Keysight 34465A Capacitor Measurement Issues? - Page 1
Forum section: electronics / testgear

author: Brando753
author_rank: Contributor
timestamp: July 28, 2020, 10:29:43 am
content: I purchased a Keysight 34465A back in 2017 but have only used it occasionally as I have not had as much time for my hobbies as I would have liked.I was measuring some caps yesterday and was getting a value different from what I would have expected. I went to verify with my Fluke 87V on the same caps, found a rather large discrepancy on the 10uF cap, tested again with a 0.1uF cap, and still found a difference. For the table below, I use ±(1% +2) for the accuracy of the Fluke 87V capacitance measurements and ±(.4% +.1) for the accuracy of the Keysight 34465A capacitance measurements as specified in the respective DMM's spec sheets. Obviously the same 10uF and 0.1uF capacitors are being measured on both meters.Test MeterTest RangeCap SizeMeasurementFluke 87V10 uF (Auto)10 uF9.95 uF ±0.12Fluke 87V100 uF (Manual)10 uF10.0 uF ±0.3Fluke 87V10,000 uF (Manual)10 uF10 uF ±2Keysight 34465A10 uF (Auto)10 uF9.482 uF ±0.038Keysight 34465A100 uF (Manual)10 uF9.52 uF ±0.04Fluke 87V100 nF (Auto).1 uF87.6 nF ±1.1Fluke 87V1 uF (manual).1 uF0.088 uF ±0.003Fluke 87V10 uF (manual).1 uF0.09 uF ±0.02Keysight 34465A100 nF (manual).1 uF140.05 nF ±0.56Keysight 34465A1 uF (auto).1 uF0.1167 uF ±0.0005Keysight 34465A10 uF (manual).1 uF0.085 uFWhat stands out to me is that the same 0.1uF capacitor measured in different ranges on the Keysight seems to be out of spec within the same meter even when accounting for the error rate. Am I correctly calculating the error rate, or is this a misunderstanding I am having. The 100nF range reports the cap at 0.13949uF, where the highest value in the 1uF range is 0.1172uF, a difference of at least 0.0223uF out of spec. The above discrepancy leads me to believe that the Keysight is returning the incorrect value and not the Fluke. I have never had personal equipment calibrated before, but my understanding of the process is no adjustments are made; it is just a confirmation that your device is operating within its specs, and it is the history of verifications (calibrations) that show a meter is stable and can be trusted. If that is the case, does this mean my Keysight DMM may be operating out of spec, and even if adjustments are made, its drift out of specs suggest this meter's measurement can not be trusted? The Keysight DMM was on for 19 hours and 35 minutes before I tested the capacitor values with a reported temperature of 25.6 C which is 2.5 C above the temperature the meter was calibrated at in the factory. The Keysight DMM was auto-calibrated within 12 hours of the measurements being taken.Just before I posted this, I went to take a look at the factory calibration certificate on the Keysight. I noticed there was no measurement of the capacitance range, is that not generally tested on these meters? See the Certificate attached.

author: gamalot
author_rank: Super Contributor
timestamp: July 28, 2020, 10:58:22 am
content: I checked my 34465A and it performed well in capacitance measurement. Has your multimeter firmware been upgraded to the latest?

author: Brando753
author_rank: Contributor
timestamp: July 28, 2020, 11:03:52 am
content: I did a firmware upgrade a few weeks ago once I learned the DIG option had been included for free, I am currently running firmware A.03.02-02.40-03.02-00.52-02-01. What a bizarre firmware versioning numbering system.

author: mawyatt
author_rank: Super Contributor
timestamp: July 28, 2020, 01:03:13 pm
content: Received the Keysight 3445A a couple weeks ago (what a nice instrument!!). The capacitance readings agree with the two cheap component testers I have and the "free" Keysight U1232A just arrived and it agrees with the 34465A. I tested 1nF, 100nF and 10uF.Best,

author: Kleinstein
author_rank: Super Contributor
timestamp: July 28, 2020, 01:16:56 pm
content: What type of capacitors were tested ?Some capacitors (electrolytic and X7R and similar) are not suitable for a stable capacitance. The 34465 may also react odd to capacitors with a lot of DA (like would old oil filled MP capacitors).For such a comparison one should use film caps like polypropylene or polyester type.

