[time-nuts] quartz thermometers

ken hartman ken at hartmans.org
Sat Mar 12 10:51:56 EST 2016


I believe - if I understand correctly - that Magnus refers to realizations
based on what has been referred to as "the Schodowski patent"

Dual mode quartz thermometric sensing device
<https://scholar.google.com/citations?view_op=view_citation&hl=en&user=tVnR8zIAAAAJ&citation_for_view=tVnR8zIAAAAJ:u-x6o8ySG0sC>
SS Schodowski
US Patent 4,872,765

as referenced here:

Resonator self-temperature-sensing using a dual-harmonic-mode crystal
oscillator
<https://scholar.google.com/citations?view_op=view_citation&hl=en&user=tVnR8zIAAAAJ&citation_for_view=tVnR8zIAAAAJ:u5HHmVD_uO8C>
SS Schodowski
Frequency Control, 1989., Proceedings of the 43rd Annual Symposium on, 2-7

Not easy to do, but truly a measure of resonator temperature variations.





On Sat, Mar 12, 2016 at 7:33 AM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> Hi,
>
> For the 10811 you can modify it to change mode and then use that mode to
> measure and trim the temperature oven.
>
> There exists crystal oscillators where the 10 MHz is a traditional SC-cut
> mode and then a 30 MHz mode is exercised which measures the crystal
> temperature. In the Microprocessor Controlled Crystal Oscillator (MCXO) one
> then measure the difference in frequency and uses this to re-synthesize a
> correction on the 10 MHz. The benefit is that it is the temperature of the
> oscillating crystal that is being measured.
> Naturally, it could be used for oven control and/or EFC control too.
>
> The MCXOs exists in manufacturing, but whenever you ask about them they
> just wonder what military project are you working on.
>
> I'd love to experiment with this form of temperature sensing one day, when
> I have time... if that ever happens...
>
> Cheers,
> Magnus
>
>
> On 03/12/2016 10:21 AM, ken hartman wrote:
>
>> Interestingly, the use of AC-cut crystals (high linear tempco of
>> frequency)
>> is found in the development of OCXOs. Using a reference AC-cut resonator -
>> in place of the final AT/SC resonator - one can learn much about the
>> thermal  characteristics of the oven loop performance. While not a precise
>> temp sensor, it is a high sensitivity  indicator of  temperature
>> variations
>> of the resonator.
>>
>> On Fri, Mar 11, 2016 at 11:44 PM, Bill Hawkins <bill.iaxs at pobox.com>
>> wrote:
>>
>> It may be that the need for that kind of resolution died out.
>>>
>>> The next step up from quartz thermometry is resistance thermometry.
>>> The linearization equation for platinum has enough terms to make it
>>> uncertain around .01 C.
>>> Temperature calibration baths usually use platinum resistance sensors.
>>>
>>> It may be that the triple point of water does not have the certainty to
>>> reach '0.0001C'
>>>
>>> Disclaimer: I only worked with industrial sensors from Rosemount, Inc.
>>> as an employee.
>>>
>>> Bill Hawkins
>>>
>>>
>>> -----Original Message-----
>>> From: Alan Ambrose
>>> Sent: Friday, March 11, 2016 11:42 AM
>>>
>>> Hi,
>>>
>>> I hope this is still relevant and not too off-topic...but since it
>>> involves crystals and tempco...
>>>
>>> Quartz thermometers (e.g. the HP 2804A) with their 'linear cut' crystals
>>> and '0.0001C resolution' seem to have been a thing from the mid-60's to
>>> the mid-80's:
>>>
>>> http://www.hparchive.com/Journals/HPJ-1965-03.pdf
>>>
>>> There still appear to be some manufacturers making the crystals:
>>>
>>> http://www.statek.com/products/pdf/Temp%20Sensor%2010162%20Rev%20B.pdf
>>>
>>> Anyone know why they died out? Did a better technology replace them?
>>>
>>> TIA, Alan
>>>
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