Products > Test Equipment
East Tester ET4410 ESR Measure
TimFox:
--- Quote from: The Electrician on July 30, 2022, 09:44:18 pm ---
--- Quote from: Martin72 on July 30, 2022, 08:46:44 pm ---
--- Quote ---If I measure it with the DE5000 at 100 kHz, the capacitance value is OL, the ESR value is ------, a bunch of dashes. However, if I set the DE5000 to measure Rs, I get a value of .014, not .0065 as it should be, but at least it gets something.
--- End quote ---
Doesn´t wonder me, the chipset the DE5000 use did not specify 100Khz as a testfrequency for such a "large" value.
In the 2000µF range, max. 1khz.
--- End quote ---
I wasn't expecting the DE5000 to get a good value for the capacitance. I only mentioned what the DE5000 got for the capacitance of the 1800 uF cap (which was OL) to compare it to what other meters get. The other meters got a negative value which shows that 100 kHz is above the self resonant frequency; but they didn't just give up and say OL.
What I want an LCR meter to do is be able to measure the ESR of a large capacitance at 100 kHz. This shouldn't be a difficult measurement due to a low value of D (high Q). Switching the DE5000 from capacitance measuring mode to the Rs measuring mode at least gives a value which is substantially in error.
Another thread from some time ago did some tests that showed that the DE5000 has difficulty making measurements when the voltage across the DUT is about 4 millivolts or less, which can be the case when measuring capacitors of this size capacitance. That appears to be the case here. But the Tonghui and Applent don't have that limitation.
--- End quote ---
Measuring the ESR of a large capacitance with a high Q (low D) is, in fact, a very difficult measurement. [Emphasis added in bold face above to original comment.]
The Electrician:
--- Quote from: TimFox on July 31, 2022, 02:48:34 am ---
--- Quote from: The Electrician on July 30, 2022, 09:44:18 pm ---
--- Quote from: Martin72 on July 30, 2022, 08:46:44 pm ---
--- Quote ---If I measure it with the DE5000 at 100 kHz, the capacitance value is OL, the ESR value is ------, a bunch of dashes. However, if I set the DE5000 to measure Rs, I get a value of .014, not .0065 as it should be, but at least it gets something.
--- End quote ---
Doesn´t wonder me, the chipset the DE5000 use did not specify 100Khz as a testfrequency for such a "large" value.
In the 2000µF range, max. 1khz.
--- End quote ---
I wasn't expecting the DE5000 to get a good value for the capacitance. I only mentioned what the DE5000 got for the capacitance of the 1800 uF cap (which was OL) to compare it to what other meters get. The other meters got a negative value which shows that 100 kHz is above the self resonant frequency; but they didn't just give up and say OL.
What I want an LCR meter to do is be able to measure the ESR of a large capacitance at 100 kHz. This shouldn't be a difficult measurement due to a low value of D (high Q). Switching the DE5000 from capacitance measuring mode to the Rs measuring mode at least gives a value which is substantially in error.
Another thread from some time ago did some tests that showed that the DE5000 has difficulty making measurements when the voltage across the DUT is about 4 millivolts or less, which can be the case when measuring capacitors of this size capacitance. That appears to be the case here. But the Tonghui and Applent don't have that limitation.
--- End quote ---
Measuring the ESR of a large capacitance with a high Q (low D) is, in fact, a very difficult measurement. [Emphasis added in bold face above to original comment.]
--- End quote ---
I worded what I was saying in an ambiguous way. Let me rephrase it; replace that sentence with this one:
"Since in this case (of a large electrolytic) we won't have a low value of D (high Q), this shouldn't be a difficult measurement."
mawyatt:
One should have a good handle on how these LCR meters work and the ranges that are within "acceptable" limits of such. Some of the higher end LCR meters display (selective) DUT current and applied voltage, these parameters are beneficial to access the viability of the DUT measurement.
One should also consider the impedance magnitude involved, a few milliohms will be difficult to accurately measure and requires a large measuring DUT current which a handheld battery powered device may have difficulty supplying.
