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Seeking understanding of what an LCR meter can measure beyond L, C, and R

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ballsystemlord:
LCR meters will read a variety of additional parameters to just LCR.

For example, Conductance, Susceptance, and Admittance. These can be calculated by inputting the reciprocal of the resistance, reactance, and impedance. So would having a meter that would compute these parameters for you be of any advantage in real-world-usage?
Tequipment https://www.tequipment.net/lcr-meters-impedance-measurement-products/lcr-meters/ , in addition to several common parameters, lists Rdc and Rac as things that LCR meters can measure. But isn't Rac just Reactance? Isn't Rdc just resistance? Am I not understanding something, or are they just using different abbreviations for things?
Interestingly, (and not that I'd spend this much on a meter), but higher end meters, like this one https://www.tequipment.net/Instek/LCR-8201/LCR-Meters/ , don't list ESR as one of the parameters that they measure. Why? Is it just hidden somewhere deep inside of their manuals (I did search the datasheet. Not a mention of the word ESR.) or is ESR something that should be seen on separate lines, one for resistance, and the other for reactance and then we manually enter/compute what our circuit will do when exposed to a part with that reactance and resistance?

Thanks!

TimFox:
According to the datasheet you posted for the full-priced LCR-8201, it can display Cseries; Cparallel; AC Rseries; and AC Rparallel, among other parameters.
A maximum of four parameters can be displayed simultaneously.
"ESR" is merely a synonym for the series resistance in a series R-C model of a component, i.e. AC Rseries.
At a single frequency, any two-terminal capacitor-looking object can be modeled as either
Cseries in series with Rseries, or
Cparallel in parallel with Rparallel.
In the latter model, you may use the conductance Gparallel = 1 / Rparallel, at your convenience.
These units compute the displayed parameters from the inherent measurement of either R + jX or G + jB .
Elementary circuit theory discusses how these vary with frequency.

Martin72:
Here“s a pdf where all questions will be answered:

Agilent Impedance Measurement Handbook

mawyatt:

--- Quote from: TimFox on May 21, 2023, 06:56:01 pm ---These units compute the displayed parameters from the inherent measurement of either R + jX or G + jB .
Elementary circuit theory discusses how these vary with frequency.

--- End quote ---

Actually the LCR measurement values are not R + jX but simply DUT voltage and current as vectors (digitized versions of magnitude and angle of sinusoids, with multiple samples taken, then sinusoid reconstructed), R +JX and all other parameters are computed from such!! 

Also a proper capacitance model should include ESL as well as ESR for a capacitor to help represent the series resonate effect, without such the "effective" capacitance can not change with frequency, and we know many types of capacitors do vary over their expected operating frequency range, thus the inclusion of ESL to represent such.

Best.

TimFox:

--- Quote from: mawyatt on May 21, 2023, 10:06:59 pm ---
--- Quote from: TimFox on May 21, 2023, 06:56:01 pm ---These units compute the displayed parameters from the inherent measurement of either R + jX or G + jB .
Elementary circuit theory discusses how these vary with frequency.

--- End quote ---

Actually the LCR measurement values are not R + jX but simply DUT voltage and current as vectors (digitized versions of magnitude and angle of sinusoids, with multiple samples taken, then sinusoid reconstructed), R +JX and all other parameters are computed from such!! 

Also a proper capacitance model should include ESL as well as ESR for a capacitor to help represent the series resonate effect, without such the "effective" capacitance can not change with frequency, and we know many types of capacitors do vary over their expected operating frequency range, thus the inclusion of ESL to represent such.

Best.

--- End quote ---

I got that upside-down.
With LCR meters using the basic mechanism of the GenRad Digibridges, the "low" end of the component connects to a virtual ground to measure the device current, while the "high" end is driven by a known value of AC voltage.
Using a phase-sensitive detector on the device current, and dividing by the voltage value gives the admittance Y = G + jB, where G comes from the "real" (in-phase) component and B comes from the "imaginary" (quadrature phase) component of the current, where the phase reference for the detector comes from the voltage.
That summarizes the actual measurement, but the built-in computation starts with these two values and applies appropriate calibration (including fixturing) to calculate the displayed values.

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