Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A)
Steve, I viewed not just the picture you referenced but all of the pictures at that site and was unable to detect ANY corrosion of any kind. What you are seeing are scratch marks in the anodized plating due to having the Rb removed from heavily plated circuit board that is used as a heat sink for the Rb. At one end of the physic package is a circular shaped housing which has some rosin left on it, a thermistor or two attached and some kind of bonding material used for mounting the heating transistors that has changed color because that part is heated when it is running; that is not corrosion. The screws attaching that item to the rest of the physic package have fiberous material for a mounting washer to buffer vibration or are used as insulators; that is not corrosion. The screws that are holding down the circuit board press down on a gold plated circular area used for grounding besides being used for a mounting point; that is not corrosion. I think you need to reboot your internal operating system and then do a serious update on your help files. BillWB6BNQ Steve . wrote: Bill, I was starting to think i may have to crack open an instrument to get a picture. But i found a reference online. http://n1.taur.dk/fe5680a-2/IMG_1375.JPG Note the corrosion around the cheaper metal parts (screws, spacers, shell). I can't speak for the FE-5680A, but when i see something like this in the instruments i maintain it's a tale-tale sign gas mitigation. Steve On Thu, Dec 1, 2011 at 12:16 AM, WB6BNQ wb6...@cox.net wrote: HUH ? What, exactly, do you mean by corroded Rb tube interfaces ? bILLwb6bnq Steve . wrote: snip Also It appears that quite a few of these have corroded Rb tube interfaces. Thanks, Steve ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
Bill, You did notice that i stated i can't speak for the FE-5680A? All that I have reference too are pictures at the moment. My help files? I don't run windows, thanks. But the reason I asked here. Also, I was under the impression that Rb ovens operated around 80c if the Rb oven gets that hot that it had oxidized... Comments on the crystal? Is the crystal heated or a LF acoustic resonator? Steve On Thu, Dec 1, 2011 at 3:25 AM, WB6BNQ wb6...@cox.net wrote: Steve, I viewed not just the picture you referenced but all of the pictures at that site and was unable to detect ANY corrosion of any kind. What you are seeing are scratch marks in the anodized plating due to having the Rb removed from heavily plated circuit board that is used as a heat sink for the Rb. At one end of the physic package is a circular shaped housing which has some rosin left on it, a thermistor or two attached and some kind of bonding material used for mounting the heating transistors that has changed color because that part is heated when it is running; that is not corrosion. The screws attaching that item to the rest of the physic package have fiberous material for a mounting washer to buffer vibration or are used as insulators; that is not corrosion. The screws that are holding down the circuit board press down on a gold plated circular area used for grounding besides being used for a mounting point; that is not corrosion. I think you need to reboot your internal operating system and then do a serious update on your help files. BillWB6BNQ Steve . wrote: Bill, I was starting to think i may have to crack open an instrument to get a picture. But i found a reference online. http://n1.taur.dk/fe5680a-2/IMG_1375.JPG Note the corrosion around the cheaper metal parts (screws, spacers, shell). I can't speak for the FE-5680A, but when i see something like this in the instruments i maintain it's a tale-tale sign gas mitigation. Steve On Thu, Dec 1, 2011 at 12:16 AM, WB6BNQ wb6...@cox.net wrote: HUH ? What, exactly, do you mean by corroded Rb tube interfaces ? bILLwb6bnq Steve . wrote: snip Also It appears that quite a few of these have corroded Rb tube interfaces. Thanks, Steve ___ 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. ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
Hi, Steve Both the lamp and the absorption cell are made out of glass (or possibly quartz - see attached image). The unit mounted to the crystal is a PTC thermistor wired directly across one of the power supplies. I suspect it's just there to heat up the xtal to a temperature close to it's knee point - absolute accuracy is not that important since the xtal is being run in a VCXO config and is locked to the Rb cell. None of the units I've looked at appear to have any corrosion on them - the discoloration you can see on that photo is just a side effect of that fact that the lamp housing (intentionally) runs very hot - about 100c. The only negative effect I've seen from this is that the fiber washers that hold the lamp housing in position get somewhat cooked and the used ones are easily damaged if you tighten up the screws too much. Regards, Pete On Thu, Dec 1, 2011 at 1:05 PM, Steve . iteratio...@gmail.com wrote: I've been paying particular attention to the discussions involving the FE-5680A frequency standards of recent attention. I do not have a FE-5680A yet, but rather I am studying what is shared from the others prior to buying. At the very least I want to know what I'm up against should I get a DOA module. It appears that these units use a heated crystal.(..i sure hope it's heater and not an acoustic resonator). Has anyone performed sub 1degree c drift testing against a known stable source? What are the performance gains by using tighter temperature control? Also It appears that quite a few of these have corroded Rb tube interfaces. My guess is the corrosion is a tale-tale sign of small amounts of rb gas leakage in combination with the raised temperatures of the tube oven? If this is the case I suppose a visual check of the tube interface for corrosion would yield a fair approximation of the tube condition? Lastly, is the Rb tube a quartz tube or is it a metal(silver lined?)canister sealed with polymer tape? Thanks, Steve ___ 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. attachment: Lamp and cells_sml.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] Heated crystal? Rb tube corrosion (FE-5680A)
