Measuring capacitor leakage - Page 1
Forum section: electronics / general

author: vindoline
author_rank: Unknown
timestamp: October 29, 2018, 07:10:58 pm
content: I have a question about measuring capacitor leakage.I want to build a 0.1-10 Hz low noise amplifier after Andreas's design. There has been quite a lot of discussion about the importance of selecting the input caps for low leakage, but little guidance on what techniques or conditions are appropriate. My understanding is that the leakage should be in the single digit nA range.Is it as simple as charging the cap to 10V while monitoring the current? I have a Keithley 616 electrometer or a Keithley 196 DMM I can use to monitor current in the nA range.What about self-discharge? Is this the same as (or a surrogate for) leakage? I can charge the caps to 10V, then remove from power and monitor the voltage drop over time with the electrometer (it's input impedance is > 2 x 10^14). The 616's resolution is poor, but I can use it's buffered output to feed my HP 3456A and log the voltage drop over time via GPIB.Also, it looks like this may take quite a bit of time. Any ideas or tips on being efficient would be welcome. Thanks!

author: doktor pyta
author_rank: Frequent Contributor
timestamp: October 29, 2018, 07:27:59 pm
content: Slightly off topic but there is another approach proposed by Mickle T.He made large foil capacitor built from smaller ones.https://www.radiokot.ru/forum/viewtopic.php?f=10&t=52829&start=2660

author: DC1MC
author_rank: Super Contributor
timestamp: October 29, 2018, 07:30:39 pm
content: Personally for the elcos I charge them with a small current until they reach the nominal voltage then measure the discharge rate.It's scary how miserable are the the wired ones, especially the axials, even bought new from reputable suppliers like Digikey and Mouser.The new tantalums and smd caps are really good.One thing that I've observed, is that for the high voltage aluminum elcos, if I let them charged without any load their internal resistance do improve a bit (discharge rate decreases after 2-3 nominal voltage to to zero by self discharge), but I have no idea if under real load this helps in any way and it does take a while.I will love to hear/read a reasonable explanation/paper about that.Maybe it will help you,DC1MC

author: MiDi
author_rank: Frequent Contributor
timestamp: October 29, 2018, 07:48:29 pm
content: How I did, alternative is to put high resistance between low noise DC source and cap, let settle/soak and measure voltage across it.Depending on how stable and noisy your PS is, the resistance has to be chosen accordingly as you do not want to measure your PS

author: Kleinstein
author_rank: Super Contributor
timestamp: October 29, 2018, 09:08:51 pm
content: Measuring the true leakage is a rather difficult task with capacitors that have a high dielectric absorption (DA). The description with an equivalent circuit made from an ideal capacitor and parallel resistor for leakage just is not a good approximation. The DA is to a first approximation modeled with another capacitor and large resistor in series, parallel to the main cap. With electrolytic caps DA is often quite strong and thus the extra cap with series resistor quite large - up to about 20%. The time constants involved can be rather long - more than hours and maybe days.So the measured voltage change during self discharge is not only due to leakage, but also (and often to a large extend) DA. Also external effects like changing temperature and maybe air pressure or sound might effect the measured voltage.To get an idea on the DA effects, one can charge a cap for maybe 10 minutes, discharge it for a few seconds with a low resistance and maybe dead short later and than measure the voltage that develops over the next minutes. With electrolytic caps this can be a significant part of the initial voltage. One might get an idea about leakage (though at a lower voltage), when the voltage finally starts to drop again.A similar effect but other direction also happens when watching a fresh charged cap: the voltage first drops quite fast and than after hours kind of settles to a much slower, about constant discharge rate that finally might correspond to the leakage rate. The initial part (like the first few hours to days) is usually dominated by DA.Other ways to measure the leakage are effected in a similar way.

