Hi, further to Thunderbolt holdover performance, if you had your thunderbolt in a room that only had ± 1 degree temperature variation when you switched it on, then it would only learn a rather weak temperature sensitivity. If it was in a room with a daily swing of 20 degrees it should learn a fairly accurate temperature sensitivity coefficient. If you switched it on in the ±20 degree environment, then moved it to the ±1 degree environment would it eventually forget the robust tempco number and substitute a more noise prone number? The question I am asking is what is the best strategy to get the best holdover performance? This question is relevant to my plans to put my TBOLT in a ± 0.5 degree environment to help the OCXO.
cheers, Neville Michie On 07/03/2009, at 2:35 PM, [email protected] wrote: > Hi there, > > Would you have the EFC plots while in holdover for us? > > You can try to place the unit into your refrigerator. That will > drop it down > to 3C or so from ambient. That will give you enough of a change so > that you > can see how the EFC changes with the two sensors.. It will also > give you a > good idea how good the OCXO itself can handle thermal shocks. > > BTW: the drift you described is quite high, it definitely busts the > CDMA > spec in both cases (CDMA: 7us/Day or so). But I am not surprised by > this if they > use the Dallas chip for temp compensation of the OCXO. > > A good GPSDO (with double oven) should not drift more than 1us per day > typically in holdover after one week of continuous operation. > > bye, > Said > > > In a message dated 3/6/2009 16:04:32 Pacific Standard Time, > [email protected] writes: > > Hello Said, > > The Tbolt that I used for the test was well aged (several months of > operation) and stable prior to the tests. It was only powered > down for the 10 > minutes or so that it took to swap out the old sensor. > > I tried to choose data sets that were fairly comparable > temperature wise. > I also chose the basic measurement interval to be 1 hour so that > temperature > would not be changing much over the hour. I am fairly confident > that the > results reflect changes due to the temperature sensor. > > I wanted to make the measurement PPS drift / degree C change / > hour but the > later model (low res) temp sensor chip would seldom produce a > recordable > change in temperature over a one hour period. > > > _______________________________________________ > 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.
