While making some measurements of low value power resistors we observed an interesting characteristic with our TH2830 and IM3536 Lab Grade Bench LCR Meters.
https://www.eevblog.com/forum/projects/power-resistor-characterization/For very low impedance levels with Kelvin Clips that were properly Open/Short Calibrated the results were agreeable for equivalent series R with a direct connected leaded fixture (B&K TL89F1) also properly calibrated EXCEPT the equivalent series inductance was often incorrect, being negative at even lower frequency measurements.
This erroneous result was traced back to the actual LCR meter's ability to INCLUDE the fixture
Cable Length Compensation which with the Kelvin Clips is ~1 Meter.
The Tonghui TH2830 has the parameter in the setup but its not activated, the Hioki IM3536 also has this parameter and its selectively activated.
The Hioki gave proper results throughout the ranges, including using the Kelvin Clips beyond their specified range of 100KHz, used to 1MHz with surprisingly good agreement with the direct TL89F1 fixture results.
To prove to ourselves this
Cable Length Compensation was the root cause and not something else, we purposely calibrated the Hioki IM3536 with the
Cable Length Compensation turned OFF. It barked at us, stating the Calibration was in question after completing such, so the IM3536 was monitoring the phase shift and noted the shift excessive and not compensated, smart meter
When we made low resistance Kelvin measurements with the IM3536 with
Cable Compensation Off, the results exhibited the negative inductance (capacitance) as "seen" with the Tonghui TH2830 (no Cable Compensation available) when also using the same Kelvin Clips.
The math behind this is within the actual computations as the meters don't actually measure R, C, or L, they measure Vector DUT Voltages and Currents and compute all the displayed parameters, and part of these computations involves calibration corrections which include
Cable Length Corrections in some LCR Meters.
Anyway, the
Cable Length Compensation is an important parameter for LCR meters that are expected to return accurate results with low impedances with Kelvin Clip type cables.
BTW, know someone is going to say, "RTFM" but we are too lazy, as for sure it's somewhere in some manual
Best,