Fluke 115 and Nanofarad Capacitance Readings - Page 1
Forum section: electronics / testgear

author: Barry A. Waters
author_rank: Contributor
timestamp: April 15, 2023, 06:20:20 pm
content: I just bought a Fluke 115 for general hobbyist & household use to augment an old Radio Shack 22-181 from the 1980's. The specs say it should be capable of reading in nanofarads (nF) to a resolution of 1 nF over a range of 1000 nF, where it jumps to uF scale. Accuracy for that range is +/- ([% of Reading] + ) and is stated as 1.9% + 2.When I attempt to measure a simple Ceramic Disc 104 capacitor (100000 pF) I expect to see somewhere around 100 nF depending on tolerance, quality, etc. and on my old Radio Shack meter I do. On the Fluke in both autoranging and manual nF settings it starts out around 370 nF and climbs to about 1.20 uF (1200 nF). I called Fluke support and they agreed that I should be seeing something closer to 100 nF and told me to take the meter back. I did and got a replacement and it does the same thing. I note that the meter appears to work in all other respects and is very accurate when testing electrolytic caps in the uF range (4.7, 10, 47, 100, 220, etc.).Is there something I and the Fluke rep are not understanding here? Could anyone who has this meter check a 104 Ceramic Cap and let me know what they get? I'm baffled. If it's a calibration issue it may have been a batch because the serial numbers of the two units are only 42 apart.Barry

author: bdunham7
author_rank: Super Contributor
timestamp: April 15, 2023, 06:27:11 pm
content: Can you check that capacitor for resistance and leave it connected for some time? If it is leaky--and yes ceramic discs can get leaky--then it might measure quite differently on meters that use different measuring methods.

author: gamalot
author_rank: Super Contributor
timestamp: April 15, 2023, 06:54:16 pm
content: Quote from: bdunham7 on April 15, 2023, 06:27:11 pmI have a Fluke 117 and it measures 100nF ceramic disc capacitor without any problem. If I connect a 1 megohm resistor in parallel with the 100nF capacitor it will measure about 400nF.

author: Swainster
author_rank: Frequent Contributor
timestamp: April 16, 2023, 11:29:14 am
content: I've got a 115 in front of me, but I dont have an equivalent ceramic cap to test your scenario. Best I can do is a 47nF film cap, which reads 46.5nF on a cheap component tester, and 48nF on the fluke. The largest ceramics that I have on hand are 1000pF which, out of a random selection of 7 pieces before I got bored, all read 1nF, and 2 of them in parallel read 2nF, so looks like the fluke is operating well within it's datasheet spec.

author: Swainster
author_rank: Frequent Contributor
timestamp: April 16, 2023, 12:26:20 pm
content: (Decided not to add this as an edit as it is new data)The plot thickens! By rooting around in a few more boxes I managed to find some unused 104 marked ceramic disks (of the budget aliexpress component kit variety). And these only read 50 to 60nF (e.g. 50nF on the cheap component tester and 60nF on the Fluke).. I was not able to measure any parallel resistance but I'm not really set up for that measurement at home - best I can do is the 100M range on an Aneng 8009. I also had a go at measuring the leakage current with a 1V bias and an old Keithley 480 picoammeter, but without setting up some shielding, all I can say is that the ceramic appears to have more leakage than a film cap (in the 10s of picoamp range), but not really quantify it. I also put a 3M resistor in series with the cap to stop/reduce oscillation.Incidentally, the Aneng capacitance measurement agrees with the fluke and the component tester, but I believe that they all use the same measurement technique so that is not too surprising. Tomorrow I will try to remember to bring the suspicious caps to the office, and try them out on an LCR meter. To be honest, my current theory is dodgy cheap capacitors, but it is possible that the multimeter style measurement technique is causing this issue.

author: Performa01
author_rank: Super Contributor
timestamp: April 16, 2023, 03:19:39 pm
content: Quote from: gamalot on April 15, 2023, 06:54:16 pmSo this is a perfect demonstration of the fact, that a DMM is not the right tool to measure capacitance.A proper LCR-meter would correctly indicate the 100 nF in parallel with 1 megohm (or the corresponding dissipation factor, according to the test frequency).

