F1109 and F1116 Pre- and Post Check

[LarryH]

Due to at LEAST two mistakes for Andrews alone and the possible effects of "bad" calibrations on these power standards, we instituted a procedure to do our own calibration comparison.  It is basically, a calibration of a 3 power sensors before and after swapping out the standard.  For the F1116, we use an 8482A.  For the F1109 at 0 dBm, we use an 8478B Thermistor mount because it is the same model Agilent uses as a standard in power measurement and below -20 dBm, we use the 8484A (or the newer model).  I then compare the before and after cal factors and expect results to be within  the RSS of the accuracies of the power standards.  A spreadsheet is handy for entering both CF charts and charting them within the RSS brackets.

This testing found a bad cal on the F1109, -20 dBm at around  14 GHz. There was a 7% spike in the cal data causing a 7% dip in the cal factors.  They only conclusion I could draw was the attenuator was not properly torqued during the calibration.  This testing was NOT performed on a recent calibration and missed the fact that the attenuator was not the correct one and causing 7-10% differences in cal factors.  Luckily, this was caught early and only affected a couple power sensors.

Conclusion: Always check this standards. Use a direct compare as above or break out a few lab sensors for an early calibration and compare to their previous cal chart.  If QA needs some standard reviews, you can log them in under that and "kill two birds".