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East Tester ET4410 ESR Measure
Martin72:
Hi,
I´ve ordered a foilcap assortment to rebuild a notchfilter like the one in the sds2000x+ thread.
In this case it should be 10nF caps, in the box there are 10pcs, so I started to measure them with my ET4410.
While the capacity value is displayed constantly up to the third digit after the comma, the ESR value is floating.
It shows something between 7.XXX and 10.XXX Ohms alternating, never stable.
I thought, ESR will be caluclated so I wonder why the cap will be stable displayed, the ESR not.
And:
Taking a different cap, an Elko with 1000µF, ESR is stable displaying.
Are the caps bad, is it because of the low value of 10nf...
Will investigate it further, with other caps.
Martin
mawyatt:
Hi Martin,
Can you try different frequencies and see if the ESR reading is still bouncing around? Does the meter have an averaging filter that can help?
For the Twin "T" Filter in the mentioned thread, the capacitance value is more critical than the ESR and the key is to try and match values of capacitance.
Edit: Likely not the 10nF caps. At the notch frequency (~1.6KHz in this case for 10nF and 10K) the capacitive reactance magnitude is equal to the resistance used, so a few ohms compared to 10K isn't going to matter much.
Best,
Martin72:
Hi,
Will do it "tomorrow".
--- Quote ---the capacitance value is more critical than the ESR
--- End quote ---
Yepp, this here is about the ESR measure behaviour itself- My thoughts viewing your model are, that you´ve measured the ESR to get an more precise model which matches better/can better compared to with the real measured one.
mawyatt:
--- Quote from: Martin72 on July 05, 2022, 11:34:19 pm ---Yepp, this here is about the ESR measure behaviour itself- My thoughts viewing your model are, that you´ve measured the ESR to get an more precise model which matches better/can better compared to with the real measured one.
--- End quote ---
Exactly, and why we measured the capacitance and ESR at the expected frequency of the notch, ~1.6KHz for the 10nF and 10K. This allowed an accurate simulation of the filter behavior as compare to the Bode Plot measured result.
The SDS2104X+ performed admirably IMO, and your HD should really shine :-+
Best,
Kleinstein:
With foil capacitors the ESR is relatively small. So consider the 10 Ohms more like 0.010 kOhms and you have 2 or 3 stable digits after the decimal.
The capacity and ESR (more the invers of it) are measured togehter as a kind of complex number. With a near ideal, low loss (e.g. 0.1% range) capacitor the noise is relatively large in the loss direction, because the absolute loss is small.
Electrolytic capacitors on the other end have quite high losses (e.g. up to the 10% range) and ESR and this allows a similar number of stable digits for the capacitance and ESR.
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