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Subject: Re: Calibrated Thermometers




"Nicholas O. Lindan" wrote in message
news:Rt58g.508$x4.183@newsread3.news.pas.earthlink.net...
> On Mon, 08 May 2006 19:11:05 -0400, "Greg "_""
> posited:
>
>>? Thoughts [calibrating/ed thermometers ????]
>
> You can always stick it up your a---. Should
> be 98.6 +-.
>
> Fever thermometers are accurate to +- .2 degrees
> and make good calibration standards: put both
> thermomters in hot water in a styrofoam cup -
> keep the water gently stirred.
>
> Only color photography is sensitive to
> temperature, and that gets processed at 100
> same as body temperature: they are both organic
> chemistry.
>
> B&W is a +-2 F game, and you only need
> to have a repeatable temperature and the ability
> to read the deviation to +-10%. A grossly
> inaccurate thermometer will do as long as
> it is linear.
>
> Temperature calibration is tough to do with
> great accuracy. A triple-point ice cell is
> the only common temperature reference.
>
> http://www.its-90.com/wtpguide.html
> http://www.omega.com/ppt/pptsc.asp?ref=TRCIII&Nav=temk03
>
> If you would rather have someone else calibrate your
> thermometer:
>
> http://www.omega.com/toc_asp/frameset.html?book=Temperature&file=INTRO_GLASS_THERM
>
> Or buy a 'Kodak Color Thermometer' or 'Kodak Process
> Thermometer' on
> ebay and be as Alfred E. Neumann: "What, me worry?"
>
> --
> Nicholas O. Lindan, Cleveland, Ohio
> Consulting Engineer: Electronics, Photonics, Informatics.
> Remove blanks to reply: n o lindan at ix . netcom . com
> f-Stop enlarging timers: http://www.nolindan.com/da/fstop/
>
B&W needs better than +/- 2F for good control. Look at
the temperature increments on the Kodak developing charts,
they are 2F and the time difference is significant.
For B&W time can be adjusted to comensate for temperature
to a greater extent than in color. One reason that color is
so sensitive is the difference in induction time of the
various layers. At a fixed temperature a particular
developer affects all the layers in a predictable way. Color
can be done at lower than 100F but usually the developer
needs some change. 100F was chosen mostly for speed of
processing since most color film is processed in automatic
machines.
Last time I looked body temp was 98.6F.
I agree entirely about accurate calibration of
thermometers, its not a trivial process. I did this as a
project in a physics lab at college back when the dinosaures
roamed.


--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com



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