[time-nuts] temperature sensor

Alan Melia alan.melia at btinternet.com
Mon Jul 21 17:58:49 EDT 2014


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" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at 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 water....steam. Water's boiling point is affected by the 
>> dissolved gasses and other contaminants.
>>
>> Alan
>> G3NYK
>> ----- Original Message ----- From: "Bill Dailey" <docdailey at gmail.com>
>> To: "Discussion of precise time and frequency measurement" 
>> <time-nuts at 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 <attila at kinali.ch> wrote:
>>>>
>>>> On Mon, 21 Jul 2014 04:39:51 -0700
>>>> Alexander Pummer <alexpcs at 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
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