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Thread: Thermometers

  1. #31

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    > On this side of the pond, the ideal would be to obtain a thermometer
    > certified by the NBS (National Bureau of Standards)

    In case you didn't know, NBS has been NIST (National Institute of Standards and Technology - mentioned in some of the earlier posts) since the late 1980s.


    - Phong

  2. #32

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    Quote Originally Posted by Phong
    > On this side of the pond, the ideal would be to obtain a thermometer
    > certified by the NBS (National Bureau of Standards)

    In case you didn't know, NBS has been NIST (National Institute of Standards and Technology - mentioned in some of the earlier posts) since the late 1980s.


    - Phong
    LOL Figures, been longer than that since I had to deal with them. But then I still remember the Atomic Energy Commission and Bureau of Biologicals. Thanks for the 'old' update.
    Mike C

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  3. #33

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    I vote for the kodak glass thermometer.

  4. #34

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    I must say the thought that a mercury thermometer enclosed in etched glass
    being able to go out of calibration to be very surprising news that I find hard to fathom.

    How could this happen?
    Claire (Ms Anne Thrope is in the darkroom)

  5. #35
    Brian Jeffery's Avatar
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    Hi all,

    thanks for your input.

    I must admit that I agree with your comments in that it's not accuracy that's most important, but consistency. That' was my reasoning for going for a digital thermometer as I'm less likely to break it. However, the Kodak thermometer that was mentioned in many posts looks just the ticket as it is housed in a metal sleeve.

    A couple of points though. When trying to ascertain the best development time for a particular film/developer combination it is probably advisable to start of with the manufacturer’s development times. However, if you’re working with a thermometer that's two degrees out you are going to under/over developing your film by nearly 20%. It'll definitely make things harder Hence it’ll be good to get a reasonably accurate thermometer.

    As to the resolution/accuracy debate. In a previous existence I was an electronics engineer and it was a common misconception that because a particular digital meter had three decimal places it was more accurate than a meter with two decimal places. It may or may not be, it depends on the quality of the meter and whether or not it's been calibrated.

    Another misconception was that a digital meter was always more accurate than an analogue one. Again, it depends on the meter.

    Anyway, I've managed to purchase a Kodak Processor Thermometer Type 3 for £5 (including postage) of Ebay. So with a bit of luck this will be my work horse for the next x years.



    Thanks again,

    Brian

  6. #36

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    Quote Originally Posted by Claire Senft
    I must say the thought that a mercury thermometer enclosed in etched glass
    being able to go out of calibration to be very surprising news that I find hard to fathom.

    How could this happen?
    Dear Claire,

    Puzzles me too.

    Cheers,

    R.

  7. #37
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    Surprising as it sounds, I've heard stories that mercury has the ability to wick through glass, very slowly. This may account for a glass thermometer getting out of calibration in it's grizzled old age.
    Gary Beasley

  8. #38
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    I have my dad's mercury in glass thermometer (Kodak, I guess...I haven't looked at it in years), but the mercury separated from itself, i.e. it's in segments. Is that common? Is there a simple fix? I'd love to use it if it were usable once again. (It must be 60+ years old.)
    John Voss

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  9. #39
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    You have to heat the theremometer enough that the mercury column rises all the way to the top and then some, forcing the bubbles together at the top. On cooling the column will retreat as on piece. Needless to say you need to be very careful not to overheat and break the thermometer in the process. Storing the thermometer in an upright position will help prevent this from recurring.
    Gary Beasley

  10. #40
    jovo's Avatar
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    Quote Originally Posted by glbeas
    You have to heat the theremometer enough that the mercury column rises all the way to the top and then some, forcing the bubbles together at the top. On cooling the column will retreat as on piece. Needless to say you need to be very careful not to overheat and break the thermometer in the process. Storing the thermometer in an upright position will help prevent this from recurring.

    Thanks, Gary...I'll try that. It'd be great to use that piece of family antiquity again.
    John Voss

    My Blog

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