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Power measurement uncertainty and AN 1449-3

Question asked by nttora on Jul 17, 2013
Hi all,

when calculating the uncertainty in a power measurement, following what's written in AN 1449-3 (page 29), I have some doubts about the "Kc" term. When would this be different than 1? When a measurement is made with sensors other than thermistors, isn't the measurement always realtive to the previously "calibrated" 50 MHz 1 mW output reference? If so, I understand there could be an error source Muc, t, Pmc and Pcal during the 1 mW "calibration" process, but why is Kc also an error source, if future measurements will be relative to that 1 mW reference?

Page 30 in AN 1449-3 says that "If the sensor is calibrated relative to the associated calibrator output frequency, Kc = 1 and u(Kc)=0". When would this not be the case?

Thanks in advance.