Re: [time-nuts] temperature sensor
What I am missing in all these discussions is what do we want to archive or is this an other paper only discussion. I am used to starting out with a goal, and tackle the challenge from there. We have a saying in German Papier ist geduldig. Translate You can write any thing on paper. Bert Kehren Hi Bert, Let me answer in two parts. 1) The issue of precision temperature sensing is so key to the field of precise time frequency that any thread that attracts more information, anecdotes, and wisdom from the group is very welcome. Quartz is such an amazing substance that its use as a precision sensor is every bit as interesting as its use as a precision timekeeper. Not everything has to be goal oriented. Some discussions on this list are pure enjoyment, others highly educational, and some simply plant seeds. Starting with concrete goals is good for a business but when working with precision timing as a hobby, as most of us are, goals are sometimes secondary to just learning or playing around. 2) If you want an example of a specific goal related to temperature, try this: There have been several discussions over the years about variable fan speed based temperature control. I can't explain it, but I've always been suspicious of this technique. It seems to me still air is inherently better than moving air. Passive (no fan) is better than active (fan). And constant velocity is better than turbulence is better than variable velocity. But I don't know for sure. That's where experiments and measurement come in. To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. /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] temperature sensor
On Sun, 20 Jul 2014 23:18:38 -0700 Tom Van Baak t...@leapsecond.com wrote: To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. May i ask what speaks about using PT100/PT1000 or NTCs? NTCs are dirt cheap, but might need some calibration first, to get to time-nuts standards. But PT100 aren't that much more expensive either. eg: The NTCALUG03 by Vishay don't look too bad, or if you want PT100 the M310 by Heraeus. The KN1510 by Heraeus look also nice, but are a tad bit more expensive (about 20USD/pcs) Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] Diodes as temperature sensors
Simple temperature sensors use the static diode characteristic, but a more accurate method is to use the slope of the characteristic, this is independent of individual diode parameters, though requires a little it more electronics to display. There are many papers on this back in the 1960/70s. Alan G3NYK From: Hal Murray hmur...@megapathdsl.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Monday, 21 July 2014, 4:58 Subject: Re: [time-nuts] Diodes as temperature sensors alw.k...@gmail.com said: Apparently, the forward biased silicon diode was temperature sensitive enough that a small D.C. amplifier could drive a meter to read-out with reasonable accuracy. Well, maybe not accurate by Time-nut standards but close enough for its intended purpose. I think that mechanism is widely used for silicon temperature sensors. There is one (or more) on most modern CPU chips as well as special temperature measuring chips such as the Maxim/Dallas DS18B20 and DS18S20. -- These are my opinions. I hate spam. ___ 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] Noise and non-linear behaviour of ferrite transformers
Hi If you have an electrostatic field to worry about, a simple shield does a fine job. If it’s a magnetic field - maybe not so much. A propagating electromagnetic field is going to be a bit tough to stop. Again it comes back to Bert’s question - what is the objective? Bob On Jul 21, 2014, at 12:24 AM, Chuck Harris cfhar...@erols.com wrote: Hi Bob, I agree, but most of the time, you can use good design practices to keep the currents flowing through the outside of the shield to a minimum... avoiding ground loops, stuff like that. Simple coax is used for shielding very high gain circuits from 60Hz noise all the time in PA systems. -Chuck Harris Bob Camp wrote: Hi Yup It is impractical to make coax that has a shield thickness of 1/3”. Even if you do, it’s not going to be very flexible. For a real world system that needs good isolation, coax is not the way to go below 100 KHz. There are a few other issues that come up, but skin depth is a big part of the problem. Another part of the equation is (as Bert points out in another thread) “how good do you need?”. Skin depth simply the point that you have knocked out 2/3 of the current. That probably isn’t what you are after when you ask for “good isolation”. The “inside” of the coax should be below 170 dbm/ Hz to be “quiet” when terminated. If you have -70 dbm / Hz noise signals running around here and there, you need quite a bit of isolation. You might have a spur spec rather than a noise floor spec to meet and that would give you different numbers to go after. In most cases you will need multiple skin depths (like 10 or more) to get the job done in a noisy environment. 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] temperature sensor
NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal 73 Alex On 7/21/2014 1:22 AM, Attila Kinali wrote: On Sun, 20 Jul 2014 23:18:38 -0700 Tom Van Baak t...@leapsecond.com wrote: To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. May i ask what speaks about using PT100/PT1000 or NTCs? NTCs are dirt cheap, but might need some calibration first, to get to time-nuts standards. But PT100 aren't that much more expensive either. eg: The NTCALUG03 by Vishay don't look too bad, or if you want PT100 the M310 by Heraeus. The KN1510 by Heraeus look also nice, but are a tad bit more expensive (about 20USD/pcs) Attila Kinali ___ 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] temperature sensor
Hi Tom I agre the educational aspect of time nuts is great and I have learned a lot but it would be even more useful if discussions include what can be attained and what may be in the reach of time nuts. I used to have a HP 2804A with matched probe prom only used it once when developing a super efficient boat air condition system running on batteries. After that used it to sort of calibrate my YSI probes and sold the unit. I do not think I need any accuracy better than 0.1 C and feel comfortable having it. But if time nuts find a way to get an affordable solution I would get one. We use fan speed temperature control and at one time I did use it on a Tbolt. May revisit it discarded it because of my concern of fan noise transferring to the XTAL in the OCXO. We use it successfully with NTC embedded in the base plate of FRK's and using a separate sensor see 0.01C. Also use heat pipes. In all cases we use voltage control do to my lack of PIC programming experience. In our work the OCXO is not in the Rb but Rb , fan and OCXO all have vibration isolation. The challenge is reliable fan start at low voltage if you want the unit stay constant over an ambient change of 10 C. Members have talked about u processor control but I have not seen any thing that works, many of the heat pipes used in laptop do have digital speed control, some one please step up to the plate. Back to the Tbolt it is tempting but right now I have to many things on my plate. I suggest controlling temperature in an enclosure within 0.1 C along with added mass to the unit, reduce other heat sources in the unit. An other approach would be a heat pipe again more thermal mass and all sides with thermal isolation to reduce ambient temperature. influence. I have an analog fan conrtol board and the plan is to make one available for those that buy a FE 5680A kit. Again maybe some one steps to the plate and designs a digital control. Bert Kehren In a message dated 7/21/2014 3:17:16 A.M. Eastern Daylight Time, t...@leapsecond.com writes: What I am missing in all these discussions is what do we want to archive or is this an other paper only discussion. I am used to starting out with a goal, and tackle the challenge from there. We have a saying in German Papier ist geduldig. Translate You can write any thing on paper. Bert Kehren Hi Bert, Let me answer in two parts. 1) The issue of precision temperature sensing is so key to the field of precise time frequency that any thread that attracts more information, anecdotes, and wisdom from the group is very welcome. Quartz is such an amazing substance that its use as a precision sensor is every bit as interesting as its use as a precision timekeeper. Not everything has to be goal oriented. Some discussions on this list are pure enjoyment, others highly educational, and some simply plant seeds. Starting with concrete goals is good for a business but when working with precision timing as a hobby, as most of us are, goals are sometimes secondary to just learning or playing around. 2) If you want an example of a specific goal related to temperature, try this: There have been several discussions over the years about variable fan speed based temperature control. I can't explain it, but I've always been suspicious of this technique. It seems to me still air is inherently better than moving air. Passive (no fan) is better than active (fan). And constant velocity is better than turbulence is better than variable velocity. But I don't know for sure. That's where experiments and measurement come in. To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. /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] temperature sensor
