Re: [time-nuts] CSAC Project(was CSAC purchase)
Hi Questions are good, it’s how you figure things out. We’re talking about a “practical” timing device design. It’s not as crazy a topic as it might seem. Some basic math: You get to a million seconds at about 11.6 days. A millisecond error over that period is one ppb. If you are off 1 ppb at T=0 and stay there, you will be off by 1 ms. If you drift so you are off by 1 ppb at the end, you will be off by less than 1 ms. At some point, you do need “rough numbers” to work out what you are going to do. Holding a few microseconds (not milliseconds, we just jumped a factor of a thousand) on a GPS based wall clock / watch is quite practical, even with poor GPS access ( = crummy antenna). With a reasonable antenna 100’s of ns are very practical, even with a cheap GPS module. The practical question would be: What am I getting from the CSAC? One basic answer might be “holdover” at less than 1 us / day. Another basic answer might be autonomous operation in a location where GPS simply isn’t available. Lots to think about. Bob > On Jan 29, 2018, at 12:44 PM, Ronald Held wrote: > > Bob; > I see what you are saying. I will wait until I get the chips d more > before asking more questions. > Ronald > > Hi > > As mentioned multiple times in the archives. As you get into the single digit > milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off > and one that is 1 ms off are both “good enough” if you are looking at it with > a > normal eyeball. > > From a design standpoint 1 ms / day / week is *way* different that 1 ns over > the > same sort of period. Design constraints *do* make a big difference. > It’s important > in any project to get them sorted early. > > If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t > going to even get into the roundoff error. You *will* need the GPS gizmo to > keep the CSAC calibrated. It is only a question of how often the beast gets > used. > > Bob > > On 1/29/18, Ronald Held wrote: >> >> > ___ > 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] CSAC Project(was CSAC purchase)
Bob; I see what you are saying. I will wait until I get the chips d more before asking more questions. Ronald Hi As mentioned multiple times in the archives. As you get into the single digit milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off and one that is 1 ms off are both “good enough” if you are looking at it with a normal eyeball. >From a design standpoint 1 ms / day / week is *way* different that 1 ns over >the same sort of period. Design constraints *do* make a big difference. It’s important in any project to get them sorted early. If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t going to even get into the roundoff error. You *will* need the GPS gizmo to keep the CSAC calibrated. It is only a question of how often the beast gets used. Bob On 1/29/18, Ronald Held wrote: > > ___ 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] CSAC Project(was CSAC purchase)
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Re: [time-nuts] CSAC Project(was CSAC purchase)
Hi As mentioned multiple times in the archives. As you get into the single digit milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off and one that is 1 ms off are both “good enough” if you are looking at it with a normal eyeball. >From a design standpoint 1 ms / day / week is *way* different that 1 ns over >the same sort of period. Design constraints *do* make a big difference. It’s important in any project to get them sorted early. If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t going to even get into the roundoff error. You *will* need the GPS gizmo to keep the CSAC calibrated. It is only a question of how often the beast gets used. Bob > On Jan 28, 2018, at 7:45 PM, Ronald Held wrote: > > Bob: > Right now I own nothing that outputs a GPS PPS. GPS watches I own do > not have that option. Maybe for infrequent resets, an independent > GPS unit is better from a design and construction POV? > Ronald > > > > Hi > > A GPS PPS output will (most likely) be more accurate than the CSAC > each time you go back to dock with the charger. A GPS module to do > everything you would ever want to do is a sub $100 sort of item. You > would still need a bit of hardware to “glue” things together (but not a lot) > and some code running on the MCU of your choice to supervise the process. > > Accuracy wise, a GPS PPS is *very* hard to beat. > > Bob > ___ > 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] CSAC Project(was CSAC purchase)
Bob: Right now I own nothing that outputs a GPS PPS. GPS watches I own do not have that option. Maybe for infrequent resets, an independent GPS unit is better from a design and construction POV? Ronald Hi A GPS PPS output will (most likely) be more accurate than the CSAC each time you go back to dock with the charger. A GPS module to do everything you would ever want to do is a sub $100 sort of item. You would still need a bit of hardware to “glue” things together (but not a lot) and some code running on the MCU of your choice to supervise the process. Accuracy wise, a GPS PPS is *very* hard to beat. Bob ___ 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] CSAC Project(was CSAC purchase)
