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- Опубліковано 18 сер 2024
- 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/w...
Alan, you are the kind of person that SHOULD be teaching in schools ! 👍
He's too good for schools.
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.
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!
Never disappointed by Alan's lectures. Great video. Thanks Alan. 73 de GI8WFA.
Thank you. I am not sure if anyone has told you but you make this extremely easy to learn and practice in application.
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.
Ya, I was already thinking about building a function generator with a 555 timer while watching the beginning :P
Yes and agree. Due all respects Hat tip for each moment of your teaching, Sir.
You have just demystified ESR for me. Seeing it on the scope explains it all for me. Thank you very much.
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.
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.
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 :)
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.
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...
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.
Indeed a very helpful lesson.
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.
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.
I've got two videos on ESR meters you can build. Here is a fun design that uses only 5 transistors:
m.ua-cam.com/video/3fiUZZlveS0/v-deo.html
And a design that I built many years ago:
m.ua-cam.com/video/bmYAgat-sOQ/v-deo.html
Wish i found your channel earlier in life, it could have saved me alot of headache. But still learning from you. Thankyou
Once again, you have scored a home run with this innovative approach to measuring ESR !!!!!!!
The best gets better.
I didn't think your method of presentation needed improvement.
But you have done it.
I suggest you are one of the best UA-cam presenters, many thanks for sharing your work !
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.
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).
w2aew Thanks for pointing that out. Extremely handy having a “TV Guide” so I can what I want to watch next:). Very cool!
I am still in the process of digging and enjoying the videos that I missed. Great teaching, Alan
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
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.
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.
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.
Very glad to hear that my videos have helped you. Congratulations on the Extra!
Thanks for showing a seldom used function of the O scope. Great review of the scope interpretations.
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.
Also take a look at the "5-transistor ESR meter" project.
Wow, great explanation on how to measure ESR and what ESR is.
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.
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.
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!
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!
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!
Hands down, best vid on youtube about this subject. Thanks.
Thank you for a very good video on the process of checking caps and calculating ESR values. I learned a lot!
you are so awesome !!!!
thanks for the videos im a EE student I love lerning from you!!!
Good luck with your studies! Be sure to share my channel with your fellow students, and your professors!
My favorite lecturer! Always enjoy class time here.
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
Never too old to learn something new. Thanks so much.
Great job. Your explanations are clear, logical and engaging. Thank you for sharing your extensive knowledge.
As yours kind of recent subscriber, UA-cam 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.
V (1+50/R) = 1 when 1 volt square wave apply to 50 ohm resistor, chained with the capacitor. Good explanation of ESR!
Stumbled across this video... and I really appreciate the tip on how to use a scope to test for ESR. Tx!
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. 😊
Another informative and useful video. Keep up the good work. Thanks Alan
Fascinating info. And *how good* it was explained!
Ha ha! "Oscillator!" :D
... That's what he said at the very end of the video. Sounded like "I'll see you later!"
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.
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!!!!
Dear w2aew, thank you very much for making and posting this video. God[Bible] Bless.
Great explanation, I will certainly use this method in the future when testing my caps..
I've been doing this for years. I do in circuit ESR testing all the time. I have belly to belly rectifier diodes across the output of the function generator. That's so a charged capacitor will be discharged and the function generator output transistors won't be blown. Always works. No point is using a square wave, sine wave does the job. Don't need no silly little ESR meter.
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.
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).
@@w2aew Thanks and 73's -W1RMD
Great video Mr Wolke
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
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
Great video! I have an oscilloscope and function generator but couldn't spring for an ESR meter... now I don't need to!
I wish collage would have show me this trick.
Awesome, and I can measure ESR with my Rigol scope.
Thanks!
Well done... did not need to see the end because of the good explaination 👍
With a VNA or LCR meter you can get a more detailed view on the capacitor.
The ESR does strongly depend on frequency...
Have a look at this video: ua-cam.com/video/kKL7RrMJeIE/v-deo.html
8 years later I build one using arduino, but using the same concept. Thanks
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.
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.
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
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.
This was exactly what I needed! Thank you! Excellent video
Very good explanation, thank you for your work on the video.
Why this work? The RC will not act as a low pass filter?
Yes, the RC will act like a low pass filter - however, at the frequency we're using, the filter would be well past it's cutoff frequency and ideally look like a short circuit (if there was no significant ESR). Thus, if there is any voltage dropped across the capacitor, it is due to the ESR. Many times the capacitance value is also degraded, resulting in the rounded pulse train (which is really just an RC low pass filtered version of the input signal)
Thanks man!
Show esta demonstração no osciloscópio, vou fazer isso aqui no laboratório usando meu DSO no telão para os alunos entenderem o que tanto falo sobre ESR.
It is mentioned that the when the capacitance goes down we will start to see an exponential curve instead of the pure square wave. But if the capacitance goes down, then we in effect have a lowpass filter with a higher cut-off frequency and should see the square wave more clearly. Or that it is faster to charge and discharge the capacitor?
