Claude wrote:
I know how to measure ADEV with frequency method (using a 53131A counter) or time difference method (using 1 PPS of a GPSDO for example) but I would like to measure ADEV in the sub-second domain (from 0.1s to 1s for example). Do I need a Time Interval Analyzer, if so, an HP 5371A is ok for that ? Or there are simpliest method ?
You may do better with a Phase Noise measurement, depending on what instruments you have available.
Generally, we think of oscillator stability over times >= 1 second in the time domain, as xDEV, and stability over times <= 1 second (or so) (offsets >= 1 Hz) in the frequency domain, as Phase Noise. Partly, this is because of the different kinds of phenomena we are concerned about on the two different scales, and partly because different measurement techniques are better suited to each of the two time scales.
These limits are not absolute, particularly if you digitize signals at a high sample rate with high resolution and do the analysis in the digital domain. Fancy xDEV/PN analyzers, such as the Microsemi 5125A, can measure xDEV down to tau = 1 mS and PN below a 1mHz offset. (But sit down before you ask the price.)
I usually measure xDEV down to 0.1 second, and PN at offsets >= 1 Hz. Of course, to measure xDEV at 0.1 second, you need to take at least ten TI or frequency measurements per second with no dead time between measurements, and with good accuracy -- so you need an instrument with very high resolution at short gate times and fairly fast data throughput. For that, I use a Wavecrest DTS2075.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
