Bob Parker ESR Meters

[willawake]

Here is a new test instrument which i received today. It is an ESR Meter based on Australian Bob Parker's famous design



It is built by EVB of Portugal. The pic above shows what you get, namely the meter, two substantial test leads (i was quite impressed they are much thicker and larger than those you usually get with a cheap multimeter. Also you get a 100 ohm 5w power resistor which you use to discharge filter capacitors in power supplies to avoid damaging the meter when you test them. You also get an owners manual which is quite comprehensive and in good English. Lastly you get a 2 year guarantee certificate.

[willawake]

Here is how the meter was packaged. The test leads were very nicely wrapped in cling film (not shown). The packaging is good. The meter was paid by paypal evening of the 9th and received morning 14th. cost was 68 euro + shipping = 74 euro.

[willawake]

here is the 100 ohm 5w resistor

[willawake]

The meter externally and internally

[willawake]

[willawake]

the pcb is of quality manufacture and the soldering is fine also

[willawake]

The caps are Nitai NP, Lelon REA 85oC and Jamicon TK



Here is the microcontroller ZiLOG Z86E0412PSC 1866 running custom firmware and also the Kingbright GaAIA 7 segment led displays



and the calibration pots

[kc8adu]

looks identical to the ea version except the case.
does yours show ea at power on? ?? at power dowm?
micro on mine even has the green dot.
i suspect that is just a repackaged ea kit.odd power button though.looks like the label retains it?

[willawake]

no it just says - at power up. at power down it says ?? .the power button is odd yes but the action is ok. i am happy because with the leads plugged in it is not going to turn on easy in my bag. it also has auto power off after 3 minutes. I have a lan tester which has a bad choice of on button and no power off. so i have to disconnect the battery otherwise when I want to use it the battery is flat.

I am not happy with the case opening though, it has latches. it would be better to have the back screwed on. apart from that the case is fine.

[willawake]

so on to the testing then. when you turn on the meter you have to touch the probes together and then press the on button again to zero them in.



Here are some test results from my collection. The sanyo was from a board in use for about a year and the Panasonic were new, the other caps were removed from unstable boards.

Sanyo WG 2200uf 6.3v : 0.0 ohm (too small to measure)
Panasonic FC 1000uf 50v : 0.01 ohm
Panasonic FC 3300uf 6.3v : 0.02 ohm
Ost 1000uf 6.3v : 0.04 ohm
Chhsi 1000uf 6.3 : 0.06 ohm
GSC LE 3300uf 6.3v (bulging) : 0.27 ohm
Gloria 1000uf 50v (bulging) : 1.1 ohm
Jackcon 1000uf 10v : (bulging) : 1.5 ohm
Jackcon 1500uf 6.3v (bulging) : 1.6 ohm
JPCON 2200uf 6.3v (bulging) 2.1 ohm
Lelon 1500uf 10v (bulging) : 2.78 ohm
Gloria 1500uf 6.3v (bulging) 5.0 ohm

So is the meter accurate? The panasonic FC 3300uf 6.3v should read 0.038 according to panasonic, so a reading of 0.02 is not bad. It doesnt really have the range to test between good low esr caps of various types.

Anyway that is not what it is for, it is for determining which caps have developed high esr and should be replaced. If you check the above table you can see that the caps which are bad have readings many times more than the good caps. They are all low esr caps taken from motherboards. In a test environment we should be checking their spec sheets to see how off spec they are. However in this quick example you can immediately spot caps which now have unacceptable esr for motherboard use. So the meter is easy to use even in a basic way.

If you think that you could use the meter to test for bad caps that will fail, no it cannot do that job. Even a cap from a bad manufacturer will test with low esr in the beginning but will not be able to perform to that spec after some months/years.

There are some notes in the manual which are relevant :

The manual notes that the device cannot discriminate between a cap which has very low esr and one which is short circuited or very leaky. So if you get a reading which is suprisingly low then you should remove the cap from the circuit and test its resistance with a multimeter.

It also notes a rare failure mode of caps where the esr is ok but the capacitance has dropped by a large amount. So if you have a circuit that is faulting but the caps measure ok then you should disconnect the caps and test them with a capacitance meter. If you dont have one you could try putting some good caps in parallel with them and see if the circuit improves.

There is another important note which says that when testing caps in circuit you have to be careful that caps are not connected in parallel and the results are thereby affected. In this case a good cap can make the esr measurement of a bad one seem ok when it is not.

Conclusion : is the meter going to be useful? well certainly it is a great addition to my toolkit. I could have used it yesterday actually. Test equipment is great because it helps you understand the situation better and adds to your knowledge of the failure mode of components. However it is important to spend your money wisely and get equipment that you can really use and need.

In the case of capacitors the visual inspection is not really enough to determine that caps have failed. we do know that some brands eventually start operating off spec without visible signs. So in those cases the meter is really useful. I will also be using it to check also the small caps that we dont usually recap to see whether they are performing on spec or not.

