SparkFun Cap Meter Kit - In Sheilded Project Box - Cheap & Fairly Accurate - Page 1
Forum section: electronics / beginners

author: SgtRock
author_rank: Unknown
timestamp: March 10, 2012, 12:51:59 am
content: Greetings EEVBees:--I recently built the SparkFun Capacitance Meter (see annotated pictures at bottom). I had to bodger the construction just a bit to get it to fit in a project box. The box has foil shielding for accuracy at lower capacitances. A green led reminds you to disconnect power, and a toggle switch is provided to switch meter on and off. Standard spacing 5mm jacks are used for clip appliance or leads. Blue button zeros the meter. Range is 1pF to 500 µF. Higher ranges can be estimated fairly accurately by connecting caps in series and doing the math. The meter works fine with a 9V wall wart in all but the lowest ranges, where a 9V battery is used to prevent the last digit from jumping around just a bit.--I highly recommend this meter for beginners with little cash. The meter kit costs about 14$ US plus shipping. My total cost, for the shielded enclosure version, using some junk box parts, was about 30$ US. Published accuracy is 2%. This meter may indeed meet is published specs, but, I was only able to characterize this meter in the lower ranges using mica caps. I was unable to catch the meter being out more than 2%. But then I was unable to prove accuracy of better than about ± 10%, and I may have introduced some inaccuracies in building. All the results in the higher ranges indicate good agreement with ratings printed on the caps. Given all the results I believe I can trust this meter as built to ± 5%. All in all a very useful device. It will see much service before I am able to buy something better, at which time I will attempt to characterize this meter more finely, and report my findings. See below link for SparkFun's Cap Meter page.http://www.sparkfun.com/products/9485"If you build a better mousetrap, you will catch better mice."George Gobel 1919 1991Best RegardsClear Ether

author: T4P
author_rank: Super Contributor
timestamp: March 10, 2012, 02:53:55 am
content: You should compare that to a better capacitance meter in perspective but anyway , are sliver mica really maximum 10% ? Wow i thought sliver mica was extremely accurate , i would use a film precision capacitor instead .

author: SgtRock
author_rank: Unknown
timestamp: March 10, 2012, 03:11:32 am
content: Dear DaveS:--Thanks for your post. I fear,I may have inadvertently mislead you. What I said was:"I was unable to catch the meter being out more than 2%. But then I was unable to prove accuracy of better than about ± 10%"--If you look at the pictures closely, you will see that the "±" each Mica Cap is noted in the pictures.All of the Mica Caps I used were either ± 0.5 pF or ± 5%. With regard to the 10% figure, I was only talking about what I could reasonably regard as proven, as to the accuracy of the "as built" meter.--I agree, that I should compare to a better meter. Hence my statement:" I am able to buy something better, ... I will attempt to characterize this meter more finely, and report my findings."--Thanks again for your interest."Before I came here I was confused about this subject. Having listened to your lecture I am still confused. But on a higher level."Enrico Fermi 1901 1954Best RegardsClear Ether

author: A Hellene
author_rank: Frequent Contributor
timestamp: March 14, 2012, 04:14:21 am
content: Ah, I could easily find out that this is theJYE Tech Capacitance Meter 060, which seems to be a straightrip-offimplementation of the legendaryChaN's Capacitance Metersince Mar. 26, 2003, with a few minor modifications; but I can nowhere see any mentions of the original designer, neither at the JYE Tech nor at the SparkFun page... Of course, I am not aware whether JYE Tech is licensed by ChaN or not; but my experience tends to dictate otherwise in this regard.Anyway, reading the schematic sheet from SparkFun I immediately recognised ChaN's Capacitance Meter. A few keystrokes revealed the source of this commercial product, which is suspiciously identical to ChaN's design with a fewelectrically unnecessarymodifications, like the display drivers omission, a controller change and the clumsy implemented addition of a third measuring scale. In my opinion, the original ChaN's design is capable of delivering better accuracy readings because ChaN has payed more respect to the under test component bias stage and the controller I/O loading by the use of drivers for the bias of the under test component and the display, since the design's reading accuracy is affected by the controller's output stage resistance (which has been measured to beRds_ON=24? ±10% at Vcc=5.0V at room temperature) as well as the heavy loading of the controller I/Os.-George

author: T4P
author_rank: Super Contributor
timestamp: March 14, 2012, 04:50:45 am
content: I remember JYE saying somewhere that it is designed by themselves ... maybe inhouse designer ? or copy ?