On Thu, 1 Dec 2011 01:00:44 -0500 Steve . iteratio...@gmail.com wrote: Note the corrosion around the cheaper metal parts (screws, spacers, shell). I can't speak for the FE-5680A, but when i see something like this in the instruments i maintain it's a tale-tale sign gas mitigation. I have to agree with Bill that there is no corrosion. At least i dont see any, but on the head of the Rb cell. From the chemistry point, Rb or the noble gas buffer in the cell will not corrode any metals if they would leak. Because noble gas are noble and nearly completely inert (at least at the temperatures we are talking about) and Rb is less noble than anything else you will find in there, hence will oxidize first. There is a very slimm chance that Rb salts (after Rb has been oxidized) could lead to an acidic reaction. But i can neither prove or disprove that with my limited chemistry knowledge. But in this case, it's not Rb or any of its salt that's the culprit. If you have a look at http://n1.taur.dk/fe5680a-2/IMG_1393.JPG you see that the corrosion around the Rb tube is at the spot where two transistors are soldered to the tube. The metal of the transistors is copper plated with tin and soldered with a tin based solder. What you'll get here is an sacrifacial anode effect, ie the copper does oxidize the less noble iron/steal. Other than that one spot, i have to say that the whole device looks like new. No dirt, no corrosion where you'd expect it. Even the solder joints look like new. Oh yes, if you mean http://n1.taur.dk/fe5680a-2/IMG_1398.JPG looks like a corroded crystal contact, i have to disapoint you. All you see there a not so ideal solder joint. Ie the solder wasnt heated well or did take too long to cool down, which lead to a partial crystalization of the surface. This then looks a little bit rough and can give the impression of corrosion if one expects a completely flat and shiny surface. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
Pete, Thanks for the pictures. I tend to trust a hermetic quartz or borosilicate tube. Looking at those pictures with a different mind set, I see now that the washers are not corroded as I had suspected. It's amazing how they resemble badly corroded washers which are so typically found in ovens in which alkalines have leaked. It's good to know that these are not leaky. Had I known this a few weeks ago I wold have picked a few up. Thanks guys, Steve On Thu, Dec 1, 2011 at 4:42 AM, Peter Bell bell.pe...@gmail.com wrote: Hi, Steve Both the lamp and the absorption cell are made out of glass (or possibly quartz - see attached image). The unit mounted to the crystal is a PTC thermistor wired directly across one of the power supplies. I suspect it's just there to heat up the xtal to a temperature close to it's knee point - absolute accuracy is not that important since the xtal is being run in a VCXO config and is locked to the Rb cell. None of the units I've looked at appear to have any corrosion on them - the discoloration you can see on that photo is just a side effect of that fact that the lamp housing (intentionally) runs very hot - about 100c. The only negative effect I've seen from this is that the fiber washers that hold the lamp housing in position get somewhat cooked and the used ones are easily damaged if you tighten up the screws too much. Regards, Pete On Thu, Dec 1, 2011 at 1:05 PM, Steve . iteratio...@gmail.com wrote: I've been paying particular attention to the discussions involving the FE-5680A frequency standards of recent attention. I do not have a FE-5680A yet, but rather I am studying what is shared from the others prior to buying. At the very least I want to know what I'm up against should I get a DOA module. It appears that these units use a heated crystal.(..i sure hope it's heater and not an acoustic resonator). Has anyone performed sub 1degree c drift testing against a known stable source? What are the performance gains by using tighter temperature control? Also It appears that quite a few of these have corroded Rb tube interfaces. My guess is the corrosion is a tale-tale sign of small amounts of rb gas leakage in combination with the raised temperatures of the tube oven? If this is the case I suppose a visual check of the tube interface for corrosion would yield a fair approximation of the tube condition? Lastly, is the Rb tube a quartz tube or is it a metal(silver lined?)canister sealed with polymer tape? Thanks, Steve ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
I had a bad experience with chinese sellers: I got a Z3815A with the Furuno GPS enclosure completely rusted and a LPFRS that I suspect was submerged in water: rusted and corroded internally tough still working... the seller has agreed to send another one. On Thu, Dec 1, 2011 at 11:18 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 1 Dec 2011 01:00:44 -0500 Steve . iteratio...@gmail.com wrote: Note the corrosion around the cheaper metal parts (screws, spacers, shell). I can't speak for the FE-5680A, but when i see something like this in the instruments i maintain it's a tale-tale sign gas mitigation. I have to agree with Bill that there is no corrosion. At least i dont see any, but on the head of the Rb cell. From the chemistry point, Rb or the noble gas buffer in the cell will not corrode any metals if they would leak. Because noble gas are noble and nearly completely inert (at least at the temperatures we are talking about) and Rb is less noble than anything else you will find in there, hence will oxidize first. There is a very slimm chance that Rb salts (after Rb has been oxidized) could lead to an acidic reaction. But i can neither prove or disprove that with my limited chemistry knowledge. But in this case, it's not Rb or any of its salt that's the culprit. If you have a look at http://n1.taur.dk/fe5680a-2/IMG_1393.JPG you see that the corrosion around the Rb tube is at the spot where two transistors are soldered to the tube. The metal of the transistors is copper plated with tin and soldered with a tin based solder. What you'll get here is an sacrifacial anode effect, ie the copper does oxidize the less noble iron/steal. Other than that one spot, i have to say that the whole device looks like new. No dirt, no corrosion where you'd expect it. Even the solder joints look like new. Oh yes, if you mean http://n1.taur.dk/fe5680a-2/IMG_1398.JPG looks like a corroded crystal contact, i have to disapoint you. All you see there a not so ideal solder joint. Ie the solder wasnt heated well or did take too long to cool down, which lead to a partial crystalization of the surface. This then looks a little bit rough and can give the impression of corrosion if one expects a completely flat and shiny surface. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
