Cheap in circuit ESR meters - Page 1
Forum section: electronics / testgear

author: FrankenPC
author_rank: Unknown
timestamp: May 23, 2014, 04:38:12 pm
content: Anyone have any experience with in circuit ESR meters? Are they actually capable of detecting dying electrolytics? Or is this just hoo-doo?http://www.ebay.com/sch/i.html?_sacat=0&_nkw=in+circuit+esr+meter&rt=nc

author: retrolefty
author_rank: Super Contributor
timestamp: May 23, 2014, 04:49:46 pm
content: I would be suspicious of any 'in-circuit' tester like this as other components wired to the capacitor would have to have an effect on the measurement?Anyone ever hear of a 'in-circuit' ohm meter? I didn't think so, so why would measuring ESR of a cap be any different?

author: FrankenPC
author_rank: Unknown
timestamp: May 23, 2014, 05:22:01 pm
content: Quote from: retrolefty on May 23, 2014, 04:49:46 pmIt seems to me the only way this type of tool would be useful is to gather readings from a known working copy.

author: Shock
author_rank: Super Contributor
timestamp: May 23, 2014, 05:27:42 pm
content: Quote from: retrolefty on May 23, 2014, 04:49:46 pmThere are in-circuit ESR testers which work well are reading these low resistances. The issues are:Needs to have close to a few hundred mV (loaded) test voltage which will avoid turning on semiconductor junctions.Two identical capacitors in parallel will throw a reading out.The ability to discharge the cap before testing (is handy).

author: geo_leeman
author_rank: Regular Contributor
timestamp: May 23, 2014, 05:32:49 pm
content: A couple hundred mV or so on the cap in circuit is fine. Watch out on the cheap ones for no protection from charged caps! They don't add the necessary high voltage cap. While not always perfect, it's a lot better than taking lots of caps off the PCB! The eyeball test for bulging is always the first pass though.

author: dannyf
author_rank: Super Contributor
timestamp: May 23, 2014, 05:45:13 pm
content: The basic way to get "in-circuit" reading is to use a low energy excitation source.There are plenty of cases where such a strategy would fail.

author: AKM
author_rank: Contributor
timestamp: May 23, 2014, 05:47:11 pm
content: MESR-100 v2 here. Has no input protection, but does the job, with little care.For testing dried capacitors, I believe even the cheapest ESR meter will suffice.

author: Retep
author_rank: Regular Contributor
timestamp: May 23, 2014, 05:49:30 pm
content: I have a version of the Bob Parker "ESR" meter. I find it quite useful for repair jobs. Though in-circuit testing is inherently inaccurate, for repair jobs I don't really care about the precise ESR, I just want to have an indication if a cap is suspect. In-circuit testing ESR is a very quick (but not 100% reliable) way to that. The ESR of bad caps is often dramatically higher than that one of a good cap, but interpreting the ESR reading requires some experience. There is quite a big gray area since the ESR of good caps vary significantly and checking the datasheet of the cap for the values to expect is hardly practical if at all possible.Another way to test a cap in-circuit is to put a scope across its terminals while the device is powered; if the cap is good there shouldn't much of an AC signal.

author: casinada
author_rank: Frequent Contributor
timestamp: May 23, 2014, 06:08:34 pm
content: I use the Peak Atlas ESR70 and is very useful but as other posters have commented you have to apply some common sense. It will allow for a very quick test of all the capacitors while on the board but once a suspicious capacitor device is detected, you have to retest again outside the board but if the capacitor is already out unless is very expensive it is better to just replace it.

author: AG6QR
author_rank: Frequent Contributor
timestamp: May 23, 2014, 06:10:01 pm
content: Agree with Retep's post. I have a Bob Parker Blue ESR meter (assembled from a kit), and it works very well and very quickly for telling which capacitors have had their electrolyte boil away and require replacement. It works in-circuit, with a low enough voltage to avoid making semiconductor junctions conduct. Multiple capacitors in parallel will fool it, of course, and low-value resistors in parallel with a capacitor will throw things off, but neither of those problems is very common, and otherwise, in-circuit testing works well.It's not a high precision instrument, but it doesn't have to be. When a capacitor starts to die due to high ESR, that causes it to heat up, which causes the electrolyte to boil away, further increasing the ESR. So when a cap goes bad, it tends to fairly quickly go really bad.

author: ErikTheNorwegian
author_rank: Frequent Contributor
timestamp: May 23, 2014, 06:15:43 pm
content: I use this esr tester, and im very happy With it. Saves me a lot of work, soldering in and out caps before testing them.CapAnalyzer 88A Series II.Video of it in use..Website..http://www.eds-inc.com/cap.html

author: FrankenPC
author_rank: Unknown
timestamp: May 23, 2014, 07:02:36 pm
content: Thanks for the feedback. Good food for thought. In the past, I've clipped one lead of a suspect cap, measured it and re-soldered it back on. But this is impossible with small bottom lead electrolytics.

author: mathsquid
author_rank: Frequent Contributor
timestamp: May 27, 2014, 02:47:44 am
content: I have this ESR meter that I paid $40-50 for. It works well and I've been happy with it.