Slow is not a problem in our applications the loop takes care of that. Will look in to PT 100. Bert Kehren In a message dated 7/21/2014 8:19:48 A.M. Eastern Daylight Time, alex...@ieee.org writes: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal 73 Alex On 7/21/2014 1:22 AM, Attila Kinali wrote: On Sun, 20 Jul 2014 23:18:38 -0700 Tom Van Baak t...@leapsecond.com wrote: To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. May i ask what speaks about using PT100/PT1000 or NTCs? NTCs are dirt cheap, but might need some calibration first, to get to time-nuts standards. But PT100 aren't that much more expensive either. eg: The NTCALUG03 by Vishay don't look too bad, or if you want PT100 the M310 by Heraeus. The KN1510 by Heraeus look also nice, but are a tad bit more expensive (about 20USD/pcs) Attila Kinali ___ 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] temperature sensor
On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Moin Bert, On Mon, 21 Jul 2014 09:02:12 -0400 (EDT) ewkeh...@aol.com wrote: The challenge is reliable fan start at low voltage if you want the unit stay constant over an ambient change of 10 C. Members have talked about u processor control but I have not seen any thing that works, many of the heat pipes used in laptop do have digital speed control, some one please step up to the plate. How about doing it the old analog way? Feed the output of the PID controller to comparator together with a sawtooth signal. That will give you a quite nice 0-100% PWM control. I'm quite sure a similar solution is possible with a NE555 as well. Of course, you would need to adjust the PID controller parameters to accomodate for the new element in the control loop. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Hello, There are two types of NTC thermistors that are (very) frequently used in spacecrafts, the Measurement Specialties (traditionally YSI, Yellow Spring Instruments) 44907 and 44908, that are 10k @ 25ºC NTC: http://meas-spec.com/downloads/44908.pdf and http://meas-spec.com/downloads/44907.pdf Both are specified in error against temperature, being ±0.1ºC for the 44908 and ±0.2ºC for the 44907, in the 0-70ºC range. I suppose that these ones are obscenely expensive, but the civilian versions are the 44006RC and 44031RC, with the same specified tolerances, and the same calibration curve, and readily available (e.g. from Farnell). I suspect that the difference between the space qualified ones and the others are quality control and traceability, and perhaps (only perhaps) a different low-outgassing epoxy coating, but probably the sensor material is the same in all of them. The advantage is that you get a quite good intial tolerance, so calibration can be simplified, since you only need to calibrate the resistance measurement device with known resistances to obtain a ±0.1ºC error from the sensors. The qualification mandated by NASA for these sensors refers mainly to MIL-PRF-23648 standard, that describes a load life test, consisting in application of maximum power specified for the themsitor during 1000h, intermittently (30min. on, 30min. off) and checking at 250, 500, 750 and 1000h that the thermistor remains in the specified tolerance in the applicable specification sheet, so I suppose that these thermistors are quite good wrt long-term stability. In applications where more stability is required, also Pt thermistors are used in spacecrafts (mainly Pt1000 and Pt2000, also others), but the problem is that depending on the wire run, they shall be measured using 4-wire techniques, and also initial calibration is not so tight (when it is so tight, they tend to be also very expensive) and not so easy (a Pt1000 has a rough variation of 3ohm per ºC). Regards, Javier On 21/07/2014 16:12, Attila Kinali wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali ___ 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] temperature sensor
I tried the On Mon, Jul 21, 2014 at 7:02 AM, Attila Kinali att...@kinali.ch wrote: How about doing it the old analog way? Feed the output of the PID controller to comparator together with a sawtooth signal. That will give you a quite nice 0-100% PWM control. I'm quite sure a similar solution is possible with a NE555 as well. I tried an analog controller first. It is very hard to implement a tunable PID controller that does PWM without using a bazillion chips. My second controller worked much better and a I wrote, uses only a single 8-pin DIP chip. The AVR uP has more analog inputs and outputs then you need and costs about $1.25 As for the fan startup. What you do is test it and store the minimum fan voltage in a constant and use that as the zero point. So the P part of the PID sets the fan voltage to the temperature error times a constant plus the zero point. A better solution is to use a tachometer fan. Then the controller does not set the fan voltage but sets the fan speed. there are still extra pins on the controller and this is one upgrade and the other upgrade is to measure absent air temperature But the simple controller does well enough. I don't see any reason at all to build a PWM controller with a comparator. Multiple sets of that hardware is built into every uP and they cost nearly nothing and come in a single 8 pin DIP. Of course, you would need to adjust the PID controller parameters to accomodate for the new element in the control loop. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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. -- Chris Albertson Redondo Beach, California ___ 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] temperature sensor
You can find an interesting solution with the INA330. In the data sheet is described a complete temperature PID controlled . http://pdf.datasheetcatalog.com/datasheets/270/255641_DS.pdf Luciano www.timeok.it On Mon 21/07/14 4:02 PM , Attila Kinali wrote:Moin Bert, On Mon, 21 Jul 2014 09:02:12 -0400 (EDT) ewkeh...@aol.com wrote: The challenge is reliable fan start at low voltage if you want the unit stay constant over an ambient change of 10 C. Members have talked about u processor control but I have not seen any thing that works, many of the heat pipes used in laptop do have digital speed control, some one please step up to the plate. How about doing it the old analog way? Feed the output of the PID controller to comparator together with a sawtooth signal. That will give you a quite nice 0-100% PWM control. I'm quite sure a similar solution is possible with a NE555 as well. Of course, you would need to adjust the PID controller parameters to accomodate for the new element in the control loop. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [1] and follow the instructions there. - Message sent via Atmail Open - http://atmail.org/ Links: -- [1] http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ 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] temperature sensor
Ice water and boiling water coupled with altitude will give you two points. Sent from mobile On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