On Thu, 1 Dec 2011 05:19:24 -0500 Steve . iteratio...@gmail.com wrote: Looking at those pictures with a different mind set, I see now that the washers are not corroded as I had suspected. It's amazing how they resemble badly corroded washers which are so typically found in ovens in which alkalines have leaked. If you mean alkaline batteries leaking with alkalines leaking, then the corrosion you see there is from something else than alkali metals. In alkaline batteries you have a potpury of different highly reactive stuff. What exactly corrodes what and how is something i cannot tell you, but it's definitly not elemental alkalimetals like you have in Rb cells. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
On 12/01/2011 11:18 AM, Attila Kinali wrote: On Thu, 1 Dec 2011 01:00:44 -0500 Steve .iteratio...@gmail.com wrote: Note the corrosion around the cheaper metal parts (screws, spacers, shell). I can't speak for the FE-5680A, but when i see something like this in the instruments i maintain it's a tale-tale sign gas mitigation. I have to agree with Bill that there is no corrosion. At least i dont see any, but on the head of the Rb cell. From the chemistry point, Rb or the noble gas buffer in the cell will not corrode any metals if they would leak. Because noble gas are noble and nearly completely inert (at least at the temperatures we are talking about) and Rb is less noble than anything else you will find in there, hence will oxidize first. There is a very slimm chance that Rb salts (after Rb has been oxidized) could lead to an acidic reaction. But i can neither prove or disprove that with my limited chemistry knowledge. But in this case, it's not Rb or any of its salt that's the culprit. If you have a look at http://n1.taur.dk/fe5680a-2/IMG_1393.JPG you see that the corrosion around the Rb tube is at the spot where two transistors are soldered to the tube. The metal of the transistors is copper plated with tin and soldered with a tin based solder. What you'll get here is an sacrifacial anode effect, ie the copper does oxidize the less noble iron/steal. You need to recall that the operational temperature of the rubidium lamp is about 130 degreed, so air and local metalurgy gets to have fun. The rubidium needs to be in glass/quartz containers as the lamp needs to be transparent to the 100 MHz RF field used to lit the lamp and the rubidium reference needs to be transparent to the 6,8 GHz field. Also, rubidium being an alkali metal we would sure want it and it's buffer gas kept safe. As I recall it (but no guarantees for correctness) would rubidium and water form a fairly potent base rather than acid. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A)
Attila, Great pictures, by the way. My experience with alkaline metal is limited to sodium, potassium and lithium. Mostly sodium, which after a long process is precipitated from sodium hydroxide as a reagent. These are all contained in an oven under very precise temperature and flow control, as the analytes which are passed over change very specific attributes of a cell. These are the results which are reported. Eventually the cell fails and the alkaline metal attacks the cheaper mounting hardware(even though the oven maintains an argon atmosphere). If not caught in time it will work it's way down the thermocouple, under the sheath and in to the support electronics. Rb is claimed to be much more active than any of the metals i have experience with so i assumed that corrosion was a preliminary sign of low life span. For completeness, I maintain the instruments in an environmental analytical laboratory. (Sulfur analyzers, CO2, CHN, Calorimeters, ion chromatograph, inductive couple plasma mass specs, gas chromatography mass spec, organic carbon analyzer. etc,etc,etc.) When i say alkalines i mean alkalies, ie, elements which belong to the alkalinity group. 99.% or better purity, traceable grade. Steve On Thu, Dec 1, 2011 at 5:36 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 1 Dec 2011 05:19:24 -0500 Steve . iteratio...@gmail.com wrote: Looking at those pictures with a different mind set, I see now that the washers are not corroded as I had suspected. It's amazing how they resemble badly corroded washers which are so typically found in ovens in which alkalines have leaked. If you mean alkaline batteries leaking with alkalines leaking, then the corrosion you see there is from something else than alkali metals. In alkaline batteries you have a potpury of different highly reactive stuff. What exactly corrodes what and how is something i cannot tell you, but it's definitly not elemental alkalimetals like you have in Rb cells. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
Mangus, Are you sure its is 130c, and not 130f? I can't really cite where i read it, Maybe the journal of applied physics, but i was under the impression that we not want to run an Rb oven much beyond 80c. Ideally i believe it was 50c, but the warm up time was a few weeks. I'd like to know why they need to run so hot Steve On Thu, Dec 1, 2011 at 6:04 AM, Steve . iteratio...@gmail.com wrote: Attila, Great pictures, by the way. My experience with alkaline metal is limited to sodium, potassium and lithium. Mostly sodium, which after a long process is precipitated from sodium hydroxide as a reagent. These are all contained in an oven under very precise temperature and flow control, as the analytes which are passed over change very specific attributes of a cell. These are the results which are reported. Eventually the cell fails and the alkaline metal attacks the cheaper mounting hardware(even though the oven maintains an argon atmosphere). If not caught in time it will work it's way down the thermocouple, under the sheath and in to the support electronics. Rb is claimed to be much more active than any of the metals i have experience with so i assumed that corrosion was a preliminary sign of low life span. For completeness, I maintain the instruments in an environmental analytical laboratory. (Sulfur analyzers, CO2, CHN, Calorimeters, ion chromatograph, inductive couple plasma mass specs, gas chromatography mass spec, organic carbon analyzer. etc,etc,etc.) When i say alkalines i mean alkalies, ie, elements which belong to the alkalinity group. 