Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
tvb wrote: do either of you have actual tempco numbers? I checked my notes and found that I did not record any free-running tempco values. My observations were based on the scale factors I had to use to get the temperature and DAC graphs in Lady Heather to overlay each other. I initially noticed it because there was a very pronounced tracking of the two graphs for one Tbolt and for the other two there was not (the temperature-compensating component of the DAC voltage is mostly lost in the noise). I had checked the actual EFC sensitivity of each oscillator in the vicinity of the operating point, so all relevant variables were more or less controlled. My impression is that the better ones are comparable to a single-oven 10811, maybe even a bit better. LH typically reports tempcos of 1e-12/C to 1e-11/C. My worse unit (and, from what I can infer from LH plots posted to the list and on-line, it appears many others as well) typically reports a tempco of 1e-10/C to 1e-9/C. Of course, the LH numbers are all to be taken with some caution since LH does not have any a priori means to separate tempco and drift. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi LH can get a bit confused about OCXO tempo. It's not really the software's fault, as you point out - the data just isn't there. Bob On Dec 14, 2012, at 5:36 AM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: tvb wrote: do either of you have actual tempco numbers? I checked my notes and found that I did not record any free-running tempco values. My observations were based on the scale factors I had to use to get the temperature and DAC graphs in Lady Heather to overlay each other. I initially noticed it because there was a very pronounced tracking of the two graphs for one Tbolt and for the other two there was not (the temperature-compensating component of the DAC voltage is mostly lost in the noise). I had checked the actual EFC sensitivity of each oscillator in the vicinity of the operating point, so all relevant variables were more or less controlled. My impression is that the better ones are comparable to a single-oven 10811, maybe even a bit better. LH typically reports tempcos of 1e-12/C to 1e-11/C. My worse unit (and, from what I can infer from LH plots posted to the list and on-line, it appears many others as well) typically reports a tempco of 1e-10/C to 1e-9/C. Of course, the LH numbers are all to be taken with some caution since LH does not have any a priori means to separate tempco and drift. 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. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
I think what I'll do is collect some data on a batch of TBolts that I have soaking here. It seems to me there's enough information that, over time, the tempco can be accurately determined. I mean, when you see LH plots with glaring diurnal patterns in both temp and DAC it's easy to roughly calculate the correlation by eye. Alternately, when the TBolt is in disciplining-disabled mode, the tempco can be inferred from temp and quadratic PPS offset residuals (EFC gain is not a factor in this case). Or for greater precision, a simple match of variations in ambient temp and externally measured frequency would do the job. I use different software to talk with my TBolts anyway, logging all communication in its native TSIP binary. I'll modify or write an automated tool to take the guesswork out of it. /tvb - Original Message - From: Charles P. Steinmetz charles_steinm...@lavabit.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, December 14, 2012 2:36 AM Subject: Re: [time-nuts] Thunderbolt oven / non-stable operating temperature tvb wrote: do either of you have actual tempco numbers? I checked my notes and found that I did not record any free-running tempco values. My observations were based on the scale factors I had to use to get the temperature and DAC graphs in Lady Heather to overlay each other. I initially noticed it because there was a very pronounced tracking of the two graphs for one Tbolt and for the other two there was not (the temperature-compensating component of the DAC voltage is mostly lost in the noise). I had checked the actual EFC sensitivity of each oscillator in the vicinity of the operating point, so all relevant variables were more or less controlled. My impression is that the better ones are comparable to a single-oven 10811, maybe even a bit better. LH typically reports tempcos of 1e-12/C to 1e-11/C. My worse unit (and, from what I can infer from LH plots posted to the list and on-line, it appears many others as well) typically reports a tempco of 1e-10/C to 1e-9/C. Of course, the LH numbers are all to be taken with some caution since LH does not have any a priori means to separate tempco and drift. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
On 12/11/2012 10:33 PM, Charles P. Steinmetz wrote: All three have Trimble 37265 OCXOs (( sorry to single out that one line )) Just a curiosity. Is there any way to check that via software? Did you just physically look under the cover, or how did you figure out which type of oscillator your thunderbolt has? Thanks, Sarah ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi The OCXO is a dumb version. It does not talk to the TBolt. There's no way to check it in software. There are a few examples out there that have late model stickers on the outside and earlier parts on the inside. There's pretty much no way to know what you have without opening up the box. When you open the box, be careful not to loose the hardware that goes on the F connector…. Bob On Dec 14, 2012, at 1:42 PM, Sarah White kuze...@gmail.com wrote: On 12/11/2012 10:33 PM, Charles P. Steinmetz wrote: All three have Trimble 37265 OCXOs (( sorry to single out that one line )) Just a curiosity. Is there any way to check that via software? Did you just physically look under the cover, or how did you figure out which type of oscillator your thunderbolt has? Thanks, Sarah ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Sarah wrote: All three have Trimble 37265 OCXOs Just a curiosity. Is there any way to check that via software? Did you just physically look under the cover, or how did you figure out which type of oscillator your thunderbolt has? You need to open it up. There is a sticker on the OXCO can: Emacs! Best regards, Charles inline: 15249ce9.jpg___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