Hi A GPS PPS output will (most likely) be more accurate than the CSAC each time you go back to dock with the charger. A GPS module to do everything you would ever want to do is a sub $100 sort of item. You would still need a bit of hardware to “glue” things together (but not a lot) and some code running on the MCU of your choice to supervise the process. Accuracy wise, a GPS PPS is *very* hard to beat. Bob > On Jan 28, 2018, at 6:19 PM, Ronald Held wrote: > > Jim: > Hmm, I was kit thinking that way. How rich could I get writing > an app that is only used for CSACs? Seems a small market ,IMO. > Monitoring sounds easier thenSW to drive a display. > Ronald > > There's a half dozen serial ascii commands to the CSAC, and a > corresponding number of output messages. None are particularly "special" > - I can't imagine needing a "display" for the telemetry, except perhaps > as a novelty. > > You'd want to periodically check the heater power, maybe? > > I'd just expose a "diagnostic interface" on a CSAC based clock, and if > you want to fool with it (or change the frequency, etc.), you hook up > your external whatever. > LE Bluetooth Serial port perhaps? > > You could write an App for a phone to talk to it, and I'm sure it will > be in the top10 on the iStore and GooglePlay within weeks. Your > retirement funding is assured. > > > > Mark: > Sounds like a good idea. I have none,but some Time-nuts have more > than one. Maybe one will loan one out? >Ronald > > > > Bob: > Now there is a snproblem, as I own nothing more accurate the data > dumping may prove usefulssni learn more. >Ronald > > Hi > > Yes, I have set up a CPU to dump all the data from a CSAC. Everything > they list in their data sheet can easily be dumped via a standard UART > interface. The serial protocol works exactly the way they describe. > > There is no “built in clock” so no ability to dump the time and date. You > can “improve” the frequency stability by sending whatever you want to the > tuning word. What you send and when you send it is entirely up to you. > The real issue is having something more accurate than the CSAC to > compare to when you do the frequency correction. > > Bob > ___ > 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] CSAC Project(was CSAC purchase)
Jim: Hmm, I was kit thinking that way. How rich could I get writing an app that is only used for CSACs? Seems a small market ,IMO. Monitoring sounds easier thenSW to drive a display. Ronald There's a half dozen serial ascii commands to the CSAC, and a corresponding number of output messages. None are particularly "special" - I can't imagine needing a "display" for the telemetry, except perhaps as a novelty. You'd want to periodically check the heater power, maybe? I'd just expose a "diagnostic interface" on a CSAC based clock, and if you want to fool with it (or change the frequency, etc.), you hook up your external whatever. LE Bluetooth Serial port perhaps? You could write an App for a phone to talk to it, and I'm sure it will be in the top10 on the iStore and GooglePlay within weeks. Your retirement funding is assured. Mark: Sounds like a good idea. I have none,but some Time-nuts have more than one. Maybe one will loan one out? Ronald Bob: Now there is a snproblem, as I own nothing more accurate the data dumping may prove usefulssni learn more. Ronald Hi Yes, I have set up a CPU to dump all the data from a CSAC. Everything they list in their data sheet can easily be dumped via a standard UART interface. The serial protocol works exactly the way they describe. There is no “built in clock” so no ability to dump the time and date. You can “improve” the frequency stability by sending whatever you want to the tuning word. What you send and when you send it is entirely up to you. The real issue is having something more accurate than the CSAC to compare to when you do the frequency correction. Bob ___ 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] CSAC Project(was CSAC purchase)
Hi Yes, I have set up a CPU to dump all the data from a CSAC. Everything they list in their data sheet can easily be dumped via a standard UART interface. The serial protocol works exactly the way they describe. There is no “built in clock” so no ability to dump the time and date. You can “improve” the frequency stability by sending whatever you want to the tuning word. What you send and when you send it is entirely up to you. The real issue is having something more accurate than the CSAC to compare to when you do the frequency correction. Bob > On Jan 27, 2018, at 7:29 PM, Ronald Held wrote: > > Bob: >Interesting but too general for me. Has anyone used a CPU to read > the CSAC outputs for time/date, and for improving frequency stability? >Ronald > > > > Hi > > “Included software” on the CSAC is a pretty short list …. There > is not much past the “stuff” to set it on frequency and read out > a few alarms. > > One thing that gets into a lot of these projects: > > We are Time Nuts and spec things in terms of time. This error > over that period is some specific number. Maybe we look at > temperature rather than sit it on the shelf for a year. The number > is still a time error. > > Pretty much everybody making devices spec’s them (and may think > of them) as frequency generating gizmos. They all spec a frequency > error over some condition (like a period of time). Unfortunately time > error and frequency error aren’t the same thing. > > This also gets into things like control loops. Generally the input is a > time error and the output is a frequency control. Same basic gotcha > the input isn’t the same as the output. Fortunately they are related > very closely to each other. > > Bob > ___ > 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] CSAC Project(was CSAC purchase)
Bob: Interesting but too general for me. Has anyone used a CPU to read the CSAC outputs for time/date, and for improving frequency stability? Ronald Hi “Included software” on the CSAC is a pretty short list …. There is not much past the “stuff” to set it on frequency and read out a few alarms. One thing that gets into a lot of these projects: We are Time Nuts and spec things in terms of time. This error over that period is some specific number. Maybe we look at temperature rather than sit it on the shelf for a year. The number is still a time error. Pretty much everybody making devices spec’s them (and may think of them) as frequency generating gizmos. They all spec a frequency error over some condition (like a period of time). Unfortunately time error and frequency error aren’t the same thing. This also gets into things like control loops. Generally the input is a time error and the output is a frequency control. Same basic gotcha the input isn’t the same as the output. Fortunately they are related very closely to each other. Bob ___ 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] CSAC Project(was CSAC purchase)