99.% or better purity, traceable grade. Steve On Thu, Dec 1, 2011 at 5:36 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 1 Dec 2011 05:19:24 -0500 Steve . iteratio...@gmail.com wrote: Looking at those pictures with a different mind set, I see now that the washers are not corroded as I had suspected. It's amazing how they resemble badly corroded washers which are so typically found in ovens in which alkalines have leaked. If you mean alkaline batteries leaking with alkalines leaking, then the corrosion you see there is from something else than alkali metals. In alkaline batteries you have a potpury of different highly reactive stuff. What exactly corrodes what and how is something i cannot tell you, but it's definitly not elemental alkalimetals like you have in Rb cells. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
All I can say, on a purely practical level, is that every Rb vapor frequency standard I've ever seen or worked on (starting with the old Eframtom FRK) has run the lamp at about 100c and the Rb cell at about 80c - the exact temperatures seem to vary a little depending on the model, but that's how it seems to work in practice. I just had a look at some of the manuals I have around here, and they seem to agree (Efratom FRS, Page 3-1) - Rubidium in the lamp is heated to a vapor state (approximately 106C) and subjected to a high energy RF field. Later on (Page 3-8) Cavity temperature of about 74C is maintained by the resonator heater control circuit. I can't find my FRK manual, but from memory it was about the same. From the LPRO-101 manual: The resonator heater power is determined primarily by the resonator control temperature of +78°C, the baseplate temperature, and the 15.3 C/W thermal resistance from the resonator to baseplate. The lamp heater power is determined primarily by the lamp control temperature of +110°C, the baseplate temperature, and the 53 C/W thermal resistance from the lamp to baseplate. SRS-PRS-10 The block temperature is sensed by two series 100kΩ thermistors, which are directly beneath the TO-220 heaters in the oven block. (Two sensors are used because the division of power will depend on the heater voltage applied to the unit.) At the operating temperature of 75°C, each thermistor will have a resistance of about 15kΩ. The control circuit will allow operation up to 90°C. (For the lamp, the nominal operating temperature is 105°C, for which each thermistor will have a resistance of about 5.5kΩ. The maximum setpoint for the lamp is 122°C.) On Thu, Dec 1, 2011 at 7:21 PM, Steve . iteratio...@gmail.com wrote: Searching for journal of applied physics Rb oven I found an older document which seconds what I had thought. http://tinyurl.com/82fupdj Steve On Thu, Dec 1, 2011 at 6:16 AM, Steve . iteratio...@gmail.com wrote: Mangus, Are you sure its is 130c, and not 130f? I can't really cite where i read it, Maybe the journal of applied physics, but i was under the impression that we not want to run an Rb oven much beyond 80c. Ideally i believe it was 50c, but the warm up time was a few weeks. I'd like to know why they need to run so hot Steve On Thu, Dec 1, 2011 at 6:04 AM, Steve . iteratio...@gmail.com wrote: Attila, Great pictures, by the way. My experience with alkaline metal is limited to sodium, potassium and lithium. Mostly sodium, which after a long process is precipitated from sodium hydroxide as a reagent. These are all contained in an oven under very precise temperature and flow control, as the analytes which are passed over change very specific attributes of a cell. These are the results which are reported. Eventually the cell fails and the alkaline metal attacks the cheaper mounting hardware(even though the oven maintains an argon atmosphere). If not caught in time it will work it's way down the thermocouple, under the sheath and in to the support electronics. Rb is claimed to be much more active than any of the metals i have experience with so i assumed that corrosion was a preliminary sign of low life span. For completeness, I maintain the instruments in an environmental analytical laboratory. (Sulfur analyzers, CO2, CHN, Calorimeters, ion chromatograph, inductive couple plasma mass specs, gas chromatography mass spec, organic carbon analyzer. etc,etc,etc.) When i say alkalines i mean alkalies, ie, elements which belong to the alkalinity group. 99.% or better purity, traceable grade. Steve On Thu, Dec 1, 2011 at 5:36 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 1 Dec 2011 05:19:24 -0500 Steve . iteratio...@gmail.com wrote: Looking at those pictures with a different mind set, I see now that the washers are not corroded as I had suspected. It's amazing how they resemble badly corroded washers which are so typically found in ovens in which alkalines have leaked. If you mean alkaline batteries leaking with alkalines leaking, then the corrosion you see there is from something else than alkali metals. In alkaline batteries you have a potpury of different highly reactive stuff. What exactly corrodes what and how is something i cannot tell you, but it's definitly not elemental alkalimetals like you have in Rb cells. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
Good afternoon, gentleman, On Thu, 1 Dec 2011 06:04:22 -0500 Steve . iteratio...@gmail.com wrote: Great pictures, by the way. These are the pictures you have posted :) For completeness, I maintain the instruments in an environmental analytical laboratory. (Sulfur analyzers, CO2, CHN, Calorimeters, ion chromatograph, inductive couple plasma mass specs, gas chromatography mass spec, organic carbon analyzer. etc,etc,etc.) Why didn't you say that you work in chemistry busines? Then i wouldnt have to overexercise my brain in a field i hardly know anything about! :-) But what i wrote still hold. We are talking about less than 1g of Rb contained sealed glas. I'd be really surprised if this leaks ins amounts that could visibly damage other metals. And if, i'd like to know what chemical process this is :-) IMHO the corrosion you see is really just a redox reaction between two different metals over a solder joint and not a leak. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Compensating phase differnces in dual frequency GPS receviers?
