#135

This video discusses how to measure the ESR (equivalent series resistance) of a capacitor using an oscilloscope and function generator. All of the capacitors tested in this video were 220uF electrolytic caps. In reality, the resistance in the plates of a dried out electrolytic capacitor can't be modeled as a simple series resistor, but for the purposes of identifying good from bad, this simplification works fine. In the video, I show the ESR meter that I made in 2006. The video for that is here:
• #5: My ESR Meter proje...
A copy of the video notes can be found here:
www.qsl.net/w/w2aew//youtube/M...

[@packratswhatif.3990]

Alan, you are the kind of person that SHOULD be teaching in schools ! 👍

[@larrybud]

He's too good for schools.

[@rodcastler1177]

I appreciate Alan's kindness of publishing the notes as well. I keep a copy near the scope to refresh my memory whenever I use this method to test my caps.

[@kc2sho]

I became interested in testing ESR in capacitors after a string of failures a little over a year ago. We have a lot of test gear around here but at the time none of the high end stuff had an ESR specific capability so I was using this method. A younger engineer was not convinced this method was plausible. We agreed to move on and not argue over this. Recently I was able to obtain a nice new fancy Ketsight E4980AL LCR meter that can measure ESR. Today I'm doing some testing with new capacitors and seeing very close numbers with both methods!

[@Mythricia1988]

Once again, w2aew saves the day. I knew it should be possible to do this, but I had forgotten the exact procedure. This brought me back up to speed. Thanks! I even had my own HP 15C at the ready... It may or may not be your fault that I own one. Or should I say, it's thanks to you that I own one. Such a great little RPN calculator to keep on my bench, doesn't distract from the task at hand like my HP Prime does with all it's (admittedly impressive) wizardry.

[@thejosh777]

So glad I’ve recently found this channel. I have binge watched a ton of these videos the past few days. A ton of amazing knowledge on a variety of electronics subjects. Very much appreciate the work you put in on these videos.

[@w2aew]

Thank you Josh - glad to hear that you have found my content useful. Did you check out the video index PDF file on the main channel page? (lower right corner of the banner graphic).

[@thejosh777]

w2aew Thanks for pointing that out. Extremely handy having a “TV Guide” so I can what I want to watch next:). Very cool!

[@krnlg]

Thanks for this - not only has this saved me money I'd have spent on an ESR meter, its also taught me how the measurement actually works! Very nice and informative video :)

[@IdeasMan101]

A great ESR capacitor testing video thank you. It is always nice to see both practical situations with a bit of theory and real life comparisons.

[@godfreydesilva5222]

Indeed a very helpful lesson.

[@octavmandru9219]

I am still in the process of digging and enjoying the videos that I missed. Great teaching, Alan

[@wa9kzy326]

Once again, you have scored a home run with this innovative approach to measuring ESR !!!!!!!

[@jonsanford0]

The best gets better. I didn't think your method of presentation needed improvement. But you have done it.

[@stephaniewilley2224]

You have just demystified ESR for me. Seeing it on the scope explains it all for me. Thank you very much.

[@BigMaxTube]

I suggest you are one of the best KZbin presenters, many thanks for sharing your work !

[@automaster209]

Thank you. I am not sure if anyone has told you but you make this extremely easy to learn and practice in application.

[@radhikagupta7023]

There are several factors in studying circuits. One resource I discovered that succeeds in merging these is the Gregs Electro Blog (google it if you're interested) definately the most useful info i've seen. Check out this awesome site.

[@peterlamont647]

Ya, I was already thinking about building a function generator with a 555 timer while watching the beginning :P

[@realpower9ir]

Yes and agree. Due all respects Hat tip for each moment of your teaching, Sir.

[@6l6tubeamp71]

That was awesome! I'm an older ME, but if we had done cool projects like this in the required EE 101 class I might have reconsidered...maybe. Love the calm and methodical step by step presentation and actual demo! I subscribed.

[@julio.alvess]

Hello Alan! I am julio from Brazil. recentily I bought an analog oscilloscope and I am loving your channel because i 've been learning alot from you...