author: A Hellene
author_rank: Frequent Contributor
timestamp: March 14, 2012, 05:27:21 am
content: Dave, by putting the JYE and the ELM schematics side by side makes clear that it is the same exactly design, based on the same measuring principle and implemented using the same exactly biasing technique as well as the same exactly critical component values -not to mention the same exactly displaying method and format... This is NOT a coincidence. After all, the term "coincidence" has only a grammatical and a philosophical value for those who are able to realise how the human mind works; not a pragmatical one.The term "coincidence" does not really exist for me: Everything that happens has acauseand aneffect; and it does not matter whether we are able to seethe connections betweenor not. Coincidence: There is no such thing, as long as somebody is able to see what has caused the action in question and to speculate --or, even better, to calculate-- the trailing effects of the aforementioned action. The explanation and demystification of this trail of actions and reactions can easily be deduced by asking a simple question:Who benefits?(aka,Follow the money). Anyway, I can understand that I may sound to be quite inflexible on this matter, since peopleare conditionedNOT to combine information; this is what makes them be quite gullible and, thus,controllable.Now, unfortunately for the JYE if they claim ownership of the idea, ChaN did release his design eight years ago; or seven years before JYE, since the latter ones released their device's manual in 2010.02.25, according to their webpage.-George<EDIT> Dear Clear Ether, I think I should apologise for derailing the thread...

author: AlphZeta
author_rank: Regular Contributor
timestamp: March 15, 2012, 05:22:19 pm
content: QuoteThe thing is there are really not that many different designs in implementing capacitance measurements. You can either measure the rise time during charging/discharging or measure the osc frequency using either RC or LC circuit to derive the capacitance value. And the theory is well understood so having similar designs doesn't mean copy IMHO.

author: A Hellene
author_rank: Frequent Contributor
timestamp: March 15, 2012, 06:57:11 pm
content: So, AlphZeta, we are definitely in agreement!If you read my previous messagescarefully, you will see that this is the very reason why Idid notuse the adverb "exactly" to emphasize the adjective "same," which characterises the degree of resemblance of the two --not so different, after all-- designs, in my second point regardingthe measuring principles. Let me quote the passage in question:Quote(Emphasis in mine)What about my other four (4) indisputable points that indicate plagiarism of the ChaN's design by a third party? I am quite certain that if someone disassembles both the binaries of the two devices will find all the proofs he will ever need to support such a claim. But I am not the one who will do it.Well, let's examine this, rationally: Yes, we can both begin designing a capacitance meter, from scratch. It is very possible that both of us will choose to use the same measuring principle. It is alright! It is also possible to also implement it using the same biasing technique; but it will be very unlikely to use the same exactly biasing component values. Of course, it will be a definite indication of one copying the work of the other if we both end up using not only the same display but the same also displaying format (four digits to display three floating point arithmetic characters for the measured value plus one alphanumeric character for the range). No! This screams that it is NOT a coincidence...Please, read carefully what I have posted at my previous message about "Coincidence." Do not forget that, every coin has two faces: If someone can talk aboutConspiracy Theories, someone else would rightfully point at the other side of the same subject matter, talking ofCoincidence Theories! A critical thinking test, now: Why, really, are we constantly listeningfrom authoritative sourcesabout the first of the two previous phrases and NEVER ever about the second one? You can readsomething really interestingI wrote about that, a few years ago in another EE discussions board.-George

author: MarkS
author_rank: Unknown
timestamp: March 15, 2012, 07:15:04 pm
content: Quote from: A Hellene on March 15, 2012, 06:57:11 pmYou make my head hurt!

author: A Hellene
author_rank: Frequent Contributor
timestamp: March 15, 2012, 08:33:26 pm
content: I am trully sorry if I made you feel sad, dear MarkS. And, that is because I do never take pleasure in hurting people.Actually, I am surprised to read such a statement because all I did was to expose my thoughts about a certain subject matter and, most importantly, to support my views with evidence and rational arguments (and not with any ad-hominem sentimental tricks that are actually switching off the critical thinking of the target --does this ring any bells?) and the "why," which is the most difficult part of the rational arguments.Again, I will humbly apologise if, somehow, I managed to hurt your feelings. Was it something I wrote at the message of the other board I linked to in the end of my previous post? Could you possibly help me realise which part(s) of my messages offended you and why, by point them out for me?Respectfully,-George