The way to think about it this: When the capacitance is large, the RC time constant is large, thus the exponential rise and fall is very long. Since we're only looking at a very small time period of a loooooong RC exponential rise, it *appears* flat. That's why you see a low-amplitude square wave when looking at a good high-value capacitor. The "step" change is due to the ESR, and the "flat" portion isn't really flat, we're just not looking at it long enough to see the rise/fall. When the capacitance is reduced, the RC time constant is much faster, and we can see a good portion of it during the on and off period of the 200kHz square wave.
Thank you for the explanation.
Appreciate your videos :-)
Pretty well explained, thanks a lot for your effort sharing your knowledge. 🎖
Can I measure the ESR up above 200KHz using this method? My Teague ESI LCR bridge is dated, but it has 300 or 400 different frequencies between 10Hz and 100KHz. It gives my ESR, impedance, capacitance, resistance, inductance, conductance, Q, dissipation, etc. I have a very similar scope. I think it is a 2245A. 73s KI7AQJ
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,
Love the drawings. Reminds me of the Forrest Mims books I used to read as a kid.
Thanks! How do you think I learned? By reading the Mims Notebooks as a kid many years ago...
Thank you for this video and your explanation. That was realy interesting for me. I've tried it today and it was realy easy.
I have enjoyed everyone of your videos. Great Job. I have learned sonmething from everyone of them.
73
Larry
I'm probably wrong here, but I would suggest that you're measuring more than just the Equivalent Series Resistance?
Wouldn't the ESR be purely the size of the step voltage rather than after the cap had gone thru it's exponential charge?
i.e. Instead of 113mV, the 'step' by itself was closer to 56mV.
Yes, at 10:20 to 10:30, this is exactly what I describe. The "step" is due to the ESR, and the exponential is due to the reduced capacitance.
Thanx for the reply.
I guess what has got me confused was that you used the 113mV figure in your calculations 13:08 to 13:30 and from those calculations, you commented that you had 6.3 ohms of ESR?
Wouldn't the 'pure' ESR be calculated using just the step change of around 56mV rather than the entire 113mV?
Yeah - I should've used just the step in the calculation to get simply the ESR. Many commercial ESR meters would use the 113mV, and I meant to mention that.
Why do the ESR charts only cover low capacitance or small caps? For example; would you measure ESR if you were working with an 80v 22000uf Nippon Chemi-Con cap?
Thanks for your work sir!
+MetallChips 85 ESR is typically most important in applications where there is a lot of ripple current (switching power supplies, inverter supplies, etc.). Monster caps like you're talking about generally have too much series inductance for the ESR to matter too much in the application.
I have a problem with my Victor v2002. It does not create square waves from 0 to Voltages. It only creates AC square waves.Ex: -1v to +1 v.
If you have a cheap function generator like I have, you can't assume that the internal impedance is 50 ohms. Having adjusted it to give 1 volt p-p on my scope with the high-impedance probe, I used a 500 ohm potentiometer across the scope terminals and adjusted until the scope indicated 500mV p-p and then measured the pot resistance. I found that the impedance of my generator appeared to be around 400 ohms.
yes, excellent point.
Hi. Good explanation. But I do not understand why you use the 113mV voltage difference to calculate the ESR. Shouldn't you rather use the initial voltage step of about 70mV? Because this is the voltage step across ESR and internal source resistance.
Very good video! I have an old (But good!) analogue Hameg HM203-6, This scope has two calibrate signal outputs of 2 volts and .2 volts called simply "cal" and the output is a squarewave on both outputs as they come from the same source...just one is attenuated internally, both run at 1khz, I used this the same way as you used your function generator and i got dramatically different results from known good and bad capacitors of the same value! I tested a quantity of used caps and found 3 of them to be bad but two of them where known to be bad anyway as they where bulging and i also have a cap meter, i must add that i do not have an esr meter but the way i have set my scope up i do now thanks to your video! The only thing i cant figure out is how to work out the output impedance of the "cal" signals, Or do i really need to know the output impedance? I would like to be able to work out the esr of any caps i measure, Any ideas? Thanks for a great video again!
Sure, search my channel for a video called "how to measure output impedance". Pretty easy to do.
i put a 1 k ohm resistor as output load and did the calculations as you did and am getting around 3 kilo ohms, That seemed a bit high! So i rigged up a potentiometer as an output load and took the 2 volts output down to 1 volt across the load and read the ohms across the potentiometer and it read 2.8 kilo ohms so i was right with my math! Thanks again teach for great videos!
Great! Not unusual for such an output impedance on the cal signal, since it was only intended to drive the input impedance of a 10x probe.
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?
Brilliant, thank you very much!.