If you consider an ideal 1000uF produces just 0.0016 ohms at 100KHz, with a DUT current of 0.1 amp this only produces 160uV across the DUT. However, a more practical measurement at 100Hz produces 1.6 ohms and 160mV across the DUT at 0.1 amp.
The DE-5000 we have produces just ~5ma maximum available current which limits the ability to sense low impedance magnitudes, the better LCR meters produce much more available current for measurements.
Best,
The Electrician:
--- Quote from: mawyatt on July 31, 2022, 01:07:46 pm ---One should have a good handle on how these LCR meters work and the ranges that are within "acceptable" limits of such. Some of the higher end LCR meters display (selective) DUT current and applied voltage, these parameters are beneficial to access the viability of the DUT measurement.
One should also consider the impedance magnitude involved, a few milliohms will be difficult to accurately measure and requires a large measuring DUT current which a handheld battery powered device may have difficulty supplying.
If you consider an ideal 1000uF produces just 0.0016 ohms at 100KHz, with a DUT current of 0.1 amp this only produces 160uV across the DUT. However, a more practical measurement at 100Hz produces 1.6 ohms and 160mV across the DUT at 0.1 amp.
The DE-5000 we have produces just ~5ma maximum available current which limits the ability to sense low impedance magnitudes, the better LCR meters produce much more available current for measurements.
Best,
--- End quote ---
The first thing I said in reply #20, my first post in this thread was: "Your problem is undoubtedly a matter of signal to noise ratio."
I've been harping on this for the rest of my posts, and it's good to have some older, experienced EEs confirm.
It hasn't been mentioned yet, but one of the limitations of the fact that the DE5000 has integrated the entire functionality of an LCR meter is that compromises were necessary. The IC process they had to use was not the best suited for low noise performance. A meter not fully integrated can use a low noise opamp, or even a fully discrete design, for the front end gain stage.
The marketing literature for the Hioki top end meters, and the Keysight E4980A meter, describe how their engineering teams expended considerable effort to reduce the front end noise. Here's some of the Keysight description of how the noise reduction affects low impedance measurements:
mawyatt:
--- Quote from: The Electrician on July 31, 2022, 04:21:39 pm ---
It hasn't been mentioned yet, but one of the limitations of the fact that the DE5000 has integrated the entire functionality of an LCR meter is that compromises were necessary. The IC process they had to use was not the best suited for low noise performance. A meter not fully integrated can use a low noise opamp, or even a fully discrete design, for the front end gain stage.
The marketing literature for the Hioki top end meters, and the Keysight E4980A meter, describe how their engineering teams expended considerable effort to reduce the front end noise. Here's some of the Keysight description of how the noise reduction affects low impedance measurements:
--- End quote ---
No doubt the chip set utilized within the DE-5000 is CMOS since it must support significant digital as well as the analog front end. Enormous strides in CMOS noise levels have been achieved over the decades including some clever signal processing to "help" with the noise. Apparently the chip set utilized is two separate chips, suspect one is analog and other is digital and they may not be produced in the same CMOS process. From experience I can tell you this is no trivial feat to implement an entire LCR meter within a couple chips, even if only modest performance....so hats off to the chip set designers!
If you check the latest CMOS Op-Amps from TI and AD you'll find some pretty good noise performers, even tho they are CMOS. This is a result of superb design, clever techniques and a good CMOS noise friendly process that's likely proprietary and not really available to the outside. Of course there are excellent bipolar Op-Amps available also, so a LCR design team would have the luxury of selecting the best Op-Amps for noise performance, the best SD ADC, the best DDS and so on, whereas the custom IC LCR designers were quite restricted and thus performance is compromised.
One area that might be beneficial to the custom chip set LCR meter types, where one could significantly "Boost" the output current for lower level impedances, which as you correctly indicate would improve the SNR. A high speed/current discrete buffer amp or something like a OPA-633 could extend the range of the chip set significantly, but you would still want this in a mains powered LCR meter, not a handheld battery powered since the power consumption would be high (why our Hioki has a very loud fan, the TH2830 fan is not as bad tho, but it only goes to 100KHz).
Anyway, that's a nice document from KS, thanks for showing!!
Best,
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