I got a few of these http://www.adafruit.com/products/374 to replace my TMP36. The idea was to get rid of the noise by using a sensor with a built-in digital interface. They are spec'd for only 0.5C accuracy but I think they are more repeatable and do much better than 0.5c for relative measurements. You can use the link above to buy them but you can also get free samples.Another advantage of the digital ones is you can install several into the heat sink and all of them only take one pin so you can add any number of these and still use the tiny 8-pin uP. Calibrate any sensor with boiling water. Either just assume it is 100C or look up the local air pressure and compute the boiling point. Or, I just happened to have a good laboratory glass thermometer, the kind that is about two feet long. Place it and the sensor in the same liquid bath and cal is close enough for anyone who is not a temperature nut. I have not yet had time to use these in a real application. but it looks like they work. Again you have to couple them well to whatever you are measuring. Do not conduct the wrong heat into any of these devices via the lead wires. On Mon, Jul 21, 2014 at 9:02 AM, Javier Herrero jherr...@hvsistemas.es wrote: Hello, There are two types of NTC thermistors that are (very) frequently used in spacecrafts, the Measurement Specialties (traditionally YSI, Yellow Spring Instruments) 44907 and 44908, that are 10k @ 25ºC NTC: http://meas-spec.com/downloads/44908.pdf and http://meas-spec.com/ downloads/44907.pdf Both are specified in error against temperature, being ±0.1ºC for the 44908 and ±0.2ºC for the 44907, in the 0-70ºC range. I suppose that these ones are obscenely expensive, but the civilian versions are the 44006RC and 44031RC, with the same specified tolerances, and the same calibration curve, and readily available (e.g. from Farnell). I suspect that the difference between the space qualified ones and the others are quality control and traceability, and perhaps (only perhaps) a different low-outgassing epoxy coating, but probably the sensor material is the same in all of them. The advantage is that you get a quite good intial tolerance, so calibration can be simplified, since you only need to calibrate the resistance measurement device with known resistances to obtain a ±0.1ºC error from the sensors. The qualification mandated by NASA for these sensors refers mainly to MIL-PRF-23648 standard, that describes a load life test, consisting in application of maximum power specified for the themsitor during 1000h, intermittently (30min. on, 30min. off) and checking at 250, 500, 750 and 1000h that the thermistor remains in the specified tolerance in the applicable specification sheet, so I suppose that these thermistors are quite good wrt long-term stability. In applications where more stability is required, also Pt thermistors are used in spacecrafts (mainly Pt1000 and Pt2000, also others), but the problem is that depending on the wire run, they shall be measured using 4-wire techniques, and also initial calibration is not so tight (when it is so tight, they tend to be also very expensive) and not so easy (a Pt1000 has a rough variation of 3ohm per ºC). Regards, Javier On 21/07/2014 16:12, Attila Kinali wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali ___ 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. -- Chris Albertson Redondo Beach, California ___ 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] temperature sensor
At 11:48 AM 7/21/2014, Chris Albertson wrote: A better solution is to use a tachometer fan. Then the controller does not set the fan voltage but sets the fan speed. there are still extra pins on My thought exactly. I have not tried it, but it seems like this would also automatically restart a stalled fan. Has anyone tried it? Did adding the second loop cause tuning problems? As for sensors, my working assumption has been that NTC thermistors give you the most sensitivity, at least compared to a Pt RTD or thermocouple. If the sensor is used inside a control loop, rather than as a measurement device, the non-linearity might not even matter since the loop should be holding it at a constant temperature. -- newell N5TNL ___ 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] temperature sensor
Hi Attila, sorry, I was out for a week, so I can respond only now. Unfortunately I have no data about the thermal resistance crystal to case. It's on my agenda since quite a while to measure the time constant. Tuning fork crystals are in general in an evacuated package, because any atmosphere would damp the vibration dramatically, and would increase the resonance resistance (which already is in the range of 50k to 100k over temperature) severely. Therefore the thermal connection is mainly through the wires directly to the crystal element. There is some contribution of thermal radiation from the cylindrical cover to the crystal, but the main mechanism is thermal conduction through the wires. But as the mass of the tuning fork is so small, it's thermal capacity is small and thus it will react pretty quickly. I really need to put this test on my agenda. Best regards Bernd DK1AG -Ursprüngliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Attila Kinali Gesendet: Samstag, 19. Juli 2014 13:46 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] temperature sensor On Wed, 25 Jun 2014 14:21:49 +0200 Bernd Neubig bneu...@t-online.de wrote: the time-nut approach for temperature measurement would be to use a temperature sensor crystal - like the good old Hewlett-Packard guys did many years ago. If you do not look for ultra-linearity of the frequency vs. temp response, there are several possible types of crystal cuts possible. The simplest one is the Y-cut or the slightly rotated Y+5° cut, which has a slope of about 90 to 95 ppm/K @ room temperature. Smaller sensor crystals are tuning-fork type crystals, which come in the same small cylindrical package as normal watch crystals. For further reading I have attached an application note for such a crystal from AXTAL. Do you have any data on the temperature resistance from case to crystal? The PT100 and NTC sensors have the nice property of having a very good thermal coupling between the sensor element and the case. But i suspect that temperature sensor crystals have a very small area that couples the crystal to the case (in order to get a high enough Q for the oscillator to work), which in turn limits the speed at which the sensor reacts to temperature changes. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Hi Bob, see my answer to Attila, which I have sent a minute ago. Bernd DK1AG -Ursprüngliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp Gesendet: Samstag, 19. Juli 2014 15:00 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] temperature sensor Hi A temperature sensor crystal is very much the same thing as a normal crystal (except for angle of cut). The mounting is pretty much the same as the crystals you have seen before. The only thing you do to improve the thermal coupling is to do a backfill with something like helium. Backfill levels are low and they vary depending on the application and the cut of crystal. The thermal resistance isnt great, but its good enough. You only have micro watts going into the resonator. Increasing the backfill would increase the damping and thus the resistance. That would increase the power dissipated in the resonator. This would defeat any gain you got from the increased backfill. For direct contact sensing, you use SAW devices rather than BAWs. If you do things right you can put the SAW directly in contact with the stuff you are sensing. The thermal resistance in that case is essentially zero. Bob On Jul 19, 2014, at 7:45 AM, Attila Kinali att...@kinali.ch wrote: On Wed, 25 Jun 2014 14:21:49 +0200 Bernd Neubig bneu...@t-online.de wrote: the time-nut approach for temperature measurement would be to use a temperature sensor crystal - like the good old Hewlett-Packard guys did many years ago. If you do not look for ultra-linearity of the frequency vs. temp response, there are several possible types of crystal cuts possible. The simplest one is the Y-cut or the slightly rotated Y+5° cut, which has a slope of about 90 to 95 ppm/K @ room temperature. Smaller sensor crystals are tuning-fork type crystals, which come in the same small cylindrical package as normal watch crystals. For further reading I have attached an application note for such a crystal from AXTAL. Do you have any data on the temperature resistance from case to crystal? The PT100 and NTC sensors have the nice property of having a very good thermal coupling between the sensor element and the case. But i suspect that temperature sensor crystals have a very small area that couples the crystal to the case (in order to get a high enough Q for the oscillator to work), which in turn limits the speed at which the sensor reacts to temperature changes. