Inductor Tester

In this video i show how to build a circuit that can measure the value of an inductor in conjunction with an oscilloscope. This is meant to be a replacement for my $10 LCR meter, which isn't very accurate, and has very poor resolution below ~1mH of inductance.
The circuit works by sending a single pulse through an inductor, which has a known capacitance in parallel with it. When current through the inductor is shut off, the L-C pair "rings" at its resonant frequency, determined by f = 1/[2pi*sqrt(LC)]. Since frequency "F" and capacitance "C" are known, the inductance can be determined.
Current through the inductor under test is limited by current limiting resistor(s), which are manually configured by toggle switches. By default, a 680 ohm resistor is connected in series with the inductor, but 220, 100, and 10 ohm resistors can be toggled as well to allow more current for the test pulse. This is because smaller inductor values need to be pulsed with a larger current to generate a readable "ringing" signal, due to their lower energy storage for a given current.
In addition to multiple resistor options, there are two capacitance values that can be tested against. By default, a 1 nF capacitor is connected in parallel with the inductor under test, but a 47 nF can be added in parallel by toggling a switch.
If you don't have an oscilloscope, it may also be possible to measure frequency using a high impedance AC coupling to a schmitt trigger which would send square wave pulses to an arduino or similar microcontroller to be measured.
This is a valuable addition to any power electronics toolkit, because inductors/chokes and transformers are used so often, and knowing the exact component values is crucial for design optimization.
However, if you're only looking for something to give you a rough approximation of inductance / capacitance, the cheap amazon/ebay LCR meters will still get the job done, and I've used this one for several years:
www.amazon.com/AITRIP-Transis...
Automatic coil winder video:
• Automatic Coil Winding...
Music Used:
Lakey Inspired - Chill Day
Lukrembo - This is for you
Kevin MacLeod - Lobby Time

[@wa4aos]

Glad I found your channel. As an engineer, we know, no one knows it all. Learning new concepts and applications on KZbin is an excellent way to TRY to keep up. Great video, THANKS !

[@FodderBoi]

Impressive electrical engineering skills. I wish I had half the ability you do.

[@martinkuliza]

Don't wish.......... KEEP PRACTISING AND LEARNING one thing i see a lot of with beginners is I WISH i knew this or that or whatever. Forget Wishing, Pull shit apart and learn what you can and if you don't know.... ASK US I suppose another thing worth mentioning is.. - Remember everything starts as 1 BASIC CIRCUIT - Then we add a circuit to that circuit to give the first circuit added functionality and before you know it we have massively complex circuits Look at his schematic again, Step by step and imagine it as separate circuits and you can actually build those separate circuits and test them so you understand what each stage does, after you do that (which will likely take you 2 weeks) YOU WILL WISH NO MORE :P

[@crazyirishman121]

That was an excellent video. You don’t waste time. You just give all the facts. It’s great.

[@rav3nx33]

Thanks for taking the time to put this out, just starting to take my inductor understanding higher; and this helped a lot. I will be building this, Ta!

[@martinhorner642]

Amazingly, I have been looking for exactly this video for quite a while now. Thank you.

[@jakobhalskov]

Very well explained and pleasant to watch :) Looking forward to follow your future projects!

[@chronobot2001]

Excellent video. I particularly liked the explanation on how to make an scr out of a npn and PNP transistor.

[@roboticus3647]

I recently stumbled across you channel. I'm happy to see another channel for technophiles! I got to this vid through your two-stage refrigerant project. I don't know anything about hvac technology, so it'll be interesting to see the progress for your LN generator.

[@djisydneyaustralia]

Very smart guy, thanks, your explanations gave me some insight as to why some components are used in unrelated circuits

[@coderhex1675]

I encounter your video and this is the most usefull project i have seen on the electronics channel.

[@AhmedSherif-mn8gu]

This is gonna be on my list of home-lab devices ! Subscribed !

[@jupiter909]

Fantastic insights into your builds, thanks!

[@Leezorc]

Brilliant. Very simple and elegant. Great Thanks for this project!

[@newburypi]

Nice video. Tagged it for the next time I expand my tool set. If anyone decides to go with arduino the could likely add some front end functions. One button test (no need to switch the tester on and to arm it) and a timer to disconnect the battery after a few minutes of idle time. Thanks again.

[@t1d100]

Super interesting and useful. The latch method is very clever. All very cool. Thank you for sharing.

