How to Measure Inductance of a Coil
Inductors are sometimes wound by the user instead of bought. In such cases, the inductance would not be stamped on the side but instead may need to be found empirically. The best way to measure inductance for an inductor like a coil (solenoid) is to use an inductance bridge or meter. If you have neither, a more indirect way is to use an oscilloscope.
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Things You'll Need
- Sine-wave oscilloscope
- 2 voltmeters
- Resistor of known resistance to close tolerance
Instructions
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Connect a resistor of known resistance and the coil in series with the sine wave oscilloscope.
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Turn on the oscilloscope and clamp the two clips of one voltmeter to the circuit on opposite sides of the coil to determine the voltage drop across the coil. Then do the same for the resistor with another voltmeter.
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Set the frequency of the oscilloscope such that the voltage drop across the resistor and inductor are the same. Finding said frequency may be a matter of trial and error. At that frequency, the resistance of the resistor and the impedance of the inductor will be equal.
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Set the resistor's resistance and the inductor's impedance equal to each other and solve for the inductance of the coil. Resistance = 2πfL, where "f" is the frequency of the oscilloscope and "L" is the coil's inductance. The resistance of the resistor has not changed from the start; it is independent of the frequency. So "L" can be solved for by arithmetic.
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Comments
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conakry
Jun 04, 2010
It's funny no one has corrected this page since the author meant to say "Function Generator" and not "Oscilloscope". You need to have a function generator (with usually triangle, sine or square wave generation) with a 50 ohm output BNC output jack. An oscilloscope measures waveforms to be seen onscreen with usually at least two BNC inputs.
