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Using WT3 to Measure an Inductor
Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds.
Measure the value of an inductor as follows:
•
Launch the WT3 software and make sure the volume is set at maximum.
•
Make sure that the inductor is not connected to any other equipment and then connect the test
leads of the WT3 unit to the inductor under test.
•
Click the "Measure Free-Air Parameters" button at the left side of the WT3 screen.
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The sweep is silent, then the impedance is plotted and the parameters are displayed.
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Read the value of the inductor in the L(e) field at the right side of the screen. The DC resistance
of the inductor is displayed in the R(e) field. Ignore all other parameters.
•
Repeat the measurement to confirm the result. Repeat measurements should be in good
agreement.
Here is a typical result when measuring a 1.0 mH inductor:
An ideal inductor would have an impedance of zero Ohms at the lowest frequencies and then the
impedance would rise with increasing frequency. The phase response of the inductance depends on the
exact circuit in which the inductor finds itself. At very low frequencies (1 Hz) the impedance
measurement reveals the DC resistance of the inductor. Notice that the impedance (blue) of the real
inductor measured above is near zero at low frequencies and rises at high frequencies as expected. The