Bob Parker ESR Meter 100khz equivalent freq? - Page 1
Forum section: electronics / testgear

author: MeganVonTincan
author_rank: Newbie
timestamp: January 23, 2016, 01:55:26 pm
content: I'm building my own ESR meter, and I'm reading the Bob Parker ESR Meter Assembly Manual (link below) for some ideas and it states "...this meter is really an AC ohmmeter with an equivalent test frequency of about 100kHz..." and I understand how it is sending bursts of 8us current pulses at a 2kHz rate. But it isn't obvious to me how he came to this "equivalent AC test frequency". Can someone explain how it's calculated? 1/8usec = 125kHz?http://members.ozemail.com.au/~bobpar/k7214.pdf

author: LA7SJA
author_rank: Regular Contributor
timestamp: January 23, 2016, 05:13:29 pm
content: The 1/8usec is chosen to make the math in the program more easy to code and still be in the 100KHz part of the wood. The 100 KHz is only to make sure you don't fully charge the capacitor, that way you can neglect the capacitor value and only se the ESR component.The page that Answers the Ultimate Question of ESR, the Universe and Everythinghttp://kripton2035.free.fr/esr-repository.htmlIf you are interested in commercial kits you will find them at bottom of the page.Johan-Fredrik

author: kripton2035
author_rank: Super Contributor
timestamp: January 23, 2016, 07:56:45 pm
content: Quote from: ErikTheNorwegian on January 23, 2016, 05:52:02 pmoverkill esr meter ... 5 opamps inside, almost no protection for an eventually charged capacitorone unused opamp and they use a 7660 to make a negative voltage ...the 2001 poptronix one is far more inventive than this one...http://kripton2035.free.fr/analog%20esr/esr-poptronix.html

author: Bryan
author_rank: Frequent Contributor
timestamp: January 24, 2016, 11:42:42 am
content: Even easierhttp://members.shaw.ca/swstuff/esrmeter.html

author: MrSlack
author_rank: Frequent Contributor
timestamp: January 24, 2016, 03:03:25 pm
content: Even easier, if you have the kit around: Scope + function generator + calculator

author: kripton2035
author_rank: Super Contributor
timestamp: January 24, 2016, 05:06:28 pm
content: it's a nice proof of concept, but you don't always have available a scope and a function generator (they are way more expensive that a simple esr meter)and I'm sure you will not test a whole board with the small clips that are on the video ...better have a simple small esr box, always available on hand, and standard probes with banana connectorsjust my 0.02$

author: Kleinstein
author_rank: Super Contributor
timestamp: January 24, 2016, 05:32:19 pm
content: There is no need for a full function generator to do the ER test with a scope. Just a simple square wave generator would do it. Could be a rather simple one wiht a 74HC14. A few of the outouts in parallel can easily drive a 50 Ohm output to about 1 V, even if powered by 3 V (2 AA cells). For in circuit measurements even less than 1 V is preferrable.

author: Shock
author_rank: Super Contributor
timestamp: January 25, 2016, 09:42:41 am
content: Take a look also at Jay_Diddy_B's esr meter he designed while here on the forums, plugs into a multimeter similar to how Daves ucurrent operates. It has 2 and 4 wire measurement plus input protection. Project here:https://www.eevblog.com/forum/projects/esr-meter-adapter-design-and-construction/It's the PCB on the left.

author: dannyf
author_rank: Super Contributor
timestamp: March 26, 2016, 02:46:24 am
content: QuoteActually he is wrong there: his meter is really measuring the (DC) resistance of the capacitor. The capacitance only comes into play if the "charge-up" is comparable to the voltage rise caused by the current bursts.

author: dannyf
author_rank: Super Contributor
timestamp: March 26, 2016, 02:47:27 am
content: Quoteoverly complicated. I have built a few of my own design that utilizes just one lowly NE5532 (or the likes).

author: dannyf
author_rank: Super Contributor
timestamp: March 26, 2016, 02:27:46 pm
content: QuoteThere are some typos in that article.QuoteI don't think there is much significance to the 8us pulse being chosen - cannot be 100% without seeing the code.Other numbers in the design are picked for a reason: the current that charges up C10 (470nf) is picked at 9.4ua (NOT 9.4ma as specified in the article) so to produce a 10mv/pulse (each pulse = 0.5ms) voltage rise on C10. With a 20x amplifier, that means voltage rise on the DUT equates to 0.5mv/pulse. With 0.5ma/5ma/50ma charge current, that means each pulse is 1ohm/0.1ohm/0.01ohm. So by counting the pulses, you know the ESR without complicated math.The design can be simplified with today's mcus.