Well, if somebody will give me a CSAC, I'll add support for it to Lady Heather ;-) Heather runs on Windows, macOS, Linux (including the RasPi), and FreeBSD. --- > “Included software” on the CSAC is a pretty short list …. There is not much past the “stuff” to set it on frequency and read out a few alarms. ___ 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] CSAC Project(was CSAC purchase)
On 1/27/18 8:10 AM, Bob kb8tq wrote: Hi “Included software” on the CSAC is a pretty short list …. There is not much past the “stuff” to set it on frequency and read out a few alarms. There's a half dozen serial ascii commands to the CSAC, and a corresponding number of output messages. None are particularly "special" - I can't imagine needing a "display" for the telemetry, except perhaps as a novelty. You'd want to periodically check the heater power, maybe? I'd just expose a "diagnostic interface" on a CSAC based clock, and if you want to fool with it (or change the frequency, etc.), you hook up your external whatever. LE Bluetooth Serial port perhaps? You could write an App for a phone to talk to it, and I'm sure it will be in the top10 on the iStore and GooglePlay within weeks. Your retirement funding is assured. One thing that gets into a lot of these projects: We are Time Nuts and spec things in terms of time. This error over that period is some specific number. Maybe we look at temperature rather than sit it on the shelf for a year. The number is still a time error. Very much so. Even here on "time-nuts" we discuss more about "frequency" - ADEV is a frequency error measure, after all. ___ 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] CSAC Project(was CSAC purchase)
Hi “Included software” on the CSAC is a pretty short list …. There is not much past the “stuff” to set it on frequency and read out a few alarms. One thing that gets into a lot of these projects: We are Time Nuts and spec things in terms of time. This error over that period is some specific number. Maybe we look at temperature rather than sit it on the shelf for a year. The number is still a time error. Pretty much everybody making devices spec’s them (and may think of them) as frequency generating gizmos. They all spec a frequency error over some condition (like a period of time). Unfortunately time error and frequency error aren’t the same thing. This also gets into things like control loops. Generally the input is a time error and the output is a frequency control. Same basic gotcha the input isn’t the same as the output. Fortunately they are related very closely to each other. Bob > On Jan 27, 2018, at 10:32 AM, Ronald Held wrote: > > Bob: >That makes sense, since you need some display short of the > included software. Might end up giany cell phone size? > Beyond my abilities, since I am a software guy, not hardware. > Ronald > > Hi > > One way or the other you will need some “smarts” to do aging compensation. > That implies adding a CPU of some sort to the “system” you are building. There > is no built in subsystem on the CSAC that will do any of this for you. You > also > need some sort of display for your “wrist watch”. Having the CPU handle that > at the same time makes a lot of sense. > > Bob > ___ > 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] CSAC Project(was CSAC purchase)
Bob: That makes sense, since you need some display short of the included software. Might end up giany cell phone size? Beyond my abilities, since I am a software guy, not hardware. Ronald Hi One way or the other you will need some “smarts” to do aging compensation. That implies adding a CPU of some sort to the “system” you are building. There is no built in subsystem on the CSAC that will do any of this for you. You also need some sort of display for your “wrist watch”. Having the CPU handle that at the same time makes a lot of sense. Bob ___ 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] CSAC Project(was CSAC purchase)
Hi One way or the other you will need some “smarts” to do aging compensation. That implies adding a CPU of some sort to the “system” you are building. There is no built in subsystem on the CSAC that will do any of this for you. You also need some sort of display for your “wrist watch”. Having the CPU handle that at the same time makes a lot of sense. Bob > On Jan 26, 2018, at 2:12 PM, Ronald Held wrote: > > Bob: > Interesting that drift rate has a stocastic component. > You mentioned adding code. Was that to the software that comes > with the chip? > Ronald > > > Hi > > The CSAC (like any vapor cell standard) has a drift (aging) process. That’s > just the way it works. It is at a *much* lower rate than a crystal > oscillator, but > it is the same sort of idea. It is one of their basic differences from a > Cesium > beam tube. > > Can you “estimate” aging in advance? Everything I’ve seen suggests that you > are simply guessing when you do. You will be right in some cases and wrong in > other cases. You can do better estimating warmup drift and short term effects. > Working out what will happen over months (or years) is not very easy. > > A *very* basic example: > > I observe a couple of units and they all go positive by 0.8 ppb / mo. I put in > some code to work with that. The unit I happen to have goes 0.8 ppb negative > a month. My code has actually made the unit 2X worse than it would have > been if I just stayed away from it. > > Yes there are papers on aging estimation. They mainly focus on coming up > with a “worst case” number. If they guess that 0.8 ppb will go on forever and > it drops off a bit from there, they did ok. For correction purposes … > not so much. > > On a practical basis, you *will* have to dock this beast up with a charger on > a regular basis. A solar powered WWVB watch is not unusual. A solar powered > Apple watch or CSAC watch … not so much. When it goes to the charger, > sync it up with GPS. > > Bob > ___ > 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] CSAC Project(was CSAC purchase)