author: Echo88
author_rank: Frequent Contributor
timestamp: October 29, 2018, 09:20:45 pm
content: For Andreas Design a single 3300µF-input-capacitor is used (or 2200µF + 1000µF).The leakage of 105°C-rated caps appear to be higher compared to 85°C-rated caps, according to my limited sample observation of 10 105°C caps vs 10 85°C caps. Also there are low-leakage-specified caps likehttps://eu.mouser.com/datasheet/2/293/e-kl-14230.pdfI tested about 10 3300µF/16V/105°C Panasonic-NHG-series capacitors and all of them were at about ~40nA after 48h at 10V, but i didnt form them at 16V before.After that i bought 10 3300µF/50V/85°C Panasonic-M-Series (16V-capacitors were not available at that from moment from the seller), formed them at 50V for about a day, so the aluminium-oxide-layer could heal/stabilize.Then i discharged them to 10V and let them stay at that voltage for 48h, i measured leakage-currents of <=5nA for 6 of them i think.I used a calibrator to generate the stable 10V and 1Meg-resistors in series with each capacitor. My 6.5-Digit-DMM 34465A was used to measure the voltages over the 1Meg-resistors, 1nA -> 1mV over the resistor. But a stable voltage-supply might also be used to generate the test-voltage.You can also use the discharge-current method you mentioned, but i guess it takes at least the same amount of time as the charge-current-measurement-method, since were basically waiting for the dielectric absorption in the cap to stabilize.If youre using the PCBs made by mimmus78: the pcb fits tightly inside a TEKO 393, if you cut of a few mm on the width of the pcb with lever scissors. Also the mentioned 3300µF/50V/85°C are bigger than the 16V-types, but still fit on the pcb and inside the TEKO 393.TL:DR:I suggest you get 10 3300µF/>=16V/85°C-capacitors, form them at their rated voltage for a day and then let them stabilize at 10V for 48h. That should get you at least one very good capacitor with <=5nA leakage-current. Remember to cool the capacitor-leads during soldering, otherwise its leakage might jump up due to the temperature-shock...at least thats what ive heard.I tried to measure the leakage-current first with my Keithley 2500 Picoampmeter, but it wouldnt show me reasonable readings (100Giga-Ohm-resistor and Keithley220-current-source was tested fine with it). I guess it didnt like the heavy capacitive component? Maybe your Keithley 196 might show this behavior also, thats why i used them 1Meg-resistor-method.

author: e61_phil
author_rank: Frequent Contributor
timestamp: October 29, 2018, 09:27:32 pm
content: @echo88: I think every transimpedance amp will have problems with high capacity directly at the input. Did you try to put a high value resistor in series? That should limit the bandwidth for the noisegain and it shouldn't matter for DC leakage current.

author: Echo88
author_rank: Frequent Contributor
timestamp: October 29, 2018, 09:42:56 pm
content: Thanks for the link doktor pyta, i also thought about realizing the input-cap with parallel-connected 100µF-foil-caps but gave up on the idea, because of the resulting size and the expected emi-noise which will be received. Seems Mickle is one step ahead again.Hmm, seems he just didnt find good electrolytic input caps and then resorted to his solution.@e61_phil: Thats a good idea phil, i might try that.

author: Andreas
author_rank: Super Contributor
timestamp: October 30, 2018, 05:36:05 am
content: Hello,I use a (stable) power supply with about 10V and a 100K resistor in series to the capacitor to measure the voltage across it with a DMM.Alternatively I used the 200mV range of my cheap 3.5 digit DMM directly as series resistor (it has 1 Meg input resistance so 1 mV = 1nA).Usually it needs 2 days forming before we get values in the nA range.I go for a constant power supply because of the dielectric absorption which makes dynamic methods difficult.(and a constant source is also that what I want to measure finally).with best regardsAndreas

author: vindoline
author_rank: Unknown
timestamp: October 30, 2018, 06:08:41 am
content: Lots of great replies. Thank you everyone!Quote from: Andreas on October 30, 2018, 05:36:05 amThanks Andreas, that makes perfect sense to me. I've got the caps forming now at 10v all in parallel. I'll add series resistors to all of them tomorrow and let them charge a few more days before screening them.

author: BravoV
author_rank: Super Contributor
timestamp: October 30, 2018, 06:39:29 am
content: I used bench PSU to measure the cap leakage in series with DMM that has 10M Ohm resistance, details ->Capacitor Leakage MeasurementExample of a polymer OSCON forming at rated Volt for about 1.5 hours, at the chart reading, Y axis = 1 volt equivalent to -> 0.1uA or -> Volt / 10M Ohm DMM internal resistance.

author: David Hess
author_rank: Super Contributor
timestamp: October 31, 2018, 10:11:48 pm
content: Quote from: vindoline on October 29, 2018, 07:10:58 pmSince this critical coupling capacitor is used as part of low frequency high pass filter, the leakage is limited by its error contribution across the following shunt resistance. Lower shunt resistance produces less noise but require a larger capacitance to maintain the 0.1 Hz cutoff frequency.Dielectric absorption in an electrolytic capacitor will require 10s of hours to days of conditioning at the test voltage before valid measurements can be made.The noise in bad parts tends to be like popcorn noise but I do not know what mechanism is behind it. Metalized film capacitors can produce their own noise from their self healing mechanism.

