Hi The way it was spec’d by HP, there was no allowance for hysteresis. They also had some issues with probe drift / calibration costs. They apparently decided to drop the product rather than update it.
Bob On Dec 9, 2013, at 9:41 AM, Azelio Boriani <[email protected]> wrote: > Is the hysteresis related to the retrace effect? If so, then I think > that the quartz thermometer may be succesfully used where the > tenperature has only small variations. > > On Mon, Dec 9, 2013 at 3:12 PM, Daniel Mendes <[email protected]> wrote: >> >> It´s still used in the oil industry as "the standard" for temp and pressure >> monitoring... >> >> Daniel >> >> Em 09/12/2013 10:28, Bob Camp escreveu: >> >>> Hi >>> >>> The Quartz Thermometer died when somebody proved that hysteresis was a big >>> deal on the probes. >>> >>> Bob >>> >>> On Dec 8, 2013, at 11:22 PM, Tim Shoppa <[email protected]> wrote: >>> >>>> Interestingly, HP for a long time sold"quartz thermometers" based around >>>> a >>>> probe with a quartz crystal with a well characterized linear temperature >>>> coefficient. They called the crystal cut "LC" (Linear Coefficient): >>>> >>>> http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1965-03.pdf >>>> >>>> http://en.wikipedia.org/wiki/Quartz_thermometer >>>> >>>> >>>> On Sun, Dec 8, 2013 at 10:55 PM, Neville Michie <[email protected]> >>>> wrote: >>>> >>>>> Hi, >>>>> I use a HP3468A multimeter to measure a PT100 platinum resistance >>>>> thermometer. It gives me resolution of one mK, but calibration is >>>>> another >>>>> matter. >>>>> It is best to use a 4 terminal device, but 2 terminal into the 4 >>>>> terminal >>>>> input works well. Thermoelectric effects and the requirement for 1 >>>>> microvolt stability >>>>> makes wiring them into your own circuit difficult. One of the great >>>>> technical difficulties is to get a resistor to compare them against, it >>>>> must be very stable, >>>>> have no thermoelectric effects and have a temperature coefficient in the >>>>> order of one PPM. I always admire the way HP designed their ohm meters. >>>>> There are other issues, however. Whereas a volt meter can connect >>>>> perfectly to a reference, a PRT can only report its own temperature. >>>>> That is no problem when you are working in a well stirred water bath, >>>>> that >>>>> will have the PRT at the same temperature as the object in the same >>>>> bath. >>>>> When you get to measure air temperature you are into serious sampling >>>>> errors, the PRT has some self heating and so is air velocity sensitive, >>>>> and >>>>> the air >>>>> you are measuring may not be the same air as is over your OCXO or item >>>>> of >>>>> interest. There is a personal plume of warm air rising from an observer, >>>>> so >>>>> you must be careful with your measurement technique. >>>>> The same problems occur with quartz crystal thermometers, which is why >>>>> they are not more commonly found in surplus. >>>>> A PT100 sensor is quite cheap, and their calibration is little short of >>>>> brilliant. However a they would cost much more if their calibration is >>>>> traceable. >>>>> For my use, I use an ice-point cell as a calibration check, with care >>>>> you >>>>> get 10mK accuracy. You only need the knowledge how to set it up, a >>>>> blender >>>>> to make ice slush, >>>>> and a picnic vacuum flask, to make your own calibration reference. >>>>> I use thermistors for air measurement, and calibrate them against the >>>>> PT100 in a thermostatic water bath. Thermistors can be run with a very >>>>> low >>>>> level of self heating and they are very sensitive, their resistance >>>>> changes 4% per Centigrade degree, and they come in high values like 100K >>>>> ohm. You read >>>>> them in a bridge circuit with a voltmeter, so they are many orders of >>>>> magnitude easier to use than a 100 ohm PRT. >>>>> They are made small enough to get them in close contact >>>>> with the object to be measured. >>>>> If you want to know about humidity measurement I can tell you much about >>>>> that, >>>>> cheers, >>>>> Neville Michie >>>>> >>>>> On 08/12/2013, at 12:40 PM, Mark Spencer wrote: >>>>> >>>>>> Sorry if this is somewhat off topic, but I'd be interested in more >>>>> >>>>> details re precision temperature measurement devices. Have been using >>>>> an >>>>> inexpensive USB temperature sensor for the last year or so to monitor >>>>> the >>>>> temperature in my lab and have been looking at the correlation between >>>>> frequency shifts in some ocxo's vs temperature changes. I should also >>>>> start taking humidity measurements as well at some point. >>>>>> >>>>>> >>>>>> Any pointers re suitable instruments to accomplish this that can be >>>>> >>>>> sourced via the usual surplus sources would be welcome. >>>>>> >>>>>> Thanks in advance >>>>>> Mark Spencer >>>>>> >>>>>> Sent from my iPad >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>> >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>> >>>>>> and follow the instructions there. >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