Bob: Interesting that drift rate has a stocastic component. You mentioned adding code. Was that to the software that comes with the chip? Ronald Hi The CSAC (like any vapor cell standard) has a drift (aging) process. That’s just the way it works. It is at a *much* lower rate than a crystal oscillator, but it is the same sort of idea. It is one of their basic differences from a Cesium beam tube. Can you “estimate” aging in advance? Everything I’ve seen suggests that you are simply guessing when you do. You will be right in some cases and wrong in other cases. You can do better estimating warmup drift and short term effects. Working out what will happen over months (or years) is not very easy. A *very* basic example: I observe a couple of units and they all go positive by 0.8 ppb / mo. I put in some code to work with that. The unit I happen to have goes 0.8 ppb negative a month. My code has actually made the unit 2X worse than it would have been if I just stayed away from it. Yes there are papers on aging estimation. They mainly focus on coming up with a “worst case” number. If they guess that 0.8 ppb will go on forever and it drops off a bit from there, they did ok. For correction purposes … not so much. On a practical basis, you *will* have to dock this beast up with a charger on a regular basis. A solar powered WWVB watch is not unusual. A solar powered Apple watch or CSAC watch … not so much. When it goes to the charger, sync it up with GPS. Bob ___ 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] CSAC Project(was CSAC purchase)
Hi The CSAC (like any vapor cell standard) has a drift (aging) process. That’s just the way it works. It is at a *much* lower rate than a crystal oscillator, but it is the same sort of idea. It is one of their basic differences from a Cesium beam tube. Can you “estimate” aging in advance? Everything I’ve seen suggests that you are simply guessing when you do. You will be right in some cases and wrong in other cases. You can do better estimating warmup drift and short term effects. Working out what will happen over months (or years) is not very easy. A *very* basic example: I observe a couple of units and they all go positive by 0.8 ppb / mo. I put in some code to work with that. The unit I happen to have goes 0.8 ppb negative a month. My code has actually made the unit 2X worse than it would have been if I just stayed away from it. Yes there are papers on aging estimation. They mainly focus on coming up with a “worst case” number. If they guess that 0.8 ppb will go on forever and it drops off a bit from there, they did ok. For correction purposes … not so much. On a practical basis, you *will* have to dock this beast up with a charger on a regular basis. A solar powered WWVB watch is not unusual. A solar powered Apple watch or CSAC watch … not so much. When it goes to the charger, sync it up with GPS. Bob > On Jan 26, 2018, at 7:19 AM, Ronald Held wrote: > > Bob: > Sounds reasonable. You suggest to let it age a year and reset > often during the year? > No way to compensate for a linear frequency drift? > Ronald > > > If you *don’t* correct the *frequency* offset, then you ultimately > have a device > that is off by quite a bit per year. The key here is that it is > frequency (and not time) > error. Once you get a significant frequency error, the amount of time > you gain or loose > goes up. You no longer are in a 0.1 second region, you are now into a > “second per > year” sort of situation. > > Some math: > > If the CSAC is at zero frequency error at the start of the year and > drifts by 10 ppb > over that year, you have an average error of 5 ppb. Keeping things > simple, you get > 1/6 second error that year. (5 / 30 = 1/6). > > If three years later, the CSAC is at 30 ppb and drifts another 10 ppb > in frequency, > you now are at 35 ppb average frequency error. You will gain / loose > more than a > second in that year. > > The real numbers are slightly different. You need to look at when > over the year the > aging happens. A device that ages a lot early on in the year will do > worse than a > device that ages linearly over the year. A device that does all it’s > aging only on the > last day would do better than either of the other cases. > > Bottom line: > > Your CSAC wrist watch is very much *not* a millisecond per year sort of > device. > Best guess is it is in the 50 to 150 ms per year vicinity in the > first year after calibration. > Based on previous posts, that is in the same vicinity as a WWVB sync’d wrist > watch and not quite as good as an typical Apple Watch. > > Bob > > > Jim: > Likely wait for your data before ordering one. Too bad the chip > price is so high, compared to a few years ago. > Ronald > ___ > 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] CSAC Project(was CSAC purchase)
Bob: Sounds reasonable. You suggest to let it age a year and reset often during the year? No way to compensate for a linear frequency drift? Ronald If you *don’t* correct the *frequency* offset, then you ultimately have a device that is off by quite a bit per year. The key here is that it is frequency (and not time) error. Once you get a significant frequency error, the amount of time you gain or loose goes up. You no longer are in a 0.1 second region, you are now into a “second per year” sort of situation. Some math: If the CSAC is at zero frequency error at the start of the year and drifts by 10 ppb over that year, you have an average error of 5 ppb. Keeping things simple, you get 1/6 second error that year. (5 / 30 = 1/6). If three years later, the CSAC is at 30 ppb and drifts another 10 ppb in frequency, you now are at 35 ppb average frequency error. You will gain / loose more than a second in that year. The real numbers are slightly different. You need to look at when over the year the aging happens. A device that ages a lot early on in the year will do worse than a device that ages linearly over the year. A device that does all it’s aging only on the last day would do better than either of the other cases. Bottom line: Your CSAC wrist watch is very much *not* a millisecond per year sort of device. Best guess is it is in the 50 to 150 ms per year vicinity in the first year after calibration. Based on previous posts, that is in the same vicinity as a WWVB sync’d wrist watch and not quite as good as an typical Apple Watch. Bob Jim: Likely wait for your data before ordering one. Too bad the chip price is so high, compared to a few years ago. Ronald ___ 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] CSAC Project(was CSAC purchase)