author: Grandchuck
author_rank: Super Contributor
timestamp: July 28, 2020, 01:31:12 pm
content: Mine is not useful for tasks like selecting matched values for filters and such. I posted about this issue:https://www.eevblog.com/forum/testgear/keysight-34465a-capacitance-issue/msg3094606/#msg3094606

author: TimFox
author_rank: Super Contributor
timestamp: July 28, 2020, 01:34:40 pm
content: I believe that all of these meters use a glorified 555-equivalent astable multivibrator as the basis for the capacitance measurement, as opposed to an LCR meter that measures the complex impedance at a specified frequency. This means that the test parameters (voltage and frequency) are not specified for an individual test, and may change with range setting. As mentioned above, some capacitor types are inherently non-linear, and the measured capacitance will vary with these parameters.

author: Brando753
author_rank: Contributor
timestamp: July 28, 2020, 01:45:16 pm
content: The 10uF capacitor was electrolytic the .1uF was Ceramic Y5V its all I had available. To clarify, are you suggesting that the capacitance is being effected by the measurement itself and that is possibly causing the differences seen?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 28, 2020, 02:14:50 pm
content: The class 2 ceramic caps are known to be nonlinear. That is the capacitance depends on the applied (DC) voltage. This could explain some of the oddities.With electrolytic caps there can be leakage current and the rather high dielectric absorption that can effect the measurement. Chances are the meters use difference frequencies and different DC bias / amplitude. So they can react different to non ideal capacitors.

author: Grandchuck
author_rank: Super Contributor
timestamp: July 28, 2020, 02:35:11 pm
content: Comparing values with other instruments indicates the problem is an intermittent issue with the 34465A. It could be affected by the type of capacitor but that is not the main point. Keysight has admitted that it is an intermittent.

author: Brando753
author_rank: Contributor
timestamp: July 28, 2020, 02:54:44 pm
content: For the sake of minimizing possible measurement issues, I will place an order on digikey for some more stable capacitors and re-test. Trying to keep the price reasonable would these capacitors be appropriate for testing?0.01uF0.1uF1uF10uFGrandchuck, I will measure them over time as well, right now trying to figure out if I can make my meters agree.

author: TimFox
author_rank: Super Contributor
timestamp: July 28, 2020, 03:39:59 pm
content: Again, a non-LCR meter ignores loss (ESR) in the capacitor, as well as non-linearity and hysteresis ("soakage", or dielectric absorption).Y5V sucks for voltage-dependence (non-linearity) and soakage. Electrolytics have high loss and leakage current.If you want low-loss, linear, stable capacitors in this range for your tests, you probably should use polypropylene wire-lead parts.10 uF is available, but somewhat expensive. The other values are readily available at reasonable price. NP0/C0G ceramic is also good. Polyester ("Mylar") and X7R ceramic are mediocre. Polystyrene is great, but now commercially obsolete. Silver mica is good, but expensive compared with NP0/C0G.

author: alotvac
author_rank: Newbie
timestamp: July 28, 2020, 03:47:38 pm
content: Might be interesting to send a sample set around for comparison by other 34465A users?

