One way to test electrolytic capacitors is to measure their capacitance. It does not tell the whole story of capacitor condition. Another usually more useful way to measure electrolytic capacitor condition is to use an ESR meter.
EEVblog #365 – ESR Meter Bad Cap Monitor Repair video gives you tips how to use ESR meter to find bad electrolytic capacitors:
An Equivalent Series Resistance Meter article has a good plan for DIY ESR meter. I have built it and found it well working. Building an ESR meter for Testing Electrolytic Capacitors has a nice table of ESR values you could expect from different capacitors and you can find another table here.
Here are links to some other ESR meter plans and information:
The Most Useful Tool for Identifying Bad Capacitors
29 Comments
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tomi says:
Testing caps with a DIY ESR meter
http://hackaday.com/2013/03/16/testing-caps-with-a-diy-esr-meter/
The entire circuit is built on stripboard, and if you’re lucky enough to find the right parts in your random parts bin, you should be able to build this ESR meter with components just laying around.
Building an ESR Meter
Building a simple ESR meter for troubleshooting electrolytic capacitors.
http://paulorenato.com/joomla/index.php?option=com_content&view=article&id=94:building-an-esr-meter&catid=4:projects&Itemid=4
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Tomi Engdahl says:
#135: Measure Capacitor ESR with an Oscilloscope and Function Generator
https://www.youtube.com/watch?v=115erzCCxgE
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.
Tomi Engdahl says:
Those devices can measure ESR:
Component tester M12864
http://www.epanorama.net/newepa/2015/09/09/component-tester-m12864/
DIY Electronics Tester Kit M168
http://www.epanorama.net/newepa/2014/08/18/diy-electronics-tester-kit-m168/
Tomi Engdahl says:
Getting a Handle on ESR with a Couple of DIY Meters
http://hackaday.com/2016/11/14/getting-a-handle-on-esr-with-a-couple-of-diy-meters/
Got a bunch of questionable electrolytic caps sitting in your junk bin? Looking to recap a vintage radio chassis? Then you might need to measure the equivalent series resistance of the capacitors, in which case this simple five-transistor ESR meter might come in handy.
Even if you have no need for an ESR meter, [W2AEW]’s video below is a solid introduction to how ESR is determined. The circuit itself comes from EEVBlog forum user [Jay-Diddy_B] and is about as simple as such a circuit can get.
#247: Circuit Fun: 5 Transistor ESR Meter circuit by EEVBlog user Jay_Diddy_B
https://www.youtube.com/watch?v=3fiUZZlveS0
Tomi Engdahl says:
Don’t let ESR waste power and cook capacitors
https://www.edn.com/electronics-blogs/power-points/4460700/Don-t-let-ESR-waste-power-and-cook-capacitors?utm_source=Aspencore&utm_medium=EDN&utm_campaign=social
There’s an important real-world aspect to the ideal capacitor, called its equivalent series resistance (ESR), which quantifies the capacitor’s effective resistance RS to RF currents.
This ESR actually has multiple constituent elements, including the part contributed by the electrodes and terminal leads, as well as that due to the dielectric, plate material, electrolytic solution, all as measured at a particular frequency. If you look at ESR in terms of the actual series resistance, the leakage resistance, and the dielectric loss, ESR goes from being just a resistor in series with an ideal capacitor to something more complicated
Why should we worry about ESR? For basic DC-only blocking circuits, ESR may have little impact. However, when you are designing a switching power supply or an RF circuit, ESR obviously affects your modeling, and real-world performance of the circuit.
Tomi Engdahl says:
ESR & Low Resistance Test Meter
https://www.eeweb.com/extreme-circuits/esr-low-resistance-test-meter
Tomi Engdahl says:
#135: Measure Capacitor ESR with an Oscilloscope and Function Generator
https://www.youtube.com/watch?v=115erzCCxgE
Tomi Engdahl says:
https://www.edn.com/glossing-over-lossy-capacitors/?utm_content=bufferacbcf&utm_medium=social&utm_source=edn_facebook&utm_campaign=buffer
Tomi Engdahl says:
“Understanding ESR In Electrolytic Capacitors | Avnet Abacus” https://www.avnet.com/wps/portal/abacus/resources/article/understanding-esr-in-electrolytic-capacitors/
Tomi Engdahl says:
Besides ESR you need sometimes to measure also capacitor leakage:
Capacitor leakage tester design & build
https://www.youtube.com/watch?v=0pySErvzUIY
https://www.youtube.com/watch?v=cW9hHjOxmQw
https://www.youtube.com/watch?v=NBUiaw18eOU
https://www.youtube.com/watch?v=X4B79BYIlbY
Invention Release! Carlson LV Capacitor Leakage Tester.
