4263B Load calibration - Page 1
Forum section: electronics / general

author: metebalci
author_rank: Frequent Contributor
timestamp: March 26, 2023, 05:57:14 pm
content: When using the Load calibration with a resistor, it also asks for the reactance naturally. I was planning to use a Vishay Z foil (Y1453) or maybe get a basic lab resistor standard but as far as I see they do not specify the reactance. What should I do in this case ? Do you use the load calibration ?I am not doing anything very sensitive, but trying to make it measure as good as possible. My device is within the calibration window still and I am using BK Precision kelvin test leads (TL89K1).

author: alm
author_rank: Super Contributor
timestamp: March 26, 2023, 07:19:33 pm
content: The point of load calibration is that you use a component with a well characterized impedance. If you don't have this, then I wouldn't do load calibration, since it's unlikely to improve anything. I would expect the reactance of foil resistors to be fairly low, but I don't have any numbers. The classic resistance standard like the L&N Rosa type resistors that are commonly offered on eBay were not at all optimized for low reactance, so I would expect those to have a fairly high inductance for the low values and capacitance for the high values.You would either need a component with a well characterized impedance, like maybe a good standard capacitor with a very low dissipation factor (ESR), or you need to use a (friend with a) better LCR meter to characterize it and then use it to correct your unit.

author: TimFox
author_rank: Super Contributor
timestamp: March 26, 2023, 07:44:00 pm
content: The Vishay foil resistors have very low equivalent series inductance and shunt capacitance, especially when compared to wirewound resistors that have both.With both parasitic components, the reactance will vary considerably over frequency.For the foil resistors, measuring them with a cheap LCR meter is probably sufficient, since the reactive components are small.(Note that medium-value wirewound resistors may actually have capacitive, not inductive, reactance at the high end of the audio range, but you need to verify this for your resistors.)

author: metebalci
author_rank: Frequent Contributor
timestamp: March 26, 2023, 08:01:03 pm
content: Quote from: TimFox on March 26, 2023, 07:44:00 pmI understand and that was what I was doing or trying to do usually but I dont know if this improves anything or even make it worse.Maybe an example. A 500R Vishay Z (0.005%), an handheld LCR meter, after open/short calibration, measures Z=499.8 theta=0.00. On 4263B, after open/short calibration, it measures Z=499.83, theta=0.00. Now, if I Load calibrate this with Z=500, theta=0.00, is it a good thing or not or does it matter for this device ?Edit: With R-X parameters, 4263B shows fluctuation around 5-10mOhms@1kHz. After load calibration with Z=500,theta=0.00, X fluctuation moves a little bit lower, something like around 0.Edit 2: I realized there is this note in the impedance measurement handbook, so I guess I can measure it with the fixture (not test leads) first, but the shorting bar might be a problem: „The impedance value of the load must be known before performing the open/short/load compensation. To measure the load value, it is practical to use the same measurement instrument, but under the best possible measurement conditions. Set the measurement time, averaging, and test signal level so that the instrument can measure the load with maximum accuracy. Also, use a test fixture that mounts directly to the instrument. Figure 4-9 shows an example of such a measurement.“

author: mzzj
author_rank: Super Contributor
timestamp: March 26, 2023, 09:00:38 pm
content: 0.005% Vishay resistor seem overkill when the meter is specified only to 0.1% impedance accuracy.Heck, measuring ordinary 2 cent 1/4W metal film resistor with good dmm should be pretty close to "good enough"Manual suggests 100 to 1000 ohm reference value for load calibration.1kOhm 1/4W metal film resistor has about 0.4pF capacitance, at 1khz the impedance would be 999.999999995 ohms.100 ohm 1/4W metal film resistor might have 10nH inductance and impedance at 1khz would be 100.0000000004 ohms.As to whether or not you should do the load calibration it probably doesn't make much difference as your example values are still within the meter specification.