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Hi, regarding the commercial availability of temperature sensor crystals, I already had pointed to the tuning fork type RKTV206, which is on the AXTAL website together with an application note. Other temperature sensing crystals are using thickness shear mode, and are basically rotated Y- cuts The most prominent cut is the Y-cut or the same with a few degrees (about 5) rotation from Y-axis. This cut exhibits a tempco of about -90 ppm/K, but is not very linear. There are a few on the market in HC-52/U size. The most temperature-linear cut was the LC-cut invented by olde Hewlett-Packard, which had a complete temperature test system offered around this sensor crystal. It is an doubly-rotated cut with some -40 ppm/K sensitivity. Sorry I am in a hurry, so I have not the time to dig the literature for you at the moment. Regards Bernd DK1AG -Ursprüngliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Attila Kinali Gesendet: Sonntag, 20. Juli 2014 18:11 An: Tom Van Baak; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] temperature sensor Moin, On Sun, 20 Jul 2014 07:55:23 -0700 Tom Van Baak t...@leapsecond.com wrote: Thanks for this level of detail. Fascinating. Is the fundamental physics behind the quartz angle-of-cut well understood, or does this fall into advanced alchemy and industrial magic? From what i gathered from my excursion into solid state phyiscs, the properties of crystals can be calculated easily. If i'm not mistaken the SC cut was calculated before it was experimentally proven (sorry, cannot find the reference for that). There are also several software packages to simulate quartz crystals. (e.g. CS-01 from maxis-01) I understand about the time constant now. Yes, on the order of a few seconds makes sense. Would it be possible to have other mounting techniques that improve environmental contact with the crystal? The problem here is, that any closer contact will lead to damping of the crystal. Probably the best solution is, as Bob Camp said, to use SAW instead of BAW. Do you know of any commercial quartz crystals (say, in the $1 to $10 range) that have been optimized for large tempco at room temperature? Or optimized for linearity over a large range (e.g., -40 to +40 C)? As Bernd Neubig mentioned, Axtal has some: http://www.axtal.com/English/Products/PiezoSensors/TemperatureSensors/ As none of the usual distributors carries them, i have no idea what the price is. Maybe Bernd can answer that question. I'm pretty sure other quartz manufacturers have some as well. I was able to test one once, a 5x7mm XO, but I don't know any more about it other than it came from Switzerland. Hmm... The only quartz manufacturer in Switzerland that is still producing anything, is AFAIK Microcrystal. I'm not aware of any other (after Oscilloquartz got bought and their quartz business integrated into Microcrystal). Unless you got it over Quarz AG (www.quarz.ch) which is merly a distributor. (Yes, they sell beauty products too... ) BTW: for some reason, i did not get the two mails from Andras Pummer which you quoted at the end of your mail. They don't seem to be in the archives either. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
docdai...@gmail.com said: Ice water and boiling water coupled with altitude will give you two points. Has anybody used a good thermometer to measure air pressure? How much does the measured temperature vary between just barely boiling and a good roiling boil? Or in various locations within a pot of boiling water? -- These are my opinions. I hate spam. ___ 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] temperature sensor
er not boiling watersteam. Water's boiling point is affected by the dissolved gasses and other contaminants. Alan G3NYK - Original Message - From: Bill Dailey docdai...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 21, 2014 5:43 PM Subject: Re: [time-nuts] temperature sensor Ice water and boiling water coupled with altitude will give you two points. Sent from mobile On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Hi: A number of decades ago I wanted an easy way to get precision temperature measurements when using HP Rocky Mountain Basic. HP was selling thermistors specified to be accurate to 0.1 deg C when you interchanged thermistors. The readout can be much more sensitive for applications like oven temperature control where you are concerned with changes in temperature. But they are very nonlinear and at first that looked like a show stopper, but when you use the Steinhart-Hart equation it turns out that the temperature is given by a linear equation that's straight forward to compute. See: http://www.prc68.com/I/Sensors.shtml#Temperature AFAICR both leads were orange orange (the color code for accuracy was lead colors) and cost about $40 each a long time ago. Modern low cost (pennies each) thermistors are typically 10k Ohms at room temperature and the Steinhart-Hart equation coefficients are not given. Once you know the equation applies it's not too difficult to make some measurements and derive the coefficients. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html ___ 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] temperature sensor
Hi: The temperature of steam can be anything above boiling water. http://en.wikipedia.org/wiki/Steam Super heating of steam was common railroad practice. Boiling pure water will get rid of any trapped gases quickly. In fact this is the recommended thing to do to tap water before using it for freshly cut roses. Of course you need to let the water cool before putting them into it. Removing the trapped oxygen makes them last longer. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Alan Melia wrote: er not boiling watersteam. Water's boiling point is affected by the dissolved gasses and other contaminants. Alan G3NYK - Original Message - From: Bill Dailey docdai...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 21, 2014 5:43 PM Subject: Re: [time-nuts] temperature sensor Ice water and boiling water coupled with altitude will give you two points. Sent from mobile On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
On 7/21/2014 11:36 AM, Hal Murray wrote: docdai...@gmail.com said: Ice water and boiling water coupled with altitude will give you two points. Has anybody used a good thermometer to measure air pressure? How much does the measured temperature vary between just barely boiling and a good roiling boil? Or in various locations within a pot of boiling water? When you are dealing with water phase changes, you are dealing with both temperature and heat. When you get up to a point like boiling, you have a mass of water which is at the local boiling point and the only thing stopping the water from going to steam phase is the amount of heat in the water. Once a pot of water is at rolling boil all of the water in the pan should be at and stay at the boiling point till it is all gone. Once you remove the heat, the boiling will slow and stop, and the temperature will begin to fall as the water loses the heat. As long as you maintain a balance between having the sensor too close to the point you are applying heat, and keeping it immersed in boiling water, you should be able to assume the local boiling point. That boiling point has to be adjusted for pressure, which affects the temp the most. Also assuming only water, and no other contaminants as mentioned by another poster. The same sort of action occurs when water freezes, along with some other oddball issues with the crystalization. You can arrive at the freezing point, and you will dwell there for some time as the water loses its heat and becomes solid. The thing that is different between freezing and boiling is that as long as you have water and are boiling the temperature will remain at boiling, and no higher. With freezing, if you are measuring water as you cool it and remove heat, it will go thru freezing with a pause as it goes to ice, then it can continue to cool as cold as you like. so when you are measuring by using ice as a reference, you should have frozen the sensor or drilled it into the center of a block of ice, and let it come to equilibrium in the ice w/o any freezing apparatus being active. It should come to the freezing point till all of the ice melts. Jim ___ 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] temperature sensor