On Wed, 30 Nov 2011 19:56:25 -0800 Peter Monta pmo...@gmail.com wrote: Hi Attila, [ L1 / L2 timing differences ] How do dual frequency receivers deal with that? I've also been toying with the idea of an inexpensive dual- or tri-band GPS SDR, especially since there are now quite a few satellites emitting L2C, the civil L2 signal. (Though I'd still like to try my hand at the fancy L2 semicodeless schemes.) I think that manufacturers calibrate out the timing differences between channels (as well as group-delay variations within a channel). There must be some remaining error, though, e.g. over temperature, depending on the filter technology. So, that'd mean there would be an automatic calibration system inside the device, because i dont have any equipment with which i could calibrate delays over a temperature range. ObTimeNuts: There's an interesting recent thesis on GPS for time and frequency metrology: http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/Feldmann_2011_Dissertation.pdf Section 5.1.3 has a few words on exactly this channel-filter-delay issue. The author measures a coefficient of 20 ps per degree for a pair of receivers. Nice disertation, but i cannot see how you come to the conclusion that this temperature coefficient is from the input RF chain. The measurement shows only a general time shift of the whole device. And the author does not draw any conclusion from it. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
The referenced photos are poor quality and taken in tungsten lighting so you really can't see much from them. Here is a photo I just took of a somewhat similar 5650A that may be new so it is still pretty shiny. http://farm8.staticflickr.com/7142/6436441767_26980890bb_b.jpg -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.
[time-nuts] Seen this? Clock generator IC....
Hello, Time-Nutters-- Seen SiLabs new clock generator chip? I have no idea of its pros and cons but it looks like it would be interesting to check into... Mike Baker --- Silicon Labs' new Si5335 web-customizable clock generator/buffer IC http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/products/clocksoscillators/clock-generators-and-buffers/Pages/pci-express-clocks.aspx?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG is the industry's easiest to customize clocking solution for addressing complex timing challenges in PCIe- and FPGA-based applications. Through its easy-to-use ClockBuilder^(TM) utility, web-customized, pin-controlled Si5335 devices are available in two weeks (no minimum ordering quantity). - Eliminates need for multiple clock generators/buffers (up to three unique device configurations can be specifie for a single part number) - Simplifies multi-chip clocking challenges by supporting any combination of differential formats (LVPECL, LVDS, CML, LVCMOS, etc.) - Exceeds performance requirements of PCIe, Ethernet and mass storage industry standards - Generates up to eight output clocks at up to four unique frequencies to 350 MHz with sub-picosecond jitter Build your custom clock: ClockBuilder^(TM) Web-Configuration Utility http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/products/clocksoscillators/Pages/Utilityintro.aspx?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG Get the data sheet: Si5335 Web-Customizable, Any-Frequency, Any-Output Quad Clock Generator/Buffer http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/Support%20Documents/TechnicalDocs/Si5335.pdf?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG - Silicon Labs 400 West Cesar Chavez Austin, Texas 78701 USA + 512.416.8600 customeri...@silabs.com http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==mailto:customeri...@silabs.com?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG www.silabs.com http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG www.silabs.com/twitter http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/twitter?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG www.silabs.com/facebook http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/facebook?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG www.silabs.com/youtube http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/youtube?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG www.silabs.com/linkedin http://mkto-a0231.com/track?type=clickenid=bWFpbGluZ2lkPXNpbGFic0JldGFjdXN0LTE2MTgtNjc3My0yLTk2MC1wcm9kLTE3MzAmbWVzc2FnZWlkPTAmZGF0YWJhc2VpZD0xNzMwJnNlcmlhbD0xMjYwNTI1NjgwJmVtYWlsaWQ9bXBiNDVAY2xhbmJha2VyLm9yZyZ1c2VyaWQ9OTkwMDczJmV4dHJhPSYmJg==http://www.silabs.com/linkedin?mkt_tok=3RkMMJWWfF9wsRonva3BZKXonjHpfsXx4uwtXqSg38431UFwdcjKPmjr1YoHTNQhcOuuEwcWGog80wVUG%2BKG ___ time-nuts mailing list --
Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A)
Hi The amount of Rb in the cell is quite small. Cell leakage would stop the unit from working. There's pretty much no way that the cell can / would cause corrosion and the unit keep working. The crystal is heated to reduce the pull range of the VCXO. Since it's locked to the Rb, improving it's temperature performance does not have a significant impact on the unit's performance. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Thursday, December 01, 2011 4:42 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A) Hi, Steve Both the lamp and the absorption cell are made out of glass (or possibly quartz - see attached image). The unit mounted to the crystal is a PTC thermistor wired directly across one of the power supplies. I suspect it's just there to heat up the xtal to a temperature close to it's knee point - absolute accuracy is not that important since the xtal is being run in a VCXO config and is locked to the Rb cell. None of the units I've looked at appear to have any corrosion on them - the discoloration you can see on that photo is just a side effect of that fact that the lamp housing (intentionally) runs very hot - about 100c. The only negative effect I've seen from this is that the fiber washers that hold the lamp housing in position get somewhat cooked and the used ones are easily damaged if you tighten up the screws too much. Regards, Pete On Thu, Dec 1, 2011 at 1:05 PM, Steve . iteratio...@gmail.com wrote: I've been paying particular attention to the discussions involving the FE-5680A frequency standards of recent attention. I do not have a FE-5680A yet, but rather I am studying what is shared from the others prior to buying. At the very least I want to know what I'm up against should I get a DOA module. It appears that these units use a heated crystal.(..i sure hope it's heater and not an acoustic resonator). Has anyone performed sub 1degree c drift testing against a known stable source? What are the performance gains by using tighter temperature control? Also It appears that quite a few of these have corroded Rb tube interfaces. My guess is the corrosion is a tale-tale sign of small amounts of rb gas leakage in combination with the raised temperatures of the tube oven? If this is the case I suppose a visual check of the tube interface for corrosion would yield a fair approximation of the tube condition? Lastly, is the Rb tube a quartz tube or is it a metal(silver lined?)canister sealed with polymer tape? Thanks, Steve ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