[@gerhardgroenewald6560]

Wish i found your channel earlier in life, it could have saved me alot of headache. But still learning from you. Thankyou

[@realpower9ir]

As an electronic newbie. With many respects I appreciate you for teaching and sharing your most valuable time and good knowledge with me and the others as well. Many regards

[@BobMellor1954]

Thanks Alan, as usual an interesting video; have been using a Peak ESR70 over the last few years, but never considered using scope and signal generator. Always look out for your video's, they are always interesting and well put over. Regards Bob

[@Daveyk021]

Wow, great explanation on how to measure ESR and what ESR is.

[@knunne1]

Thank you for a very good video on the process of checking caps and calculating ESR values. I learned a lot!

[@emptech]

Your demonstration reminds me as a young kid reading in a physics book about the internal resistance of a cell (battery). I could not imagine that a cell actually had a resistor inside, of course, growing up and getting educated, I found that you treat the cell as a perfect cell, has an infinite current capability but has an imaginary resistor in series. A practical method of measuring the internal resistance was to measure the voltage open circuit, then apply a load across the cell until the voltage went to 50 percent, then you measured the resistance of the load. It's all so simple once you think about it. Good job! Jim BTW, I've owned various instruments that can measure capacitors, but for years, you never heard about ESR. I purchased a good quality B&K that does all that, you can change the frequency, voltage, etc, a lot different than determining the values based on the capacitive reactance.

[@BillCodyColorado]

Great job. Your explanations are clear, logical and engaging. Thank you for sharing your extensive knowledge.

[@anks888]

Good video Alan. Ive been using this method in circuit for many years. Its a good test to make a "its good" versus "its bad" decision. Never really considered working out the actual ESR as with your meter a bad cap it obvious.

[@Panhead49EL]

Instead of buying an ESR meter I think it makes more sense to save for an oscilloscope and a function generator. Thank you for all your videos.

[@w2aew]

I've got two videos on ESR meters you can build. Here is a fun design that uses only 5 transistors: m.kzbin.info/www/bejne/aZfMho2QoduYiZI And a design that I built many years ago: m.kzbin.info/www/bejne/mJ68cpqXqZKmhbM

[@DAVET38]

Another informative and useful video. Keep up the good work. Thanks Alan

[@tomsmith3045]

This is great! Excellent tutorial. If you aren't sure of your generators output resistance, or if you want to check it, you can use a low inductance resistor in place of the capacitor, and measure it. Then you can confirm that the 50 ohm or whatever output resistance, as well as your leads, are really what you think they are.

[@automaster209]

I would like to thank you for these awesome videos. Being in the automotive field I was really good with the electronics on the automobile but with these videos and notes it is helping me learn quite a bit of electronics that will also assist in helping me pass my Amateur Extra license test, as well as better understanding my little electronic projects I have been putting together.

[@w2aew]

Very glad to hear that my videos have helped you. Congratulations on the Extra!

[@FRRRRAAANNK]

Never too old to learn something new. Thanks so much.

[@dave-d]

My favorite lecturer! Always enjoy class time here.

[@xenia5101]

Thanks for showing a seldom used function of the O scope. Great review of the scope interpretations.

[@tonythediyer8537]

Nice tutorial, I am now checking ESR on my caps. I also plugged you on Eevblog for your Op amp tutorial and your PLL tutorial, excellent (under a different user name). I just seem to understand your examples and explanations better than others. It is almost like many others are just showing off what they know, but you actually are explaining in a way that even I can understand. Thanks!

[@phatman808]

Thank you for putting that into words. w2aew and Dave from EEVBlog both really seem interested in TEACHING people and making otherwise super complicated EE concepts accessible. If these guys were professors in my school maybe I'd have gone the EE route instead of CS!

[@The_Absurdistt]

Hands down, best vid on youtube about this subject. Thanks.

[@philippe5394]

Hello Alan, I suppose both voltage measured are Vpp. I made the exercise with my scope Rigol DS2072A and the JDS6600 generator, with success, on a good cap and also on two bad caps picked out of a PC Psu. Many thanks Alan, this is a clear demonstration.

[@warywolfen]

Here's a tip. Electrolytic caps often deteriorate over time, if they aren't used. This is because the oxide dialectric tends to deteriorate if they go for an extended period without receiving a polarizing voltage. The result is a leaky capacitor. To rejuvenate it, hook it up to a P.S, set for a low voltage. Then put a ma meter in series, to monitor the current, and also, to make sure it doesn't go too high. As the current drops, continually increase the voltage, until it's at its rated working voltage.