Yes but water can be superheated too if there are no nucleation points for bubbles to form and like super-cooling this can amount to a couple of deg C in a very clean container. However the vapour cannot be superheated without increasing the pressure .as in a steam engine, or autoclave. I may not be as accurate as temperature nuts would like but unless you are very sure of your conditions it is probably more reliable. I notice the wiki on temperature scales doesn't include boiling water (or steam) these days, but if does say is 17mK low of an exact 100 :-)) http://en.wikipedia.org/wiki/Temperature_scales#International_temperature_scale_of_1990 I note it doesnt actually say where you place the sensor :-)) Alan G3NYK - Original Message - From: Brooke Clarke bro...@pacific.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 21, 2014 9:11 PM Subject: Re: [time-nuts] temperature sensor Hi: The temperature of steam can be anything above boiling water. http://en.wikipedia.org/wiki/Steam Super heating of steam was common railroad practice. Boiling pure water will get rid of any trapped gases quickly. In fact this is the recommended thing to do to tap water before using it for freshly cut roses. Of course you need to let the water cool before putting them into it. Removing the trapped oxygen makes them last longer. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Alan Melia wrote: er not boiling watersteam. Water's boiling point is affected by the dissolved gasses and other contaminants. Alan G3NYK - Original Message - From: Bill Dailey docdai...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 21, 2014 5:43 PM Subject: Re: [time-nuts] temperature sensor Ice water and boiling water coupled with altitude will give you two points. Sent from mobile On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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. ___ 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] temperature sensor
Steam superheats only if the pressure is raised above standard pressure, otherwise, steam at standard pressure will be exactly 212F, or 100C. -Chuck Harris Brooke Clarke wrote: Hi: The temperature of steam can be anything above boiling water. http://en.wikipedia.org/wiki/Steam Super heating of steam was common railroad practice. Boiling pure water will get rid of any trapped gases quickly. In fact this is the recommended thing to do to tap water before using it for freshly cut roses. Of course you need to let the water cool before putting them into it. Removing the trapped oxygen makes them last longer. Have Fun, Brooke Clarke ___ 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] temperature sensor
Hi If you look at the people running very precise thermometers (sub 0.001C) they are doing better with thermistors than with PRT’s. Both the PRT’s and the thermistors come with notes on them requiring on location re-certification below he 0.01C level. A triple point of water cell is typically what’s used for both. Bob On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
On Mon, 21 Jul 2014 18:00:59 -0400 Chuck Harris cfhar...@erols.com wrote: Steam superheats only if the pressure is raised above standard pressure, otherwise, steam at standard pressure will be exactly 212F, or 100C. Uhm.. you are the second one claiming this. Could you please explain what physics limits the temperature of vapor? The ideal gas equation says that p*V/T = const, ie that the temperature can rise at a constant pressure, as long as the gas is allowed to expand. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
Tom wrote: There have been several discussions over the years about variable fan speed based temperature control. I can't explain it, but I've always been suspicious of this technique. It seems to me still air is inherently better than moving air. Passive (no fan) is better than active (fan). And constant velocity is better than turbulence is better than variable velocity. But I don't know for sure. There is no such thing as still air, unless there is no temperature gradient. If there is any temperature gradient (typically due to power dissipation), there will be convection currents. In a closed space (for example, internal to a TBolt or in a sealed box that encloses a TBolt), these convection currents will set up a flow pattern that may be benign or malicious with respect to keeping a particular part of the device at a constant temperature. If the part you are particularly interested in is a creator of thermal gradients (as the OCXO in a TBolt is), analyzing this gets very complicated very fast. Fans (speaking here of fans that circulate air internal to a closed volume, not fans that exchange air between the inside and outside of a volume) tend to mix up the air and reduce thermal gradients. Then, the question becomes whether the circulation due to the fan has a patterned or a random thermal flow. Typically, a random (diffused) pattern is best -- but it is relatively hard to achieve. With careful design, active circulation is usually better than passive convection. However, careful design is not easy. Also, fans raise a concern about vibration, which is a real worry with any precision oscillator. One other possibility is to use passive techniques to randomize (more or less) the passive convection. This can be achieved (to a degree) by filling the internal volume with low-density, very porous insulation. On a larger scale, a sealed box of, say, 2 cubic feet can be filled with common packing peanuts and the isolated object placed in the middle. Air will still circulate by convection, but in a more random manner. (There will also be less bulk circulation, so the thermal gradient will be somewhat larger than before.) Applied to a TBolt, one might fill the inside of the TBolt itself with smaller pieces of styrofoam (irregular shapes perhaps 6 or 7mm in size). [Spheres (styrofoam beads) may pack a bit too tightly for this, impeding airflow more than desired.] The same can be done for a sealed box that encloses a TBolt or other oscillator. I have achieved very good results with this method, when properly applied. I have done a fair amount of experimenting with and without fans (but one must recognize that there are so many variables, even a lot of experimenting really only scratches the surface), and have always found that passive circulation (within sealed volumes) works very well when the object ultimately being controlled is an ovenized oscillator. For tight control, which is needed for precision voltage references, DAQ circuits, and other precision process-control applications, I do use a thermostatically operated fan to exchange air between the outermost sealed volume and ambient -- but even this I usually find unnecessary if the ultimate object is minimizing the frequency drift of an ovenized oscillator. Finally, re.: fan control. For a brushless DC fan to run slowly, you need to feed it full voltage with pulse-width modulation (PWM). Even then, they will not run all that slowly. The Microchip TC642B fan controller (8 pin IC, about $1.20) is a very handy part when you need a wide range of fan speeds. It uses commutation noise to sense fan rotation, and has a stall routine that gives the fan a kick if it stalls (NB: this is a feature of the 642B, absent on the 642). So, not only will it run the fan at its lowest possible self-sustaining speed, you can also run the fan much slower than its self-sustaining speed by letting it stall and be restarted periodically. The fan looks like a windmill with three sheets to the wind below its self-sustaining speed, but it works extremely well and this operation does not damage the fan or the controller. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] temperature sensor
Thank you Charles . As a first step I will fill one of my Tbolt boxes with small foam particles. Sounds like a good idea. I have one unit where I have given particular attention to low power from the power supply. Bert Kehren In a message dated 7/21/2014 7:43:49 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Tom wrote: There have been several discussions over the years about variable fan speed based temperature control. I can't explain it, but I've always been suspicious of this technique. It seems to me still air is inherently better than moving air. Passive (no fan) is better than active (fan). And constant velocity is better than turbulence is better than variable velocity. But I don't know for sure. There is no such thing as still air, unless there is no temperature gradient. If there is any temperature gradient (typically due to power dissipation), there will be convection currents. In a closed space (for example, internal to a TBolt or in a sealed box that encloses a TBolt), these convection currents will set up a flow pattern that may be benign or malicious with respect to keeping a particular part of the device at a constant temperature. If the part you are particularly interested in is a creator of thermal gradients (as the OCXO in a TBolt is), analyzing this gets very complicated very fast. Fans (speaking here of fans that circulate air internal to a closed volume, not fans that exchange air between the inside and outside of a volume) tend