Interesting, even Hackaday refers to your XJW01 "Calibration" with the Kelvin leads attached, see snip below.
Calibrate the meter
It's time for calibration. It's not a super-obvious procedure, but it is fairly easy.
First, measure the included resistors as accurately as possible. There should be a 40R, 1K, 3K, 9K, 10K and 100K resistors. Go nuts with 50 power line cycles, averaging, 6,5 digits, 4-wire measurements and all that. We will use the measurements you've done to calibrate the meter to.
Once you've measured the resistors to an accurately enough degree, it's time to start the calibration procedure:
Turn the unit on
Perform a short test lead calibration. Clamp the Kelvin clips together and press the "Zero" button
Perform an open test lead calibration. Disconnect the kelvin clips and press the "Zero" button
Hold down MENU for approximately 3 seconds, this will bring up the options menu
Press RNG to enter calibration mode, the display should now show "Z0"
For the calibration, we will adjust the instrument to exactly match the previously measured resistor values (as well as some other parameters). Use the CLR (up) and SP/ESR buttons (down) to adjust the values. Use FREQ to go to the next parameter and QTY to go back.
Set the values of the different parameters as follows:
Step Target Value Notes
Z0 Z=0 Short the Kelvin clips
Z1 Z=0 Short the Kelvin clips
Z2 Z=0 Short the Kelvin clips
R1 40R resistor
Connect the resistor and try to match what you previously measured with your multimeter
R1X θ=0 Leave the resistor connected
R2 1K resistor
Connect the resistor and try to match what you previously measured with your multimeter
R2X θ=0 Leave the resistor connected
R3 10K resistor Connect the resistor and try to match what you previously measured with your multimeter
R3X 0 pF Leave the resistor connected
R4 100K resistor
Connect the resistor and try to match what you previously measured with your multimeter
R4b 100K resistor
Connect the resistor and try to match what you previously measured with your multimeter
R4X 0 pF Leave the resistor connected
G1 3K resistor
Connect the resistor and try to match what you previously measured with your multimeter
G1X 0 pf
Leave the resistor connected
G2 9K resistor
Connect the resistor and try to match what you previously measured with your multimeter
G2b 9K resistor
Connect the resistor and try to match what you previously measured with your multimeter
G2X 0 pf
Leave the resistor connected
PhX θ=0 Connect the 1K resistor
After calibration, make sure to save your changes with the Hand/Auto button!
https://hackaday.io/project/175641/instructionsNot trying to divert nor get into a useless argument as so often happens, nor play word games.
Just curious how one does as you say "a Calibration to the Instrument BNC terminals". Since these instruments are 4 terminal measurements, how does one Calibrate such.
How do you connect a reference resistor or capacitor (or reference short) directly to the 4 BNC terminals without some sort of cables/leads, or does the instrument have a "built-in" calibration means which includes input switching relays and Reference components inside the instrument?
If one has a known set of Calibration cables/leads which are well known and characterized, I can see how these could be utilized with the external Reference components and the lead effects "backed out" to the BNC connectors, sort of like with a VNA.
If this is true then I can see how one could do an Open/Short Compensation with whatever cables/leads or fixture that is attached to the 4 BNC instrument connectors and Compensate for such by means of mathematically removing these external effects.
BTW we do agree with the basic HP terminology regarding LCR Calibration and such, but when the 2 lab grade instruments we posses utilize completely different terminology, as does the Handheld LCR meter, and all different as shown, then the term "LCR Calibration" becomes a much more broad coverage term.
Our best guess to all this is the XJW01 establishes it's internal Calibration coefficients with the supplied Kelvin Clips by means of measuring various external reference components as shown in the Hackaday article, and does not mathematically remove these Kelvin clip effects to move back to the BNC terminals, please advise if this assumption is incorrect. Whereas a proper lab grade instrument utilizes a special "fixture" of know effects to establish a measurement reference plane at the BNC terminals at the instrument Calibration and Verification (which requires such with lab grade certified reference fixture and components), and then the Calibration/Correction/Compensation/Normalization or whatever we call it, the Short and Open are performed with the intended usage cables/leads or fixture. The instrument will mathematically remove the effects of this Open/Short procedure, and in some cases will also take into account the effects of the measurement cable length.
Anyway, not trying to get into a useless argument here, just trying to understand how this instrument achieves said results. If we had one of these XJW01 instruments then we would know how all this works, and with the relatively low cost might be worth acquiring just to learn something

Best,