[@BlondieSL]

Nice. What I really like, beside the circuit, is how nice the box printed out. It looks like you also print on clear glass (no texture). I do the same thing because on the cases I design, I like the ultra smooth faces rather than textured. Plus, my "textured" bed glass got all chewed up when I first got this crap printer. LOL The extruder dug right into it and slid across the surface, creating a trench. So that would mess up a textured-look face. The other side of this particular bed also has a different texture, but the glues and stuff I've used are so embedded into the texture that nothing I do removes it. Not even Isopropyl alcohol. LOL So yeah, smooth faces on cases are excellent. A suggestion for a future video would be in fact adding an Arduino to this, with the math and code. Personally, I use Nextion displays as they are a wondrous screen. You can code right in the display itself as well as create the most amazing "pages" with many objects on them. For Arduino to send (or receive) data to/from the display, is not load heavy at all. Plus, one does NOT need to use the horrible Nextion libraries!! Anyway, this might be a nice complete project that would look amazing and reduce switches to only the power switch. Yes, the Nextion has "soft buttons" that can be sent to Arduino to do whatever the physical buttons were doing.

[@weldit1251]

Just stumbled across your channel.... You're awesome bro. Good work!

[@alocin110]

Your vidoes and experiments are the best. Your knowledge about the electronics is so superior and the way you tackle the problems and find the issues are amazing. I love to watch your videos and it really a great learning channel. I subsribed to your channel and enjoy watch the clear ideas and implementations. Thank you for sharing. You are the best on YT>

[@awesomecronk7183]

For the electronic output, maybe "amp it then clamp it"? Boost the voltage so that small ones get captured, then clamp it with zeners so it still can't exceed the 5V limit.

[@liveen]

at this point you'd have to introduce something to compensate/filter noise as well though, which in itself means more control there as well. It's a good idea though, but I get that the creator wanted to keep things a bit simpler, even though it means less accuracy. Easier for us plebs to understand while also being something that won't be too complicated to maintain

[@isururanaweera376]

Thank you very much. Learned a lot of valuable information. I appreciate the effort put into explaining it so simply on video❤

[@arniesneider7163]

Love your channel, it's all the stuff I'm interested in:)

[@JohnUsp]

Awesome, please, continue doing videos like this one.

[@failvail2399]

Man I just found this channel, thank God

[@trevorhunt6083]

Excellent video.. concise and very informative.. thanks 👍

[@Mike__B]

Man I would have loved this when I was teaching an E&M lab class, we'd do one experiment with an RLC circuit and we'd power it with a square wave and try to find the inductance but regardless of what setup we'd use the inductance measured from the time constant decay would have discrepancies from the measured inductance based on the cycle frequency and could never figure out which one is "right" because the inductors have been in the department for years were theoretically "20mH" but without knowing trying to problem solve why I always got discrepancies was impossible.

[@marcosdalmeida6629]

Very nice video, especially for the ones like me that are starting :)) Very well explained, thanks a lot

[@papalevies]

I love these homemade lab equipment projects

[@TheBypasser]

Nice, although afaik there is a frequency shift due to the oscillations decaying in amplitude. I usually go with the "frequency-sweep" approach, that is sweeping the frequency on a series RLC while looking for a peak voltage across the resistor.

[@NeonblueIndustries]

Wow! Kick ass Bro! Thank you! Great videos!

[@CNCmachiningisfun]

Perhaps you could use the LC tank circuit as the phase shift element in a PLL, thereby automating the frequency extraction process.

[@Robothut]

You can make a Latch with the remaining Inverter gates as well, reducing the parts count of the design.

[@EJEuth]

Very interesting your device/tester. If possible, I would like to see a continuation, probably using an add-on in the output. I guess those clamping diodes you have mentioned would shift or dampen the oscillation too much, and most jellybean Op-Amp would not work. Instead, I imagine a simple stage of most signal BJT transistor (HFE > 100) could be used to decouple & perform the saturation/cut (probably 5~10x gain), while sending its output to a frequency meter function of a DMM, for instance.

[@SteveWard]

Keep in mind some frequency-related effects for core materials. For instance, the powdered iron core loss might be worse than the 1nF cap at ~500khz. Also, solid steel slug cores will have large eddy currents, especially at 10s of kHz. Maybe worth trying bigger capacitors to lower the testing freq? My quick and dirty method for measuring high power inductors, especially over wide range of current or flux density, is to apply a fixed voltage pulse to the inductor from a low impedance source, could be large electrolytic cap, with a mosfet and measure the current response during the pulse with a current transformer or shunt or hall-effect sensor. For instance, 5V applied to 1mH gives a current rise rate of V/L = di/dt or 5A per millisecond (keep the pulses short!).