tvb wrote: the tempco can be inferred from temp and quadratic PPS offset residuals (EFC gain is not a factor in this case) It would be interesting (to me, at least) to know the spread of EFC gains from a reasonable population of Tbolts. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi The real answer to that is going to be a that depends kind of thing. The population of units in the basement are all within 20% of each other as measured by LH's auto tune process. Bob On Dec 14, 2012, at 2:51 PM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: tvb wrote: the tempco can be inferred from temp and quadratic PPS offset residuals (EFC gain is not a factor in this case) It would be interesting (to me, at least) to know the spread of EFC gains from a reasonable population of Tbolts. 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. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Warrenm tvb posted Were you able to test how quickly, or how well, the filter learned the tempco of the OCXO? Only at a couple of very general data points. Using a very Bad unit, the Kalman filter had an effect, although not very good in under 1/2 day. After a week or so on a good unit, it helped maybe 3 to1 with ageing and Temperature TC. Not contributing vs your information in detail or quality. But here is some terse information from Trimble regarding holdover for the Tbolt. This voltage steers the oscillator correcting for temperature and aging effects by using a Kalman Filter. The Kalman filter works by observing the behavior of an oscillator over temperature and time while GPS is locked. This is called the training period. http://trl.trimble.com/docushare/dsweb/Get/Document-8428/ kind regards, Björn ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi Michael, Nice, clean plots. Thanks for sharing. Ah, but does correlation imply causation? Note that crystal resonators, even inside an oven, are also sensitive ambient temperature sensors. As temperature changes the OCXO drifts off-frequency -- the TBolt then sees the average PPSns diverge and adjusts the DAC in order to reduce this accumulated time error and to keep the OCXO on-frequency. Try computing the tempco of your oscillator using this raw data (and look up the EFC gain setting). I'm surprised to see the PPSns error got so large (over 100 ns peak to peak). Is your TBolt using a factory default time constant? The plots suggest it has been set too high given the environment. /tvb - Original Message - From: Michael Perrett To: Tom Van Baak ; Discussion of precise time and frequency measurement Sent: Wednesday, December 12, 2012 1:06 AM Subject: Re: [time-nuts] Thunderbolt oven / non-stable operating temperature Although ignorant of why, I have a pretty good of idea of what is happening. There is a 1:1 correlation between the TBolt temperature output reading and the rest of the TBolt reported values. In particular the estimate of the TBolt accuracy (10 MHz ppb), the PPS Offset and the controlling DAC voltage. It acts like the environment temperature is sensed by the tmep chip, which, I believe, changes the DAC voltage and the self estimates of the goodness of the TBolt changes proportionally. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi The later TBolt OCXO's have temperature performance similar to an HP10811. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims Sent: Tuesday, December 11, 2012 9:36 PM To: time-nuts@febo.com Subject: [time-nuts] Thunderbolt oven / non-stable operating temperature Although the Trimble oscillator has superb phase noise performance, it has TERRIBLE temperature sensitivity. It appears to be a single oven oscillator, not a double oven. The PWM'ed fan temperature control implemented in Lady Heather effectively makes the unit a double oven. Also, by stabilizing the temperature of the rest of the tbolt electronics and power supply (if included in the temperature controlled box) you get additional performance out of the unit. Some testing indicates that a temperature stabilized tbolt/power supply can improve the performance by an order of magnitude (around 30% of that is due to issues outside of the oscillator can). And yes, Lady Heather can control the Tbolt DAC. There is a PID controller in there for controlling the DAC (based upon the 1PPS error signal, if I remember correctly... it could be the OSC error signal). ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi I suspect that to use the temperature chip data, it needs to be running on GPS for several days while ramping temperature. After that, put it in holdover, observe the time drift over the next four hours with a similar ramp. Since they work with the later chip, the ramp would have to be pretty aggressive (many degrees C per hour). Bob On Dec 10, 2012, at 11:23 PM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: That temperature sensor does have an effect on the final outcome as it is part of the internal equation. So buffering the ambient temperature is important. I've heard this before, but the evidence I have seen does not seem to support the proposition. While switching the Dallas chip in one, I used the opportunity to bring the chip temporarily outside of the Tbolt housing on a cable to investigate whether the Tbolt makes any internal use of the temperature data. Neither freeze spray nor bringing a soldering iron near the chip, when it was outside of the Tbolt housing and the Tbolt housing was well insulated from the changes in chip temperature, seemed to have any effect on the operation of the Tbolt, either normal or in holdover. I have also run Tbolts with the newer (wrong) temperature chips for long periods, and have not observed any systematic differences in performance between them and units with the older chips, either in normal operation or in holdover. In Tbolts with the newer chips, the reported temperature often has little connection with the actual temperature and, at times, jumps abruptly, yet the Thunderbolts operate normally with no corresponding jumps in operating parameters. My supposition/conclusion is that the temperature sensor was provided so telcom operators could get a rough idea of the temperature in remote cell-site transmitter shacks, not for internal use by the Tbolt. As long as the Tbolt is housed so that its reported temperature does not change too rapidly, the oven control loop will keep the crystal very close to its set temperature over a wide range of ambient temperatures. I have used this approach and have also actively controlled the housing temperature, and have not observed any material difference in frequency or timing stability between the two approaches. 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. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Bill wrote: Well, perhaps you are not looking close enough. That is you need to be observing at a finer level of comparison. The changes, observed here and at another location, are in parts in 10-10 to 10-11 range, sometimes larger. At one of the locations there was a direct correlation to the air conditioning cycle. It is not clear what part of my message you are referring to. My main point was that the information from the DS1620 temperature sensor does not appear to be used internally by the Tbolt. In my observation, subjecting the sensor alone (thermally isolated from the rest of the Tbolt) to wide temperature swings (-10 to +120 C) did not produce any observabe effect on the operation of the Tbolt. If the temp sensor data were used internally by the Tbolt, one would expect a significant effect from such a wide swing -- one that couldn't be missed. If that large and fast a reported temperature swing produced effects only at the e-10 or 11 level, I would attribute it to imperfect thermal isolation of the Tbolt from the temperature stimulus (i.e., stimulus affecting the oven temperature or EFC circuitry of the Tbolt), not as the Tbolt's response to the temperature change reported by the DS1620 sensor. If you were referring to my side point -- that allowing slow changes to the Tbolt housing temperature does not appear to be materially different from regulating the housing temperature -- my observations were that this was true down to at least 5e-13. Of course, there are two variables -- total swing and rate of change. By slow, I mean a rate of change of 0.25C per hour or less [DS1620 reported temperature]. My diurnal swings are no more than 2C per day and usually less [DS1620 reported temperature] (they can be as much as 5 or 6C seasonally, but those changes happen over weeks). A/C cycling likely subjects the Tbolt to a significantly greater rate of change than what I mean by slow, even if basic precautions are taken (e.g., putting it in a cardboard box). 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
If it is used for tempco it should affect the temp by stabilizing offset with temp changes correct? Maybe a more correct approach would be to disconnect it and test. Has been awhile since I read that testing stuff. Doc Sent from mobile On Dec 11, 2012, at 6:39 AM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: Bill wrote: Well, perhaps you are not looking close enough. That is you need to be observing at a finer level of comparison. The changes, observed here and at another location, are in parts in 10-10 to 10-11 range, sometimes larger. At one of the locations there was a direct correlation to the air conditioning cycle. It is not clear what part of my message you are referring to. My main point was that the information from the DS1620 temperature sensor does not appear to be used internally by the Tbolt. In my observation, subjecting the sensor alone (thermally isolated from the rest of the Tbolt) to wide temperature swings (-10 to +120 C) did not produce any observabe effect on the operation of the Tbolt. If the temp sensor data were used internally by the Tbolt, one would expect a significant effect from such a wide swing -- one that couldn't be missed. If that large and fast a reported temperature swing produced effects only at the e-10 or 11 level, I would attribute it to imperfect thermal isolation of the Tbolt from the temperature stimulus (i.e., stimulus affecting the oven temperature or EFC circuitry of the Tbolt), not as the Tbolt's response to the temperature change reported by the DS1620 sensor. If you were referring to my side point -- that allowing slow changes to the Tbolt housing temperature does not appear to be materially different from regulating the housing temperature -- my observations were that this was true down to at least 5e-13. Of course, there are two variables -- total swing and rate of change. By slow, I mean a rate of change of 0.25C per hour or less [DS1620 reported temperature]. My diurnal swings are no more than 2C per day and usually less [DS1620 reported temperature] (they can be as much as 5 or 6C seasonally, but those changes happen over weeks). A/C cycling likely subjects the Tbolt to a significantly greater rate of change than what I mean by slow, even if basic precautions are taken (e.g., putting it in a cardboard box). 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. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi The only place the sensor *might* be used is during holdover. There is no practical reason to use it while the TBolt is locked to GPS. *If* it's used in holdover, it gets trained by watching the control voltage and the temperature while the beast is locked to GPS. That information is then used when it goes into holdover to improve time drift while in holdover. The first test would be to put one in holdover and see if the DAC voltage changes at all while it's there. If it changes, the next step would be to see if the change is simply a function of time (= aging correction). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Dailey Sent: Tuesday, December 11, 2012 10:45 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt oven / non-stable operating temperature If it is used for tempco it should affect the temp by stabilizing offset with temp changes correct? Maybe a more correct approach would be to disconnect it and test. Has been awhile since I read that testing stuff. Doc Sent from mobile On Dec 11, 2012, at 6:39 AM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: Bill wrote: Well, perhaps you are not looking close enough. That is you need to be observing at a finer level of comparison. The changes, observed here and at another location, are in parts in 10-10 to 10-11 range, sometimes larger. At one of the locations there was a direct correlation to the air conditioning cycle. It is not clear what part of my message you are referring to. My main point was that the information from the DS1620 temperature sensor does not appear to be used internally by the Tbolt. In my observation, subjecting the sensor alone (thermally isolated from the rest of the Tbolt) to wide temperature swings (-10 to +120 C) did not produce any observabe effect on the operation of the Tbolt. If the temp sensor data were used internally by the Tbolt, one would expect a significant effect from such a wide swing -- one that couldn't be missed. If that large and fast a reported temperature swing produced effects only at the e-10 or 11 level, I would attribute it to imperfect thermal isolation of the Tbolt from the temperature stimulus (i.e., stimulus affecting the oven temperature or EFC circuitry of the Tbolt), not as the Tbolt's response to the temperature change reported by the DS1620 sensor. If you were referring to my side point -- that allowing slow changes to the Tbolt housing temperature does not appear to be materially different from regulating the housing temperature -- my observations were that this was true down to at least 5e-13. Of course, there are two variables -- total swing and rate of change. By slow, I mean a rate of change of 0.25C per hour or less [DS1620 reported temperature]. My diurnal swings are no more than 2C per day and usually less [DS1620 reported temperature] (they can be as much as 5 or 6C seasonally, but those changes happen over weeks). A/C cycling likely subjects the Tbolt to a significantly greater rate of change than what I mean by slow, even if basic precautions are taken (e.g., putting it in a cardboard box). 