author: mawyatt
author_rank: Super Contributor
timestamp: July 28, 2020, 04:27:06 pm
content: The 5 devices I have all agree within reason for various (film, ceramic and electrolytic) 10nF, 100nF, 1uF, 220uF and 470uF caps. The devices are 2 of the cheap "Component Testers", a Keysight 34465A, a Keysight 1233A and a old (20yrs) Fluke 87. As expected the film types agree the closest, followed by the ceramic and electrolytics.Of course one should use a proper LRC instrument for accurate capacitor measurements, but for general checking and matching like caps these devices should suffice.Best,

author: Kleinstein
author_rank: Super Contributor
timestamp: July 28, 2020, 04:40:23 pm
content: AFAIK the capacitance mode with the 34410 was more like an after-though (the hardware allowed it, though not the more normal way) and is using a slightly unusual mode. This way the effect of losses / leakage can be different than with other meters. Normally the measurement with the electrolytic cap should work better though, if the cap is not used in reverse.Still it would be nice if one could also check electrolytic caps - that's what the larger ranges are useful for. A small battery in series may help to to provide some bias.Mylar caps are not ideal, but still not that bad. So they should be still OK. One can find relatively large PP caps (e.g. up to some 50 µF, but bulky) as motor-capacitors. If unused they should also be OK.Possible issues with the capacitance ranges on the 34465 could be worth a quick test.

author: mawyatt
author_rank: Super Contributor
timestamp: July 28, 2020, 04:47:44 pm
content: Quote from: alotvac on July 28, 2020, 03:47:38 pmGood idea. I'll donate a custom PCB which the caps can mount too if someone will send the precision caps. The PCB is used for precision resistor measurements (4 resistors of various types, 0603,0805, 1206, or leaded, jumper selectable) and has a thermistor for PCB temperature recording.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: July 28, 2020, 04:51:44 pm
content: This directly plugs into the DVM from panel. Precision DVM calibrator (DC, AC and R) shown on 34465A, the two 34401As have the Resistor Calibration PCB device mentioned.Best,

author: Grandchuck
author_rank: Super Contributor
timestamp: July 28, 2020, 04:52:21 pm
content: Quote from: Brando753 on July 28, 2020, 02:54:44 pmLooking forward to your results. Also interested in the grounding/shielding tip offered by Keysight (I hope you give that a try). In my case, it helped some but the 34465A is not really a reliable capacitance instrument, IMHO. Otherwise it is a fine instrument!

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: July 28, 2020, 05:50:54 pm
content: mawyatt, interesting setup.I never used my 34461A and 34465A for capacitance measurements, those are the domain for dedicated LCR meters. LCR can tell you so much more than mere DMMs when it comes to testing capacitance and the health of capacitors.I looked through my annual calibration reports from Keysight for these meters, as it contains a lot more info than the certificate. Capacitance is indeed not included in the calibration.

author: mawyatt
author_rank: Super Contributor
timestamp: July 28, 2020, 06:14:45 pm
content: Quote from: NoisyBoy on July 28, 2020, 05:50:54 pmThe setup is very convenient, no tangling leads to deal with. They also serve as a very good zero ohm (2 & 4 wire) and zero voltage reference, just rotate CCW 90 degrees. I've also found that the PCBs are ~5 degrees F warmer than ambient (77F) using the on-PCB thermistor. These DVM and Resistor Calibrators support various components, thus the possibility of using them for the Precision Capacitors.Agree, the DVM should not be considered as "Precision Capacitance" measuring devices, that's what LRC meters are for!!! However, they can certainly be considered as "Precision Resistance & Voltage/Current" measuring devices, which is what they were intended to be.Best,