[@HyperspacePirate]

Good advice, thanks. I did notice a slight discrepancy in inductance on the 1nF vs 48 nF caps with certain core materials, so i guess that explains it

[@denz37]

Can u made tutorial of it

[@lalogarcia6686]

Excellent video!!

[@ukaszlipski4663]

I love to learn things like this.

[@nf4x]

Your slow turn-on may be due to browning out your HC14 STs. They can source or sink 4mA, so at 5V you need like 1.3K Rg to keep the current in range. You might experiment with this a little to see if things improve. Otherwise another gain stage or gate-driver to allow a higher gate current will improve the situation / get you past the miller plateau faster.

[@Debraj1978]

One important point: The waveform that we observer on oscilloscope is the "damped" waveform. And damped waveform frequency is not same as the resonant frequency. Resonant frequency = wn = 1/sqrt(LC) Damped frequency = wd = wn*sqrt(1 - zeta^2) And zeta = (R/2)*sqrt(C/L) Overall, is the resistance of the inductor is significant, you can still calculate the L value by measuring the "R" separately and making correction to the damped waveform. That way, you will get better accuracy of the inductance measurement.

[@Debraj1978]

I am exactly making this for measuring the transformer inductance. There is a similar video from "Diodegonewild". He uses the setup for Q-factor measurement to find coil short on transformer.

[@wizrom3046]

I would have preferred a free running oscillator where the freq is based on the test inductor. Then a microcontroller could take a freq measurement over a long period like a couple of seconds, and then give you a quite accurate inductance reading on a little display.

[@peterschets1380]

Also add noise.

[@moustafaesber3690]

Very beautiful and important video

[@abdelghanisiradj3026]

Please can you make an electronic circuit that can calculate inductance without an oscilloscope

[@isaacmarkovitz7548]

You might want to try a Maxwell or Hay's Bridge. You will need a stable AC supply and an AC multimeter. It's probably also worth getting a decent capacitor.

[@vobinhthu5299]

This project is very good!

[@koalabanana1998]

very useful might try building one

[@anthonywilliams7052]

You could do a frequency sweep for an estimate, then resweep in the range where you saw resonance for more accuracy.

[@SC.243k]

Great work

[@Basetonic]

Nice video and I like the project! But SCRs are Silicon Controlled Rectifiers, not Relays.

[@barbasbandas6665]

Great video. How about continuing the arduino measuring thing? Maybe add an lcd screen too. It would be awesome and you could even try to sell a kit. Cheers!

[@Yorumcu63]

Great video

[@tonygomes6306]

THIS ONE IS GREAT... THANK YOU

[@roganthoerson1909]

khz still seem to be on the high side for measuring with an Arduino no ?

[@ebarbere]

Great channel.

[@mohbit3336]

Hey can you use it to measre inductance while transformer or inductor in circuit ?

[@Dragonrider616]

Loved the video, but what pins did you use on the schmidt trigger?

[@StormBurnX]

This makes me want to compare a transistor latch vs an optoisolator-based latch

[@xtevesousa]

There are inductor testers that detect shorted turns by the much higher damping, Could you do a test adding a shorted turn to see how much it effects the ressonance frequency?

[@edwarcastro4590]

I don't have a oscilloscope or arduino what can I do to check the value of the inductor?? I would appreciate your suggestion.

[@_tiredofidiocy_]

There is simpler method. Just apply step voltage to inductor for short period of time and measure speed of increasing of current in the beginning of transient dI/dt. The inductance will be calculated as Voltage / (dI/dt). Using this method you can also observe how the inductance decreases while current rises and dI/dt also increases (meaning current rises faster). You can measure saturation current which is important for power applications using this method.

[@Space_Reptile]

i would love a followup where you show off the "scopeless" readout method

[@csu9242]

Consult ebay and look for a Belco LCR bridge, the better one has an additional poti for defining the coil-Q, but it’s hard work to work with ..

[@niknam.]

many thanks buddy!!!

[@dandan-gf4jk]

Now do a capacitance meter! But for reliable pF measurement

[@proffesor4709]

6:51 if u have always connected the 680 ohm resistor and u connect another parralel resistor, doesnt the resisteance decrease?

[@lavy9740]

Hey man great project! I have a question about your toggle resistors. Since the 680 ohm is hardwired, when you toggle a different resistor wouldn't the resistance add to the 680 in parallel? For example, with the 220 switch flipped, the resistance of it paralleled with the 680 would be around 166 ohms. Does having a precise resistance value there not matter or am I missing something? Keep up the good work btw, I love analog electronics and I'm working towards my EE. Guys like you are a great inspiration and help me gain a better intuition for circuit design. Love.

