EEVblog 1465 - Your Multimeter Can Measure Inductors

Handy tip on how you can use your multimeters capacitance range to measure inductors, using the reciprocal method.

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#ElectronicsCreators #Multimeter #Measurement

[colingale]

I love tool tricks like this, please do more.

[asserslab]

What you need now is a firmware update so that the multimeter calculates the reciprocal for you and handles the units properly ;)

[brainndamage]

Two other useful methods: create a parallel LC circuit with a known C, feed it with a signal generator through a series resistor, find the resonant peak and calculate L from it (if L is sufficiently large, you can use your phone as a signal gen). You can also measure the Q by measuring where the voltage falls to 1/sqrt(2). The other method is to feed the L through a small current sense resistor (in the GND side) with pulses starting from 0 duty cycle, increasing very slowly. Look at the rate of increase of current through the sense resistor, calculate L from it. If your pulser can provide enough current you can even measure the saturation current. You can build a pulser circuit with just a 555, mosfet, catch diode, and a handful of passives.

[JanCiger]

Great tip, Dave, didn't think of using a multimeter like that. Not very accurate but plenty good to get a ballpark value which is often enough (and the inductors are rarely precise components anyway). 👍

[EricAdamsonMI]

Thanks for sharing -- I've known this "trick" for decades, but it's still worth pointing out!

[seanet]

This would be a good test for a late first or early second year engineering student.

Htey would know the theory but can they put it into practice.

It is obvious when you think about it that the capacitance measurement must be using non DV waveform so from first principals, you can get the conversion as an inverse from impedance.

I've only ever used this a couple of times, normally a check to make sure the inductor is still good rather than looking for a value but it is a good trick to know if your short an LCR but there are some decent very budget options for these measurements in the hobbyist and student space

[oeckel]

You really got a lot of people this year... I'll admit you had me thinking for a while.

[kissingfrogs]

i liked the "short the temperature leads" trick to get the internal temperature but this is the first time I have heard of using capacitance four measuring inductance

[slypig]

I has no idea what you were talking about, but I liked the way you presented it.

[demoncloud]

I have made a Big Capacitance measurement device with Cypress PSoC 4 using the build in Current Source and ADC, not very accurate but it can measure FAST and thousands of uF in a blink.
The idea is to charge up the capacitor with current and measure 5RC time constant, which is the time required to reach Vcc voltage.

[ingolfmuller]

Nice trick. It tooks me almost 7 long minutes to understand the deeper meaning. 🙈 Congratulations!! You put in big effort!! 👍👍

[insoft_uk]

Dave is so good at April Fool videos, I decided to see what this year’s is and comes over as very convincing as usual 👍, some of the other channels first 30sec to 1min April Fool tho not Daves

[pnjunction]

Nice one, Dave! I had to think about it for a minute 🙂

[andycristea]

I measure large inductances by sticking the coils on my tongue. Based on what AM radio station I pick up in my head, I can tell the inductance +/- 10%. It's a good technique but takes years to master.

[PhilRookemusic-educator]

Was just looking for a way to do this with my multimeter to make a 110 uH coil for an EFHW antenna - but being an Aussie myself, I also enjoyed your Aussie approach "Get on there ya bastard" LOL. Helpful and entertaining at the same time.

[hanedoggy]

"That's good enough for Australia." Love it... Great video!

[odindimartino]

The method I use (make a LC circuit with a reference capacitor and measure the resonance frequency ) work mostly for small values so it cans be useful

[horiamorariu]

Great video, as usual. A couple of years ago, I did this experiment, but did not make the step forward - I simply didn't see the utility of this, at the time.
But yes, as presented by you, is really useful.
You are a Genius, as usual. Cheers!

[dennissloatman]

EE here in "the States." Excellent tip, Dave! I have never considered this - good tip for field work (which I do for a living). Love your videos - keep up the excellent work!

[urugulu]

well since you essentially need a scope to pull this off anyway (for probing the meter)
you can just aswell use the test signal gen for probe compensation for that purpose.
some scopes can generate a variable frequency on that output which is quite handy too