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. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Guys, So much speculation on how the Tbolt uses it's temperature sensor data. Having spending hundreds of man hrs and thousands of Tbolt running hrs, testing all kinds of things to find ways to improve my Tbolt's performance. This is what I've found happens on My Non E TBolt with version#3 firmware, when in an indoor environment concerning it's temperature sensor. During normal operation my Tbolt uses the temperature and ADC data to in its Kalman filter that then can predict a simple linear temperature constant, and simple linear ageing rate. Starting from a factory reset, it has something it will use in under 1/2 day. If the temperature has not been thru a few cycles and /or the Ageing is still at a high initial cold start rate and still changing, the Kalman filter can give very poor results and actually make things worse. It gets better as time goes on, and after a few days with a predicable Osc, the Klaman filter will improve enough to help. But the **Only** time the Kalman filter is used is during Holdover. It does this by adjusting the EFC voltage in small steps making a simple linear ramp as a function of time, Plus a simple linear output as function of delta temperature. I've also found that if the Temperature chip is the new one that gives only about 1 deg of resolution, All still works the same, But during hold over instead of seeing small continuous DAC changes as temperature changes, you see Big EFC steps. It is a shame the Kalman filter is not also used during normal non holdover run time. With a more advanced PID control loop it could be made to work much better. As it is, because the known systematic error information is not used as a feed-forward term to help the PID loop, any temperature change or ageing that does take place during control has to be totally corrected by an error signal. In short this means there will be unnecessary errors caused by both changing temperature or time if the Oscillator is not perfect. The bottom line is, these errors then limits how good of control you get, and why the Tbolt should be in a stable, less than 0.1 deg /hr environment to get the best performance from it. (or can use LH's temperature controller or use an external double oven Oscillator) So what does this mean for the average Nut's Tbolt? Mostly nothing. The only time the temperature sensor has any effect is during holdover. If the Tbolt is going into holdover long enough for any of this to have an effect there are many worse things to be concerned about. If the Tbolt does not go into holdover, none of the aging rate or temperature data is used (except for an over temperature alarm). There is one exception that I have tested for: If the Tbolt has a high resolution temperature sensor and a good Osc where both the aging rate and the temperature TC are constant enough to be correctly modeled by the simple linear 1st order predictor used in its Kalman filter, then the open loop Kalman filter correction can improve the frequency accuracy over time by 3 to 1 or better during very long holdover periods like days. ws *** ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Warren wrote: During normal operation my Tbolt uses the temperature and ADC data to in its Kalman filter that then can predict a simple linear temperature constant, and simple linear ageing rate. * * * But the **Only** time the Kalman filter is used is during Holdover. It does this by adjusting the EFC voltage in small steps making a simple linear ramp as a function of time, Plus a simple linear output as function of delta temperature. I've also found that if the Temperature chip is the new one that gives only about 1 deg of resolution, All still works the same, But during hold over instead of seeing small continuous DAC changes as temperature changes, you see Big EFC steps. That all sounds like the way it should work, if the temp sensor data is used internally by the Tbolt. My notes indicate that I tried cooling and warming the isolated sensor during holdover and observed no effect. However, the Kalman filter may not have been operating because I tested the unit immediately after it reached basic stability, before it had time to learn anything. So what does this mean for the average Nut's Tbolt? Mostly nothing. I agree. I presume that most time nuts would not ordinarily rely on a GPSDO during holdover -- particularly, a long holdover. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Another thing that could of effected the results when measuring the effect of a low resolution sensor chip during holdover, is that it is real hard for the Klaman filter to learn anything useful from it, without some careful manipulation of the variables. Mostly all it would normally record would look like seemingly random freq changes with no temperature change and then large temperature changes but with very little frequency change. ws Charles P. Steinmetz charles_steinmetz at lavabit.com posted Warren wrote: During normal operation my Tbolt uses the temperature and ADC data to in its Kalman filter that then can predict a simple linear temperature constant, and simple linear ageing rate. * * * But the **Only** time the Kalman filter is used is during Holdover. It does this by adjusting the EFC voltage in small steps making a simple linear ramp as a function of time, Plus a simple linear output as function of delta temperature. I've also found that if the Temperature chip is the new one that gives only about 1 deg of resolution, All still works the same, But during hold over instead of seeing small continuous DAC changes as temperature changes, you see Big EFC steps. That all sounds like the way it should work, if the temp sensor data is used internally by the Tbolt. My notes indicate that I tried cooling and warming the isolated sensor during holdover and observed no effect. However, the Kalman filter may not have been operating because I tested the unit immediately after it reached basic stability, before it had time to learn anything. So what does this mean for the average Nut's Tbolt? Mostly nothing. I agree. I presume that most time nuts would not ordinarily rely on a GPSDO during holdover -- particularly, a long holdover. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi Warren, Starting from a factory reset, it has something it will use in under 1/2 day. And that would explain my and Charles' null results. Nice. If the temperature has not been thru a few cycles and /or the Ageing is still at a high initial cold start rate and still changing, the Kalman filter can give very poor results and actually make things worse. It gets better as time goes on, and after a few days with a predicable Osc, the Klaman filter will improve enough to help. Were you able to test how quickly, or how well, the filter learned the tempco of the OCXO? It is a shame the Kalman filter is not also used during normal non holdover run time. With a more advanced PID control loop it could be made to work much better. Yes (although please define much; are you talking 1% better or 10% better or 2x better). Would it be possible to implement this advanced PID in LH? Or as a first step, and to veryify your conclusions, would it be possible for LH to control the DAC during TBolt hold-over mode? As it is, because the known systematic error information is not used as a feed-forward term to help the PID loop, any temperature change or ageing that does take place during control has to be totally corrected by an error signal. In short this means there will be unnecessary errors caused by both changing temperature or time if the Oscillator is not perfect. I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during hold-over mode (where there is no GPS noise) but not for normal operation. So what does this mean for the average Nut's Tbolt? Mostly nothing. The only time the temperature sensor has any effect is during holdover. Thanks for stating both these facts so clearly. I cringe every time I hear someone replacing a 1C DS1620 sensor in their TBolt. The TAPR TBolts I tested years ago worked equally well regardless if they were 1C TBolts or ten milli-C TBolts. /tvb ___ 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] Thunderbolt oven / non-stable operating temperature
Although the Trimble oscillator has superb phase noise performance, it has TERRIBLE temperature sensitivity. It appears to be a single oven oscillator, not a double oven. The PWM'ed fan temperature control implemented in Lady Heather effectively makes the unit a double oven. Also, by stabilizing the temperature of the rest of the tbolt electronics and power supply (if included in the temperature controlled box) you get additional performance out of the unit. Some testing indicates that a temperature stabilized tbolt/power supply can improve the performance by an order of magnitude (around 30% of that is due to issues outside of the oscillator can). And yes, Lady Heather can control the Tbolt DAC. There is a PID controller in there for controlling the DAC (based upon the 1PPS error signal, if I remember correctly... it could be the OSC error signal). ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Mark wrote: Although the Trimble oscillator has superb phase noise performance, it has TERRIBLE temperature sensitivity. It appears that most do but some don't. Between the results I have seen posted on the list (Lady Heather screen shots) and my own data, they seem to fall into two groups. I have two with excellent oscillator tempcos, but a third unit I have is about 100x worse and the sign of its tempco is reversed compared to the first two. That one appears to consume approximately the same oven power as the other two, and heats the housing approximately equally, so the oven does not appear to have a gross failure. All three have Trimble 37265 OCXOs. I initially thought the third unit's oven controller was broken (low gain). Then I noticed that the great majority of posted Lady Heather plots appear to be from units similar to that one, with the much higher tempco and reversed tempco sign compared to my two low-tempco units. But I have seen a few other plots that appear to be from units similar to my first two. The two with the low tempcos do not appear to be inferior to other Tbolts with respect to stability, PN, or aging. I'm inclined to think that all 37265 OCXOs are supposed to work like my first two, and that the ones with large tempcos are the result of a supply or manufacturing error (most likely, a mismatch between the oven set point and the crystal). But who knows? There do seem to be many more of the ones with large tempcos around. It would be interesting to take a few 37265s apart to see if there are any obvious differences between the high- and low-tempco units, and if tweaking the oven set points would reduce the tempcos of the high-tempco units. 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
tvb posted Were you able to test how quickly, or how well, the filter learned the tempco of the OCXO? Only at a couple of very general data points. Using a very Bad unit, the Kalman filter had an effect, although not very good in under 1/2 day. After a week or so on a good unit, it helped maybe 3 to1 with ageing and Temperature TC. Yes (although please define much; are you talking 1% better or 10% better or 2x better). Much is a 2 to 10 times improvement in the errors cause the undesirable compensated effects. As an example, say your unit gives a 1e-10 freq ripple error when you turn on the over head Air condition, then that would go down by a factor of 3 or so. Of course you could also just move your unit away for the AC and get a similar improvement. For the best performance improvement, you do both. Would it be possible to implement this advanced PID in LH? Or as a first step, and to verify your conclusions, would it be possible for LH to control the DAC during TBolt hold-over mode? Yes, There is already a very flexible, but very user unfriendly 'prove of concept' version, in LH. It does have some of the feed-forward capability already there, along with lots of other things, as part of the many undocumented features of the external advanced PID controller now in LH. but I do not see a reason for using it during hold over, Because the Tbolt S/W already does a good job with that now. but the external PID does help the non holdover mode. LH's external PID even works remotely over the internet. So I have, in the past, controlled someone's Tbolt from my computer, getting better results than where available from the Tbolt's internal PID. (Works until the connection is lost). The terms I think that are available in the latest LH's internal PID controller are Phase error, Freq error, time, Dac offset, and maybe temperature. Basically for the feed-forward in hold-over mode, just need to add the sum of K1 x temp_change (since start of holdover) with K2 x lapse_time (since start of hold over) to the Dac value (since start of hold over) The hard part is to automatically find the best value for K1 and K2 during run time. In LH all the various variable K values are manually set. Last count I think the Advanced PID had 7 or 8 K's that could be