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What's the best way to measure the resistance and inductance of a coil at a given frequency? I need these parameters for my LTSpice-Simulation which assumes an RL series circuit.

The coil has 8 windings and is printed on a PCB. The eDesignSuite from STMicroelectronics estimates an inductance of 1.72µH. DC-resistance is approx. 1.27Ohm (measured).

Will the resistance at 13.56MHz be equal to the DC-resistance? (How can I verify this?) How can I verify the inductance of the coil at approx. 13.56MHz?

Thanks!

Michael Haar
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  • In my opinion "the best" would be using a Network Analyser (NA) to plot the impedance over frequency. Then use that plot to make an RLC model of the inductor. Many years ago I used an HP NA that could do that. NAs are expensive though. More practical if you do not have an NA is in inductance meter which can show you ESR as well. It might not measure at 13.56 MHz though. This might not matter, it depends on what accuracy you need. I sense that you need to learn about the parasitics in components, Google "inductor model", for example: http://www.ee.bgu.ac.il/~spice/Additional/non_linear_pres.pdf – Bimpelrekkie Jan 21 '19 at 13:14
  • Thanks for the feedback. Unfortunately I only have a function generator, an oscilloscope and some multimeters. Maybe I should change the word "best" to "easiest" or "cheapest"... – Michael Haar Jan 21 '19 at 13:52
  • An inductor of around 1.7 uH will have an impedance of about 150 ohms at 13 MHz and that's quite low. You can just measure the ESR (DC series resistance) at DC and assume it remains the same at 13 MHz. Then in the simulator add an ideal 1.72 uH inductor in series. With this equipment there isn't much more you can do. – Bimpelrekkie Jan 21 '19 at 14:02

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I don't know what kind of equipment you have exactly but if you have a function generator that can output a decent sine signal at 13.56 MHz you should be able to use that in conjunction with an oscilloscope to get a reasonable measurement of the inductance. Be aware that proper probing techniques at these kind of frequencies are necessary in order to get a usable result. This interesting article by Tektronix explains the process quite clearly: https://www.tek.com/document/application-note/capacitance-and-inductance-measurements-using-oscilloscope-and-function-ge

Midas Gossye
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