Hi Need to drink my coffee first and type messages second.
The Time is doing a “LSB” change of some sort. It’s not sick, there’s either a problem with the string or something like that. The EFC is not moving at an alarming rate based on the plot. Simple things to do: Unplug the software and fire up a terminal program. Run it into the Diag port just like the other stuff. Set it to 9600 8:N:1 and type the following: *IDN? that should give you a string identifying the unit properly and show that things are hooked up right. :SYSTEM:STATUS? That will show you a mega screen of everything that’s going on.The screen includes the time offset and predicted holdover numbers. :DIAG:ROSC:EFC? That will show you the EFC voltage in percent of range. It runs over a +/- 100% range. Running things this way for a bit will let you eliminate any software issues from the mix. If things still look odd, do a: :DIAG:LOG:READ:ALL? That will show you any alarm outputs or odd things going thump in the night. Bob > On Nov 14, 2014, at 7:13 AM, ed briggs <[email protected]> wrote: > > The EFC is probably not sick, it is still in the middle of it's range, and > has moved only a small amount. I would let it run for another week and see > if it starts to head back down. As I mentioned in a previous post, I had to > run my z3816a for several weeks before it settled down. After that period of > time, my Z3816 settled into the EFC range of 581240-581280 and a predicted > uncertainty in the 100-200ns/24 range - but it took a month to get there) > > Important note: it seems that the Lucent *reports the PPS TI error > differently* than previous units. This will make comparisons between this > unit and the older unit difficult. > > Another time-nut sent me the data file from Z38xx attached to a Lucent GPSDO, > and I noticed that most of the values TI values had only zeros to the right > of the decimal point. (almost all but not all). This made the data look > like the TI jumped around in discrete steps of 1.0 * 10e-8 . That is the > reason you see the 'strata' and 'plateaus' in your plot that you don't see in > previous z3801,3805,3816 plots. The peaks in the +/- 40 ns range are the > same as on my Z3816a (which uses the same GPS receiver). > > The data file also had quite a few 0.000000000 TI values, which bounced then > to 1.0e-8 etc. So somewhere in the data paths, someone is doing the > equivalent of a floor(TI error). So if you calculate averages on this kind of > data and compare it to averages or SD on previous units, the results will be > misleading. > > It's possible that the program Z38xx is incorrectly parsing these values and > 'stripping the digits to the right' performing a floor(TI). I can't tell > because I only have the data after Z38xx parsed it. Somebody who has one of > these units and Z38xx could open the debug screen and capture it to a file > and see if the '1 PPS to TI ns relative to GPS" has zeros to the right of the > decimal point most of the time, or the response to the :PTIM:TINT? is > 'stepping' as I described above. > > BTW - what do you see as the predicted uncertainty. > > Regards > > Ed > > _______________________________________________ > 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. _______________________________________________ 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.
