I love tool tricks like this, please do more.

@ipr724

2 жыл бұрын

Next year.

@Boffin55

2 жыл бұрын

Dave does a great tool trick like this once a year

@colingale

2 жыл бұрын

@@Boffin55 yup, i was so tired when i made this comment I "Should" have checked the date first then made my comment. Well played Dave, well played.

@josephlunderville3195

2 жыл бұрын

Almost got me, I'm just on the other side of the date line and queued it up on the 31st...

@ipr724

2 жыл бұрын

@@josephlunderville3195 Got it on 31st too.

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

@Volcanoelectricity

Ай бұрын

Problem is the accuracy is so piss poor you could never really properly calibrate it. That's a big problem if anyone ever wanted to use this meter at work, where equipment needs to be regularly and fully calibrated.

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.

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). 👍

@tejonBiker

2 жыл бұрын

If you read about the saturation of magnetic cores in the forums on internet you will get the same conclusions, the values on inductors are more fuzzy than R or C.

@envisionelectronics

2 жыл бұрын

April fools.

@tejonBiker

2 жыл бұрын

@@envisionelectronics It's a shame that here in Mexico this video shows at 31 of March, hahahaha, well, this video give me some ideas.

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

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

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

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

April fool to you too. The capacitor measurement uses a relaxation oscillator and measures the frequency that is proportional 1/C. I.e. Smaller C gives higher frequency. The relaxation oscillator can be as simple as a built in Schmitt trigger inverter and the dmm measures the period for a direct conversion to capacitance. Putting any inductor in place of the capacitor with a dmm set to capacitance is just a short circuit. The relaxation oscillator just won't oscillate. It was good to see the 10G ohm resistor I sent to you in mailbag in use too. Great joke video.

@denny9931

2 жыл бұрын

He practically got me on this one until i read your comment and started thinking about it in another way.

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

@godsinbox

Жыл бұрын

this video hasnt aged well. the date has been lost and its in the general pool of misinformation on the web. is this what we want for future generations?

@mcpoogle9058

Жыл бұрын

@@godsinbox what do you mean

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

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

@EEVblog

2 жыл бұрын

A really old school trick.

@miklov

2 жыл бұрын

Had no idea about that. Mine will show internal temperature with no probe connected instead.

@ryanb8302

2 жыл бұрын

Why would you want the internal temperature of your multimeter?

@kissingfrogs

2 жыл бұрын

@@ryanb8302 Cause it would be closely related to ambient room temperature if you wanted to measure that. I often do.

@ryanb8302

2 жыл бұрын

@@kissingfrogs I see

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

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

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.

@Galileocrafter

2 жыл бұрын

I've soldered and programmed a kit with the same principle for my programming class at uni. Pretty neat!

@mrstijntje

2 жыл бұрын

Measuring at 1 times RC would yield a better accuracy. The curve is steeper so every error in reference voltage amounts to a smaller error in calculated capacitance. This acutually works with inductors too.

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.

@teresacodilan7809

2 жыл бұрын

At least one electrical engineer has read your comment.

Absolute champion!

that was *way* more complicated than i thought it was going to be

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!

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!

Pretty neat trick, thanks Dave!

@EEVblog, hats off. You are really good at this 😉

Nice measurements tools.

I love this stuff Dave, cheers. It'd be great if you could do a vid series on basic field service noob tips for CAN, voltage drops, traps for young players. I know this has been covered before, back in the day but there's a lot of young blokes on the tools that can benefit from your knowledge. Speaking from a guy who's leveled up from you're years of content. Love your work, always a big thumbs up,!!! (Edit: read what I typed 😜)

Great video Dave, Your tool tips are great 👍. This would have been very useful and save lots of money. I'm definitely waiting for next video.... I subscribe this channel 10 years back for these kind of videos. Not mail bag or fundamental Fridays

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

@BrianG61UK

2 жыл бұрын

That's what I've done in the past. Make parallel tuned circuit and use a little negative dynamic resistance circuit to make it oscillate and then measure the frequency.

This is actually very very useful! I always wanted an LCR meter but couldn’t really justify the expense

It's interesting that for some of the meters the frequency changed with the capacitance. I wonder if those use the capacitor in an oscillator and then measure the resulting frequency to calculate the capacitance value (as opposed to measuring the time it takes to charge the capacitor which is how I had assumed it measured them).

That was a really good trick! I never would have figured that out myself.