author: bdunham7
author_rank: Super Contributor
timestamp: April 16, 2023, 03:33:02 pm
content: Quote from: Performa01 on April 16, 2023, 03:19:39 pmYou can always make such declarations when given specific circumstances, but in other circumstances things change. Think about the intended use of the DMM in question. Now consider measuring a 35µF motor start capacitor that may or may not be charged to as much as 400V. Now what is the right tool?Besides, measuring the DCR is within the grasp of the OP even if he had no other instruments. Yes, these and most DMMs will interpret leakage as additional capacitance. I suppose that's not in the manual (I haven't looked) but probably a lot of the intended users of the F11x products wouldn't understand anyway.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 16, 2023, 05:01:36 pm
content: Ouch! With a sister meter (a 117) and another 115 both reading values nearer what would be expected it sounds like my experience is the odd man out so back the meter goes (for the second and final time!). I ordered another 115 from a totally different supplier in another state to insure I don't get one from the same batch as the two I've had. We'll see how that goes.In the interim I tested both cheap ceramic Y5V 104Z KCK (several) and better blue plastic cube 1J63 1ND (several) with no joy while my Radio Shack 22-181 read all just fine at around 100 nF <OR> .1 uF. Damn...Thanks to all who responded! I'll chime back in when my THIRD 115 is in hand...Barry

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 16, 2023, 06:06:23 pm
content: You know that Fluke doesn't repair the Fluke 11x series? If there is something wrong with it they simply destroy it.

author: bdunham7
author_rank: Super Contributor
timestamp: April 16, 2023, 06:37:49 pm
content: Quote from: Barry A. Waters on April 16, 2023, 05:01:36 pmHow close were the other meters? Can you try measuring the DC resistance of the capacitorswith the meter in question?Can you check what the meter reads in the capacitance range with an open circuit (no leads)?Whatever you have going on there is weird and the only explanation I can think of is some sort of leakage either inside or outside the meter. Having two of them with the same problem seems extraordinarily unlikely unless there is a production issue and the problem managed to get by their QC and calibration. The only F11x model I have is a 116 and it correctly reads capacitors down to single-digit nF with almost exact accuracy, +/- 1 count, so that would be my expectation for yours as well.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 16, 2023, 07:43:38 pm
content: Quote from: BeBuLamar on April 16, 2023, 06:06:23 pmYeah, I would imagine that the entire production, calibration and QC process is heavily automated for such a low end (for Fluke) series with little human intervention and not deemed worth repairing if any of them come back. Mass production = Mass disposal? Too bad....Barry

author: Barry A. Waters
author_rank: Contributor
timestamp: April 16, 2023, 08:00:30 pm
content: Quote from: bdunham7 on April 16, 2023, 06:37:49 pmThe second 115 has been repackaged for return and is not accessible. The other meter (Radio Shack 22-181) was within the 20% tolerance for the ceramics 104s and the 5% tolerance for the blue cube 1J63s, which is what I would expect. If the third 115 shows up and has the same issue I will perform your tests. I assume testing the resistance would be the same as if I was testing a resistor. What would I be looking for result wise? For your 'open circuit' test are you asking for what the meter reads in the capacitance setting with no leads attached?Barry

author: bdunham7
author_rank: Super Contributor
timestamp: April 16, 2023, 08:21:37 pm
content: Quote from: Barry A. Waters on April 16, 2023, 08:00:30 pmYou mentioned having and testing a 117 and another 115 as well. What results did those give? I would expect your plastic capacitors to read virtually the same on all meters, but of course the Y5V ceramics will vary wildly with measurement method and voltage.Testing a capacitor for DCR should eventually give an open circuit indication (>60M) although it can take a moment to get there. Yest, the open circuit test can be just the meter with no leads set for capacitance. It should read no more than 2 counts. This is actually a calibration and performance test point.I should have asked--how exactly are you connecting the meter to the capacitors? Is it standard test leads with alligator clips and the tests are hands-off? Or something else?

author: Barry A. Waters
author_rank: Contributor
timestamp: April 16, 2023, 09:38:44 pm
content: Quote from: bdunham7 on April 16, 2023, 08:21:37 pmThose were meters belonging to posters above that reported theirs working as I expect mine too.Barry

author: Martin72
author_rank: Super Contributor
timestamp: April 16, 2023, 09:40:49 pm
content: Quote from: Barry A. Waters on April 15, 2023, 06:20:20 pmI guess the fluke use dc-signal for cap testing, therefore the lower the cap is, the worser it gets.QuoteWe got several 117 here and 1 or 2 115, can check this tomorrow - Could be interesting because we never used them for cap testing.QuoteThere is a calibration "manual" avaible, the cap function won´t be calibrated.https://dam-assets.fluke.com/s3fs-public/114_____cieng0200.pdf?c6lU5ClGysQYEd1McgX5RgPYq8k60kdP

