From: "Poul-Henning Kamp" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] HP5359A non-linearities Date: Tue, 18 Dec 2007 00:28:34 +0000 Message-ID: <[EMAIL PROTECTED]>
> In message <[EMAIL PROTECTED]>, Magnus Danielson writes: > >Fellow time-nuts! > > > >I have been making some measurements on the HP5359A using the DTS2070C. > >I am adjusting the period and measure that. > > > >Initially it is apparent that the HP5359A does not hit the mark, > > The 5359A doesn't work quite the way you would expect, the trigger > is just sort of a trigger for an internal trigger, from which the > pulse will be delivered, very precisely (if properly calibrated). > > It's kind of strange, once you've read their explanation, it makes > sense. I have spent my time over the operating and service manual to figure it out, so I have a fair idea of how it ticks, and when operating in the frequency/period mode it triggers itself. What I have been doing is measuring the acheived period time vs. "dialed" period time. The startable VCO is indeed a strange beast, but it makes kind of sense. You don't know when the trigger gets there, but once it does, you want to count some number of 129/128 * 10 ns clocks and then analogue interpolate the last fractional 129/128 * 10 ns in about 50 ps steps, or about 1/200 fraction of that. It is very similar to the startable VCO in the 5370B, but with a different ratio (257/256). You could use some other method than the startable oscillator, but all methods depend upon some means of measuing the trigger error relative some stable clock and then maintain that allignment error somehow while adding some arbitrary programable delay value to output an output event. Regardless of method, we can expect a variance of jitter and variance of step- size/non-linearity. I was kind of interested in verifying the properties before using it to test lesser counters than the DTS-2070C. ;-) Normal time-nut activity I guess. Cheers, Magnus _______________________________________________ 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.