author: Brando753
author_rank: Contributor
timestamp: July 29, 2020, 09:31:23 am
content: Quote from: TimFox on July 28, 2020, 03:39:59 pmYea I am going ahead and ordering four Polypropylene capacitors from Digikey, I replaced the Polyester one with a10 uF PolypropyleneThe four capacitors I will test between my meters is now:0.01 uF0.1 uF1 uF10 uFQuote from: mawyatt on July 28, 2020, 04:47:44 pmMawyatt, the design you have is cool; I figured I would order a PCB board from JLCPCB, which has two banana plugs connecting to the caps and then put a banana jack for an earth grounding point for a ground fill. Do you have a Manufacturers Product Number for those banana plugs, they look nice. This was what I was planning to do:Grandchuck, if a board is used like Mawyatt's design, I don't think there will be any need for grounding as there won't be a cable outside of the meter, but an earthed point on the PCB could go to an earth-fill on both sides I suppose.Quote from: Kleinstein on July 28, 2020, 04:40:23 pmYea, I was aware it was a late addition to the meter, but still, it leaves me a little perplexed by the values I am seeing. Once I get a more stable capacitor in, we will be able to rule out if its just the cheap electrolytic and ceramic caps causing the odd readings or if there is more here. I would expect a meter that specifies its accuracy to measure within the error rate specified i.e., ±(.4% +.1) for the Keysight of what it reports. If the capacitance of the capacitor is changing under test, then there is not much that can be done, but that is what getting the more stable caps will show.

author: Grandchuck
author_rank: Super Contributor
timestamp: July 29, 2020, 01:49:37 pm
content: One of my attempts is pictured below. It helped just a bit. Other attempts:1/ different electrical outlets2/ different locations in the lab3/ other capacitors4/ other rooms in my home5/ grounding and shieldingIn my case it is an intermittent situation (just as Keysight indicated). Good luck with your experiments!

author: mr.fabe
author_rank: Regular Contributor
timestamp: July 29, 2020, 10:51:14 pm
content: I have a Keysight 34461A that I can test for comparison purposes. The capacitors used for the measurements will be mica, polystyrene, polycarbonate, polyester, or tantalum types, depending on the capacitance range using an IET Labs RCS-502 box. The caps have a 1% tolerance.The four vaues I will test will be...0.01 uF0.1 uF1 uF10 uFSince I will be using a precision decade box, I can test any specific value needed. Just let me know...

author: mawyatt
author_rank: Super Contributor
timestamp: July 30, 2020, 12:32:29 am
content: Quote from: Brando753 on July 29, 2020, 09:31:23 amI don't know the part number as these came from eBay which is hit or miss. I ordered some jacks and they arrived and were not what was shown or described, and these were from the same source. So I have a bunch of various plugs and jacks from eBay and they all are different, plus most took months to arrive!! I usual order stuff from eBay well in advance (many months) of anticipated use, then sift thru the junk to hopefully find something useful!Best bet is to order the banana plugs from Digikey, Mouser or Newark so you can be sure to get what you want.The design you show has 3 places for the plugs, I don't think this will work on the 34465A since it's input is configured like the 34401A where the inputs are arranged in-line with standard banana type separation (19.05mm I believe). If you look at my PCBs the plugs are located in the 4 corners in-line, so just plugs into the top 4 jacks on the meter. It supports 4 devices and selectable by jumper, so support 4 caps on a single PCB. Rotated 90 degrees CCW (see image) also becomes a really good zero ohm shunt as you can see (bounces around ~+-0.0001 ohm), this is not a relative measurement but does have Offset Comp ON as shown.I have a PCB I'll donate to pass around with the 4 gold plated plugs if someone will send the precision caps, as I don't have any. Since I only have 1 spare PCB if enough folks want these I can reorder. Here's some PCB views.Best,

