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I have one more question related to my cheap Aneng SZ08 multimeter, which I've purchased recently and am discovering its capabilities. This question is related to the capacitance measurement mode.

To test the capacitance measurement function, I've used three different capacitors. The first one was 10uF (no voltage was indicated on the body.) When I touched the probes to its outputs in one way, the meter read around 10uF. When I changed the probes polarity (touched another output with another probe,) the meter read nothing.

Does the polarity matter while measuring capacitance with a multimeter?

Another capacitor was 25V 100uF. When I connected probes in one way, the meter read about 100uF, but when I've changed the polarity, it read about 190 uF. What caused that?

I also have a larger capacitor, marked 450V 4.7uF. Here, the meter reads nothing in both cases. Why did that happen?

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Yes and no - polarity does not matter when measuring capacitance in general, it's just that the actual capacitors you are measuring do care and also how the meter measures capacitance.

You are measuring electrolytic capacitors and they are polarized capacitors that require the correct polarity to work correctly and without getting damaged. They can only be reverse-biased by about 1V or so before you start getting extra leakage or start damaging the cap.

And you don't know how your multimeter tries to measure the capacitance. It might try to charge it to some voltage and discharge it and measure time how long it takes to charge and discharge. If so, we don't know which voltages it uses.

If the polarity is wrong then the cap is charged in reverse and there is excess leakage current then the meter can't obviously measure the time it takes to charge and discharge the capacitance because the leak makes it to take longer to charge and indicates a larger capacitor being measured.

We also don't know why your meter was unable to measure the 450V 4.7uF capacitor. Maybe it is too small to be measured. Read the multimeter manual for that.

A manual should explain how each multimeter mode and feature works, so that you know when and how and why it gives you the results it does, or does not give a result at all. Another such feature is the continuity detection, it may work very differently to another multimeter so one might indicate continuity and another doesn't. If you don't have a manual, or it does not say for what and how it can be used, well, then you don't know that. That's the difference between a $20 and a $200 multimeter.

Or maybe the capacitor is broken so measuring it won't give a result.

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    \$\begingroup\$ To add to this answer, the way good capacitance meters measure capacitance is by applying a small (generally 30 mV peak) AC voltage and measuring the resulting current. This gives you an impedance, and that's then converted to capacitance that's displayed on the screen. Good LCR meters will also separate out the reactive and resistive components of the impedance to give you the ESR as well; simple capacitance meters built into multimeters might just assume the ESR is much smaller than the capacitive reactance and ignore it. \$\endgroup\$
    – Hearth
    Nov 1, 2023 at 18:51

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