https://www.youtube.com/watch?v=LhovRIM5xAo
Tomi Engdahl says:
Check capacitor leakage with an LED
https://www.youtube.com/watch?v=FmTZZB1Ndqk
Tomi Engdahl says:
#135: Measure Capacitor ESR with an Oscilloscope and Function Generator
https://www.youtube.com/watch?v=115erzCCxgE
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 project from 2006
https://www.youtube.com/watch?v=bmYAgat-sOQ
This video shows the design and use of an ESR meter that I built in 2006. I recently used this meter to find some bad electrolytic caps in an LCD monitor I’m working on, and thought it would be a cool project to share. Here is a PDF scan of the schematic:
https://www.qsl.net/w/w2aew//youtube/W2AEW_ESRmeter.pdf
Tomi Engdahl says:
3 Ways to Check Capacitors in Circuit with Meters & Testers
https://www.youtube.com/watch?v=qDABYKoVO4Q
Learn How to check bad Capacitors in circuit boards with ESR and Fluke multimeter, ESR meter reading is ohms and Fluke capacitor reads microfarads uf mf of a cap, see below for “capacitor meters”
Tomi Engdahl says:
Inexpensive Capacitor Leakage Tester
https://www.eevblog.com/forum/beginners/inexpensive-capacitor-leakage-tester/
Replacing Capacitors in Old Radios and TVs
https://antiqueradio.org/recap.htm
Tomi Engdahl says:
https://circuitdigest.com/electronic-circuits/capacitor-esr-meter-circuit-using-555-timer-ic
Tomi Engdahl says:
https://electronics.stackexchange.com/questions/103112/esr-meter-are-in-circuit-readings-accurate
Tomi Engdahl says:
Acceptable Vloss in capacitor.
https://www.antiqueradios.com/forums/viewtopic.php?f=6&t=310808
I have recently purchased a great little tool to help test components with. It seems to work great and automatically identifies what component you are testing and it’s values. (Probably old news to most but I’m like a kid in a candy store with it) Anyway, with regard to caps, what is an acceptable voltage loss percentage? I’m working through this old northern electric 626 and will not replace the caps if they are testing good. I realize they may act differently in circuit and functioning but for now I’ll just pop in what’s way out of whack. Thanks!
Any voltage loss % does mean the old capacitor is drying out. Does not get better and gets worse over time. Best to replace all old capacitors at the same time. Makes a dependable radio.
Unless your tester can test capacitors at their rated voltage, it won’t find the bad capacitors in your radio. The general rule is that all the paper capacitors and almost all the electrolytics are bad. If you can’t test them with high voltage applied, just replace all of them.
Paper [& electros] – particularly the higher voltage types – will [almost] always show some Vloss though, regardless of their state. You can probably figure on a couple of % or more being pretty standard for paper & electros (if you even bother to measure the latter!).
I wouldn’t be surprised if old papers are up around 5%~10% or so simply due to materials & construction, not age or service-related deterioration. It’s also something of a pointless test in many cases, since (amongst other reasons) it doesn’t scale linearly with applied voltage – a cap that tests with a 1V drop @ the 3V supplied by a simple tester will show 30% Vloss, but the same cap might only drop 4V @ its rated 400V i.e. 1% Vloss and be perfectly within specs for its type.
Vloss is the dissipation factor readout in these meters. 9% is D=0.09. Word is those testers use a 1 kHz test signal.
Those yellow axial caps that people use sometimes have a dissipation factor of <0.01, or 1% at 1 kHz.
A random high-end Kemet cap has a 0.04% dissipation factor. That'd be D=0.0004.
In general, you should replace that style of cap straight away as they're so far past their working lifetime even if you randomly happen to find one that "works" it very quickly will stop doing so…but that is a fun tester and is pretty useful in a lot of situations!
