I'm pretty new to using my LCR meter and checking ESR of caps. I know the basics of reactance. I'm taking apart an ATX PSU, to learn from and try in LTspice, (until I can't re-create the control chips right).

Checking the ESR's out of circuit, @100kHz, of THT and SMD Tantalum's, most 100nF-1uF are sub- 1ohm or far lower. A lot of 1n-100n are 1-2 ohm's.

There's are two 1nF w/ 21 ohm, a 10nF at 5.7ohm. They are the standouts, over 1nF. IDK what voltage these are rated, but they are on the switching side, that does not use a PFC section, and all voltages under 170Vdc.


Then for 2 ceramic cap 1kV caps (for the Flyback trans), the 220pico is 182ohm, 3.3n is 11.2ohm.

There's a poly.cap 1nF @24ohm


How typical is that ? This MS5308 LCR meter can also display the capacitance while showing other things like ESR. That changes w/ freq and size, and I'm not sure the pattern, and IDK how this does it "calculations". It times out and can't drive big caps at higher freq's.

And I do know the basic math and complex numbers for this stuff, but that's simple ideal parts.

 

Ceramic caps should not have ESR as high as you mention.

You say you can’t test ‘big’ caps at higher frequencies. Do you mean physically big or high capacitance? Higher capacitance can’t be tested at high frequency because the signal source will clip due to low impedance.

 

I looked at a couple of 1 KV ceramic datasheets, no esr shown.

But dielectric has to be pretty thick I would imagine, so think ESR
for low valued caps like 220 pf would be quite high.


Regards, Dana.

 

Kemet has a tool K-SIM (this is a 1KV 220 pF) :