistor. Connect the positive terminal of the function generator to the remaining free side of the resistor and the negative terminal to the remaining free side of the inductor.
- 2
  Connect the first input of the oscilloscope to the output of the function generator and connect the second input to the junction between the resistor and inductor.
- 3
  Switch on the oscilloscope and the function generator. Adjust the volts/division and time/division settings on the oscilloscope until both signals are visible on the screen. Change the output frequency setting of the function generator until the junction voltage is observed to be half the input voltage. The following equation can then be used to determine the inductance:
  
  L= R*sqrt(3)/(2*pi*f)
  
  sqrt() means that everything within the brackets is square-rooted. "R" is equal to the resistor value (100 ohms) and "f" is equal to the frequency at which the junction voltage is observed to be half the input voltage.

Science