[@GeorgeGeorge-xj2bc]

Electrolytic capacitors in electronic repairs are the most replaceable components and are bought in hundreds in every lab.Only from a small UPS and a dead 10 inch portable TV i replaced about 30 capacitors.Even those who measured as good are replaced also with the defect ones."Capacitor rejuvenation" is Bs.

[@csimet]

Stumbled across this video... and I really appreciate the tip on how to use a scope to test for ESR. Tx!

[@CharlieTechie]

Very good explanation, thank you for your work on the video.

[@OIE82]

Very good video from way back. I don't know, but there is something about an analog meter that is so satisfying to use. I am gonna have to check out that ESR meter video and build me one.

[@w2aew]

Also take a look at the "5-transistor ESR meter" project.

[@swebphone]

Thank you for this video and your explanation. That was realy interesting for me. I've tried it today and it was realy easy.

[@Vitaliuz]

Fascinating info. And *how good* it was explained!

[@bloodedge]

Thanks you very much, i did the request for this video :) I did get a tek 465b this week, am going to have lots of fun now :D

[@hugofrisk1889]

This was exactly what I needed! Thank you! Excellent video

[@tonycross8101]

Great explanation, I will certainly use this method in the future when testing my caps..

[@321reh]

Thank You Alan for This Awesome Video!!! I Never Knew I Have all the equipment to do a ESR check. And all I have to do is use my handy dandy Voltage Divider Rule To compute the ESR value!! Nothing New here,,Another A+++++++ Video..You Should have taught me in College!!!!

[@bertondroid]

Well done... did not need to see the end because of the good explaination 👍

[@Amir-kz6yq]

Great video Mr Wolke

[@marinhopduarte]

Another great video whith another great explanation. Always inspiring.

[@yezhao26]

Nice method! I tried it and it works well when the frequency range is between 10kHz and 100kHz. The results match with the LTspice simulation, which helps me understand the theory. Thank you!

[@kevingray707]

Excellent video. Please keep your videos coming. They are so helpful. Would be nice to see how to actually find bad caps in a circuit.

[@w2aew]

Unfortunately there really isn't a bulletproof way to test for bad chips in-circuit. This is because other devices and circuitry in parallel with the capacitor under test can give you a false 'good' reading.

[@jospicant]

Hi. I know an instrument call Capacheck wich is possible to measure bad capacitors on board without remove it. It cost about 100 Euros. Best Regards

[@w2aew]

Jose Pico All instruments like this can be affected the same way - other devices on the board can mask a bad cap. In general - a bad ESR reading will usually be reliable, but a good ESR reading could still show up when testing a bad cap in-circuit, due to other circuit components.

[@KD0RC]

Excellent as always Alan - Thanks!

[@harrypehkonen]

Ha ha! "Oscillator!" :D ... That's what he said at the very end of the video. Sounded like "I'll see you later!"

[@yosmanyhernandezsanchez9760]

Pretty well explained, thanks a lot for your effort sharing your knowledge. 🎖

[@larryrenaud7462]

I have enjoyed everyone of your videos. Great Job. I have learned sonmething from everyone of them. 73 Larry

[@ozzymandius666]

Excellent. This channel is a fount of wisdom. Now all I need to do is be able to measure the inductance of my cheap function generator. I guess I could hook it up to a nanovna, on its input only side.

[@suppersreadysuppers1822]

Very good video explaining ESR

[@YanickT]

Thank you for this video. I knew this but i had never see it on scope. Realy interesting :)

[@damiandomanski1845]

*BEST explanation on YT ! THANK YOU !*

[@garygranato9164]

100% agree, you beat me to it by 5 years !!!

[@complex_variation]

you are so awesome !!!! thanks for the videos im a EE student I love lerning from you!!!

[@w2aew]

Good luck with your studies! Be sure to share my channel with your fellow students, and your professors!

[@ernestb.2377]

Nice video. Thanks for that. It is interesting to see the average voltage measured when scope is DC coupled. I was a bit confused first, as I have first expected zero volt. So for AC it is "short circuit" but for DC it is an "open circuit", or very high impedance, that averages the square wave value. I needed to "re-think" it. 😊

[@yorkeR177]

Wow, these videos are really well done.

[@clytle374]

Great channel, tomtektest mentioned one of your videos. Subscribed!