On 12/01/2011 11:18 AM, Attila Kinali wrote: Other than that one spot, i have to say that the whole device looks like new. No dirt, no corrosion where you'd expect it. Even the solder joints look like new. And I did not attempt to clean anything before I took the pictures, either. The only dirt was a grey tint above and below the oven, where the convection had deposited all non-gaseous dirt. I have a few of these, two of which have appear to have actual corrosion (rust red spots) on the outside, but are just as clean inside. I wonder what that does to the magnetic properties to the case. Posting to nuts is dangerous:-) So far the page has had 243 non-bot visitors, 20 people downloaded all the full resolution images, and it cost me 10GB this week. An impressive figure considering the topic. /Kasper Pedersen ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
On Thu, Dec 1, 2011 at 12:10 PM, Bob Camp li...@rtty.us wrote: Hi The amount of Rb in the cell is quite small. Cell leakage would stop the unit from working. There's pretty much no way that the cell can / would cause corrosion and the unit keep working. This is exactly what I was getting at with my original post. /If/ The cell can leak it will corrode the neighboring material, then signs of corrosion would be a tale-tale sign that a DOA module is not easily repairable without additional parts. For what it's worth, I'll share some repair/ lab experiences. Per my experience with heated ovens operating between 30c and 100c, in non carrier atmosphere, an alkali leak of 10 parts per billion, at a rate of two weeks, will cause corrosion in nearby low grade metallic parts in 6-8 months. Notice the strange units ppb/2wk, and wide range of conditions (30c - 100c) these are the natural terms of the problem, which is all i have to work with. These numbers were determined empirically by sampling a nearby junction and sending the sample to the metals lab for analysis. 10ppb/two weeks is a slow leak, but a leak none the less. 10ppm? It's amazing to see what alkalines can do to components, solder joints, vias, and burried traces on multiple layer boards. To be fair, the oven temperature, operating voltage, and chopping frequency are major contributors to the damage I have seen as well. But it all starts with a leak. This one time an instrument had failed and I eventually figured out which circuit was at fault, upon visual inspection of the board i noted several vias which were dull, almost as if they were oxidized in some manor. But it was only a handful if vias, all localized. Under a 300x microscope I pushed the micro browser tip in to the via, the dull solder(or what was once solder) came oozing out like putty. Keep in mind this was at 300x, and room temperature. Sure, leaded solder appears somewhat plyable at 300x when browsing with micro probes, but this was different. Very different. Being very strange to me, I poked around all the damaged vias for awhile. I noted that they had very high electrical resistance and was more so a capacitor than a resistor or junction (but it was suppose to be a via connection..) and it pitted my gold plated browser tip. I was not happy to destroy a good HP micro browser, but at least i did find the problem with circuit. I also noted that the plated through-holes, which made up the vias as well, was no longer plated and the plating and nearby circuit appeared to have undergone electrolysis. I cleaned the board with de ionized water, dried it, and manually jumped around the vias with light gauge wire. Problem fixed. Unfortunately I did not have the solder analyzed. I'm still curious as to what had happened to the solder. Steve The cryst.l is heated to reduce the pull range of the VCXO. Since it's locked to the Rb, improving it's temperature performance does not have a significant impact on the unit's performance. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Thursday, December 01, 2011 4:42 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A) Hi, Steve Both the lamp and the absorption cell are made out of glass (or possibly quartz - see attached image). The unit mounted to the crystal is a PTC thermistor wired directly across one of the power supplies. I suspect it's just there to heat up the xtal to a temperature close to it's knee point - absolute accuracy is not that important since the xtal is being run in a VCXO config and is locked to the Rb cell. None of the units I've looked at appear to have any corrosion on them - the discoloration you can see on that photo is just a side effect of that fact that the lamp housing (intentionally) runs very hot - about 100c. The only negative effect I've seen from this is that the fiber washers that hold the lamp housing in position get somewhat cooked and the used ones are easily damaged if you tighten up the screws too much. Regards, Pete On Thu, Dec 1, 2011 at 1:05 PM, Steve . iteratio...@gmail.com wrote: I've been paying particular attention to the discussions involving the FE-5680A frequency standards of recent attention. I do not have a FE-5680A yet, but rather I am studying what is shared from the others prior to buying. At the very least I want to know what I'm up against should I get a DOA module. It appears that these units use a heated crystal.(..i sure hope it's heater and not an acoustic resonator). Has anyone performed sub 1degree c drift testing against a known stable source? What are the performance gains by using tighter temperature control? Also It appears that quite a few of these have corroded Rb tube interfaces. My guess is the corrosion is a tale-tale sign of small amounts of
Re: [time-nuts] Heated crystal? Rb tube corrosion (FE-5680A)