author: MiDi
author_rank: Frequent Contributor
timestamp: November 01, 2018, 07:16:07 am
content: My 0.1-10Hz LNAsettles in max 10 minutes to steady state (0V->10V).I cannot recognize any significant settling after that.So DA for my unit does not have a great impact.

author: Andreas
author_rank: Super Contributor
timestamp: November 01, 2018, 07:19:29 am
content: Hello,DA is filtered out by the 0.1 Hz high pass.Thats why you dont see itwith best regardsAndreas

author: Echo88
author_rank: Frequent Contributor
timestamp: November 01, 2018, 07:50:16 am
content: @David Hess: I didnt see that effect myself in electrolytic capacitors. Which types did you test to see that effect / how do you measure the caps?I was always wondering how the DA affects noise measurement.How big is the impact in noise-error/how long is the settling-time when you connect a low noise reference, say an LTZ, while the input voltage before was 0V and the input slowly ramps up to LTZ-voltage due to DA?I only know that the AN124 states that a settling time of 24h is required for meaningful results?

author: wraper
author_rank: Unknown
timestamp: November 01, 2018, 08:03:54 am
content: Quote from: Echo88 on October 29, 2018, 09:20:45 pmYou make extraordinary generalized claim based on sample of 2. There are a lot of different capacitors with different electrolyte and different purity of aluminium. Both 85oand 105ocan vary a lot. It's just temperature rating, not "type". If you need guaranteed low leakage, buy low leakage serieshttps://eu.mouser.com/datasheet/2/293/e-kl-14230.pdf

author: Echo88
author_rank: Frequent Contributor
timestamp: November 01, 2018, 08:25:56 am
content: I make claims based on my measurements of 10 caps with 105° specification compared to 10 measured caps with 85°C-spec, which is also mentioned by other people who tested 105°C-specified caps.I changed my wording to "The leakage of 105°C-rated caps appear to be higher compared to 85°C-rated caps, according to my limited sample observation. Also there are low-leakage-specified caps likehttps://eu.mouser.com/datasheet/2/293/e-kl-14230.pdf".Im not willing to spend a big amount of money/time to leakage-test various caps and as you state that there are big differences in seemingly same caps, please share your knowledge.

author: MiDi
author_rank: Frequent Contributor
timestamp: November 01, 2018, 08:28:55 am
content: Rule of thumb:85°C types have lower leakage then 105°C typeslower voltage types have lower leakage then higher voltage typesEcho88 is not the only one who measured this, there is evidence of this effect.All low leakage claimed types are 85°C rated, this should be good enough indicator.Sure you cannot rely on small quantity measurements for generalized statements.

author: wraper
author_rank: Unknown
timestamp: November 01, 2018, 08:31:38 am
content: Quote from: Echo88 on November 01, 2018, 08:25:56 amYou bought 2 series from one manufacturer. Isn't it wildly exaggerated to make conclusion about all capacitors in the wild based on that? Heck, you could get a different batch of those and receive opposite result. If you bought 20 different 105oC capacitors and 20 different 85oC then you could at least make a humble conclusion that resultscouldextent to capacitors as a whole.

author: wraper
author_rank: Unknown
timestamp: November 01, 2018, 08:33:40 am
content: Quote from: MiDi on November 01, 2018, 08:28:55 amNichicon datasheet says they can supply 105oC variant as well.

author: wraper
author_rank: Unknown
timestamp: November 01, 2018, 08:38:34 am
content: Quote from: Echo88 on November 01, 2018, 08:25:56 amIt would be much more meaningful if you bought 1 capacitor of 10 different series instead of 10 capacitors from single series which are from the same batch.

author: Echo88
author_rank: Frequent Contributor
timestamp: November 01, 2018, 08:51:13 am
content: It would be meaningful if you either state info about caps that you tested (did you?) or you send me a large amount of money to test different caps from all manufacturers, so i can make conclusions that benefit all members here.

