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| LCR meter opinion |
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| indman:
--- Quote from: nctnico on January 26, 2022, 07:55:13 pm ---You have to check the specs for the LCR meter. --- End quote --- This is fair, but now I see that 3 different instruments have readings at 10 and 100kHz differ by more than 200 times! What testimony should I trust in such a case? How do you reconcile this with such a measurements below? |
| rsjsouza:
--- Quote from: Martin72 on January 26, 2022, 07:06:02 pm ---Yepp. Today afternoon a test with an wima mkp10 cap, 2.2µF: 1Khz: U1733C ST2830 DE5000 2.102µF 2.103µF 2.103µF D0.001 D0.000 D0.000 10Khz: 2.105µF 2.106µF 2.104µF D0.018 D0.000 D0.000 100Khz: 2.351µF 2.389µF 2.121µF D0.232 D0.015 D0.081 Still nothing to worry, next test perhaps with a 3.3 or 4.7µF - although it makes no sense at 100khz because of the high cap value. --- End quote --- Thanks for doing this comparison, Martin. MKP tends to have a larger tan δ variation in comparison to similar materials (interesting TDK article) My Reed R5001R reads the following on a few capacitors lingering around. All MKP 2,5 µF3,9 µF6,8 µFFreqCtan δCtan δCtan δ1 kHz2,3790,0033,5350,0006,8010,00110 kHz2,3400,0153,5090,0076,7540,006100 kHz2,230,0993,470,0826,890,065 |
| Martin72:
--- Quote from: indman on January 26, 2022, 07:46:03 pm ---I strongly disagree, there is reason for concern, because the difference in the results for U1733 20 times, for DE-5000 - 80 times! --- End quote --- Hi, What have we done... We´ve measured cap values beyond their claimed specs. In a meter-range with mostly undefined specs(in case of the de5000, for the two others I must have a look in their specs.) This is not the way it should go. Normally you got a look at the datasheet from the cap-manufacturer, on which frequency the values based. For example, wima their special snubbercaps, all the values mentioned in the spec were measured with 10khz. It makes no sense to measure the cap with 100khz and judging about the displayed values. Apart from this: I´ve taken some oscilloscope pics from the testfrequencies. There´s an interesting behaviour on the keysight u1733c and de5000. Both sending a sinewave to the DUT, which amplitude decreases the higher the testfrequency get. So far, so good, the ST2830 does it too. But, while the sinewave of the ST2830 is still an ac signal at 100Khz, the two others their signals are getting above zero-crossing. --- Quote ---MKP tends to have a larger tan δ variation in comparison to similar materials --- End quote --- Indeed, it´s getting more and more interesting for me, therefore I´ll do more cap-measurings and post them here. |
| indman:
--- Quote from: Martin72 on January 26, 2022, 08:46:58 pm ---But, while the sinewave of the ST2830 is still an ac signal at 100Khz, the two others their signals are getting above zero-crossing. --- End quote --- A similar effect is also mentioned here and how do you explain it? https://www.eevblog.com/forum/testgear/any-one-mod-the-de-5000-for-1mhz-frequency/msg2673546/#msg2673546 |
| Martin72:
Let me think about for a while.. It could be the reason, why the u1733c and de5000 showing more dissipation than the st2830. Could, not will. Here the pics.. |
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