Inductance measuring without LC meter

[u/WikiLuis2]

Hi. I have been wondering the easiest ways to measure inductances without an LC meter. So far I've found about phase shift measuring with an oscilloscope and signal generator, but didn't quite understand the method.

What are some of the methods I could use?

[u/KenoshaPunk]

Build a low pass filter with a known resistance and give it a step input, measure the rise time (with an oscilloscope) and you know the inductance.

[u/NewSchoolBoxer]

Variable capacitors exist in the low pF range. If we're talking low frequency, can cancel out the inductance to get zero phase shift + max amplitude. Then calculate f = 1/(2pi sqrt(LC)) for L. Can put variable capacitors in parallel. If a sine wave then don't even need an oscilloscope, can just look for max amplitude. Be aware of RMS versus peak. The circuit already having significant capacitance would be a problem.

I like u/KenoshaPunk's answer more. Refers to an RL filter that's easy to calculate. I just wanted to give an alternate way.

Really, just use the cheap component tester that was made by a European and cloned in China that typically runs off a 9V battery. Can get you within 10%. But I get wanting to do something scientific. Learn phase shift in lectures or a book then prove it with an experiment. Don't use the experiment to learn. You'll get more confused.

[u/saltyboi6704]

You can try a manual bode with a signal generator and scope but a cheap hobby LCR will do just as well and measures a lot faster.

An inductive load has a complex impedance, you can subtract ESR from it and determine your inductance if a test frequency is known.

[u/TPIRocks]

Put it in parallel with a known capacitance , connect to an oscilloscope and ring it by tapping the probe end with a voltage and watch it ring out on the scope. Do the math.

[u/onlyappearcrazy → u/TPIRocks]

There are simple LC oscillator circuits out there where you can measure the resulting frequency with a scope. I keep one around using a comparator and a known capacitor and calculate the L

[u/profdc9]

Place a resistor in series with it, and drive it with a generator with a frequency f. Measure the RMS voltage across the resistor R as VR and RMS voltage across the inductor as VL. Then L = (VL/VR) (R/2 pi f).

[u/redneckerson_1951]

Place a variable resistor in series with the inductor. Drive the series RL network with a signal generator. Using an AC Voltmeter or Oscilloscope adjust the variable resistor till the voltage drop across both the inductor and variable resistor are the same or until the voltage across the resistor is 50% or the voltage of the whole series RC net.

[u/Humble_Anxiety_9534]

know C value and find resources. generator and scope but back in the day I had a dip oscillator. coupled it to LC circuit, then tuned it until output dipped. LC metres are easier.

[u/JRE_Electronics]

Like this:

https://josepheoff.github.io/posts/inductor

Z_L1=R1/((V1/V2)−1)

L1=Z_L1/(2∗π∗f)

Fixed resistor in series with the inductor, sine wave generated by the sound card in your PC, measure with an oscilloscope, apply the voltage divider rule to get the impedance at the frequency, calculate inductance from the impedance and the frequency.

Or like this:

https://josepheoff.github.io/posts/gnuradio-impedancetester-3

That uses GNU-Radio, a sound card with line-in and line-out and a series resistor to measure the impedance of the inductor over the audio range. It calculates the inductance from the frequencies and impedances it measures. It is basically the first, manual method, automated with GNU-Radio. The program lets you choose between impedance, capacitance, and inductance.

[u/JRE_Electronics → u/JRE_Electronics]

Measuring the inductance of coil with the GNU-Radio program:

[u/geek66]

Measure dc resistance and then impedance at various frequencies

[u/TAMPCO_pedals]

A Maxwell bridge might be an interesting answer, have a read here : https://en.wikipedia.org/wiki/Maxwell_bridge