author: Brando753
author_rank: Contributor
timestamp: July 30, 2020, 06:50:01 am
content: Quote from: mawyatt on July 30, 2020, 12:32:29 amAh that's a shame, I always have a hard time searching digikey or mouser for connectors that are just like I want for some reason, the ones you had which appear to be both jacks and plugs seemed really cool. I am just going to go withthesesince each board only needs two of them then.Quote from: mawyatt on July 30, 2020, 12:32:29 amThe third hole is a grounding jack, not a plug, so it should ideally not extend much below the board, but if it does then, I can just use it as a solder point for a wire to earth ground. The grounding jack was put in because of Grandchuck's mention of a possible grounding issue to give as much shielding as possible, and it does not have to be used; you would have two plugs for the meter and one jack for earth ground.The only problem I see with using your boards is the caps I found on Digikey are kind of big. The 10 uF cap is L 42mm x W 27mm x H 18.mm with a lead spacing of 37.5mm even the small .1 uF cap is 7.2mm x 6.0mm x 11mm with a lead spacing of 5mm, could any of these fit on your board? I got these caps because of the range of capacitance is suitable for testing, they are not super expensive (less than $5 each), they are Polypropylene so they should be stable, and they all have tolerances no greater then ±5% (the .1uF and 1uF being ±2%).I am ordering several extras of the .1 uF and 10 uF (just the two) to make 2~3 extra sets of them to mail out; I am limited on how many I can make cause even at only the two boards it will cost me roughly $14 per set, so I can't give out a bunch sadly. Mawyatt If you don't need the banana jacks/plugs or PCB board, I can send you all four caps when I get everything. I will take initial measurements on my meter before I send any caps out so we can get a reference between multiple meters on the same caps.Quote from: mr.fabe on July 29, 2020, 10:51:14 pmI would greatly appreciate it! More data points the better.

author: mawyatt
author_rank: Super Contributor
timestamp: July 30, 2020, 03:03:37 pm
content: Quote from: Brando753 on July 30, 2020, 06:50:01 amThe spacing between the top hole (+) and bottom hole (-) is ~30mm, the normal spacing for the leaded resistors is ~14mm. I can see how you can fit all 4 capacitors. If you go to the larger center hole on the bottom then you have ~33mm.Having an on-PCB thermistor is beneficial to record the measurement temperature.Wondering if I should order more PCBs if enough folks are interested, maybe build up a few completed units to ship around? Think the total cost with quality polypropylene caps would be ~$25, so not too expensive. Shipping around the US should be ~$5 since these will likely fit into a standard Priority small box.I can assemble a unit with your supplied caps if you want.Best,

author: Brando753
author_rank: Contributor
timestamp: July 30, 2020, 03:51:06 pm
content: Quote from: mawyatt on July 30, 2020, 03:03:37 pmI have already purchased the capacitors I listed from Digikey yesterday, I purchased: 2x 01uF, 5x .1uF, 2x 1uF, 5x 10uF. If you want one of the sets I can mail it to you when it arrives. This is enough capacitors for 2 complete sets of all four cap sizes and 3 half sets (.1uF & 10uF only).My concern with your board design is with respect to the size of the caps, not just the lead spacing, again if we take the 10uF capacitor and lay it out on a board with the 4 banana plugs in standard spacing like your board has it would look like this:where the cap is over the jack spacing. And that is just a single capacitor of the set. Either way, I figure a cheap order from jlcpcb with shipping should cost around $15 and have enough boards to make all the sets even if each board only has a single cap on it. I ordered enough banana plugs to make one board per cap if necessary.

author: mawyatt
author_rank: Super Contributor
timestamp: July 30, 2020, 05:56:26 pm
content: That's a big cap!! Probably better to go with your custom PCB designed for that big cap rather than try and adapt to use my PCB. Don't worry about sending the caps unless you want me to measure them and mount them on one of my PCBs and return it to you.Since you are going to roll your own PCB for this big cap, why not include a couple smaller caps in parallel so you can trim and of course mount smaller caps as the main capacitance (think that's what you were going to do)? Also consider including a accurate thermistor to record PCB temperature. I've found that the PCBs I've shown are about 5 degrees F above ambient when mounted to the 34465A or 34401A. Later when I start a log of various measurements (have precision voltage references also, LM399 & LTZ1000 based, ADR4550, LT1236, ADR01, and ADR435) I'll record very accurate temperatures.Didn't realize you had already ordered the caps, what brand did you order?Good luck and keep us posted on your progress.Best,

author: egonotto
author_rank: Super Contributor
timestamp: July 30, 2020, 08:02:47 pm
content: Hello,can someone use a scope and measure the voltage of the Capacitor measurement from Keysight 34465A?Best regardsegonotto