to mix up the air and reduce thermal gradients. Then, the question becomes whether the circulation due to the fan has a patterned or a random thermal flow. Typically, a random (diffused) pattern is best -- but it is relatively hard to achieve. With careful design, active circulation is usually better than passive convection. However, careful design is not easy. Also, fans raise a concern about vibration, which is a real worry with any precision oscillator. One other possibility is to use passive techniques to randomize (more or less) the passive convection. This can be achieved (to a degree) by filling the internal volume with low-density, very porous insulation. On a larger scale, a sealed box of, say, 2 cubic feet can be filled with common packing peanuts and the isolated object placed in the middle. Air will still circulate by convection, but in a more random manner. (There will also be less bulk circulation, so the thermal gradient will be somewhat larger than before.) Applied to a TBolt, one might fill the inside of the TBolt itself with smaller pieces of styrofoam (irregular shapes perhaps 6 or 7mm in size). [Spheres (styrofoam beads) may pack a bit too tightly for this, impeding airflow more than desired.] The same can be done for a sealed box that encloses a TBolt or other oscillator. I have achieved very good results with this method, when properly applied. I have done a fair amount of experimenting with and without fans (but one must recognize that there are so many variables, even a lot of experimenting really only scratches the surface), and have always found that passive circulation (within sealed volumes) works very well when the object ultimately being controlled is an ovenized oscillator. For tight control, which is needed for precision voltage references, DAQ circuits, and other precision process-control applications, I do use a thermostatically operated fan to exchange air between the outermost sealed volume and ambient -- but even this I usually find unnecessary if the ultimate object is minimizing the frequency drift of an ovenized oscillator. Finally, re.: fan control. For a brushless DC fan to run slowly, you need to feed it full voltage with pulse-width modulation (PWM). Even then, they will not run all that slowly. The Microchip TC642B fan controller (8 pin IC, about $1.20) is a very handy part when you need a wide range of fan speeds. It uses commutation noise to sense fan rotation, and has a stall routine that gives the fan a kick if it stalls (NB: this is a feature of the 642B, absent on the 642). So, not only will it run the fan at its lowest possible self-sustaining speed, you can also run the fan much slower than its self-sustaining speed by letting it stall and be restarted periodically. The fan looks like a windmill with three sheets to the wind below its self-sustaining speed, but it works extremely well and this operation does not damage the fan or the controller. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
Re: [time-nuts] temperature sensor
Hi, as a bit of a temperature nut, here are some observations. Diodes work as temperature sensors, but better is the trans-diode, a bipolar transistor with collector connected to base. Sensitivity about 2.2 mV/K, I did not use them much in spite of their linearity and low cost. PT100 is only useful with a four terminal measurement with an HP3468A instrument or equivalent measuring 4 terminal ohms. It is stable to one milli-Kelvin and I use it for measuring the temperature of thermostatic water baths when calibrating thermometers. The sensor has self heating, and is poor in placement on small components, with high thermal resistance to measured item and high heat conduction along leads. Without the HP measuring instrument the PT100 relies on the resistors it is compared with. Although the PT100 specs are good, resistors that can match those specs are very expensive, so to set up a measuring bridge requires a lot of expensive technology in resistors and stable amplifiers. If you wont go that far you are better off with thermistors. Thermocouples only compare temperatures, so cold reference is a problem as are cold junction compensators. With only 40 microvolts/Kelvin they need good to very good amplifiers. They are small and are not compromised by using microscopically fine wire. They can measure tiny items with very little heat transmitted along the wires. they have no self heating.I use them in a Pile of six elements to measure Relative Humidity to a precision of 0.1% RH in an appropriate portable instrument. One logging instrument I have built uses three thermocouples with ICL7650 amplifiers and a AD590 common cold junction sensor. A four channel logger produces data that is reduced by spreadsheet to three temperatures. Copper /constantin is a good pair, sensitive (40uV/K), reasonably linear and the copper solves many switching and amplifier circuit problems. Thermistors are useful. They are available in tiny packages, sealed in glass. With high impedance their self heating can be negligibly small. As has been pointed out they comply well to a general calibration curve. If Paralleled with an equal value resistor, or connected in an equal value resistance bridge, they are linear over about 20C range. They are very sensitive (4%/K), and so need no special amplifiers. They prove quite stable. Calibration is done with a known PT100 sensor and a HP3468A in a thermostatic bath (Colora or Haake). Tested devices a placed in a copper tube immersed 10cm (4 inches) at least. Icepoint cell, in a Dewar flask (Thermos) with shaved ice gives a temperature at zero C to 0.01C. Test thermometer inserted 15 cm. Hypsometer, a boiling point cell has special splash and radiation shields, gives measurements stable to 1mK, but after all the corrections needed to a Fortin barometer for temperature etc, relies on knowing local gravity to some accuracy. If the local geoid is assumed with usual corrections the ice-point is still more reliable as an absolute standard. Conduction along leads is a major consideration, even with fine (0.002 ) copper leads, a typical installation needs 20mm immersion. It is a logarithmic function, the immersion error, I allow about 50mm to be sure with thermocouple sensors into a 3mm hole drilled into aluminium plate edge wise to measure the plate temperature. You only have to do a few experiments to find that this is necessary. cheers, Neville Michie ___ 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] temperature sensor
One cheap device that has a fairly predictable tempco over a fairly good range of temperatures is the lowly ceramic resonator - especially the low frequency variety (e.g. 400-500 kHz) having a reasonably straight line temperature versus frequency curve. If one already has a decent frequency reference on hand, it might be interesting to characterize it for both linearity and retrace. Depending on the needed accuracy, I would suspect that it would be easily beat by a calibrated and dithered DS18B20 or a thermocouple - not to mention an LC or even a Y (a.k.a. parallel) cut quartz crystal-based oscillator, to name but two. 73, Clint KA7OEI ___ 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] temperature sensor
To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. Ok... a couple hours of reading later ;-) My excursion into temperature measurement has brought some results: 1) PT sensors can be secondary standards for temperature calibration. But standard industrial sensors do not have the stability or linearity of the standard grade sensors. But at least they do not break when you glare at them. Those in ceramic housing are supperior to those in glass or metal housing. Thin film are inferior to wire wound. (in terms of stability and accuracy, thermal coupling is a different matter) (the price for a commercial standard grade PT sensor seems to be in the order of 3kusd) 2) The uncertainty of the calibration of the standards grade PTR seems to be in the order of 100uK to 10uK. 2) Making a triple point of water cell for calibration with an accuracy better than 10mK seems to be quite simple and doable at home, most likely something around 1mK is achievable. Also judging the quality of the cell is quite simple: make multiple of them, the one with the highest temperature is the most accurate one. 3) A well done ice bath gets you into the ballpark of 10mK accuracy. Most of the error is due to impurities and gas in the water. The air pressure effect is much smaller (and thus inconsequential) unless living on a high mountain. Also an ice bath is easier to do than using an triple point cell. 4) There are people on ebay who sell very pure Gallium and Indium that could be used for (not so accurate) melting/freezing cells for ~29.7°C and 156°C. (if anyone knows what the non-nut would use those for, please tell me) 5) The book Traceable Temperatures by Nicholas and White is a very good reading on temperature measurement and calibration. It explains the procedures with what can go wrong and what accuracies are achievable. It also contains a list of references for further reading. I did not have a look at those yet, but from the titles they look very reasonable. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