author: branadic
author_rank: Super Contributor
timestamp: November 01, 2018, 09:08:32 am
content: I have tested different caps available at Reichelt for the low noise amplifier of Andreas too and found cheap Yageo 85°C caps to be low leackage. After forming them over a 24h time span on a 9V block an arrangement of 1.000µF/25 || 2.200µF/35V showed <5nA.https://www.mikrocontroller.net/topic/207061#3164476-branadic-

author: Echo88
author_rank: Frequent Contributor
timestamp: November 01, 2018, 09:38:11 am
content: The pdf-link inhttps://www.mikrocontroller.net/topic/207061#3164476is not available anymore. Ive found the following document:https://tadiranbatteries.de/pdf/applications/leakage-current-properties-of-modern-electrolytic-capacitors.pdfis it the one you mentioned ?Good read about the increased leakage after soldering and the healing-effect/tunneling.

author: branadic
author_rank: Super Contributor
timestamp: November 01, 2018, 10:32:48 am
content: QuoteYes, seems like they renamed the file.-branadic-

author: vindoline
author_rank: Unknown
timestamp: November 01, 2018, 01:22:47 pm
content: I'm testing 12 Nichicon KL series series caps right now. This is Nichicon's "low leakage" type. I'll report the results when I have them - probably this weekend.

author: vindoline
author_rank: Unknown
timestamp: November 03, 2018, 02:29:55 pm
content: OK. As promised here are my initial capacitor leakage results. All of the caps in this test were brand new and purchased from Mouser. I Used Nichicon UKL series 25V (2 @ 3300 uF, 5 @ 2200 uF, 5 @ 1000 uF).To start all of the caps were connected in parallel on a breadboard and charged to 24.5 V via a 1 K resistor and a PD TP340 power supply. After the caps had charged to near 24.5 V the resistor was removed. The caps were allowed to form at 24.5 v for about 2 days. The caps were then discharged for a day. At this point the circuit was modified to give each cap its own 1 Meg resistor to ground to monitor the voltage drop (and thereby leakage). The caps were then charged to 10.00V. The total charging/leakage current was monitored by a Keithley 196 DMM. Once the total charging current was in the microamp range, the 1 Meg resistors were shunted by jumpers to speed up final charging. After about 3 days the total leakage current was 100 nA. At this point, the jumpers were removed from the 1 Meg resistors and the individual cap leakage current calculated by measuring the voltage drop across the resistors with an HP3456A DMM (1 mV = 1 nA). The results are:1. 3300 uF 3.60 nA2. 3300 uF 2.78 nA3. 2200 uF 0.63 nA4. 2200 uF 0.19 nA5. 2200 uF 0.04 nA6. 2200 uF 0.25 nA7. 2200 uF 0.17 nA8. 1000 uF 17.14 nA9. 1000 uF 10.65 nA10. 1000 uF 37.22 nA11. 1000 uF 14.10 nA12. 1000 uF 12.54 nAThe real surprise for me is how poorly the 1000 uF caps performed. For some reason, I expected the lower value caps to have lower leakage. The 2200 uF caps appear amazing.**edit: corrected pA to nA due to my inability to do math!**

author: Andreas
author_rank: Super Contributor
timestamp: November 03, 2018, 02:41:03 pm
content: Quote from: vindoline on November 03, 2018, 02:29:55 pmHmm,shouldn´t it be 1 mV/1 Meg = 1 nA instead of 1 pA? if you measure the voltage across the 1 Meg resistor?with best regardsAndreas

author: vindoline
author_rank: Unknown
timestamp: November 03, 2018, 02:47:27 pm
content: Quote from: Andreas on November 03, 2018, 02:41:03 pmYup, sorry. Corrected. Lack of coffee!

author: DC1MC
author_rank: Super Contributor
timestamp: November 03, 2018, 06:25:18 pm
content: You've got a real winner on 5.Could you please use a cheap ESR meter to see if there is a correlation between these measured leakage and ESR ?Cheers,DC1MC