Are there any other (mosfet)heaters on the oven cavity? Seems that heating from one point is going to create a large temperature gradient which would probably effect spatial phase congruency. I believe this problem exists on the two mosfet configuration as well. Anyway, my idea is to remove the mosfet heaters, wrap my own heater using light gauge nichrome (aka, fuse wire), mica insulator and build a proper heater/oven assembly. Finally, pot it all together with some sauereisen ceramic cement. Nice, clean, controlled gradient. Maybe I'm over thinking the whole thing too. I guess I'll find out when I start my experimenting. Steve On Thu, Dec 1, 2011 at 9:52 AM, Arthur Dent golgarfrinc...@yahoo.comwrote: The referenced photos are poor quality and taken in tungsten lighting so you really can't see much from them. Here is a photo I just took of a somewhat similar 5650A that may be new so it is still pretty shiny. http://farm8.staticflickr.com/7142/6436441767_26980890bb_b.jpg -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. ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
The LPFRS has 2 heating elements on both tube ends and a crystal glued on the tube. On Thu, Dec 1, 2011 at 9:46 PM, Steve . iteratio...@gmail.com wrote: Are there any other (mosfet)heaters on the oven cavity? Seems that heating from one point is going to create a large temperature gradient which would probably effect spatial phase congruency. I believe this problem exists on the two mosfet configuration as well. Anyway, my idea is to remove the mosfet heaters, wrap my own heater using light gauge nichrome (aka, fuse wire), mica insulator and build a proper heater/oven assembly. Finally, pot it all together with some sauereisen ceramic cement. Nice, clean, controlled gradient. Maybe I'm over thinking the whole thing too. I guess I'll find out when I start my experimenting. Steve On Thu, Dec 1, 2011 at 9:52 AM, Arthur Dent golgarfrinc...@yahoo.com wrote: The referenced photos are poor quality and taken in tungsten lighting so you really can't see much from them. Here is a photo I just took of a somewhat similar 5650A that may be new so it is still pretty shiny. http://farm8.staticflickr.com/7142/6436441767_26980890bb_b.jpg -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. ___ 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] Using GPS 1PPS for accurate period measurement
I finally have a need to ask a question about time measurement! I want to measure the accuracy of a 1Hz signal from a real time clock (RTC) chip with an integrated TXCO allegedly good for +/- 2ppm accuracy. My employer is too tight to buy a good frequency counter, but I do have a GPS module outputting 1PPS. If I use a little micro running at 16MHz from a jellybean crystal to measure the period of the 1PPS signal from the GPS concurrently with measuring the period of my test signal, will I be able to get accuracy of sub ppm? My resolution for a single period is 62.5 ppb, but this is a lot different to accuracy. I could easily count multiple periods, as I do not need fast results. My thought is that the 16MHz will have jitter and a pronounced drift, but that as the measurements of my reference and signal are done nearly concurrently, the errors will be very small. The need for this is that the RTC chip for a product has the engaging property of shifting it's frequency by several ppm after being soldered to the board, and I need to characterise this to get accurate timing for the product. -- Tom Harris celephi...@gmail.com ___ 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] Using GPS 1PPS for accurate period measurement
Hi Ok, 62.5 ppb at 1 second would be 62.5 ns. that sounds right for a 16 MHz clock. Your accuracy will be related to the offset between the two 1 ops events (divided TCXO and GPS PPS) and the accuracy of your crystal. With some luck you can get the crystal frequency to 1 ppm by counting it against the GPS pps output. If the TCXO pps is within 100 ms of the GPS pps, you should get about 100 ppb accuracy. The trick is to keep the TCXO pps that close. Can be done, but it takes some fiddling. Simple answer - yes you can do it. Longer answer - spend the $30 or $50 on an auction site counter and just do it the right way. You will spend way more than that working out all the details even if you only make minimum wage. Bob On Dec 1, 2011, at 7:41 PM, Tom Harris wrote: I finally have a need to ask a question about time measurement! I want to measure the accuracy of a 1Hz signal from a real time clock (RTC) chip with an integrated TXCO allegedly good for +/- 2ppm accuracy. My employer is too tight to buy a good frequency counter, but I do have a GPS module outputting 1PPS. If I use a little micro running at 16MHz from a jellybean crystal to measure the period of the 1PPS signal from the GPS concurrently with measuring the period of my test signal, will I be able to get accuracy of sub ppm? My resolution for a single period is 62.5 ppb, but this is a lot different to accuracy. I could easily count multiple periods, as I do not need fast results. My thought is that the 16MHz will have jitter and a pronounced drift, but that as the measurements of my reference and signal are done nearly concurrently, the errors will be very small. The need for this is that the RTC chip for a product has the engaging property of shifting it's frequency by several ppm after being soldered to the board, and I need to characterise this to get accurate timing for the product. -- Tom Harris celephi...@gmail.com ___ 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] Using GPS 1PPS for accurate period measurement
Hi Is your GPS module a GPSDO or is it something more basic? If it's a GPSDO, then it's accuracy is not an issue. If it's a basic navigation board, then it could easily be off by enough to impact the results. Bob On Dec 1, 2011, at 7:41 PM, Tom Harris wrote: I finally have a need to ask a question about time measurement! I want to measure the accuracy of a 1Hz signal from a real time clock (RTC) chip with an integrated TXCO allegedly good for +/- 2ppm accuracy. My employer is too tight to buy a good frequency counter, but I do have a GPS module outputting 1PPS. If I use a little micro running at 16MHz from a jellybean crystal to measure the period of the 1PPS signal from the GPS concurrently with measuring the period of my test signal, will I be able to get accuracy of sub ppm? My resolution for a single period is 62.5 ppb, but this is a lot different to accuracy. I could easily count multiple periods, as I do not need fast results. My thought is that the 16MHz will have jitter and a pronounced drift, but that as the measurements of my reference and signal are done nearly concurrently, the errors will be very small. The need for this is that the RTC chip for a product has the engaging property of shifting it's frequency by several ppm after being soldered to the board, and I need to characterise this to get accurate timing for the product. -- Tom Harris celephi...@gmail.com ___ 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] Compensating phase differnces in dual frequency GPS receviers?