tuned. I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during hold-over mode (where there is no GPS noise) but not for normal operation. The reason it works even during normal operation is that the GPS noise is mostly plus and minus (basically AC), where as the time drift and temperature drift errors are in one polarity. When these AC errors are filtered thru the LP integrator of the PID, the GPS noise cancels but the DC time and offset errors, even though smaller than the GPS noise, tend to dominate short term. Short term being less than the PID's Time constant. ws Tom Van Baak tvb at LeapSecond.com Posted Hi Warren, Starting from a factory reset, it has something it will use in under 1/2 day. And that would explain my and Charles' null results. Nice. If the temperature has not been thru a few cycles and /or the Ageing is still at a high initial cold start rate and still changing, the Kalman filter can give very poor results and actually make things worse. It gets better as time goes on, and after a few days with a predicable Osc, the Klaman filter will improve enough to help. Were you able to test how quickly, or how well, the filter learned the tempco of the OCXO? It is a shame the Kalman filter is not also used during normal non holdover run time. With a more advanced PID control loop it could be made to work much better. Yes (although please define much; are you talking 1% better or 10% better or 2x better). Would it be possible to implement this advanced PID in LH? Or as a first step, and to veryify your conclusions, would it be possible for LH to control the DAC during TBolt hold-over mode? As it is, because the known systematic error information is not used as a feed-forward term to help the PID loop, any temperature change or ageing that does take place during control has to be totally corrected by an error signal. In short this means there will be unnecessary errors caused by both changing temperature or time if the Oscillator is not perfect. I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Although the Trimble oscillator has superb phase noise performance, it has TERRIBLE temperature sensitivity. It appears that most do but some don't. Between the results I have seen posted on the list (Lady Heather screen shots) and my own data, they seem to fall into two groups. I have two with excellent oscillator tempcos, but a third unit I have is about 100x worse and the sign of its tempco is reversed compared to the first two. That Mark, Charles, This is interesting and I'd like to pursue it. I still have a pile of original TAPR-Thunderbolts here so without too much effort I can gather tempco statistics for you. I tested the TAPR lots for phase noise and ADEV and DS1620 granularity, but did not test free-run tempco of the OCXO. rant Please don't use the word TERRIBLE. It's relative to XO, TCXO, OCXO, DOCXO, etc. This is time-nuts, not some feel-good audiophile list. We are allowed to make objective experiments and use scientific notation. The units for tempco involve Hz and C, or dF/F per K, etc. Given that, do either of you have actual tempco numbers? /rant Bob, do you have experience or an explanation for the bi-model tempco grouping that they have observed? Thanks, /tvb ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hello Tom, the GPS noise dominates for typical double oven OCXO's where the tempcos are very small (say below 5E-012 per degree C). On single oven units, the tempcos are typically 50 to 200 times larger, and thus the required EFC change over temperature is also that much larger. If I am not mistaken Thunderbolts have double oven units, and Mini-T's have single oven units? That EFC change can only be done through either prediction (sensing temperature and applying a correction factor) or through generating a phase error that feeds through the loop system. Crystal aging also typically requires a constant phase error which will in turn create a constant change in EFC voltage to correct for aging until active aging compensation can measure and apply this change in EFC. The magnitude of this phase error typically depends on the loop gain and the rate of change of the crystal frequency over time. In summary, we see fairly significant improvements in single oven systems with active compensation even during GPS reception, and we don't see much improvement in double oven units for temperature, but similar improvements for double oven units on aging. Now double oven units typically have SC-cut crystals, and single oven units typically have AT-cut crystals where the AT cuts typically have larger aging and retrace than SC cut crystals, so that can skew the performance in favor of double oven units as well. Bye, Said In a message dated 12/11/2012 19:41:58 Pacific Standard Time, warrensjmail-...@yahoo.com writes: I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during hold-over mode (where there is no GPS noise) but not for normal operation. So what does this mean for the average Nut's Tbolt? Mostly nothing. The only time the temperature sensor has any effect is during holdover. Thanks for stating both these facts so clearly. I cringe every time I hear someone replacing a 1C DS1620 sensor in their TBolt. The TAPR TBolts I tested years ago worked equally well regardless if they were 1C TBolts or ten milli-C TBolts. /tvb ___ 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] Thunderbolt oven / non-stable operating temperature
Ended up with a gently used trimble thunderbolt a few months ago, and been trying to figure out the best settings to use (time constant, damping, etc.) for best performance. I got distracted though. There is something which I find rather annoying, and I'm spending more time messing with this factor than actually observing the performance at different damping / time constant / etc... The temperature seems to be aprox 20C above ambient temperature rather than a steady 40C. I thought the purpose of the oven was to keep the temperature stable. When I adjust the thermostat because I'm chilly, the thunderbolt gets warmer too (but not by as much) I've tried (seemingly, to me) everything: light insulation putting the unit in a spot away from drafts putting the unit in a place away from drafts in a shoebox with light insulation with a fan blowing in it (currently in a cupboard in this state, and the temp seems to fluctuate the least, but still by more than 1-2 degrees centigrade) I feel like shouldn't need to fuss with ambient conditions this heavily for an OCXO, and find myself researching construction / design for a DIY outer-oven to wrap the thunderbolt in. Anyone have experience with non-stable temperature on a trimble thunderbolt? I've also noticed (monitoring with Lady Heather's Disciplined Oscillator Control Program v3.10 by John Miles aka KE5FX) the thunderbolt unit sometimes flags an alarm briefly (and I rarely ever manage to write it down before the screen updates or the alarm goes away) and the last one I was able to catch before it went away was related to temperature. Should I be getting a steady / non-flucturating 40C or something if the oven is working normally? Thanks in advance, Sarah ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi The oven in the OCXO keeps the crystal at a constant temperature. It is normal for the TBolt it's self to idle 10 to 20C above ambient. The temperature sensor is located near the 9 pin D connector. It shows a temperature somewhere in between the ambient and the OCXO case temperature. Some have mounted speed controlled fans to keep the TBolt case at a constant temperature. Bob On Dec 10, 2012, at 5:15 PM, Sarah White kuze...