author: splin
author_rank: Frequent Contributor
timestamp: November 04, 2018, 05:22:47 am
content: Quote from: vindoline on November 03, 2018, 02:29:55 pmThe TP340 24h stability spec @10V is 3mV and the temp coefficient is 2.3mV/C. Given the 3300uF/1Mohm time constant is nearly 1 hour, it is very difficult, if not impossible to make accurate sub nA leakage current measurments with this setup - 1mV of change in the power supply voltage translates to 1nA of apparent leakage current if the P/S voltage change occurs much quicker than the time constant.DA makes it worse as the time constants are much longer. Every measurement will reflect the P/S ripple, drift and LF noise over the last hour or so. (I guess your meter will reject the 100/120Hz ripple and higher frequency noise when measuring the DC voltage across the 1Meg resistor). Your measurements are probably OK down to the nA level but not the 2 decimal points you show. A bit like measuring sea level rise by making spot measurements in the face of tides and waves.The TP340 isn't bad but it would be much better to use a precision reference, even one of those dirt cheap AD584 ebay ones. Of course you could monitor the P/S voltage if you have a good enough meter to verify the P/S drift is not significant. Even then, ideally you would want to average the leakage current measurements over long periods - several hours at least, preferrably a day or more.Alternatively, just open circuit the capacitors and measure the voltage every day for a few days, weeks or longer, but make each measurement as short as possible if your meter has 10M ohm input impedance, especially for the smaller capacitors - or compensate by estimating the charge lost during each measurement.Don't forget to note the temperature as the electrolytic's leakage increases significantly with temperature. The change in dimensions of the capacitor with temperature will likely also change its voltage given that the plate spacing changes but the charge doesn't. Added comment about P/S ripple.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 04, 2018, 09:10:44 am
content: Quote from: splin on November 04, 2018, 05:22:47 amA agree that open circuit measurement is likely the better way.With electrolytic caps, there is not much change in plate spacing as it is the surface oxide layer, but there can still be some effects from temperature and air pressure, moving the cap. This can make the voltage go up or down.

author: vindoline
author_rank: Unknown
timestamp: November 04, 2018, 01:43:17 pm
content: Quote from: splin on November 04, 2018, 05:22:47 amI was concerned about the PS stability as well. My TP340 performs significantly better than the specs you quote above. I'm seeing about a 200uV drift over 18 h, and if all of that is due to Tc, the Tc is about 240 uV/CQuote from: splin on November 04, 2018, 05:22:47 amI completely agree that the measurements are not accurate to two decimal points, however I do think that the test is valid to compare the relative leakage of the group of caps I'm testing. All of the voltage measurements were taken within several minutes, after the system was allowed to stabilize for about 3 days. The purpose of the exorcise is to choose the best input caps for Andreas's .1-10 Hz amp, not to obtain a theoretically best accurate measure of leakage.Quote from: splin on November 04, 2018, 05:22:47 amI have a Keithley 616 electrometer with about 10^14 input impedance. While it might be fun to measure the caps open circuit, it would take an unreasonable amount of time and I want to actually build the amp someday!Thank you though for your careful thinking on the subject. You've brought up some excellent points!

author: jfphp
author_rank: Regular Contributor
timestamp: November 04, 2018, 02:10:04 pm
content: A very useful -- but old -- instrument for capacitor leakage mesurement is the HP 4350A.

author: BFX
author_rank: Frequent Contributor
timestamp: November 04, 2018, 06:32:59 pm
content: And what about using SMU for example Keithley 2400 is able measure current in pA.

author: vindoline
author_rank: Unknown
timestamp: November 08, 2018, 02:34:59 pm
content: Quote from: DC1MC on November 03, 2018, 06:25:18 pmSure! Here it is:Cap Nominal Measured Leakage ESR D1 3300 uF 3.28 mF 3.60 nA 0.0 0.0842 3300 uF 3.26 mF 2.78 nA 0.0 0.0803 2200 uF 2.28 mF 0.63 nA 0.0 0.0894 2200 uF 2.26 mF 0.19 nA 0.0 0.0865 2200 uF 2.28 mF 0.04 nA 0.0 0.0846 2200 uF 2.27 mF 0.25 nA 0.0 0.0877 2200 uF 2.27 mF 0.17 nA 0.0 0.0858 1000 uF 978.9 uF 17.14 nA 0.1 0.0859 1000 uF 974.3 uF 10.65 nA 0.1 0.08210 1000 uF 974.8 uF 37.22 nA 0.1 0.08311 1000 uF 976.0 uF 14.10 nA 0.1 0.08912 1000 uF 979.5 uF 12.54 nA 0.1 0.085All the measurements were made with a DER DE-5000 LCR meter. I'm afraid that there doesn't seem to be enough resolution to find a correlation

author: Vtile
author_rank: Super Contributor
timestamp: November 09, 2018, 04:44:07 pm
content: These current measuring setups in nA/pA range are also a good demonstration of the pressure sensitivity of the capacitors.The reformation current behavior of the oxide / dielectric in some metal sheet based (small) capacitors that have been sitting at the drawer for a decade or longer are wild. I'm using my Manhattan mk1 10.0000 V reference and 100 Meg needle FET-VOM in series configuration and the needle doesn't know where to settle with some caps.