Tomi Engdahl says:
https://www.instructables.com/What-is-a-Bad-Capacitor/
Tomi Engdahl says:
Capacitor voltage loss (Vloss)
https://www.buizenradioclub.nl/media/kunena/attachments/1089/CapacitorvoltagelossVloss.pdf
Additionally a new parameter is output for capacitors with more than 5000 pF and low
quality factor. This parameter is the voltage loss (Vloss) immediately after a load pulse.
Some older paper capacitors make problems to get the right capacity. The error can be
more than 100%. Also other instruments have problems to measure the right capacity for
that capacitors. For type of capacitor a voltage loss of more than 10% is measured, so the
Tester gives you a warning hint with the Vloss.
VLOSS = Initial capacitor voltage loss due to the energy required to complete the
switchover operation
Capacitor voltage loss (Vloss)
Additionally a new parameter is output for capacitors with more than 5000 pF and low
quality factor. This parameter is the voltage loss (Vloss) immediately after a load pulse.
Some older paper capacitors make problems to get the right capacity. The error can be
more than 100%. Also other instruments have problems to measure the right capacity for
that capacitors. For type of capacitor a voltage loss of more than 10% is measured, so the
Tester gives you a warning hint with the Vloss.
VLOSS = Initial capacitor voltage loss due to the energy required to complete the
switchover operation (see Figure 4).
Voltage loss after a load pulse, Vloss 1
[ With the measurement of capacitors with big capacity values the voltage loss after the
loading is analysed. The reached load voltage is lost with electrolytic capacitors after a
short periode. This voltage loss can be caused by a parallel connected resistor. But I
assume, that this voltage loss of electrolytic capacitors is caused by a internal load
dispersion directly after the load pulse. By loading the capacitors with the 470 kohm
resistor, as it is done for little capacity values, this dispersion is already done after
switching o the current. No voltage loss is detectable for this case. But if you load the
same capacitor with a short current pulse, you can also detect the voltage loss for
capacitors with lower capacity. The same e ect with lower loss can also be noticed for
ceramic type capacitors.
I have noticed, that capacitors with more than some % voltage loss are suspect. Especially
noticable with respect to the voltage loss are older paper type capacitors, which are for
other measurement a problem too.
The TransistorTester can only
determine the voltage loss, if the measured capacity is more than 5000 pF.
Tomi Engdahl says:
All You Need To Know About ESR METER To Fix Stuff. How To Use Test Capacitors Inductors Short Finder
https://www.youtube.com/watch?v=bMUzTGnvrbU
Here we take a look at the various and curious ways we can use an ESR Meter! Learn how to test and recognise bad capacitors, test and measure unknown inductors and even trace short circuit MOSFETS using an ESR meter
CHAPTERS
00:00:00 Intro
00:00:47 What Is ESR
00:05:06 Testing Capacitors
00:10:34 How Does ESR Meter Work?
00:12:00 Bad Capacitors (type 1)
00:14:19 Bad Capacitors (type 2)
00:16:56 Measuring Inductors
00:30:39 Short Circuit Finding In VRM
00:38:04 That’s Not A Knife!
00:40:04 Conclusion
Tomi Engdahl says:
https://en.m.wikipedia.org/wiki/ESR_meter
Tomi Engdahl says:
need to consider also the frequency they are measured for that ESR specification. Data sheet will tell you the ESR at a particular frequency.
Tomi Engdahl says:
All You Need To Know About ESR METER To Fix Stuff. How To Use Test Capacitors Inductors Short Finder
https://www.youtube.com/watch?v=bMUzTGnvrbU
Tomi Engdahl says:
https://caps.wiki/wiki/Measuring_Capacitance_and_ESR
ESR
Normally, a lower ESR is better. There is no magic number for what “correct” ESR is because it’s a rated value for them. The value should be less than a kΩ, and depending on the quality of the capacitor should probably be less than 100Ω. Identifying the type of capacitor and finding new examples with similar ratings online to compare to will be a helpful option here. Looking at similar capacitors from DigiKey, Mouser, etc and seeing what values the manufacturers rate them for can give you an idea of what “normal” is.