[@koharaisevo3666]

Yes it would be added in parallel but the value of the resister isn't important it just change the amplitude of the oscillation and make it easier to measure, what you care about is the frequency of the oscillation.

[@taylorboultinghouse8296]

Yes, adding the other resistors in parallel with the 680 ohm resistor drops the overall resistance. This is because as the inductors get smaller their response to the smallest current (from 680 ohm resistance) decreases. The parallel resistors allow for the current to be increased and therefore increasing the amplitude of the frequency response. I hope this helps. I'm pursuing a BSEE as well. Cheers!

[@lctrstone8302]

That's what I noticed

[@AnalogDude_]

VERY Cool, but how about CD4053? or CD4066 or ADG419 and CD4044 S/R latch / CD4013 flip flop?

[@zim2493]

What is the suitable pulse duration time?

[@terrymay2970]

I enjoyed your project and plan to try to replicate it. Also liked the project box you used, could you provide a source, or at leat a brand neme?

[@gonzagaribotti9852]

"I built the circuit , but I have a problem. The pulse enters the gate of the MOSFET correctly, but when measuring at the anode of the MUR120G diode, the pulse is inverted. The MOSFET I used is a 3N80C with an RDS on of 4.8 ohms, instead of the RF540 which has an RDS on of 77 mohms

[@andrewdoherty737]

SCR - silicon controlled RECTIFIER

[@seanchallenge]

Awesome 😎

[@willyrivero470]

Great video, thanks! Would you be so kind to tell me where do I have to connect the oscilloscope probes?

[@HyperspacePirate]

I probe the anode side of the diode connected to the MOSFET

[@willyrivero470]

@@HyperspacePirate Thanks so much.

[@subramaniamchandrasekar1397]

Where can I buy that miniature push button on the test jig? Need to replace one in my transistor tester. Regards.

[@Dragonrider616]

They're really cheap on amazon. I got a set of something like 150 or so for about 10 dollars (approximately).

[@csu9242]

This resonance- and triggermode ist good for bigger inductors. But for amateurpurposes in micro and nanoranges only a well tested LCR Wheatstonebridge is fitting, but Nanohys are difficult to define and the potis of such a bridge are often scratching and to find the zeropoint is annoying. And bridges in multipurpose digitalmeters are failing for coils having to work up to 200 MHz for amateur applications, ie cristall oscillators. And to take the PLL or freerunning oscillator mode you need a perfect working microwave osci with a range over several octaves and a frequency counter synchronized by gps or dcf77. And then the Thomson formula has to be transformed and your sunday is over ..

[@Dc_tech386]

So you mean to tell me all ferrite core have it’s own operations frequency to get good power results

[@sayantanmaiti2513]

why u didn't used 555 for pulse generation??

[@mohbit3336]

Hey I looked up the IRF540N RDS-ON =40milloohms so the maximum current that the LC circuit can draw in while charging up the LC circuit to store energy in case of 10ohm resistor is 4.5/(10+0.04)=0.432amps I hope this is correct since I'm designing a similar circuit to your's thanks any way your design is so helpful I used the oscillator part but with lower Mosfet RDS-ON =2.5 IRLB ohm

[@xhunter3437]

Nice🔥

[@ZeekSuds]

Build any synthesizers? This type of thing would make some good analog wave forms

[@HyperspacePirate]

i've definitely thought about it. Not really a music guy though

you're a GOD

[@acmefixer1]

It should be possible to use some of the unused inverters to replace the two transistors. The 1N4148 diode has a breakdown voltage of 75V *minimum*; my guess is that the actual value is above 100 volts. Also the diode in the MOSFET should protect the device. Thanks for the interesting project. My one drawback is that I don't have a 'scope that gives measurement of waveforms so I wouldn't be able to use this project.

[@shauni_jade]

you still can use the time divisions to eyeball the time between peaks and calculate the frequency as 1/T

[@acmefixer1]

@@shauni_jade I've measured many inductors by paralleling a capacitor and finding the resonant frequency then calculating the inductance. It's simpler than measuring pulses, and with a signal generator or receiver it's more accurate.

[@boonedockjourneyman7979]

Very good.

[@tnt-hv6qw]

very cool thank you

[@neail5466]

Why just don't use microcontroller triggering? Don't get me wrong it is always better to know the way, still a mc can reduce the bulk. Are there any inherent limitations I am missing out?

[@charanvemula2623]

Sir,can you make a video that represents how electricity is produced from tidel weaves

[@ethanmarlatt797]

Video has been up for awhile, but thought I would ask why you used the Schmitt Trigger output to drive a MOSFET instead of just using the pulse that it generated?

