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You can measure the capacitance and the esr of capacitor directly in the circuit?

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eletmoraes

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If you want to measure the capacitance and also the internal resistance of said capacitor directly on the board or in the circuit, is possible ?
 

KlausST

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Hi,

On a pcb the capacitor usually is connetced to other components.
During measurement there will be current to the other connected components that affect the measurement result.

You may try to test the capacitor on the pcb, but the results are not reliable.

Klaus
 

andre_teprom

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He is presumably referring to the bulk capacitor placed at the final stage of a power supply. For this application would not be hard to take the whole current and voltage from it.

However, the procedures needed for measuring ESR requires specific steps that certainly would turn impossible to do that without put in risk the other circuits supplied by it.
 

Kripton2035

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I have an old poptronix esr meter I use often. it can be used in circuit because the injected signal is around 200mV and does not interfere with semiconductors on the board.
https://kripton2035.free.fr/analog%20esr/esr-poptronix.html
if you can measure capacitance with such a small signal it would be ok then
I also have a recent deree de5000 lcr meter, and I can measure capacitance and esr in circuit with it because the test signal is small also around 500mV.
https://kripton2035.free.fr/LCR%20meters/lcr-deree5000-cl.html

you are limited to the fact that if capacitors are in parallel, you will measure the total capacitance, and this if-s often the case inside power supplies. if one capacitor only is bad, you won't be able to find it without desoldering.
 

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