author: Brando753
author_rank: Contributor
timestamp: July 30, 2020, 08:10:39 pm
content: Yea, it is a big cap. The board I am planning is just a fancy holder for the cap, not much more. All I want to see is if I can get my two meters to agree, see if the range issues go away, see if my meter agrees with other 34465A's, and finally see if the intermittent issue reported by Grandchuck shows up on these stable capacitors with and without the earth plane. I'm not sure I understand what the point would be in placing multiple caps in parallel would be, I want a stable measurement, I don't care what the actual value is so long its constant over time and meters. The plan is to mount a single cap per board, and the board design is so that any of the caps can attach to it. As for the thermistor, that's a good idea. I reached out to Digikey to see if I could add anything to my order before they shipped out, but they said it was too late; I might hold off before I order them since the boards will take 15 days or more anyways and I can make sure I don't need anything else. I have never used a thermistor in a design before, so I am not sure what makes one more accurate over any other, I was looking at thisNTCG163JX103DTDSbut would like some advice. Granted, without having two logging meters, I can't log temperature and capacitance at the same time. However, it is still nice to have the ability to measure the board temperature, and my fluke can average at least.The caps I ordered were the ones I linked earlier specifically:Vishay KP1830310061 for 0.01 uFVishay BFC241641004 for 0.1 uFVishay BFC241671005 for 1 uFVishay MKP1848S61070JP2C for 10 uF

author: Brando753
author_rank: Contributor
timestamp: July 30, 2020, 08:11:21 pm
content: I can, one moment.

author: Brando753
author_rank: Contributor
timestamp: July 30, 2020, 08:18:44 pm
content: Keysight 34465A Measuring 0.1 uF cap:Keysight 34465A Measuring 1uF cap (Had to change time scale):

author: Grandchuck
author_rank: Super Contributor
timestamp: July 30, 2020, 08:28:26 pm
content: With 10 nF capacitor connected ... waveform attached.

author: Grandchuck
author_rank: Super Contributor
timestamp: July 30, 2020, 08:38:09 pm
content: With 50 mS time base.

author: mr.fabe
author_rank: Regular Contributor
timestamp: July 30, 2020, 11:19:57 pm
content: I ran a few comparisons between the 34461A, U1733C, and an LC103...

author: mawyatt
author_rank: Super Contributor
timestamp: July 31, 2020, 01:07:13 am
content: Quote from: Brando753 on July 30, 2020, 08:10:39 pmSince you haven't ordered these I would try and get a thermistor with a higher "B" value, Keysight has some notes on this. I have different types (chip, bead and hermetic) but the ones I use are 10K with "B" value of ~3940.I was discussing parallel to try and home in on a specific value, 1.0uF or 10.0uF for example. Those caps look nice, Vishay makes nice components, their resistors are really stable, so suspect these caps will be good as well.BTW don't use USPS shipping from JLCPCB, I had an order that took over 6 weeks to arrive. I pay extra and use DHL, it costs much more but the delivery is reliable and quicker.Best,

author: Brando753
author_rank: Contributor
timestamp: July 31, 2020, 12:48:26 pm
content: Quote from: mr.fabe on July 30, 2020, 11:19:57 pmWithout looking at the error values those all look very reasonable, if I was getting numbers matching like that I would not be so worried. I Will see if I can replicate when I get the Polypropylene caps boards together.Quote from: mawyatt on July 31, 2020, 01:07:13 amI took a look for any app notes by keysight and I could only find two mentions App Note titled 'Practical Temperature Measurements' which describes what they are but not any good criteria for selecting ones that best with this meter and then again in the "Keysight Truevolt Series DMM Operating and Service Guide" where it warns:Quoteand then says to learn more read the already mentioned app note. Even though the menu options on my meter clearly support a 10K thermistor... Would one like theB57221V2103J060work well?