author: bdunham7
author_rank: Super Contributor
timestamp: April 16, 2023, 11:00:53 pm
content: Quote from: Martin72 on April 16, 2023, 09:40:49 pmWith a 0.22µF capacitor (an accurate and very good one) it does as shown in attached photo. The connection of a 10X PP215 probe causes the reading to change from 220nF to 235nF.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 16, 2023, 11:45:37 pm
content: Quote from: Martin72 on April 16, 2023, 09:40:49 pmThat would be VERY much appreciated! Any ceramic or film cap in the nF range from 1 nF to 999 nF would be excellent!Barry

author: Swainster
author_rank: Frequent Contributor
timestamp: April 17, 2023, 07:56:59 am
content: For my particular case, the suspicious 100nF ceramic caps were tested on a hand held LCR meter and a nanoVNA - all confirm that the true capacitance really was arounf 50-60nF. I also found another budget kit of ceramic disc caps, and this was even worse! only 42nF capacitance for a 104 marked cap. In fact, in this particular kit, the 683 marked parts measured 50nF-ish vs 40nF-ish for the 104. I guess that you really only get what you pay for (though the cheap SMD kits are usually quite OK).So the verdict - my Fluke 115 is innocent, whereas cheap kits of ceramic disk caps, not so much. Plus I learned that the markings on cheap ceramics should not be relied upon.

author: Martin72
author_rank: Super Contributor
timestamp: April 17, 2023, 05:31:17 pm
content: Hi,To my surprise we have at least 5 pcs Fluke115...I´ve test them all with the same result - No problems..For the pic I got four from the five, bought between 2009 and 2020, on the desk, everyone measures the same type of cap (ceramic, 100nF).After this I´ve connected a bnc cable to the scope - unfortunately I´ve forgot to make a pic from the 100nF measure...Will repeat it tomorrow.Martin

author: Barry A. Waters
author_rank: Contributor
timestamp: April 17, 2023, 10:11:26 pm
content: Quote from: Martin72 on April 17, 2023, 05:31:17 pmThat's OUTSTANDING! Thank you Martin!I tested several of the 100 nF and 220 nF caps I was using with the meters over the weekend in a charging circuit today on the DS1054Z and found them all to be close enough for my purposes (hobbyist). Even the wonky Ceramic Y5V 104Z KCKs came out OK (0.000066 s / 554 ohm = 119 nF) so I'm sure my problem is not faulty caps. Can't wait for the third meter to show up and see what's what!Barry

author: Martin72
author_rank: Super Contributor
timestamp: April 17, 2023, 10:31:09 pm
content: I find it remarkable that you already had such problems with two 115.Not that it is a general error in the batch.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 18, 2023, 11:35:51 am
content: I don't have problem with Fluke DMM but I do have problem with the Fluke IR3000FC unit. It uses the IR port on Fluke 189, 289, 187, 287 DMM to provide the Fluke Connect to connect to cell phone. I bought 2 units and one works but the other one doesn't. I keep exhanging about 3 of them and still not finding one that worked. So Fluke sent a rep to see me and the first thing he did was to upgrade the firmware and after that none of the units work. He gave up. And to this day I don't know how to buy a Fluke IR3000FC and make sure it would work. The serial number on the units that didn't work are all over the place. Not the same batch I don't think. Also the one that worked before he updated the the firmware has the lowest serial number.So I mean it could happen to have a bunch of them not working right.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 18, 2023, 07:30:46 pm
content: *** NOTE: The assertion below that the Test Leads were the issue is INCORRECT. The REAL issue was ME holding the capacitor leads in contact with the Test Leads with thumb and forefinger! See later posts for details ***And I have discovered the problem. It's not the meter itself but the meter's test leads. It's like they are acting as additional storage capacity and making the the smaller caps look larger than they really are. If I dispense with the leads entirely and insert the cap leads directly into the meter's test lead sockets then everything reads as it should. The Radio Shack 22-181 I have has a dedicated Cap/Resistor test port so that's why it was reading OK - no lengthy test leads involved with it.The test leads that came with the 115 are 55 Inches long so I guess that's a lot of insulated copper when you think about it. I cobbled together a 4 Inch long set and Voila, the meter reads nF caps as spec'ed. I am a happy camper once again!For those of you who were kind enough to test read some caps and reported success with your meters in the nF range, how long were the test leads you used? I'm thinking the shorter the better. I think I'm going to put something together with two banana plugs and a spare header connector so I can have a 'plugin test port' for these things with NO test lead length to worry about.Thanks to everyone who assisted on this as it was driving me nuts! I just couldn't believe such a meter would have a problem like that. I feel bad about turning one in but at least I had my epiphany before I returned the second one. Now what to tell the wife about the third one that arrives tomorrow...Barry

