[time-nuts] temperature sensor

Bob Camp kb8tq at n1k.org
Tue Jul 22 01:30:39 UTC 2014


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.chris at 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 <brooke at 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 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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>> 
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> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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