[@AntiqueRadioandTV]

Very interesting. I have all the equipment here to try that. Thanks! 73s Tom

[@glenwoofit]

Really interesting video. I'm sure I will use that test... Thanks.

[@ka2cqj]

Alan, an informative video.

[@hqiu6828]

V (1+50/R) = 1 when 1 volt square wave apply to 50 ohm resistor, chained with the capacitor. Good explanation of ESR!

[@phoenixcrp]

I came across this video and, as all your other stuff, it is just amazing. Thanks for that. I have used a similar setting to try and measure a battery's series resistance. I have used fully charged and fully discharged cordless drill batteries for this exercise. To my surprise I have not blown up my function generator. The traces in the oscilloscope are quite similar to those when you test a good and a bad capacitor, respectively. I believe I can calculate the battery's internal resistance and from the plots I think I can get a reasonable good idea of battery SOH or even it's SOC if you want to leave your imagination free. I may be imagining things but could you please give us your opinion about this topic?

[@helipilot727]

Great video! I have an oscilloscope and function generator but couldn't spring for an ESR meter... now I don't need to!

[@mizyeh]

Thanks a lot , learn a new thing from this video :D

[@gearstil]

Very informative video, Thank you!

[@iu6asc]

Very good i love your videos !

[@automaster209]

This is an excellent video.

[@kenlogsdon7095]

Outstanding! Thank you!

[@ohmedarick1]

Thank you for the video It was very helpful!!

[@kinddata]

Thank for the video. I wonder if you could try this on a battery to get internal resistance. Battery chemicals can go bad too.

[@dmottern1952]

Great video!

[@meaninthemirror]

Excellent video. Thank you.

[@nicknicolosi1]

I wish collage would have show me this trick. Awesome, and I can measure ESR with my Rigol scope. Thanks!

[@AdamFraserKruck]

Love the drawings. Reminds me of the Forrest Mims books I used to read as a kid.

[@w2aew]

Thanks! How do you think I learned? By reading the Mims Notebooks as a kid many years ago...

[@cosminbel79]

Hi Allan, nice video as allways😊 I have a small suggestion for you: maybe it's more accurate if in the formula mentioned by you for calculating ESR, 50 could be exchanged with Rin for better readability; However, brilliant explanation!

[@surgingcircuits6955]

Great video, as usual, w2aew. I had noted from an article (a while back) a very similar technique. Going to post my notes to see if you would be willing to comment...

[@surgingcircuits6955]

Requirements: An Oscilloscope And A Simple Signal Generator Setup: 1) Output of the generator; connect a BNC "tee" adapter. Run a 50-ohm BNC cable from the tee to the scope with a 50-ohm BNC terminator on the scope input. Terminator note: You can use a 50-ohm "pass-through" terminator on the scope end of the BNC cable. You should also be able to use, instead, another BNC "tee" on the scope input, with an "endcap" terminator on one side and the cable coming in on the other side of the tee. 2a) On the other side of the tee, connect a banana plug BNC connector with a set of DMM-type probes or alligator clips. 2b) On the other side of the tee, connect another BNC cable that has alligator clips on its other end. 3) Setup the signal generator to produce square waves at about 100-kHz with about 100mv peak-to-peak amplitude as seen on the attached scope, and no DC offset. Turn the scope's v/div to 5mv/div with time/div at 1 micro-sec, and AC coupling of the input. 4a) Shorting the probes together will display on the scope about one division high. It is basically a square wave with large narrow peaks at each leading edge. View the horizontal part's p-p amplitude. 4b) Try it with a decade resistor box in series with the probes. Should clearly see each one-ohm increase on the scope display with the probes shorted together as well as with the probes across a good electrolytic capacitor. Testing: - With the probes across a GOOD capacitor in-circuit there should be little, if any, change in the scope display as compared to when the probes were shorted (since, depending on the frequency, a capacitor should look more-or-less like a short circuit to AC. - Across a BAD capacitor, usually the display will be almost-totally off the screen. Some caps will look marginal, making the display go from about one div p-p up to about 3 to 5 divs; which probably corresponds with somewhere between 5-ohms and 20-ohms of ESR???). Comments: - Can test IN or OUT of circuit!!! -- In-circuit, low-amplitude is probably desirable; probably less than +/- 0.4v so the signal doesn't turn ON any semiconductor junctions. - Probably reliable for 10-uF 10v to at least 1000-uF 100v. - Adjusting the frequency for different capacitances might be helpful; especially if non-electrolytics are to be tested.