author: Martin72
author_rank: Super Contributor
timestamp: April 18, 2023, 08:10:01 pm
content: Ah !

author: gamalot
author_rank: Super Contributor
timestamp: April 18, 2023, 08:17:12 pm
content: 55 inches of test leads should not cause any problem here, most of the test leads for multimeters in the world are similar to this length.

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2023, 08:27:08 pm
content: Quote from: Barry A. Waters on April 18, 2023, 07:30:46 pmI tried my F116, which should yield the same results, using the TL175 leads and insulated alligator clips that came with the meter. I got exactly 220nF with my .22µF 'standard' and 7nF with a 6800pF mylar, so all within 1 count. Moving the leads around and even putting 1A @ 1kHz through a cable wrapped around one test lead 5X only resulted in a few counts of deviation. So either you have some industrial-grade interference at your location or something else is going on.Are your leads twisted together or touching or something? I took no special precautions with mine. Did you try measuring DCR? Also, when you are turning the meter on, are you holding down any buttons, such as to defeat the power-off or backlight-off functions?

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2023, 09:01:15 pm
content: Quote from: Barry A. Waters on April 18, 2023, 07:30:46 pmWelcome to the world where precise measurements are a science on their own !However those of us with a few years under the belt will have seen many a twisted wire trimmer in a circuit used as some final trimming/tuning.To the observant, long lead effects on measurements are just normal.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 18, 2023, 10:58:50 pm
content: Quote from: bdunham7 on April 18, 2023, 08:27:08 pmI can't speak to your success with the TL175 Test Leads as that is an upgrade from the Test Leads that currently come standard with a new Fluke 115. Perhaps you could repeat your test with the lesser quality Test Leads the 115 comes with?Barry

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2023, 11:20:02 pm
content: Quote from: Barry A. Waters on April 18, 2023, 10:58:50 pmWhich ones are they? The TL75 with plain red and black probes? And were you using the slip-on alligator clips or something else?I'll try the TL75 before I finish this post.......and I'm back, no change using TL75 and the older Fluke alligator slip-ons.I keep begging you to measure DCR, and if you do also try measuring the DCR of the leads when shorted together. I had a strange problem recently with older but unused Fluke leads (TL71 IIRC) where there was a tarnish or something on the probe tips that had to be polished off--isopropyl didn't help--and I think it may have been outgassed stuff from the silicone leads. I was getting strange DCR readings up to 30R when shorting the leads, after polishing with "Barkeepers Friend" I now have 0.2R pretty reliably. I'm not saying that's your issue, but if using your own custom leads fixes the problem entirely I don't know how it could be anything else. It certainly isn't a natural characteristic of test leads, especially not in the 100nF region. 5-10pF, perhaps, but these meters and their measuring method doesn't get near those values.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 19, 2023, 01:52:02 pm
content: Quote from: bdunham7 on April 18, 2023, 08:27:08 pmYes... ME! And THAT was my issue. Thank you for not giving up on me bdunham7, even when I thought I had found my problem. As you and gamalot have pointed out, the Test Lead length of 55" is common and should not be the problem, and it wasn't (I have added a note to this effect in my post stating the leads were to blame above).I was holding each lead of the capacitor in contact with its test lead with thumb and forefinger for lack of suitable alligator clips. I now assume I was measuring the capacitance of the capacitor AND the human tissue surrounding the contacts. The electrolytics measured OK because my fingers only threw things off +/- 1 uF, not really enough to notice. With nF stuff it was MORE than enough to notice, hence my dismay.What a stupid problem to havePlease feel free to tell me so!Barry(Who now has a fresh pair of mini-alligator clips)

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 20, 2023, 02:44:03 pm
content: Now you sucessfully get Fluke to destroy 2 perfectly good meters.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 20, 2023, 09:12:41 pm
content: Quote from: BeBuLamar on April 20, 2023, 02:44:03 pmAnd how would that be so?Barry