Hi Attila, So, that'd mean there would be an automatic calibration system inside the device, because i dont have any equipment with which i could calibrate delays over a temperature range. I suppose they could do that---provide a weak broadband source (say a comb) combined with the antenna signal prior to the channel filters, and provide a reference channel for this calibration signal to compare against on-line. Or they could calibrate just once at production time, which would be less expensive---the system would then compensate open-loop based on temperature. Nice disertation, but i cannot see how you come to the conclusion that this temperature coefficient is from the input RF chain. The measurement shows only a general time shift of the whole device. And the author does not draw any conclusion from it. Well, it would have to be the front end. DSP doesn't drift with temperature. Cheers, Peter ___ 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] Heated crystal? Rb tube corrosion (FE-5680A)
On the FE-5680A, there are two mosfets on the lamp housing - one of them is purely a heater, and the other is the drive FET for the RF lamp exciation signal. I assume the designers figured it was going to run pretty hot anyway and they might as well use the heat for something useful. In practice, the lamp housing temperature seems to be fairly uniform - probably becasue the other end of it is attached in a way (PCB soldered to the heater cup and fibre washers) that gives it a quite high thermal resistance. The lamp is attached to the housing using what appears to be RTV silicone at the base and does not touch the housing at other points. See the attached photo. The cell cavity has a single MOSFET heater on it and is thermally insulated by a sheet of what looks like FR4 PCB materal at one end and the support for the C-field coil (which seems to be made of similar stuff) at the other end. This sort of level of temperature control seems to be characteristic of small Rb standards based on what I've seen. Regards, Pete On Fri, Dec 2, 2011 at 4:46 AM, Steve . iteratio...@gmail.com wrote: Are there any other (mosfet)heaters on the oven cavity? Seems that heating from one point is going to create a large temperature gradient which would probably effect spatial phase congruency. I believe this problem exists on the two mosfet configuration as well. Anyway, my idea is to remove the mosfet heaters, wrap my own heater using light gauge nichrome (aka, fuse wire), mica insulator and build a proper heater/oven assembly. Finally, pot it all together with some sauereisen ceramic cement. Nice, clean, controlled gradient. Maybe I'm over thinking the whole thing too. I guess I'll find out when I start my experimenting. Steve On Thu, Dec 1, 2011 at 9:52 AM, Arthur Dent golgarfrinc...@yahoo.comwrote: The referenced photos are poor quality and taken in tungsten lighting so you really can't see much from them. Here is a photo I just took of a somewhat similar 5650A that may be new so it is still pretty shiny. http://farm8.staticflickr.com/7142/6436441767_26980890bb_b.jpg -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. ___ 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. attachment: RbLamp_sml.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] Using GPS 1PPS for accurate period measurement
Le 02/12/2011 01:53, Bob Camp a écrit : Hi Ok, 62.5 ppb at 1 second would be 62.5 ns. that sounds right for a 16 MHz clock. Your accuracy will be related to the offset between the two 1 ops events (divided TCXO and GPS PPS) and the accuracy of your crystal. With some luck you can get the crystal frequency to 1 ppm by counting it against the GPS pps output. If the TCXO pps is within 100 ms of the GPS pps, you should get about 100 ppb accuracy. The trick is to keep the TCXO pps that close. Can be done, but it takes some fiddling. I don't think that the measurements have to be done concurrently. The GPS pps signal will have a low ns jitter, possibly defined in the data sheet, that can in this context be ignored if measurements are take over a long period as can that for the RTC. So for me, I would characterise the micro first, counting cpu cycles per GPS PPS period. If that is done over enough periods, a good indication of the measuring devices rate against a known standard will be known. (1) Then measure the RTC pps using the same procedure. (2) Finally adjust the result from 2 by that of (1). However, even that will be more costly than renting a counter. ___ 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.