On 1/25/18 3:28 PM, Ronald Held wrote: Jim; No need to order in the spring or fall anymore? Looking forward to your data. Ronald you and me, and a bunch of other folks as well ___ 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] CSAC Project(was CSAC purchase)
Jim; No need to order in the spring or fall anymore? Looking forward to your data. Ronald no kidding - there's a well known issue when MicroSemi took over building CSACs from Symmetricom, these things (like many precision timing widgets) have a "recipe" and it's easy to "lose the recipe" or find that there's unexpected and unknown components to the recipe. Take a look at data sheet revs for the CSAC.. full temp range, then all of a sudden around rev G or H, temperature range is quoted at 0-35C operating, *0-40C non-op*. I asked the sales rep if they ship them with icepacks in styrofoam like mail order cheese in the summer - that UPS truck gets way over 40C inside. As always, this was discussed on the list and is in the archives. That being said, I have no complaints about Microsemi being forthcoming about the issue and helping us to understand the nature of the problem. And they claim to have fixed the problem. Hopefully, this summer, I'll have some data from a "narrow temp range" CSAC against GPS 1pps in an environment where there's no gravitational effects, and fairly small temperature fluctuations. Bob: Maybe I benefited a little by not buying a few years ago? Ronald Just to be clear, the current data sheet has the temperature range back to -10 to +70C. They most certainly had a major headache on their hands for several years straightening things out. I have not seen any complaints about the “new” (post rework) version of the part. Bob Aaaas ___ 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] CSAC Project(was CSAC purchase)
Hi > On Jan 25, 2018, at 5:47 PM, Ronald Held wrote: > > Nigel; > Will read the PDF carefully. > Ronald > > > "if it runs for years (or even months)" sounds like an informed comment:-) > > When searching for some data recently I came across a report which > might be relevant. > > "A Second Look at Chip Scale Atomic Clocks for Long Term Precision > Timing", written by > Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic > Institution, details their > experience with a number of earlier and more recent CSAC modules and > their findings make > for very interesting reading. > > At the time of writing a copy is available here > > www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > > Tim: > Only three times worst then CSACs? > Ronald > > > y those Woods Hole guys. > > Their temperature-compensated 5 milliwatt crystal oscillators can be > back-corrected (linear drift model) to a few tens of milliseconds over a > year and they make a convincing case they know how to do this. > > Their similar graphs for CSAC oscillators are maybe a factor of three > better. > > Tim N3QE > > Bob: > Does it make sense to reset yearly if the offset is milliseconds? Tenths? > Ronald If you *don’t* correct the *frequency* offset, then you ultimately have a device that is off by quite a bit per year. The key here is that it is frequency (and not time) error. Once you get a significant frequency error, the amount of time you gain or loose goes up. You no longer are in a 0.1 second region, you are now into a “second per year” sort of situation. Some math: If the CSAC is at zero frequency error at the start of the year and drifts by 10 ppb over that year, you have an average error of 5 ppb. Keeping things simple, you get 1/6 second error that year. (5 / 30 = 1/6). If three years later, the CSAC is at 30 ppb and drifts another 10 ppb in frequency, you now are at 35 ppb average frequency error. You will gain / loose more than a second in that year. The real numbers are slightly different. You need to look at when over the year the aging happens. A device that ages a lot early on in the year will do worse than a device that ages linearly over the year. A device that does all it’s aging only on the last day would do better than either of the other cases. Bottom line: Your CSAC wrist watch is very much *not* a millisecond per year sort of device. Best guess is it is in the 50 to 150 ms per year vicinity in the first year after calibration. Based on previous posts, that is in the same vicinity as a WWVB sync’d wrist watch and not quite as good as an typical Apple Watch. Bob > > > Actually it was not quite what it sounded like. What I was trying to > say was “free runs” > for years or even months. Any device that is re-calibrated will have > the aging drift zeroed > out in that process. As noted in another post, CSAC’s have gone > through some growing > pains. The Woods Hole paper came out sort of at a low point in the process. > The > current crop of CSAC parts seem to be more reliable than the ones Woods Hole > reported on. I’ve seen failures over the years, but not a lot of them …. > > Bob > > > Tom: > That PDF was interesting. Not certain I would've one. > Ronald > > >> www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > Also see the very nice presentation: > > "Challenges of precise timing underwater" > http://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resources/Gardner_OBS_Timing_ATG_20150427.pdf > > /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 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] CSAC Project(was CSAC purchase)
