Commercial capacitor tester gizmo, or my scope and signal gen combined? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: January 31, 2012, 06:31:00 pm
content: Looking at buying one of these:http://www.peakelec.co.uk/acatalog/jz_esr70.htmlbut as I have a Philips / Fluke 100 meg Combiscope (digital and analogue) PM3380B oscilloscope, and a basic cheap signal generator that will go from 10 Hz to 1 Mhz, am I buying a fancy box with little or no more functionality than I can create with the signal gen and the scope combined? If the scope and the gen hooked up correctly together will do the job as well, why do some sites suggest a diode in one of the probe lines, and some make no mention of this? I am a bit of a sucker for electronic gizmos, I have to say..... , but I am also a bit tightThanks.

author: flolic
author_rank: Frequent Contributor
timestamp: January 31, 2012, 06:53:21 pm
content: I check my electrolytics with scope and FG, as described here:http://geoffg.net/Measuring_ESR.htmlIt works very well, but it can be little awkward sometimes.Dedicated ESR meter is for sure more user friendly, but I'm still resisting temptation to spend hard earned $$ on it...

author: saturation
author_rank: Super Contributor
timestamp: January 31, 2012, 09:11:54 pm
content: Using a premade hand held meter will be faster and convenient if you do a lot of parts measurement; those values just give you a general idea of what they are suppose to be; they mostly use fixed frequencies which are tied to test frequencies set by manufacturers to generate the component's spec sheets. But since ESR, L and C are dependent on frequency, it really won't give you the full story of what your parts do in an application unless you measure these parameters closer to the frequency of your application.By using a scope, a function generator and some parts, as example as flolic linked, will give you an impedance analyzer, which you can then calculate L, C, ESR, then derive Q, DF, etc., plus make bode plots to really characterize these components. Such analyzers can do 'everything' but run in the $10,000-30,000 range but with the technique you can do a similar thing with just your bench gear; it would be limited in accuracy to the scope's vertical accuracy and any errors in the set up.The IEEE did a study of how this can be done formally, and have a slightly more elaborate set up:http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5208199A simple way to do this was related to this recent post on eevblog:https://www.eevblog.com/forum/product-reviews-photos-and-discussion/bk-879b-lcr-meter-problem/msg86793/#msg86793

author: w2aew
author_rank: Super Contributor
timestamp: February 01, 2012, 12:27:47 am
content: I'd say - use the FG can scope when it's convenient. Since measuring precise values of ESR isn't generally very important (if you are just testing for bad caps), you can get by very well with a homemade ESR meter when you don't want to break out the FG and scope. Here's a video (that I've posted here before) of the ESR meter that I made back in 2006.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 01, 2012, 05:26:42 am
content: Quote from: saturation on January 31, 2012, 09:11:54 pmI can't believe the IEEE published something as simple as using a sweeper & Oscilloscope.I look forward with bated breath to their paper on "How to use a screwdriver!"VK6ZGO

author: saturation
author_rank: Super Contributor
timestamp: February 01, 2012, 12:05:03 pm
content: I would guess a goal is to be able to demonstrate or make measurements in schools who can't afford an impedance analyzer, such as in India. In some third world countries, if they can't get a copy of a western school's lab they'd be considered 'backward' in the local education culture, so publishing a low cost method and getting peer acceptance could show that a low cost version is viable.Quote from: vk6zgo on February 01, 2012, 05:26:42 am

author: lavo-1
author_rank: Regular Contributor
timestamp: February 22, 2012, 09:47:56 pm
content: Quote from: w2aew on February 01, 2012, 12:27:47 amI love your all Video Blogs, your straight forward approach to teaching us Luddite's to the finer points of scopes and test equipment is a breath of fresh air and I am inspired to make one of your ESR meters to help me at work as I often find bad caps in the sub sea cameras that are used in my job.We are advised by our company to return these faulty cameras to be repaired, but due to working off shore we often in need of getting the cameras working if the spare is as usual of a lower quality..I often find bad caps, duff resistors or shorted voltage regulators are usually responsible for most of our camera failures, this is probably due to the huge temperature changes these cameras experience above and below sea level.I have hand written a copy of the schematic from the your video, but as more an industrial electrician by trade I need a bit of help with understanding the circuit.I am hoping to build this cheaply and I will probably use a LM358 (already have one in parts bin) for the DC restore and I have just ordered a 4049 Buffer, but I am wondering what is best to use for the moving coil display?Should I order a cheap Chinese analogue DMM and butcher the display or should I use some other part with the same spec (which I do not know) as your meter?Would greatly appreciate a bit of help on this matter

author: w2aew
author_rank: Super Contributor
timestamp: February 22, 2012, 10:40:34 pm
content: Quote from: lavo-1 on February 22, 2012, 09:47:56 pmI'm glad you enjoy my videos. The LM358 should work ok, since its input common mode range includes ground, and that's a requirement for this application. As for the moving coil meter - I prefer an analog meter movement for this. The voltage at the 0.1uF cap (just below the 1N4148 diode on the right of the schematic) is the parameter that we're interested in. It will be at it's "max" value when the test leads are shorted - simulating a good capacitor. If you use a DMM here, then you'll have to make yourself a table which relates the DMM reading to the ESR reading. To me, it's just easier with an analog meter movement for this application - max is ZERO, and anything less than MAX indicates some level of ESR (which you can calibrate easily with some fixed resistors). So, any analog meter movement will work, or even an old VOM will work. You may just have to adjust the resistance between the diode-cap and the meter to get the full scale reading with the leads shorted.Please let me know if you have more questions.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 01, 2012, 07:10:05 pm
content: Quoteis there any other way possible getting this article? or similarly content elsewhere? PM? or elsewhere? i'll pay if needed to and if price is right (only paypal for intl). i'm not ieee member, just a hobbiest. registering is quite a something for me, probably ended up by asking what ee qualification i have... noneotoh, currently i'm trying to figure out how to do impedance analysis V=IZ in complex or phasor format. math intensive, i havent passed yet. my head is spinning. sigh. almost surrender.

author: olsenn
author_rank: Frequent Contributor
timestamp: March 01, 2012, 07:37:06 pm
content: I'll have to measure the capacitance of my ebay teflon capacitors at 10MHz using my rubidium frequency generator and precision benchtop multimeter. Then again, I'll probably never get around to doing that

author: kripton2035
author_rank: Super Contributor
timestamp: March 02, 2012, 01:25:10 pm
content: again, take a look at my esr meters pagehttp://kripton2035.free.fr/esr-repository.htmlI'm sure you will find one to build yourself with components already in one of your drawers...the "winner" for now being this one (not that expensive in fact) :http://kripton2035.free.fr/digital%20esr/esr-go-russian.htmlthe scope method is nice to know, but an even simple meter is really more handy.

author: saturation
author_rank: Super Contributor
timestamp: March 02, 2012, 02:21:36 pm
content: Write for a copy if no success let me know, IEEE members only get one journal for free, your parent specialty, and this is one I don't get:http://eprints.iisc.ernet.in/cgi/request_doc?docid=42706&_action_null=Request+a+copyQuote from: Mechatrommer on March 01, 2012, 07:10:05 pm

author: robrenz
author_rank: Super Contributor
timestamp: March 02, 2012, 02:38:28 pm
content: Some interesting scope/FG techniques toward the bottom of this.http://www.jammaboards.com/guides/Capacitor_Testing.pdf