You mentioned it’s not a good idea to test in circuit. One of the features people say about esr meters is that you can use them to test in-circuit. It would be interesting to see the func gen/oscil being used as an in-circuit tester, or is that a bad idea for reasons not explained?
i just bought a cheap kit function generator that outputs 1Hz-20MHz sine/square/triangle signal, and only use that to check in-ckt the ESR of a Capacitor.
using a sinewave @100kHz 200mVpp.
Use a Potentiometer to trim the input impedance of the function generator.
Also use voltage divider to get the capacitors ESR :)
3:16, kindly clarify the consequences of setting the 1vp-p square wave below ground and reverse biasing the capacitor. I'm not sure if it would affect the results as the displayed voltage drop would be identical whether the electrolytic cap is forward biased or not...thanks in advance.
+Nelson Chua Electrolytic caps are polarized - reverse biasing can potentially cause damage to the cap.
+w2aew True, when it goes back to the actual circuit. But with regards to this ESR test, at 1vp-p, it would be trivial, correct?
Yeah, you don't actually connect ground to your test circuit anywhere, so 1v p-p is 1v p-p no matter what the reference to ground is.
Thank you very much for your instructive videos! The ones on ESR have kept me busy, measuring, calculating and building. One question on this video please: when using the 113mV to find the ESR, shouldn’t you have used the around 50mV ‘initial step’ instead? Best regards, Robbert.
yes, i caught the error after I uploaded
*BEST explanation on YT ! THANK YOU !*
100% agree, you beat me to it by 5 years !!!
Thank for the video. I wonder if you could try this on a battery to get internal resistance. Battery chemicals can go bad too.
Very good video explaining ESR
very good presentation and home made esr meter. however, it was the use of an hp15c beast that did the trick for me ;-)
thank you for this video. But howto measure the ESR of small caps i.e. 10pF, where the Xc is >> ESR ?
This technique is really only applicable to larger value electrolytic caps >>1uF. For small caps like 10pF, ESR or loss tangent is never really a failure mode. To characterize, you generally need a higher frequency analyzer (like impedance analyzer or VNA).
At 7:28 the waveform is at ~500mV level (half way dc coupled) and I was very intrigued because my expectation was that it will be at gnd level... so I may forgot about the generator's dc offset of 500mV which can't be shorted to gnd via a cap...Self taught lesson :)
Hi Alan: Most ESR meters that I have seen or used, typically would have a frequency UP to 100Khz. Why do you recommend 200Khz and more?
Higher frequencies make it easier for the meter to show ESR for lower value capacitors.
This might be a silly question, but wouldn't the ESL of these capacitors start skewing the results if the oscillator frequency increases past the DUT's resonance?
I am curious how the operating frequency can be set to a certain frequency if the ESL varies quite a bit between capacitors under test, pushing resonance around. Is it just assumed that ESL and 1/jwC are negligible for these caps between 100kHz - 300kHz?
Yes, generally I am making the assumption that the ESL is negligible at these frequencies. For very large value capacitors, you can lower the frequency and run the same test. Ideally, I like to use a frequency where the nominal 1/jwC is less than 1 ohm for the capacitor being tested.
Gotcha, thanks!
Another great video whith another great explanation. Always inspiring.
Hi! I just want to ask what specific model this oscilloscope that you're using? I'm planning to buy an ESR meter but I just want to ask if my old Tektronix 465b has this function? Just trying to save money. Thanks in advance! And by the way, your tutorials are very informative. :-)
I was using a Tektronix 2465 in this video. The 465B could also be used, except that it doesn't have the voltage cursors, so you'll have to make the voltage measurements using the divisions on the screen. Of course, you'll need a function generator also...
Thanks a lot! I'll try this one tomorrow. :-)
Amazing video but as a noob I'm a little confused about the tee connector.
All BNC Tee connectors I can find are 50Ω or 75Ω . Does that not add a second 50Ω series resistance to the circuit when combined with the internal 50Ω resistance of the signal generator?
Thanks for such a clear and informative video that's still teaching people almost a decade after upload!
The 50 or 75 ohm tees do NOT have a series resistor in them. This only refers to the characteristic impedance of the transmission lines (coax) that they're designed to work with. The BNC connector varies slightly between the 50 and 75 ohm varieties.
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!
Thanks, Alan. Succinct and useful.
Thanks a lot , learn a new thing from this video :D
Extra bonus points for using an HP 15C :)
Brilliantly explained! You should teach at universities 👍
Really interesting video. I'm sure I will use that test... Thanks.
Thank you Alan for a great Video.
Is this the way, that most ESR meters work? Sending a 200 kHz signal in to the capacitor and then analyze the difference in voltage?
Or do they use a different method?
Most of the DIY designs I've looked at use a test signal in the low hundreds of kHz and measure the AC voltage drop. I don't know what methods are used by commercial units.
Alan, great videos. Can you show us how to use fun gen and the scope to test components as opposed to octopus??? Thanks
+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.
Great channel, tomtektest mentioned one of your videos. Subscribed!