Nigel; Will read the PDF carefully. Ronald "if it runs for years (or even months)" sounds like an informed comment:-) When searching for some data recently I came across a report which might be relevant. "A Second Look at Chip Scale Atomic Clocks for Long Term Precision Timing", written by Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic Institution, details their experience with a number of earlier and more recent CSAC modules and their findings make for very interesting reading. At the time of writing a copy is available here www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf Tim: Only three times worst then CSACs? Ronald y those Woods Hole guys. Their temperature-compensated 5 milliwatt crystal oscillators can be back-corrected (linear drift model) to a few tens of milliseconds over a year and they make a convincing case they know how to do this. Their similar graphs for CSAC oscillators are maybe a factor of three better. Tim N3QE Bob: Does it make sense to reset yearly if the offset is milliseconds? Tenths? Ronald Actually it was not quite what it sounded like. What I was trying to say was “free runs” for years or even months. Any device that is re-calibrated will have the aging drift zeroed out in that process. As noted in another post, CSAC’s have gone through some growing pains. The Woods Hole paper came out sort of at a low point in the process. The current crop of CSAC parts seem to be more reliable than the ones Woods Hole reported on. I’ve seen failures over the years, but not a lot of them …. Bob Tom: That PDF was interesting. Not certain I would've one. Ronald > www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf Also see the very nice presentation: "Challenges of precise timing underwater" http://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resources/Gardner_OBS_Timing_ATG_20150427.pdf /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] CSAC Project(was CSAC purchase)
Hi Things have to get pretty deep to be fully isolated from the seasons down to the “digits past the decimal” level. It *does* bring up an interesting place to set up your temperature stabilized timing lab though. The commute back and forth might be a bit of a chore :) Bob > On Jan 25, 2018, at 3:42 PM, jimlux wrote: > > On 1/25/18 11:20 AM, Bob kb8tq wrote: >> Hi >> One of the unique features of underwater timing is that the sea bottom >> temperature >> (once you get well away from a coastline) is *very* stable. In some >> deployments, the “random” >> nature of ambient temperature that we fight all the time in the rest of the >> world, simply is not >> present. The device sits at 2.345 C and that’s it ….. > > > It helps that water density has a maximum at a particular temperature - water > that is warmer or colder tends to float up above it. I was just looking it up > and found apparently that does vary with salinity, too... oh no, another > miniscule factor to account for - is there a "seawater density nuts" list... > > Let's see, the bottom of Lake Tahoe (fresh water, so no salinity variation) > is probably fairly stable at 4C. Or any other freshwater later that actually > gets cold enough, and doesn't freeze to the bottom - so the deeper Great > Lakes would probably work. How warm does the bottom of Lake Superior get in > late summer? > > > > > > > ___ > 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] CSAC Project(was CSAC purchase)
On 1/25/18 11:20 AM, Bob kb8tq wrote: Hi One of the unique features of underwater timing is that the sea bottom temperature (once you get well away from a coastline) is *very* stable. In some deployments, the “random” nature of ambient temperature that we fight all the time in the rest of the world, simply is not present. The device sits at 2.345 C and that’s it ….. It helps that water density has a maximum at a particular temperature - water that is warmer or colder tends to float up above it. I was just looking it up and found apparently that does vary with salinity, too... oh no, another miniscule factor to account for - is there a "seawater density nuts" list... Let's see, the bottom of Lake Tahoe (fresh water, so no salinity variation) is probably fairly stable at 4C. Or any other freshwater later that actually gets cold enough, and doesn't freeze to the bottom - so the deeper Great Lakes would probably work. How warm does the bottom of Lake Superior get in late summer? ___ 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] CSAC Project(was CSAC purchase)
Hi Just to be clear, the current data sheet has the temperature range back to -10 to +70C. They most certainly had a major headache on their hands for several years straightening things out. I have not seen any complaints about the “new” (post rework) version of the part. Bob > On Jan 25, 2018, at 3:31 PM, jimlux wrote: > > On 1/25/18 9:39 AM, gandalfg8--- via time-nuts wrote: >> At the time of writing a copy is available here >> www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > > "While results from an early batch of CSACs have been largely positive, later > units have not performed as well. The CSAC specifications have changed, > reflecting a decrease in reliability and accuracy of more recent units." > > no kidding - there's a well known issue when MicroSemi took over building > CSACs from Symmetricom, these things (like many precision timing widgets) > have a "recipe" and it's easy to "lose the recipe" or find that there's > unexpected and unknown components to the recipe. > > Take a look at data sheet revs for the CSAC.. full temp range, then all of a > sudden around rev G or H, temperature range is quoted at 0-35C operating, > *0-40C non-op*. I asked the sales rep if they ship them with icepacks in > styrofoam like mail order cheese in the summer - that UPS truck gets way over > 40C inside. > > As always, this was discussed on the list and is in the archives. > > That being said, I have no complaints about Microsemi being forthcoming about > the issue and helping us to understand the nature of the problem. And they > claim to have fixed the problem. > > Hopefully, this summer, I'll have some data from a "narrow temp range" CSAC > against GPS 1pps in an environment where there's no gravitational effects, > and fairly small temperature fluctuations. > > ___ > 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] CSAC Project(was CSAC purchase)