You don't use ice as a reference. With ice water, the same principles apply that apply to boiling water. This is why these are convenient calibration check points. Sent from mobile On Jul 21, 2014, at 3:51 PM, jim s jwsm...@jwsss.com wrote: On 7/21/2014 11:36 AM, Hal Murray wrote: docdai...@gmail.com said: Ice water and boiling water coupled with altitude will give you two points. Has anybody used a good thermometer to measure air pressure? How much does the measured temperature vary between just barely boiling and a good roiling boil? Or in various locations within a pot of boiling water? When you are dealing with water phase changes, you are dealing with both temperature and heat. When you get up to a point like boiling, you have a mass of water which is at the local boiling point and the only thing stopping the water from going to steam phase is the amount of heat in the water. Once a pot of water is at rolling boil all of the water in the pan should be at and stay at the boiling point till it is all gone. Once you remove the heat, the boiling will slow and stop, and the temperature will begin to fall as the water loses the heat. As long as you maintain a balance between having the sensor too close to the point you are applying heat, and keeping it immersed in boiling water, you should be able to assume the local boiling point. That boiling point has to be adjusted for pressure, which affects the temp the most. Also assuming only water, and no other contaminants as mentioned by another poster. The same sort of action occurs when water freezes, along with some other oddball issues with the crystalization. You can arrive at the freezing point, and you will dwell there for some time as the water loses its heat and becomes solid. The thing that is different between freezing and boiling is that as long as you have water and are boiling the temperature will remain at boiling, and no higher. With freezing, if you are measuring water as you cool it and remove heat, it will go thru freezing with a pause as it goes to ice, then it can continue to cool as cold as you like. so when you are measuring by using ice as a reference, you should have frozen the sensor or drilled it into the center of a block of ice, and let it come to equilibrium in the ice w/o any freezing apparatus being active. It should come to the freezing point till all of the ice melts. Jim ___ 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] temperature sensor
Hi At least where I have lived around the country (and actually measured the tap water) the “stuff” in the hard water has come out in the 100 ppm range. Each time I’ve asked about it, the answer comes back: “we add (trade name of stuff) to the water to make it hard so the pipes last longer”. Anything under 30 ppm is pretty soft water. Now, does that have a massive impact on the boiling point - nope. Checking your barometer is a better thing to do than checking your TDS meter if you are calibrating the boiling point. Now for the triple point …. you need good clean water. Bob On Jul 21, 2014, at 7:05 PM, Chris Albertson albertson.ch...@gmail.com wrote: Steam is always 100C in open air at sea level BUT there are real problems if you try to use it Steem quickly condenses back to water. If you think you can see steam you are mistaken. What you see is water aerosol that is condensed when stem hits the colder air. Water in vapor form is invisible in air. For the same reason clouds are water, not vapor. If you place the sensor in steam it is hard to really know what you have. Is it a mixture of vapor, re-condenced vapor and air. And then what about the thermal conductivity? You really can't know. But with water it is pretty easy to see that it is nearly 100% water. Experiment with tap water v. RO water and I doubt you will find much difference as hard water has only maybe 12ppm dissolved minerals. Same with dissolved gasses O2 and N2 at room temperature are present at the small fraction of a gram per liter but at 100C there is not much gas in the water. Remember the raise in boiling point is (from memory) about .5C per mole per liter and how many moles stuff is in a liter of 100C tap water? You can calculate the effect. But I'm thinking it's way below the 0.001C level. Air pressure or altitude above sea level will make a real difference. I once tried to cook rice at 12,000 feet. It didn't work. On Mon, Jul 21, 2014 at 1:11 PM, Brooke Clarke bro...@pacific.net wrote: Hi: The temperature of steam can be anything above boiling water. http://en.wikipedia.org/wiki/Steam Super heating of steam was common railroad practice. Boiling pure water will get rid of any trapped gases quickly. In fact this is the recommended thing to do to tap water before using it for freshly cut roses. Of course you need to let the water cool before putting them into it. Removing the trapped oxygen makes them last longer. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Alan Melia wrote: er not boiling watersteam. Water's boiling point is affected by the dissolved gasses and other contaminants. Alan G3NYK - Original Message - From: Bill Dailey docdai...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 21, 2014 5:43 PM Subject: Re: [time-nuts] temperature sensor Ice water and boiling water coupled with altitude will give you two points. Sent from mobile On Jul 21, 2014, at 10:12 AM, Attila Kinali att...@kinali.ch wrote: On Mon, 21 Jul 2014 04:39:51 -0700 Alexander Pummer alex...@ieee.org wrote: NTC are not that very stable, they are amorphous material winch could recrystallize slowly and therefore change it's electrical behavior , PT100 style is more reliable since it is pure metal How long is the time constant for NTCs? I guess, it wouldn't matter for most of the measurements we do, as NTCs need to be calibrated before precision measurements anyways. Unless one measures over several months, or years. But on this timescales, i wouldn't really trust an off the shelf PT100 either. Not unless i measure its stability For use in GPSDOs and OCXOs, i guess it doesn't really matter, as long as the NTC stays within spec. There an external loop corrects for the variation/drift of the measurement. While we are at it: what is a good way to calibrate/characterize temperature sensors that is available to hobbyists? Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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
Re: [time-nuts] temperature sensor
Hi If you want to hit 1 mK with your home made triple point cell, you will need a source of very clean water and some luck with materials and cleaning processes. If you want to go below that level, you will need an isotope readout on your water source. Rain water, and mid-continent well water are a bit different in their composition …. If I remember correctly, you want the mid-continent deep well stuff, but only from the “right” sort of well. Yes I’d bet there is a water isotope nuts mailing list somewhere …. Bob On Jul 21, 2014, at 8:10 PM, Attila Kinali att...