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Measure capacitor ESR with any LCR meter?

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kc1980:
Can capacitor ESR be reliably measured with any LCR meter?  One would think that THAT is exactly what the LCR meter is designed to do, but there are other factors to consider (e.g. frequency).

I think it very much depends on the meter. Some meters are true L/C/R meters only, are very crude and only measure charge/discharge time or oscillation frequency in a simple circuit, others pass an AC voltage across the device under test and measure the phase and magnitude of the current. That makes it simple to derive the purely capacitive and resistive components.

As you say though, that is just at one frequency, and both R and C values can change massively with frequency. A cap that looks fine at 100kHz may degrade horribly at 1MHz. Ideally you want to be able to sweep the values, but then you start getting into the realm of scalar and vector network analysers.

NiHaoMike:
I have read somewhere that if you have a signal generator, oscilloscope, and a known (low value) resistor, it is very easy to measure the ESR. Make a voltage divider out of the capacitor and resistor, set the frequency high enough that capacitive reactance is negligible, then measure the voltages.

ThunderSqueak:

--- Quote from: NiHaoMike on July 01, 2010, 07:32:00 pm ---I have read somewhere that if you have a signal generator, oscilloscope, and a known (low value) resistor, it is very easy to measure the ESR. Make a voltage divider out of the capacitor and resistor, set the frequency high enough that capacitive reactance is negligible, then measure the voltages.

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http://octopus.freeyellow.com/99.html

Something like that?

Pyr0Beast:

--- Quote from: kc1980 on July 01, 2010, 05:19:46 pm ---Can capacitor ESR be reliably measured with any LCR meter?  One would think that THAT is exactly what the LCR meter is designed to do, but there are other factors to consider (e.g. frequency).

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No.

LCR meter measures inductance, capacitance and resistance, but not ESR of capacitor.
You have ESR meter for that.