author: mawyatt
author_rank: Super Contributor
timestamp: July 31, 2020, 02:03:33 pm
content: The 34465A has both 5 and 10K settings for thermistors, but the App Note indicates only 5K. Think the App note is old and Keysight has included a more modern value with the 10K in the 34465A. Since you are just interested in a small temperature range around room temp I'm sure the 10K is OK, and that's what I use. I have both 5K and 10K is various packages, but use the 10K because they are 1% tolerance, my 5Ks are 3% I believe.I like the hermetic sealed devices rather than surface mount, like this one.https://www.digikey.com/product-detail/en/tewa-sensors-llc/TTDO-10KC3-8/1912-TTDO-10KC3-8-ND/12367418The device you've selected should be fine, but if you haven't ordered yet consider the hermetic thermistor indicated. If you want to get really accurate you could calibrate with ice and boiling water.Will be interesting in seeing how well other 34465A compare. One could create a somewhat standard array and send around the US in a month or so and then remeasure upon return to confirm & compare readings.You might consider making your PCB with a set of headers, so you can "jumper" different cap values for measurement. The small additional resistance and capacitance shouldn't be a factor. This is what I did with the resistor setup, but this was arranged so the extra resistance of the headers and jumpers didn't effect the readings in 4 wire Kelvin measurements. The force header and jumper are "outside" the sense header and jumper, and the sense header and jumper carry no current so no IR drop.Best,

author: AndyC_772
author_rank: Super Contributor
timestamp: July 31, 2020, 03:39:46 pm
content: HiI have a 34465A. Here's a few measurements of a 100n 1206 capacitor on different ranges:99.43n (100n range).0982u (1u range).099u (10u range)For comparison, the same cap measured on my Fluke 89 IV94.4n (100n range)0.100u (1u range)Not sure what the spec is meant to be, but I certainly wouldn't describe the Keysight as faulty.

author: mawyatt
author_rank: Super Contributor
timestamp: July 31, 2020, 04:41:20 pm
content: I just made a few measurements with a kludged up mylar film capacitor array trying to center at 100.00nF.Keysight 34465A100.05nF0.1000uF00.100uF000.10uFKeysight U1233A100nF00.10uFFluke 870.100uF00.09uFBest,

author: gamalot
author_rank: Super Contributor
timestamp: July 31, 2020, 06:06:54 pm
content: Here are some test results of my Soshin 1uF mica capacitor, I also completed some tests in other ranges, and there is no problem except the loss of significant digits.

author: Brando753
author_rank: Contributor
timestamp: July 31, 2020, 06:39:52 pm
content: Quote from: mawyatt on July 31, 2020, 02:03:33 pmMan, those are so much more money then the cheap surface-mount ones, but if you know they work well with the meter, I will go with them. I want these boards to mount on similar to your setup, and I fear if I try and place all the caps on the board, it will make it unwieldy to use. The more postings I see from people, the more I fear my unit may be defective, but when the caps come in, I will be able to see for sure; I Will find out soon enough, I suppose.Quote from: AndyC_772 on July 31, 2020, 03:39:46 pmIf I did the math correctly then the Fluke 89 IV with an accuracy of ±(1% +5 counts) is reporting the caps to be within the range of 93.0 ~ 95.8, the Keysight should have an accuracy of ±(.4% +.1%) giving a range of 98.93 ~ 99.93. So one of your meters could be slightly out of spec, or it could be the cap type, the Fluke manual for that specific meter does mention the accuracy is only for film type and better capacitors. Either way, your different ranges don't disagree with each other, so they are internally consistent, which is more then I can say about my meter.Quote from: mawyatt on July 31, 2020, 04:41:20 pmAgain more reason for me to believe that my meter may be faulty, thanks for checking.Quote from: gamalot on July 31, 2020, 06:06:54 pmYea, the Keysight 34465A is definitely within spec with it reporting the value anywhere within .9941 ~ .1.0041, man I need to get myself an LCR meter one of these days that must be nice to have.