[@HyperspacePirate]

making sure there's no repeat triggerings from switch bounce

[@ethanmarlatt797]

@@HyperspacePirate I was under the impression that the transistor latch circuit was meant to eliminate switch bounce, is the MOSFET just an extra precaution?

[@HyperspacePirate]

@@ethanmarlatt797 theoretically the peak current could be really high so i didn't want that going through the small switch or tiny BJTs

[@ethanmarlatt797]

@@HyperspacePirate Ah okay, thanks for replying! Looking forward to next update in your cryocooler series!

[@jamescollier3]

nice!!

[@Aboudy1989]

I wish you would try to replicate don smith resonant transformer and make some useful energy out of resonating transformer

[@patrickbennett4043]

Are you planning to make a flyback transformer?

[@RicoElectrico]

Why not use CD4093 as an RS latch? This would simplify stuff considerably.

[@PureCoKayne]

Sir is there any chance you could use another music backing track? It's the same one used in Kerbal Space Program when you're in the build editor. I'm purely asking because hearing it makes me impatiently look away from your videos at my main monitor CONSTANTLY thinking I've left the game open. Fair enough if not but oboy edit : wait this video's is different! This one's okay! To be specific, it's the backing track at 9:20 of your 5000V Power supply, or the one played at the start of the magnetic remote control video.

[@JosePerez-il5qy]

Great video. Thank you for that. Can you do a similar circuit, but instead, to detect the most efficient frequency to be used in an unknown ferrite core? Since there are different composites for ferrite cores, not knowing the specifics will not make it easy to choose the frequency to be used in a switching application. You would need to try from several tens of kilohertz up to maybe 1 MHz. A circuit to determine the most efficient frequency will certainly be VERY handy.

[@liveen]

Could have something with software, maybe? Like a program controlling a mosfet, measuring the ringing and stability, and doing a sweep across a large frequency range automatically? With the speed of electrons and components in circuits, this could be something only limited by the clock speed of the processor of the program

[@JosePerez-il5qy]

​@@liveen Hello LiVeen. Thank you for your suggestion. Yes, using a microcontroller is a sure thing and as you said, sweeping a specific frequency range. About the uProcessor clock, I use a PIC microcontroller using from 20 to 40 Mhz and they cover the range very well. The measuring part is the one that I am asking for. You know, how to determine the best frequency out of the measures over the frequency sweep. Since I was thinking about custom switching power supplies, I had the idea to measure the combination of voltage and current produced by different frequencies but I was asking to see if there is any better idea around for determining the best frequency for a specific ferrite core.

[@liveen]

​@@JosePerez-il5qy well from what I remember the resonant frequency is a big deal in ferrite efficiency. I can imagine that if you manage to find the resonant frequency at a low frequency, you could for example be safe in using an exponent of that frequency (like 10 times higher for example) while keeping the correct ringing, just at a higher rate, kinda like octaves in music. A C1 and a C2 are the same notes, just with exponents on the frequency, achieving the same general resonance between them. So the same is probably true with inductance. If so, you could probably figure out what qualifies as the best resonant frequency, what things are measured, then implement that with a low frequency range (so its easier for a simple board to pick up through noise, and then for the actual real-world example, you multiply the frequency and there ya go. Obviously, since this would be low frequency, it would get you to the general area of where the resonant frequency is, when used irl, but it would at least be a start. BUT: I dont really know exactly what methods are used to figure out the right frequencies, so I wouldn't know what things to measure and what filters etc are necessary

[@sayedroni7035]

Thanks

[@swp466]

Nice video, except the R in SCR stands for rectifier, not relay...

[@alexloktionoff6833]

Actually, you could make a latch /*actually RS trigger*/ from two spare Schmitt triggers elements and resistors! The transistors could be better used in MOSFET gate driver to make ON/OFF edges sharper and not overload Schmitt trigger.

[@cosmiccashcosmiccash8358]

Change the world!

[@joejane9977]

great fun

[@Tr0nism]

6.9 nice!

[@gallium-gonzollium]

7:35 “6.9x higher to be exact” *nice*

[@indianinventionboy]

#nice_video

[@EasyOne]

nice

[@mohinderkaur6671]

Nice build. Why not add a microprocessor to automate it and directly display the inductance? And Arduino or PIC should be ok and 20x2 or 16x2 lcd

[@alt3241]

Or use bistable latch controlled by comparator for oscillator the frequency driving a switch that on / off controls a constant current source to a capacitor resister filter for a linear voltage output . 15 transistors or less .