@gmail.com wrote: Ended up with a gently used trimble thunderbolt a few months ago, and been trying to figure out the best settings to use (time constant, damping, etc.) for best performance. I got distracted though. There is something which I find rather annoying, and I'm spending more time messing with this factor than actually observing the performance at different damping / time constant / etc... The temperature seems to be aprox 20C above ambient temperature rather than a steady 40C. I thought the purpose of the oven was to keep the temperature stable. When I adjust the thermostat because I'm chilly, the thunderbolt gets warmer too (but not by as much) I've tried (seemingly, to me) everything: light insulation putting the unit in a spot away from drafts putting the unit in a place away from drafts in a shoebox with light insulation with a fan blowing in it (currently in a cupboard in this state, and the temp seems to fluctuate the least, but still by more than 1-2 degrees centigrade) I feel like shouldn't need to fuss with ambient conditions this heavily for an OCXO, and find myself researching construction / design for a DIY outer-oven to wrap the thunderbolt in. Anyone have experience with non-stable temperature on a trimble thunderbolt? I've also noticed (monitoring with Lady Heather's Disciplined Oscillator Control Program v3.10 by John Miles aka KE5FX) the thunderbolt unit sometimes flags an alarm briefly (and I rarely ever manage to write it down before the screen updates or the alarm goes away) and the last one I was able to catch before it went away was related to temperature. Should I be getting a steady / non-flucturating 40C or something if the oven is working normally? Thanks in advance, Sarah ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi Sarah, The temperature you are seeing is that of a Dallas IC mounted on the main PC board. You are seeing the ambient temp of the board, not inside the OCXO oven. Regards, Tom - Original Message - From: Sarah White kuze...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, December 10, 2012 5:15 PM Subject: [time-nuts] Thunderbolt oven / non-stable operating temperature Ended up with a gently used trimble thunderbolt a few months ago, and been trying to figure out the best settings to use (time constant, damping, etc.) for best performance. I got distracted though. There is something which I find rather annoying, and I'm spending more time messing with this factor than actually observing the performance at different damping / time constant / etc... The temperature seems to be aprox 20C above ambient temperature rather than a steady 40C. I thought the purpose of the oven was to keep the temperature stable. When I adjust the thermostat because I'm chilly, the thunderbolt gets warmer too (but not by as much) I've tried (seemingly, to me) everything: light insulation putting the unit in a spot away from drafts putting the unit in a place away from drafts in a shoebox with light insulation with a fan blowing in it (currently in a cupboard in this state, and the temp seems to fluctuate the least, but still by more than 1-2 degrees centigrade) I feel like shouldn't need to fuss with ambient conditions this heavily for an OCXO, and find myself researching construction / design for a DIY outer-oven to wrap the thunderbolt in. Anyone have experience with non-stable temperature on a trimble thunderbolt? I've also noticed (monitoring with Lady Heather's Disciplined Oscillator Control Program v3.10 by John Miles aka KE5FX) the thunderbolt unit sometimes flags an alarm briefly (and I rarely ever manage to write it down before the screen updates or the alarm goes away) and the last one I was able to catch before it went away was related to temperature. Should I be getting a steady / non-flucturating 40C or something if the oven is working normally? Thanks in advance, Sarah ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Sarah, The reported temperature is not the oven temp, but rather the temp of the circuit board just behind the DB-9 serial connector. As far as I know, the actual oven temp is not available outside the OCXO. Regards, geo On Mon, Dec 10, 2012 at 5:15 PM, Sarah White kuze...@gmail.com wrote: Ended up with a gently used trimble thunderbolt a few months ago, and been trying to figure out the best settings to use (time constant, damping, etc.) for best performance. I got distracted though. There is something which I find rather annoying, and I'm spending more time messing with this factor than actually observing the performance at different damping / time constant / etc... The temperature seems to be aprox 20C above ambient temperature rather than a steady 40C. I thought the purpose of the oven was to keep the temperature stable. When I adjust the thermostat because I'm chilly, the thunderbolt gets warmer too (but not by as much) I've tried (seemingly, to me) everything: light insulation putting the unit in a spot away from drafts putting the unit in a place away from drafts in a shoebox with light insulation with a fan blowing in it (currently in a cupboard in this state, and the temp seems to fluctuate the least, but still by more than 1-2 degrees centigrade) I feel like shouldn't need to fuss with ambient conditions this heavily for an OCXO, and find myself researching construction / design for a DIY outer-oven to wrap the thunderbolt in. Anyone have experience with non-stable temperature on a trimble thunderbolt? I've also noticed (monitoring with Lady Heather's Disciplined Oscillator Control Program v3.10 by John Miles aka KE5FX) the thunderbolt unit sometimes flags an alarm briefly (and I rarely ever manage to write it down before the screen updates or the alarm goes away) and the last one I was able to catch before it went away was related to temperature. Should I be getting a steady / non-flucturating 40C or something if the oven is working normally? Thanks in advance, Sarah ___ 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.
