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

--- Quote from: TimFox on May 28, 2023, 02:45:18 am ---Note that for a real capacitor with a reasonable Q value, the equivalent parallel and series resistances RP and RS are very different.

--- End quote ---
Which, of course, brings us to the question, what's the actual resistance if series and parallel produce such different results?
(It's probably academic, but it's still interesting.)
TimFox:
The wrong question.
For the component ("capacitor"), the choice between series and parallel models depends on the circuit you are designing:
Typically, the series model is easier to calculate in a power-supply filter capacitor, but the parallel model is easier to calculate in an RLC parallel-resonant circuit.
For the guts of the device ("dielectric"), the basic physics is often better described with Q = 1/D, which is a somewhat weak function of frequency for many materials.
The component also has parasitic resistances (connections in series and leakage in parallel) packaged along with the dielectric.
At a fixed frequency, there is no difference in operation between the series and parallel models.
coromonadalix:
aaaaaand  the serial or parallel DUT   can be impacted by all parts around it or are in the same circuit, it is not an absolute way to troubleshoot

jwet:
These alternate inverted units are not just arithmetic - they can be more useful in certain ranges- for instance- if you were measuring 1 milli ohm and had three digits, would you like to see .001 ohms or 983 Siemens (or mhos in the day).  This used to be more important when units had fixed LED displays and hardware defined interfaces.  Make sure the instrument covers the range you need, this will make sure it can measure it.  In the above example, a modern unit might display 1.02 milli-ohm (the inverse of 983 mhos)
ballsystemlord:
Thanks, guys. That just leaves the last one:
Is Rac (Resistance AC) just another way of saying Xc/Xl (e.g. Marketing had the idea of calling it Rac), or is it some special other measurement?
(I give a link with examples in the OP.)

Unless  you have anything to add regarding the other 2:
https://www.eevblog.com/forum/testgear/seeking-understanding-of-what-an-lcr-meter-can-measure-beyond-l-c-and-r/msg4883012/#msg4883012

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