How about reading the signal with another wattmeter of the same published uncertainty? If the reading is the same on both meters, or more accurately the two readings fall within a tighter tolerance than the published uncertainty, the real uncertainty has to be much less than the published uncertainty of each meter, right? To make this more convincing, the two meters should be of different make and calibrated at different places, so as to minimize the expectation of systematic error.
Essentially this is what I did in my precompliance facility, and it's not really limited to a specific kind of equipment or measurement. In order to convince myself my test equipment was functional, I would feed the output of my rf signal source into my spectrum analyzer, and checked that the analyzer read the same amplitude and frequency. It's a real good bet that if the readings are substantially the same (within manufacturer's tolerances), that the calibration is still okay, because if you suppose that one of the machines is out of tolerance, then the other machine has to also be out of tolerance by exactly the same amount and in the same direction. Application of Occam's razor leads to the conclusion that both machines are operating correctly. ---------- >From: [email protected] >To: [email protected] >Subject: Measurement Uncertainty >Date: Fri, Jun 14, 2002, 3:31 PM > > > > > Dear All: > > I am looking for the most accurate measuring device to determine the amplitude > of a RF sine wave with the lowest possible uncertainty . For now lets > assume I am trying to measure a 80dBuV sine wave between 30MHz to 1GHz > from a 50 ohm source and other signal componets not at the intended frequency > is at least 80dB down. The standard choices are spectrum analyzer with ~2dB > uncertainty, receiver with ~1dB uncertainty or watt meter with ~0.5dB > uncertainty. > All uncertainty's are assumed to be with an expanded uncertainty of K=2. > > Does anyone know of a method or device that can do better than the watt meter? > Let's limit the discussion to a device that costs <$20K. > > Thanks, > Keith Hardin > Lexmark International Inc. > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