I love how the 121GW was actually almost bang-on with the 150mH inductor - it has shown 161mH, which you have commented as "not too far off", but then the LCR meter at 7:46 showed almost exactly the same, so 121GW was not off that much :D. It has more error for smaller inductors though.

Been waiting all year for this video.

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

This is a must test when I get home.

didnt think of that, thats awesome

Wow! I was always wondering what could be the inductance of the high voltage lines on those poles near my house. Now I can climb right up and find out! brb...

Awesome sauce.

Wow great episode 👏 👌 Thank you very much 💝

Thanks! I'll give this a try

@inspectormills3290

2 жыл бұрын

Well, I tried it with my Crenova multimeter and the capacitance displayed was always OL.

Thanks dave. This is helpful.

Not getting a result with an old Fluke 83 original! By the manuals I can find all the old Fluke 80's work by charging with a fixed current and testing voltage -- updating only once a second -- rather than testing at frequency. They walk you through though how to estimate large capacitances quick by using the ohm-meter though since it's also a constant current source, so I still got a useful tool added to my belt today!

fantastic video, works a treat! (I have the 87V though so it was pretty much guaranteed to work)

@EEVblog

2 жыл бұрын

What accuracy did you get?

@Zardox-The-Heretic-Slayer

2 жыл бұрын

@@EEVblog it was pretty much the same as yours with a hair of a difference either way - I have the same inductor test box as you so I just tried it with that

@EEVblog

2 жыл бұрын

@@Zardox-The-Heretic-Slayer Nice! It's a handy box. Had a bit of a hard time with the SMD inductor though, tricky to probe those little suckers.

@Zardox-The-Heretic-Slayer

2 жыл бұрын

@@EEVblog I use an offcut of an old gold plated PCB (from old RAM sticks so the pitch is perfect for general components) to measure SMD stuff like that. using 4-wire measurement on that seems to be pretty accurate; good enough for England!

You got a lot of them this year, Dave! haha... Good on ya.

Before I had sufficient money to buy an impedence analyser, I did my own pen and paper calculations with a cheap oscilloscope and a kenwood audio spectrum generator. Dave makes the point that you need to understand basic science before you take the next leap. Tedious - maybe. A whole lotta fun ? - definitely !

Cool trick thanks, I sometimes forget about it but those ~$15 component testers also do a decent job at testing inductors and they can test the lower values too, I can't verify its accuracy, but now I could compare it to my meter at least.

@greywolf271

2 жыл бұрын

You know you can make your own measurement test set with better accuracy ? Just use a kelvin bridge.

Fascinating

I have a set of yumcha LCR tweezers it's surprisingly accurate

Here I was about to build a variable frequency signal generator... This is much easier. Thanks!

Fun video. Oh! Dave your finger hurts, wish you recover soon.

I love it!, now I'm going to have to try it! 🙂

nice tip.

Very cool. Makes me wonder if it would be advantageous/convenient to have multimeters perform a mathematical operation (in real time) on a measurement. Basically, integrating the calculator into the device.

nice tip. thanks

Very interesting trick.

Very useful trick.. Thank you

Nice trick for sure 😊

great tip.Thnaks Dave. Also, quick question as i might have missed it... can this be used in (unpowered) circuit?

With these typical values I just use my audio interface. Plenty of software programs that are able or function as a RLC meter. I have seen also smartphone apps.

Actually ive got a brand new electric shower i fitted but it let out the majic smoke after 1st power up. I found 2 inline inductors on the power to the control pcb. Aqualisa Lumi 10.5KW, a pretty expensive shower. Its a touch sensitive front panel on/off. So im wondering if the inductors are really needed? As i linked them both out, but havent tested it yet. I think i blew it when i had power going to shower when i connected molex connector for panel pcb. Which blew the inductors. I wouldnt mind getting it working

Neet. I'm trying to tune an electronic speed controller, this would be great for a close enough measurement of phase inductance.... a shame my meter doesn't even do capacitance. :(

*Golf clap* Bravo Sir, Bravo.

This got burried beyond all recognition. Thanks for all your efforts. Being australian, makes you come a couple hours to early for such jokes.

Probably not something I'll need to use in my tool set, but thanks for sharing! On the subject of metres I was in the market for an upgrade the last few days and really wanted the 121gw but there's not really been a comprehensive review on the final build with latest firmware? I ended up going for the bm786 instead but kind of kicking myself now after watching this and seeing you pull the 121 out 🤣

@EEVblog

2 жыл бұрын

The 786 is a great meter, don't worry about it.