[time-nuts] Thunderbolt oven / non-stable operating temperature
I feel like shouldn't need to fuss with ambient conditions this heavily for an OCXO, and find myself researching construction / design for a DIY outer-oven to wrap the thunderbolt in. Anyone have experience with non-stable temperature on a trimble thunderbolt? The temperature you see is not from the OCXO but from the thermometer chip near the RS-232 connector. The DS1620 is probably at fault and the rest of the Thunderbolt is operating as it should. I've see a lot of Thunderbolts and the most common failure mode of the non E revision DS1620 thermometer is for them to display -55 degrees C although it could just have erratic output like yours. The erratic temperature that it is reporting could cause the processor to try to compensate for the erratic jumps and cause the Thunderbolt output to be less stable. The DS1620 should be replaced. -Arthur ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
On 12/10/2012 5:22 PM, Bob Camp wrote: Hi The oven in the OCXO keeps the crystal at a constant temperature. It is normal for the TBolt it's self to idle 10 to 20C above ambient. The temperature sensor is located near the 9 pin D connector. It shows a temperature somewhere in between the ambient and the OCXO case temperature. Some have mounted speed controlled fans to keep the TBolt case at a constant temperature. Bob Bob, others: Ah, so then it's probably fine. Thanks, the other posts which followed seem to be in agreement with yours. ... Now then. Suppose I'll likely return my efforts to finding a time constant that makes sense for my particular tbolt / usage needs. ___ 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] Thunderbolt oven / non-stable operating temperature
I believe that the high temperature alarm you see is triggered at 50 degrees C. If that is what you're seeing without artificially raising the temperature of the Thunderbolt by insulating it so it can't radiate the heat, what I said about replacing the chip is correct but if it is staying within a few degrees over the course of the day and is in the 40 degree C range without being insulated, the DS1620 thermometer chip is o.k.. -Arthur ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
On 12/10/2012 6:10 PM, Arthur Dent wrote: I believe that the high temperature alarm you see is triggered at 50 degrees C. If that is what you're seeing without artificially raising the temperature of the Thunderbolt by insulating it so it can't radiate the heat, what I said about replacing the chip is correct but if it is staying within a few degrees over the course of the day and is in the 40 degree C range without being insulated, the DS1620 thermometer chip is o.k.. My particular thunderbolt seems to be from 2004, so I guess that manual is at or around checked: ThunderBolt[tm] GPS Disciplined Clock User Guide Version 5.0 5.0 is a version of the manual published in 2003 Table C.2.2 Environmental Specifications: Operating Temp: -0°C to +60°C Storage Temp: -40°C to +85°C ... so I guess I shouldn't worry about a few degrees of difference in the reported temp, especially considering that the sensor in question isn't on the OCXO itself. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Sarah, That temperature sensor does have an effect on the final outcome as it is part of the internal equation. So buffering the ambient temperature is important. You do not need to go crazy, but having it contained in a box with some small amount of heat applied and maintained by some controlling mechanism would be a good way to go. The amount of heat depends upon what extremes your location experiences over the day/week/year and the effective insulation of the container. Ideally you would want no temperature change, but, obviously, that is not practical, so a one degree variance would be a reasonable goal. BillWB6BNQ Sarah White wrote: On 12/10/2012 6:10 PM, Arthur Dent wrote: I believe that the high temperature alarm you see is triggered at 50 degrees C. If that is what you're seeing without artificially raising the temperature of the Thunderbolt by insulating it so it can't radiate the heat, what I said about replacing the chip is correct but if it is staying within a few degrees over the course of the day and is in the 40 degree C range without being insulated, the DS1620 thermometer chip is o.k.. My particular thunderbolt seems to be from 2004, so I guess that manual is at or around checked: ThunderBolt[tm] GPS Disciplined Clock User Guide Version 5.0 5.0 is a version of the manual published in 2003 Table C.2.2 Environmental Specifications: Operating Temp: -0°C to +60°C Storage Temp: -40°C to +85°C ... so I guess I shouldn't worry about a few degrees of difference in the reported temp, especially considering that the sensor in question isn't on the OCXO itself. ___ 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.
Re: [time-nuts] Thunderbolt oven / non-stable operating temperature
Hi Charles, Well, perhaps you are not looking close enough. That is you need to be observing at a finer level of comparison. The changes, observed here and at another location, are in parts in 10-10 to 10-11 range, sometimes larger. At one of the locations there was a direct correlation to the air conditioning cycle. BillWB6BNQ Charles P. Steinmetz wrote: That temperature sensor does have an effect on the final outcome as it is part of the internal equation. So buffering the ambient temperature is important. I've heard this before, but the evidence I have seen does not seem to support the proposition. While switching the Dallas chip in one, I used the opportunity to bring the chip temporarily outside of the Tbolt housing on a cable to investigate whether the Tbolt makes any internal use of the temperature data. Neither freeze spray nor bringing a soldering iron near the chip, when it was outside of the Tbolt housing and the Tbolt housing was well insulated from the changes in chip temperature, seemed to have any effect on the operation of the Tbolt, either normal or in holdover. I have also run Tbolts with the newer (wrong) temperature chips for long periods, and have not observed any systematic differences in performance between them and units with the older chips, either in normal operation or in holdover. In Tbolts with the newer chips, the reported temperature often has little connection with the actual temperature and, at times, jumps abruptly, yet the Thunderbolts operate normally with no corresponding jumps in operating parameters. My supposition/conclusion is that the temperature sensor was provided so telcom operators could get a rough idea of the temperature in remote cell-site transmitter shacks, not for internal use by the Tbolt. As long as the Tbolt is housed so that its reported temperature does not change too rapidly, the oven control loop will keep the crystal very close to its set temperature over a wide range of ambient temperatures. I have used this approach and have also actively controlled the housing temperature, and have not observed any material difference in frequency or timing stability between the two approaches. 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. ___ 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.