author: AndyC_772
author_rank: Super Contributor
timestamp: July 31, 2020, 07:04:43 pm
content: Bear in mind, the lead capacitance may be significant too. I made a fairly rudimentary effort to keep the probe leads in approximately the same place between measurements with the same meter, but not between one meter and the other. There's room to be a good deal more scientific in the way the measurement was done.If it's helpful, I have an HP 4395A with impedance analysis kit, so I may be able to determine the "true" capacitance of the cap (if, indeed, there is such a thing in an absolute sense when it comes to real, non-ideal components), as well as any non-ideal behaviour that may make it appear to have a different capacitance when measured in different ways.

author: TimFox
author_rank: Super Contributor
timestamp: July 31, 2020, 08:19:43 pm
content: Lead capacitance should not be significant at 10 nF with a proper connection. It becomes important when using a tweezer probe to measure below 10 pF or so.Series inductance will become important at high frequencies, but the multivibrator measurement does not deal with it in a well-defined manner. On a true LCR meter, one will see the displayed capacitance value increase with test frequency, as the increasing inductive reactance starts to cancel the decreasing capacitive reactance at higher frequencies.

author: mawyatt
author_rank: Super Contributor
timestamp: July 31, 2020, 08:51:50 pm
content: Wondering for those that don't have a LRC meter, but have an sine-wave signal source. That with an accurate known resistance, build a simple voltage divider with the test capacitor. Make a couple low frequency measurements with the 34465A, and calculate the capacitance.I know the 34465A is accurate at low frequencies as I've got a precision 50% duty cycle with low impedance discrete CMOS driver from a precision reference (see image). The reference reads 4.99988VDC and the AC reads 2.49965VAC @ 250Hz square wave (ideally should be Vref/2). So the 34465A is handling the square wave and harmonics well at this frequency range.I just used a cheap $10 eBay function generator with sine output at 1003.5Hz, generator amplitude was 3.5393VAC, amplitude across 100nF test cap was 0.55449VAC, and series resistor was 9.99536K. Gator clip leads wired things together (see image below) and a little circuit analysis will show the capacitance as:C = [1/(wR)]*{squareroot( (Vg/Vc)^2 -1)} or 100.03nF which agrees reasonably well with 100.05nF 34465A reportsEdit: added couple more measurements of a 9.51nF per 34456A and 9.60nF using voltage divider method, and 0.9831uF vs 0.9840uF.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: August 01, 2020, 07:00:08 pm
content: Went ahead and built a 4 capacitor test version on the Precision Resistor PCB and included a 1% thermistor. This has a 1uF, 0.056uF, 10nF and 1nF Mylar capacitors, I picked values as close to the standard type as I had, but didn't bother to trim to get any closer.Quick readings are 0.9993uF, 055.00nF, 10.009nF and 01.010nF and temperature 26.6C.I'll begin logging this with the precision resistor and precision voltage logs when we start that effort, but before we need to get these 34401A calibrated to the 34465A.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: August 03, 2020, 04:19:09 pm
content: I've just noted that jumpering the low side jack to the 10A jack under the Capacitor measurement slightly reduces the last digit randomness.Best,

author: Brando753
author_rank: Contributor
timestamp: August 03, 2020, 09:15:56 pm
content: Digikey order has come in, I will place the order for the mounting boards this weekend, from just using alligator clips I noticed the Fluke and Keysight seem to be matching perfectly, so it's very much likely the characteristics of the cheap caps that was causing the reading anomaly. I will log the capacitance when I get the boards in. Will keep everyone updated.Here is a picture of the 10uF cap next to an Atmega328 for size reference.

author: The Electrician
author_rank: Frequent Contributor
timestamp: August 03, 2020, 10:46:53 pm
content: Those measuring capacitors with a DVM should read this:https://www.eevblog.com/forum/testgear/about-capacitance-measurement-with-dvms/msg489690/#msg489690It only applies fully to electrolytics, but the discussion of how DVMs measure capacitors applies to all cap types.