Wonder how good this will be to find those inductors with a short. Must go grab a meter, grab inductor and a wire to make a shorted turn around the core, and see how it changes.

Hey Dave great video as always. I believe the keysight (old agilent) LCR meter is somewhat affordable. roughly $450 if i remember correctly. Id love to see a video on conducting a loop impedance check or rotor influence check on a brushless motor.

@EEVblog

2 жыл бұрын

You can get the same functionality for under $100 these days though.

@jamesttol

2 жыл бұрын

@@EEVblog oh I agree completely. I was just pointing out the value of the lcr meter you used. But yeah, rotor influence check please :)

I don't think that's supposed to be a triangle wave at 2:23 with the fluke. Looks more like the charge/discharge cycle of a cap subjected to a square wave. I think that it's basically using a DC measure of capacitance using time constants.

What typical frequency is used for capacitor and inductor 'printed' value references? From the video it sounds like 1Khz.

I'm sort of confused because what I think is happening is that some DMMs dont measure impedance, but they measure the time constant repeatedly on each update. Hence the frequency sort of increases with the capacitance values and ranges I might be wrong tho Atleast when I did this on my meter it didn't even measure the inductor

Multimeters which measure capacitance are a fairly newfangled thing for me I was assuming it was slightly more clever than just seeing how long it took to charge 👍

I'm more impressed by that 10 GOhm resistor! I didn't know they made such high resistor values. I remember one of my professors scoff at the idea of 1 GOhm!

@rocketman221projects

2 жыл бұрын

Mouser has 10 TΩ resistors in stock, they're not cheap though.

@ElTwOJaY

2 жыл бұрын

@@rocketman221projects What would the purpose be of such large resistors?

@rocketman221projects

2 жыл бұрын

@@ElTwOJaY The one that Mouser has is rated for 30 KV, so it's probably intended for high voltage measurement. It would only have a 3 nA load at 30 KV.

@uwezimmermann5427

2 жыл бұрын

@@ElTwOJaY they can be used in transimpedance amplifier configurations to measure very small currents (fA - nA). I have some resistors which are contained in quartz tubes and labelled with powers of ten It literally says 10¹² Ω on the part.

@ElTwOJaY

2 жыл бұрын

@@uwezimmermann5427 hmm interesting, I am not much of an RF guy.

Oh Dave! Excellent tip on 1st of April! Who knew? DMMs on steroids!!

Well that's cool, unfortunately my Fluke 117 isn't good at it at all. It can't even be used on larger ones. The only one I got read reliably was a 100mH coil. I looked at it at the scope and it sends the pulse super random. Had to capture it, and it's a 120mV pulse, lasting 1.2ms, whenever it wants to. Surprisingly though, it reads capacitance great, down to the 10nF level.

man... forget about the "one day difference" in Mexico this day comes in December!

Yes! Protek 505/506 can do it. :-)

Neato!

Great video as always! Anyone knows what is that switchable L-C-R blue box that says OpenSource on the corner?

Hi Dave, did you catch wind of the Fluke 87 recall? I got an email from Amazon saying there's a recall of the one I bought in 2021 and to test and ship it back to Fluke at their expense.

@EEVblog

2 жыл бұрын

I heard something about the jacks? Don't know the details.

Hmm, my meter keeps reading 0.104nF. Must be that time of year to replace the battery!

I have 2 very old multimeters (over 20 years) and one has no capacitance measure and the other has slots to measure both on through hole components.

Dave , or if someone knows , more info on the " open source " board used in video ? Thanks again

I got to the 5:40 mark before it hit me. Damnit!

Great 👍

Dave, they don't output a triangle wave but rather a pulse. The priciple is called a charge balance. It's what you likely learned in high school about capacitors: Switch on a voltage in a RC circuit and you get an exponential charging function. Do a little bit of maths and you can calculate the C, provided you knew the R. Some of these do it exactly like that and this is where you don't get the triangle wave and others use a constant current source which results in the triangle. The idea behind the triangle wave is that you can easily calculate the slope by doing a linear fit which then leads to easy calculation of the C.

@EEVblog

2 жыл бұрын

Yeah, well, that's just, like, your opinion, man.