How is the supplier? well EVB have a good service and good communications so i would recommend them as a supplier. How about the price? well all test equipment is expensive and especially devices which are not produced and sold in large quantities. There is quite a bit of work to assemble one of these units so there has to be some consideration of that also. The other suppliers offer similar prices too so its ok.

[willawake]

here are the links, some of them again.

Bob Parker http://members.ozemail.com.au/~bobpar/esrmeter.htm

Suppliers :

EVB (Portugal) http://clientes.netvisao.pt/greenpal/ (assembled unit)
E-Leader (Australia) http://www.monitortest.net/ (kit or assembled unit)
John Jukes (Canada) http://www.flippers.com/ (kit or assembled unit)

[Decade]

A good choice willawake !
Guess you can trust the readings comming from Bob P ESR meter, got one myself but the older version, had it for 4 or 5 years and I tell you it has saved me lot of time searching for caps with high esr lurking arround in PSU,s.
Measure a whole bunch of low ESR caps in parallel like on a mother might fool you

[PeteS in CA]

So is the meter accurate? The panasonic FC 3300uf 6.3v should read 0.038 according to panasonic, so a reading of 0.02 is not bad.

Catalog Z ratings are max, not typical, IIRC.

[chilli_sauce]

I've joined the forum to update the information regarding the ERS meter which I recently purchased. Here's the e-mail exchange.

Hi Vitor,

the ESR meter arrived today, I haven't tested a faulty cap yet, but it seems
to work fine. I was disappointed there were not probes as described at
badcaps.net, a review you link to in your feedback.

John



Hi John

Thanks for your feedback, sorry for disappoint you about the probes issue, a
few days after the link on review be posted, I got notified by my probes
supplier that he was no longer able to supply me the mentioned test leads,
That way I was forced to remove all information about them from webpage,
meter manual etc. once again I apologize for that situation.

Best Regards

Vitor



I have no problems with Vitor or the ERS meter, in fact I would have bought it had I known it came without leads or the resistor.

John

[steve6375]

Hi
I bought the Atlas ESR meter from Peak Electronics in UK. It shows ESR and capacitance. It comes with test leads and two small gold-plated croc clips. You have to press a button to start the measurement, but the good thing is that it switches itself off after a minute or so.
I have used it to test motherboard caps in-circuit and it works well - just make sure you get the version with the latest firmware. I bought mine from Farnell and it was a very old model and constantly hung! Peak upgraded it for free and now works well.
cheers
Steve

[willawake]

http://www.peakelec.co.uk/acatalog/jz_esr60.html

looks great.

US shop $169
http://www.anatekcorp.com/testequipment/atlasesr60.htm

[davmax]

Unfortunately this Atlas meter is only good for verifying caps that are worse than the Ultra low ESR types. Certainly it can tell if a cap is really bad. The data sheet indicates worst case resolution at 20milliohms and an accuracy of +- 20milliohms. There is little hope of measuring below 40 milliohms with any confidence.

Is it worth buying if caps are cheap?

[davmax]

I am now a fortunate owner of a Bob Parker’s ESR meter built from a kit. I chose the kit because the meter spec does not include an accuracy statement, just resolution. The original design was aimed at differentiating large differences of ESR to help techs quickly identify a failed electro cap with high ESR. I was interested in the accuracy on the lower scale 0.01 to 0.99 ohm. A range that would be useful for detecting early shifts in ESR with ultra low ESR caps. The best resolution is 10 milliohm and at the lower end of the scale each 0.01 step represents a significant ESR shift so it is very useful to tune the instrument accuracy. So I checked calibration and found that the low range was reading high compared with the other ranges. I calibrated the low range with a 0.068 ohm resistor. This caused the other ranges to read low so the circuit current controlling resistors had resistors connected in parallel to increase the current a achieve calibration.



The result is that I have confidence that readings are within a 10% accuracy.



Bob’s design is very clever and simple. I evaluated whether to change a few components right at the circuit front end. (A mod that would ensure charged caps were totally discharged). I found that all the research Bob has done made it hard to improve.



I have found the unit excellent in measuring “in circuit” caps (only single caps, the ESR is usually too low when trying to measure the parallel connected 4-6 VRM output caps).



Normally caps will be discharged, it is always important to ensure that the caps are totally discharged or the readout will be wildly inaccurate.



With low ESR caps it is very important the zero the lead resistance, this can be easy to forget.



Excellent at a reasonable price A$79.96.

[davmax]

A correction I calibrated the ESR low range with a 0.68 resistor and checked with a 0.068 resistor.

A good value to calibrate would be 0.5 ohm using 2 x 1 ohm resistors in parallel. Using ten in parallel (0.1) is a good check point.

I found Bob Parker very helpful in establishing how to calculate the prospective accuracy before I purchased the kit.

[capamatic]

I`ve recently purchased the EVB ESR Meter and wonder wether it can be used on other types of capacitors i.e. Tantalum, Polyester, Mylar, Ceramic ? Although these rarely fail, they can sometimes be part of the problem. I am aware the EVB tester cannot be relied upon for low capacitance ESR testing.