On 1/25/18 9:39 AM, gandalfg8--- via time-nuts wrote: At the time of writing a copy is available here www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf "While results from an early batch of CSACs have been largely positive, later units have not performed as well. The CSAC specifications have changed, reflecting a decrease in reliability and accuracy of more recent units." no kidding - there's a well known issue when MicroSemi took over building CSACs from Symmetricom, these things (like many precision timing widgets) have a "recipe" and it's easy to "lose the recipe" or find that there's unexpected and unknown components to the recipe. Take a look at data sheet revs for the CSAC.. full temp range, then all of a sudden around rev G or H, temperature range is quoted at 0-35C operating, *0-40C non-op*. I asked the sales rep if they ship them with icepacks in styrofoam like mail order cheese in the summer - that UPS truck gets way over 40C inside. As always, this was discussed on the list and is in the archives. That being said, I have no complaints about Microsemi being forthcoming about the issue and helping us to understand the nature of the problem. And they claim to have fixed the problem. Hopefully, this summer, I'll have some data from a "narrow temp range" CSAC against GPS 1pps in an environment where there's no gravitational effects, and fairly small temperature fluctuations. ___ 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] CSAC Project(was CSAC purchase)
Hi One of the unique features of underwater timing is that the sea bottom temperature (once you get well away from a coastline) is *very* stable. In some deployments, the “random” nature of ambient temperature that we fight all the time in the rest of the world, simply is not present. The device sits at 2.345 C and that’s it ….. Bob > On Jan 25, 2018, at 2:06 PM, Tom Van Baak wrote: > >> www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > Also see the very nice presentation: > > "Challenges of precise timing underwater" > http://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resources/Gardner_OBS_Timing_ATG_20150427.pdf > > /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 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] CSAC Project(was CSAC purchase)
> www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf Also see the very nice presentation: "Challenges of precise timing underwater" http://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resources/Gardner_OBS_Timing_ATG_20150427.pdf /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] CSAC Project(was CSAC purchase)
Hi > On Jan 25, 2018, at 12:39 PM, gandalfg8--- via time-nuts > wrote: > > > > Hi > > The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as > “typical”. There is also a temperature spec of 0.4 ppb. If both are correct > for your sample (*and* aging is linear ) you would be out by roughly 10 ppb > per year. There also is a voltage stability spec that might be impacted > depending > on how you manage power. > > Taking the 30 ppb = 1 second number, you are at a 1 second / year rate after > 3 years. > At that point, you have already drifted by a second, if the assumptions are > correct. > This makes a massive assumption that the aging stays at the “typical” rate > for years. It’s a very good guess that it does not. Is it going to be 1/3 or > 1/10 > of typical over that period? Who knows. > > Bottom line, you are going to be pretty far from 1 second per 100 years with > a CSAC based wrist watch, if it runs for years (or even for months). It > *will* > do *way* better than a TCXO or OCXO based watch over months or years. > It’s still not perfect. > > Bob > > - > > "if it runs for years (or even months)" sounds like an informed comment:-) Actually it was not quite what it sounded like. What I was trying to say was “free runs” for years or even months. Any device that is re-calibrated will have the aging drift zeroed out in that process. As noted in another post, CSAC’s have gone through some growing pains. The Woods Hole paper came out sort of at a low point in the process. The current crop of CSAC parts seem to be more reliable than the ones Woods Hole reported on. I’ve seen failures over the years, but not a lot of them …. Bob > > When searching for some data recently I came across a report which might be > relevant. > > "A Second Look at Chip Scale Atomic Clocks for Long Term Precision Timing", > written by > Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic > Institution, details their > experience with a number of earlier and more recent CSAC modules and their > findings make > for very interesting reading. > > At the time of writing a copy is available here > > www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > Nigel > GM8PZR > > > > > > ___ > 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] CSAC Project(was CSAC purchase)