@eevblog: Confusor gave result of 161.7 uH, The RCL 161.23 I think more of "bang on"

Shouldn't the capacitive reactance be negative? Maybe that could explain some effects.

Thats basically what a lot of multimeters with inductance built in do internally, with some calibration....

What a useful impedance box. Was it a mailbag item maybe?

@EEVblog

2 жыл бұрын

Yes, mailbag some time back.

Good one; I'd have to measure my multimeter's cap-meter frequency some time

I still don't understand inductive loads. A good idea for a video would be a summary of the best free online electrical engineering courses and channels. I love the content from Big Clive, and Fran and you, but I don't have the understanding to properly appreciate them.

@vgamesx1

2 жыл бұрын

The simplified answer is an inductor is a lot like a capacitor, just replace voltage with current and capacitance with magnetic fields, you put current though it, it charges up a magnetic field which restricts current flow until it's full then it becomes just a wire, afterwards it does the opposite when current flow stops feeding its charge, thus it smooths out changes in current, similar to how a capacitor smooths changes in voltage.

Why do most multimeters don't include an inductance measuring function? It would be very useful

Youre hilarious 😂😂 thx for the vid.

Can you measure shorten rotor windings?

Isn't the Reactance formula at 3:14 only valid for sine voltage?

good one :D

Do other countries also use lower case omega ( ω ) as short for 2 pi f?

@extremgear

2 жыл бұрын

yes we do in France , at least at school

@uwezimmermann5427

2 жыл бұрын

yes, it is common use in electronics and electrical engineering - both in Europe and the US. We teach it here in Sweden and I know it from German and American text books as well.

Please note that it is not always easier to probe on the bottom.

This video left me somewhat confused. Are you suggesting the capacitance mode on a multimeter will always read the inverse of inductance? How does it depend on the test frequency?

@EEVblog

2 жыл бұрын

It should do, neat trick huh. Give it a try.

@wthornton7346

2 жыл бұрын

Dave answered that in the video. You need to consider the equations for impedance, they show the relationship of frequency to capacitance and inductance.

@erikdenhouter

2 жыл бұрын

Don't forget to convert the value on the display to mF first, and then the inverse answer will be in mH.

@frosty129

2 жыл бұрын

@@EEVblog thanks, I’ll try this

Hi Dave, Great video, never thought of that. Your variable L C R box on the left looks useful and well made, would you post some details please? Thanks ct1igu

@oida97

2 жыл бұрын

It's from KainkaLabs: kzread.info/dash/bejne/nKappdKnc8i4hcY.html

@ct1igu401

2 жыл бұрын

@@oida97 Thanks

Hey Dave, very interesting video. If you know a trick, could you make a short video about measuring extremely small inductors as well ? I'm trying to reverse engineer the components between a balun and a printed antenna on a small 2.4GHz transmitter and I have no Idea on how to measure them. Many Thanks !

@EEVblog

2 жыл бұрын

You'll need a proper LCR meter at the very least and a decent probing setup for them.

@ammocraft

2 жыл бұрын

@@EEVblog A review of LCR meters would be great at some point. The cheap ones seem to struggle with low value inductors, such as used in antenna loading coils and tuned circuits for HF.

@anschflck8049

2 жыл бұрын

@@EEVblog Thanks for the feedback. I have a DER EE DE5000 model LCR meter, but I only get resistance values when checking the components. I cross compared those resistances with values from component datasheets and it's probably a 4.7nH component, but it's not certain. Some datasheets were disagreeing and it just feels unfulfilling to not be able to truly measure.

@Artichoke4Head

2 жыл бұрын

@@anschflck8049 if you post on eevblog forum you get best advice from expert with experience on the item and some times you realize someone else actually solve that issue already and happy to share the results

@peterpv0001

2 жыл бұрын

The components in such a 2.4 GHz balun will have quite small values as their impedances will be in the 50 ohms (at 2.4 GHz) range, so caps between 0.5 pF to 30 pF and inductors of a few nH would be what you might find. To measure those you generally need quite expensive equipment. Also at 2.5 GHz you will need to use components that are specified at such a high frequency. What an RF engineer might do to reverse engineer this circuit is to measure the impedance at the antenna (without the antenna) using a VNA. Store the plot (or Smith chart) of that impedance. Then desolder a component and replace it with a known value, keep replacing until you get a similar curve back. Do that for all components.

No April’s fool? That looks real.

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