At 08:50 PM 5/10/2008, John Miles wrote... >Accuracy ratings for digital displays are commonly specified as a >percentage >+/- 1 LSD. So given tolerances of +/- 1 dB +/- 1 LSD for the analyzer >and >+/- 1 dB for the DUT, 2.01 dB is technically within spec.
No. The stated spec was peak to peak, so tolerances at both points must be accounted for. The stated conditions were: spec: "2 dB p-p" analyzer accuracy: "around 1 dB" (I assume exactly 1 dB absolute = +/- 1 = 2 dB p-p, since nothing further was stated) A measurement of "2.01 dB p-p" (which was also stated) could be measured from a DUT with 0.01 dB p-p, or from one with 4.01 dB p-p (max error at both peak and trough). In the former case, an actual peak of 0.01 might be measured as 1.01 and an actual trough of 0 as -1.00, for a measured p-p of 2.01. In the latter, an actual peak of 2.01 might be measured as 1.01 and an actual trough of -2 might be measured as -1.00, again for a measured p-p of 2.01. Such a measurement cannot be used to claim compliance with the spec (given the stated measurement accuracy). If significant digits were to be factored in, then the example should have included a spec tolerance. Since the figures 1.99, 2 and 2.01 were mentioned, it's reasonable to assume the "2" is an exact number lying between the other two. Even if the spec is only to a single significant digit, a measurement of 2.01 still doesn't meet the spec, since it guarantees compliance no better than 4.01, as stated above. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