author: Echo88
author_rank: Frequent Contributor
timestamp: November 11, 2018, 11:29:59 am
content: @Vtile: Do you mean atmospheric pressure dependence?@e61_phil: Thanks for the tip with the necessary serial resistor for the capacity measurement with the Electrometer. With 1M in series to the measured 40µF foil cap i get about 40nApp noise (way too much for qualitative measurements of different caps) and with a 1G-resistor in series i get about 50fApp.Just a little bit more than the electrometer-noise itself including triax-cable which is about 30fApp.

author: Vtile
author_rank: Super Contributor
timestamp: November 11, 2018, 08:39:56 pm
content: Quote from: Echo88 on November 11, 2018, 11:29:59 amPressure source doesn't matter (I would assume), if it translates to mechanical force and then again internal pressure.In my case I just poked the capacitor with finger (which resulted a change of the electron flow) and after that repeated it with a few tools to verify it were pressure.Long time ago I did read interesting article (from someones homelab) about the ideas how the DA have also mechanical aspects in electrolytics (or let say caps with soft dielectric materials as I can't recal), which makes sense considering the fluid is disturbed and also the distance (etc.) of the plates changes.

author: e61_phil
author_rank: Frequent Contributor
timestamp: November 15, 2018, 08:20:46 am
content: Is it really a constant current flow or is it a current flow because you changed the capacitance while pressing with your fingers?What happend if you release the pressure? If the effect comes from changes in capacitance, than the amount of current increase should become a current decrease.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 15, 2018, 08:31:38 am
content: Using the fingers to apply "pressure" would also add a thermal disturbance.

author: Vtile
author_rank: Super Contributor
timestamp: November 15, 2018, 08:29:35 pm
content: Quote from: e61_phil on November 15, 2018, 08:20:46 amWhat do you mean about constant? Yes, it is change of capacitance I would assume. Not induced spike / ESD, while my throw together "indicative measuring setup" is far from optimized nor my measuring device even close to "metrology grade".Quote from: Kleinstein on November 15, 2018, 08:31:38 amNo this is not temperature (at least not conducted), but good point to remember for hobbyist like me.Here is a short video clip, as you can see this far from professional setup, but merely indicative. The range is +-2.5mV over aprox. 100MOhms, center zero. For professionals this is nothing new, but us newb on/off hobbyist these at times comes around the corner. Some types are more sensitive than others, like the first polymer film cap I were testing (poking around after a workday) originally could be used probably as a microphone so sensitive it is.https://youtu.be/3HFX_nMm6D0

author: Kleinstein
author_rank: Super Contributor
timestamp: November 16, 2018, 09:26:21 am
content: I had not expected that much effect of mechanical pressure on a film cap. So an interesting video - at least the first half.What type of capacitor is it, and what voltage ?

author: e61_phil
author_rank: Frequent Contributor
timestamp: November 16, 2018, 10:27:15 am
content: Great video! Thanks a lot.With constant I meant if the current decreases again under constant pressure to determine if it is a leakage or capacitance effect.

author: Vtile
author_rank: Super Contributor
timestamp: November 16, 2018, 07:12:57 pm
content: Quote from: Kleinstein on November 16, 2018, 09:26:21 amHehe.I just left that there that someone might have been interested where the needle moves after.DC Film capacitor, PP, 0.33uF, 250V - Farnell: 2529137The pressure applied is much more than what someone would apply to component like this in any normal use. The old film capacitor 'mic' without a body on the other hand doesn't like pressure at all edit: (...nor temperature). The actual leakage might be something else than seen on the video clip because stray fields and the cap had been electrified for an hour or so total.@e61_phil Thanks.I'm running a new experiment, let see.Edit. ....and managed to delete the video, while editing.

author: Vtile
author_rank: Super Contributor
timestamp: November 18, 2018, 01:14:47 am
content: I did re-run the experiment I managed to delete from the recorder yesterday, a much quicker this time.It seems that the current jumps about 2.5 pA under 260 grams of weight and returns back to starting point. When the pressure is removed it go down the same amount and returns.Funny meter to play with in the bench and at the field. Interesting enough the wooden board (HV test box) behaves much better considering ESD than my "ESD" mat.https://youtu.be/K4KDn3gZjao