Hi guys, Thanks for all the guidance!
I was ultimately able to make this work by applying various suggestions from the list. In the end I needed to offset the uBlox in order to get a good read and then fix this in post processing. I checked the pulse before and after making the offset, and the frequency seemed unaffected. Originally as part of the experiment I was considering the FS-725 as a perfect reference for simplicity (we all know that does not match reality) and if that assumption is made, it is possible where the pulses do overlap (that is they cross over and you start to see very large millisecond counts), to remove 1 second from the time and get the negative delta. Obviously this only works when you assume the reference is right even when it's wrong, which is not desirable in many cases. However there was still a gotcha - it seems it is possible for it to "flip" within a single pulse so that you end up with some very strange results. I couldn't think of any good way to compensate for that so I went with the offset approach. We did find some interesting things when looking at the performance of a relatively low cost GPS receiver (uBlox M8Q) when compared to the output of an SRS FS-725 which was being disciplined by the 1PPS of a Microsemi S650. We've got a paper being considered, but I'd love to share it here for critical feedback once it's published. Thanks again to everyone! Kind Regards, Peter Membrey ----- Original Message ----- From: "Magnus Danielson" <mag...@rubidium.dyndns.org> To: time-nuts@febo.com Cc: mag...@rubidium.se Sent: Monday, 23 May, 2016 08:38:50 Subject: Re: [time-nuts] Capturing a 1PPS signal with a Keysight 53230A Hi, On 05/02/2016 08:12 PM, Tom Van Baak wrote: >> * DC >> * 50Ohm >> * Bandwidth filter enabled > > DC and 50R is ok. I would not use the filter; you want the fastest edge > possible. > > You forgot to mention the most important setting of all - the trigger > voltage. Check the signal at your inputs with a 'scope. I typically use 1.0 > VDC, unless the 'scope suggests otherwise. Oh, and turn of "auto" from trigger voltage, many counters tries to fix it way quicker than the PPS occurs. The 53131/132 has this issue with PPS. Cheers, Magnus _______________________________________________ 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. _______________________________________________ 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.