@kinali.ch wrote: To satisfy my curiosity and get actual data I'd like to place 6 or more tiny analog high-resolution temperature sensors all around the OCXO of a Trimble Thunderbolt. That's high-resolution both in temperature and in time. In other words, no fake accuracy averaging allowed. The goal is to observe thermal gradients in real-time and see how good, or how bad, the correlation is among crystal temperature, case temperature, and DS1620 temperature sensor (which is mounted a considerable distance from the OCXO). The same technique, and maybe even the same conclusions, might apply to Rb. Ok... a couple hours of reading later ;-) My excursion into temperature measurement has brought some results: 1) PT sensors can be secondary standards for temperature calibration. But standard industrial sensors do not have the stability or linearity of the standard grade sensors. But at least they do not break when you glare at them. Those in ceramic housing are supperior to those in glass or metal housing. Thin film are inferior to wire wound. (in terms of stability and accuracy, thermal coupling is a different matter) (the price for a commercial standard grade PT sensor seems to be in the order of 3kusd) 2) The uncertainty of the calibration of the standards grade PTR seems to be in the order of 100uK to 10uK. 2) Making a triple point of water cell for calibration with an accuracy better than 10mK seems to be quite simple and doable at home, most likely something around 1mK is achievable. Also judging the quality of the cell is quite simple: make multiple of them, the one with the highest temperature is the most accurate one. 3) A well done ice bath gets you into the ballpark of 10mK accuracy. Most of the error is due to impurities and gas in the water. The air pressure effect is much smaller (and thus inconsequential) unless living on a high mountain. Also an ice bath is easier to do than using an triple point cell. 4) There are people on ebay who sell very pure Gallium and Indium that could be used for (not so accurate) melting/freezing cells for ~29.7°C and 156°C. (if anyone knows what the non-nut would use those for, please tell me) 5) The book Traceable Temperatures by Nicholas and White is a very good reading on temperature measurement and calibration. It explains the procedures with what can go wrong and what accuracies are achievable. It also contains a list of references for further reading. I did not have a look at those yet, but from the titles they look very reasonable. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] temperature sensor
That is a great idea. Thank you. I can see use for this on more then one project. I have some really poor preforming traction motors on a small robot. This is one of those flap your forehead why did I not think of something so simple? events. I'll call it a kick starter BTW, one project, years ago needed stable temperer. They placed the part in a vacuum. If you really do need to decouple from the ambient a vacuum gap will do it. ... I and has a stall routine that gives the fan a kick if it stalls (NB: this is a feature of the 642B, absent on the 642). So, not only will it run the fan at its lowest possible self-sustaining speed, you can also run the fan much slower than its self-sustaining speed by letting it stall and be restarted periodically. -- Chris Albertson Redondo Beach, California ___ 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] Calibration of Temperature Sensors
Most portable temperature standards are defined at the freezing point of various pure materials The most common temperature for calibration is the ice point of very pure water. A triple point cell is one of the most accurate (least uncertain) available. For most uses, an ice point bath will meet our needs. Ice point baths are both inexpensive and has a low uncertainty if properly prepared. If the technique is correct, an ice point bath can reproduce within a few hundredth of a degree C at any altitude. For information on ice point bath construction and use, see the NIST technical note 1411. http://www.nist.gov/pml/upload/TN1411.pdf Note the use of distilled water and pure ice made from distilled water. The ice point bath works better for me if it is stirred from bottom to top just before measurements are taken. Minerals and salt (water softener) in the water or ice really mess up the measurements!!! Fluke Corporation is a good source for information and equipment. http://us.flukecal.com/products/temperature-calibration Michael Smith KB0EW ___ 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] Temperature sensor
You don't want to do freezing point tests with gallium... it really likes to supercool without freezing. A gallium triple point cell is the way to go. Good reading here: http://www.nist.gov/calibrations/upload/met15-79.pdf I once built some precision temperature measurement equipment that we calibrated against an ice bath (using purified, degassed, DD water) and boiling water (pressure corrected). The devices were then sent off to one of the national labs where they did calibrations against water and gallium triple points (and who knows what else). Our cheapo calibrations agreed in the millidegree area. Their final calibration polynomial was something like a 23rd order poly... ___ 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] temperature sensor
Absolutely nothing limits the temperature of steam in air. It can easily be superheated to thousands of degrees F. However, at the water/steam interface, the steam will be exactly 100C at standard pressure as it vaporizes. Even if the water is full of dissolved matter, and has a slightly higher boiling point. When I calibrate thermometers, I always use well stirred ice water, and well stirred boiling water. I can't see getting enough dissolved matter in distilled water to make enough of a difference in the boiling point to matter to me. -Chuck Harris Attila Kinali wrote: On Mon, 21 Jul 2014 18:00:59 -0400 Chuck Harris cfhar...@erols.com wrote: Steam superheats only if the pressure is raised above standard pressure, otherwise, steam at standard pressure will be exactly 212F, or 100C. Uhm.. you are the second one claiming this. Could you please explain what physics limits the temperature of vapor? The ideal gas equation says that p*V/T = const, ie that the temperature can rise at a constant pressure, as long as the gas is allowed to expand. Attila Kinali ___ 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] temperature sensor
On Mon, Jul 21, 2014 at 5:54 PM, Bill Dailey docdai...@gmail.com wrote: You don't use ice as a reference. With ice water, the same principles apply that apply to boiling water. This is why these are convenient calibration check points. How much does the measured temperature vary between just barely boiling and a good roiling boil? Or in various locations within a pot of boiling water? It is very uniform temperature, that is after is gets to really boiling.Certainly NONE of the water is over 100C or as soon as it gets over it phase changes and released a lot of heat. I think it is just because of water's high heat of vaporization that the temperature is uniform, kind of a feedback loop. Ice water tends to be at the melting point of ice but it lacks the automatic feedback at the micro scale that boiling has. It depends on the conductivity of water and we all know there can be gradient and even that water can reach below 0C and remain liquid. -- Chris Albertson Redondo Beach, California ___ 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] temperature sensor
The maximum temperature of saturated steam temperature depends on pressure; unsaturated steam does not. At work, we just finished a project using steam at over 800F to drive a jet mill. Brent http://en.wikipedia.org/wiki/Superheated_steam On 7/21/2014 5:39 PM, Attila Kinali wrote: On Mon, 21 Jul 2014 18:00:59 -0400 Chuck Harris cfhar...@erols.com wrote: Steam superheats only if the pressure is raised above standard pressure, otherwise, steam at standard pressure will be exactly 212F, or 100C. Uhm.. you are the second one claiming this. Could you please explain what physics limits the temperature of vapor? The ideal gas equation says that p*V/T = const, ie that the temperature can rise at a constant pressure, as long as the gas is allowed to expand. Attila Kinali ___ 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] temperature sensor
Message: 4 Date: Mon, 21 Jul 2014 19:50:07 -0400 (EDT) From: ewkeh...@aol.com . As a first step I will fill one of my Tbolt boxes with small foam particles. Sounds like a good idea. Sounds like an invitation to ESD damage. Maybe dissipative foam. -- Chris Caudle ___ 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] Time in Phone System
Hi: Every phone in my house that has an LCD shows the correct date time, but I have never set any of them. I expect that there's date and time information being sent in the header of every phone call, maybe even before the first ring along with the Caller ID info. Where to get technical details on the data format/protocol? -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html ___ 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] Time in Phone System
Yes, the caller ID data has time in it. There are chips out there that decode caller ID. I signaling format isially is the old Bell 202 modem protocol. The caller ID devices sort of half way answer the phone line when it detects the incoming call and the caller ID info is sent after the first ring. ___ 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.