[@w2aew]

My only comments are that the 50 ohm termination isn't really needed since the capacitor shorts it out anyway. Just put the BNC tee and clip leads right at the scope to avoid transmission issues and reflections at the scope. Also, I never recommend in-circuit testing because other devices (including capacitors) in parallel will often affect the results.

[@afterthought138]

excellent video.

[@dimitrioskalfakis]

very good presentation and home made esr meter. however, it was the use of an hp15c beast that did the trick for me ;-)

[@mbainrot]

for my alp1022C DSO + Attiny24 (set to ring at around 220Khz give or take) i had to do two probes, one to trigger, one to measure and then set an upper limit filter (low pass?) on channel 1 (my measure channel) and tuned the filter to the point where i got some noise but didn't end up with it being unreadable. Then I got it to work :) This is one I think where an analogue scope would rane supreme edit: to give it some impedance I put a 52R resistor off the pin that was generating the signal

[@qzorn4440]

a great video. thanks.

[@rosshollinger8097]

Thanks, Alan. Succinct and useful.

[@Control_Wis]

Great video

[@ovalwingnut]

So good (informative) I'm back for a 2nd helping. p.s. GR8T MC skills. Thank You.

[@slimh2080]

another great vid thanks

[@cashewmilkfan]

GREAT VIDEO VERY INFORMATIVE!!

[@AdmiralQuality]

Great stuff, thanks!

[@tonyd1149]

Dear w2aew, thank you very much for making and posting this video. God[Bible] Bless.

[@W1RMD]

Very educational. I feel like I'm going to college for free. Reminds me of Forrest Mims the way you draw your easy schematics. Interesting feature of your calculator that you push the division (or multiplication etc.) sign AFTER the numeric entry.

[@w2aew]

Thanks. I learned a lot from the old "Engineers Notebook" series of books by Forrest Mims. The calculator uses an entry method called RPN (reverse polish notation). It is more efficient when computing complicated formulas. It's quite common in engineering circles (rarely used by casual calculator users).

[@W1RMD]

@@w2aew Thanks and 73's -W1RMD

[@justpaulo]

As yours kind of recent subscriber, KZbin decided to recommend me this old video of yours. I must say that I appreciate a lot your channel. Your I&Q modulation or Smith chart tutorials are very very good and useful. However in this video I think you should not have used the full 113mV but rather the ~80mV of initial jump. As you said the capacitor value decreases over time. In this example it decreased so much that Xc is no longer ~0 at 200KHz. Using the full 113mV you are mixing the ESR + Xc in the calculation. In other words, imagine you have an ideal capacitor (ESR=0), but small enough such that 50Ω*C > 50Ω @ 200KHz). In that case you'd see the output going practically from 0 to 1V. Using ~1V as Vr in your formula would lead to a very high ESR. Yet the ESR =0, and what we observe is the charging & discharging of the capacitor which is small enough for that to happen even at 200KHz. PS: obviously this does not changes the conclusion that the capacitor shown is damaged and the ESR is still ~5Ω anyway.

[@ConsertandoTudo]

8 years later I build one using arduino, but using the same concept. Thanks

[@joeG9100]

Great Video, Don't need to be an engineer to understand it. The last part calculation is the best, using HP 15C Which what I used in the day and still have. Thanks,

[@electronic7979]

Useful video

[@anorthernsoul153]

Brilliantly explained! You should teach at universities 👍

[@vladimirpetrovic1316]

Alan, great videos. Can you show us how to use fun gen and the scope to test components as opposed to octopus??? Thanks

[@w2aew]

+Vladimir Petrovic You can basically do the exact same thing as shown here - except replace the step-down transformer with a 1:1 audio transformer (commonly found inside old scrap telephones), and drive one side of the transformer with the function generator.

[@samykamkar]

Thanks for the explanation and demo!

[@cohenlegend692]

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[@phillipderek5150]

@Cohen Legend instablaster =)

[@cohenlegend692]

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[@cohenlegend692]

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[@phillipderek5150]

@Cohen Legend Happy to help :)

[@howardpilot4590]

Great site, are you able to put in various sensors( mechanical, temperature, pressure etc.)into the circuits?

[@CarlosAndresEsparza]

Brilliant, thank you very much!.