Products > Test Equipment
East Tester ET4410 ESR Measure
The Electrician:
Here is an example of how extremely low loss capacitors can overwhelm even the best LCR meters. On eBay are offers for very high performance capacitors from Ukraine left over from the USSR military. I bought some of them and this is a .5 uF polystyrene capacitor. One half microfarad is rather large for a polystyrene capacitor. Here is what the Hioki IM3570 gets for a measurement at 10 Hz:
At first glance it looks like the measurements of a very low loss cap. But, wait a minute! The ESR is negative!! The D value is negative!? The IM3570 just can't do it! And, even though the D is negative, look at its value: .000017. WOW!!
This is a situation like TimFox described where the only hope of getting a value is with calorimetry.
mawyatt:
Your frequency is only 10Hz, try a higher frequency.
Best,
Martin72:
Oh, indeed.
Nanofarad and some Hertz...won´t fit.
The Electrician:
--- Quote from: mawyatt on July 26, 2022, 10:45:34 pm ---Your frequency is only 10Hz, try a higher frequency.
Best,
--- End quote ---
As I said in the sentence just before the image, the measurement is at 10 Hz. I showed that because that's the frequency where the IM3570 got negative values for ESR and D.
Here are the measurements at 1 kHz and 10 kHz. This is the highest Q capacitor I have:
TimFox:
Regardless of whether data sheets have been written carefully, it's important to note the complex (mathematically) nature of the impedance of a capacitor-looking component.
Since there is a small (hopefully) but finite coupling (or leakage) between the in-phase (real) and quadrature (imaginary) components in a real machine, the capacitance and ESR of a high-Q component are going to affect each other, specifically the displayed (small) resistance will suffer a small effect from the (larger) measured reactance, which in turn is inversely proportional to the displayed capacitance.
A practicable specification for a physically realizable meter (not a legal fiction) is the maximum resolvable Q factor (or minimum D), or the maximum Q for a given accuracy of the displayed Q.
Too many people look at a data sheet and assume that the component can meet any combination of the line items simultaneously, without reading or understanding the relationships (e.g., maximum voltage, maximum current, and maximum power that cannot be safely applied simultaneously.)
The negative D value reminds me of my missed Nobel prize when I measured a negative noise factor on a very-low-noise RF amplifier due to a slight miscalibration of the apparatus.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version