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 20, 2023, 10:36:52 pm
content: If you returned them and they accepted them they are going to destroy the ones you sent back.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 21, 2023, 01:41:07 pm
content: Quote from: BeBuLamar on April 20, 2023, 10:36:52 pmBut the scenario that you portray above and which so disturbs you is not what happened.Barry

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 22, 2023, 12:01:45 pm
content: So you didn't return the meter?

author: Barry A. Waters
author_rank: Contributor
timestamp: April 22, 2023, 01:14:33 pm
content: Quote from: BeBuLamar on April 22, 2023, 12:01:45 pmIf you were to read my posts above you may gain a better understanding of what transpired.Barry

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 22, 2023, 03:50:29 pm
content: I read that you brought the meter back and they replaced it in the first post. In another post you said the second meter is packed for return and no accessible. To my best understanding you returned 2 meters. Isn't that so?

author: Barry A. Waters
author_rank: Contributor
timestamp: April 25, 2023, 12:24:06 pm
content: Quote from: BeBuLamar on April 22, 2023, 03:50:29 pmNo. I would suggest you slow the speed of your reading and place more emphasis on comprehension.Barry

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: April 25, 2023, 12:50:55 pm
content: Quote from: Barry A. Waters on April 25, 2023, 12:24:06 pmI would have to agree with BeBuLamar.In reply#7, you stated: "it sounds like my experience is the odd man outso back the meter goes (for thesecondand final time!). I ordered another 115 from a totally different supplier in another state to insure I don't get one from thesame batch as thetwoI've had. We'll see how that goes.So what that you went through 2 meters because of operator error. It's no big deal.

author: Swainster
author_rank: Frequent Contributor
timestamp: April 25, 2023, 01:39:08 pm
content: I think the point of contention is that the meters had been destroyed. While its not impossible, i personally doubt it as Fluke Service will probably run the meter through the official performance test before destroying them. I think it's been established that they would have passed this test.

author: Barry A. Waters
author_rank: Contributor
timestamp: April 25, 2023, 04:56:32 pm
content: I heartedly agree with Swainster and 4thDoctorWhoFan (Tom Baker is the only REAL Dr. Who!) but what Mr. BeBuLamar keeps repeatedly missing is the statement below in Reply #22:Quote from: Barry A. Waters on April 18, 2023, 07:30:46 pmWhen the 2nd meter was repackaged for return two other posts convinced me to reopen it and keep digging. That process left me thinking that additional capacitance in the leads was to blame (incorrect) but that the 2nd meter (as well as the 1st) was fine (correct).I'm a person that believes if someone is going to lay blame for something on someone's doorstep it is best that they know what they are talking about. Mr. BebuLamar did that and after repeated attempts could STILL not correctly determine that only 1 meter was returned. That it was returned under advisement from a fluke Tech Support person seems to also have escaped Mr. BeBuLarmar's attention.Why he is so concerned over the fate of a low-end consumer piece of equipment I do not know. Fluke is capitalized at somewhere over $25B and if they destroy returned items that's their way of saying "We don't care one iota about that. It's not economical for us to do anything else with it.". Maybe he will call them and get them to change their destruction policy (if they indeed have one).He may also wish to call Lowes and inquire about their policy regarding returned items because that is where the one meter that was returned went. Unfortunately, I don't think Lowes cares much about it either. (Entertaining Bonus Material Coming Up!)When I returned the ONE and ONLY meter the person at the Returns Desk said they couldn't do an exchange but had to issue a Credit and then re-Debit the amount on the card that was used originally. OK, net zero so no problem but the guy seemed confused about how to do it. Ultimately he got me another meter and off I went. A few days later I noticed the Credit at the bank but no subsequent Debit. A quick perusal of the return receipt backed this up. Credit issued but no Debit.I called the store and sure enough things were amiss. The guy should have scanned and Debited the replacement meter before I left. The guy I spoke with asked if I could come in with the packaging but I don't live in the town where it was bought and only go there every now and then. They also could NOT take payment via Credit Card over the phone (company policy) so what does the guy say? Don't worry about it. Keep it!Tempted? For about 10 seconds BUT you can't go through life like that as Karma will get you SO I was able to drop in today and pay. The person at the desk looked at me like I was stupid for returning to pay for it since I'd gotten away clean and I feel the guy that told me to keep it did so only because it was a hassle and he didn't want to deal with it. Go figure!Barry