That's a wonderful paper by those Woods Hole guys. Their temperature-compensated 5 milliwatt crystal oscillators can be back-corrected (linear drift model) to a few tens of milliseconds over a year and they make a convincing case they know how to do this. Their similar graphs for CSAC oscillators are maybe a factor of three better. Tim N3QE On Thu, Jan 25, 2018 at 12:39 PM, gandalfg8--- via time-nuts < time-nuts@febo.com> wrote: > > > Hi > > The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as > “typical”. There is also a temperature spec of 0.4 ppb. If both are correct > for your sample (*and* aging is linear ) you would be out by roughly 10 ppb > per year. There also is a voltage stability spec that might be impacted > depending > on how you manage power. > > Taking the 30 ppb = 1 second number, you are at a 1 second / year rate > after 3 years. > At that point, you have already drifted by a second, if the assumptions > are correct. > This makes a massive assumption that the aging stays at the “typical” rate > for years. It’s a very good guess that it does not. Is it going to be 1/3 > or 1/10 > of typical over that period? Who knows. > > Bottom line, you are going to be pretty far from 1 second per 100 years > with > a CSAC based wrist watch, if it runs for years (or even for months). It > *will* > do *way* better than a TCXO or OCXO based watch over months or years. > It’s still not perfect. > > Bob > > - > > "if it runs for years (or even months)" sounds like an informed comment:-) > > When searching for some data recently I came across a report which might > be relevant. > > "A Second Look at Chip Scale Atomic Clocks for Long Term Precision > Timing", written by > Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic > Institution, details their > experience with a number of earlier and more recent CSAC modules and their > findings make > for very interesting reading. > > At the time of writing a copy is available here > > www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > Nigel > GM8PZR > > > > > > ___ > 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] CSAC Project(was CSAC purchase)
Hi The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as “typical”. There is also a temperature spec of 0.4 ppb. If both are correct for your sample (*and* aging is linear ) you would be out by roughly 10 ppb per year. There also is a voltage stability spec that might be impacted depending on how you manage power. Taking the 30 ppb = 1 second number, you are at a 1 second / year rate after 3 years. At that point, you have already drifted by a second, if the assumptions are correct. This makes a massive assumption that the aging stays at the “typical” rate for years. It’s a very good guess that it does not. Is it going to be 1/3 or 1/10 of typical over that period? Who knows. Bottom line, you are going to be pretty far from 1 second per 100 years with a CSAC based wrist watch, if it runs for years (or even for months). It *will* do *way* better than a TCXO or OCXO based watch over months or years. It’s still not perfect. Bob - "if it runs for years (or even months)" sounds like an informed comment:-) When searching for some data recently I came across a report which might be relevant. "A Second Look at Chip Scale Atomic Clocks for Long Term Precision Timing", written by Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic Institution, details their experience with a number of earlier and more recent CSAC modules and their findings make for very interesting reading. At the time of writing a copy is available here www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf Nigel GM8PZR ___ 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] CSAC Project(was CSAC purchase)
Hi The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as “typical”. There is also a temperature spec of 0.4 ppb. If both are correct for your sample (*and* aging is linear ) you would be out by roughly 10 ppb per year. There also is a voltage stability spec that might be impacted depending on how you manage power. Taking the 30 ppb = 1 second number, you are at a 1 second / year rate after 3 years. At that point, you have already drifted by a second, if the assumptions are correct. This makes a massive assumption that the aging stays at the “typical” rate for years. It’s a very good guess that it does not. Is it going to be 1/3 or 1/10 of typical over that period? Who knows. Bottom line, you are going to be pretty far from 1 second per 100 years with a CSAC based wrist watch, if it runs for years (or even for months). It *will* do *way* better than a TCXO or OCXO based watch over months or years. It’s still not perfect. Bob > On Jan 24, 2018, at 3:59 PM, Ronald Held wrote: > > Jim: > One around 1s/y, one 6 s/y and one 11 s/y. I was looking to do > better than 1 s/100 years, but that was for the CSAC. > Ronald > > > 1 second/year is quite good - about 30 ppb. It's a bit tricky (like all > things time-nutty) - the "aging" on a TCXO could be that good - but the > instantaneous frequency control might not be that good. 1ppm is pretty > vanilla for a TCXO over a fairly wide temperature range, so 30 ppb at > "constant skin temp" (say, 5 C range) is probably reasonable. > > I've got some test data here for some fancy TCXOs intended for space > with a spec of 2ppm aging first year and then 1ppm/year after that. The > actual aging in the first year was 0.08 ppm, at 70C. Some of the other > oscillators in the lot were 0.02ppm, 0.05ppm. > > So, I think the spec here is "covers all the things that can go wrong", > but by cherry picking, you could do better. > > (or, our system design could tolerate several ppm aging over years, and > "run of the mill" for Vectron was actually a lot better) > ___ > 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] CSAC Project(was CSAC purchase)
Jim: One around 1s/y, one 6 s/y and one 11 s/y. I was looking to do better than 1 s/100 years, but that was for the CSAC. Ronald 1 second/year is quite good - about 30 ppb. It's a bit tricky (like all things time-nutty) - the "aging" on a TCXO could be that good - but the instantaneous frequency control might not be that good. 1ppm is pretty vanilla for a TCXO over a fairly wide temperature range, so 30 ppb at "constant skin temp" (say, 5 C range) is probably reasonable. I've got some test data here for some fancy TCXOs intended for space with a spec of 2ppm aging first year and then 1ppm/year after that. The actual aging in the first year was 0.08 ppm, at 70C. Some of the other oscillators in the lot were 0.02ppm, 0.05ppm. So, I think the spec here is "covers all the things that can go wrong", but by cherry picking, you could do better. (or, our system design could tolerate several ppm aging over years, and "run of the mill" for Vectron was actually a lot better) ___ 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.
