Solution
Early versions of WTS devices were shipped without amplitude accuracy correction data stored for generator and analyzer channels, so there were no warranted performance limits for these specification parameters. As a result, the typical amplitude accuracy performance depended on the user performing a combined path loss compensation for each generator and analyzer channel.
- If the WTS device under test has not previously been adjusted, then the as found performance of the device will not be considered warranted, and the as found limits will reflect the unadjusted performance of the device.
- If the device is adjusted by National Instruments, or if you use Calibration Executive to adjust the device, then accuracy correction data is stored on the device, and any future calibrations will compare the as-found performance against the warranted accuracy specifications.
To determine if the device has been adjusted by National Instruments or Calibration Executive, do the following:
- Use the NI-VISA Test Panel in Measurement & Automation Explorer (MAX) to query the SCPI command CALibration:RF:LATest:ADJustment? which will return the last adjust date.
- If the query returns the string 12/31/1903 6:00:00 PM then the device has not been adjusted and therefore does not have the path loss compensation.
Since there was no internal compensation on these devices, the tolerance of the amplitude accuracies is larger than the published specifications. For this reason, when these devices are calibrated by National Instruments or by Calibration Executive, the as-found amplitude accuracy performance of the device is compared against larger limits that are representative of the uncompensated amplitude performance of the WTS device.
The only verification tests that are affected when the amplitude is uncompensated are Generator Amplitude Accuracy, Generator Relative Channel Accuracy, and Analyzer Amplitude Accuracy. All other specification parameters are compared against the warranted specifications during the device calibration.