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  1. #31

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    The Kodak Process Thermometers are readily available, and are a great calibration standard for the home. Technically illegal to ship by USPS, however. (HazMat.) At least be sure the shipper puts a lot of plastic bags around it, so it doesn't drip if it breaks. (The USPS won't have a good sense of humor about Mercury dripping out of a package.)

    The Weston "Miroband" dial thermometers are readily calibrated against one, they have the nut to turn the shaft with.

  2. #32
    Mainecoonmaniac's Avatar
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    I thought digital thermometers were always accurate and more accurate than dial thermometers. I guess this case cleared any misconceptions on digital thermometers. I have a spirit type glass thermometer that I know is accurate to verify my dial thermometers. Don't like to use my glass one because I know I'll break it

  3. #33

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    They can be more accurate but they do need to be cabibrated regularly, as does any thermometer, no thermometer holds its calibration forever digital or traditional.

  4. #34

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    Overnight my trusty long-column alcohol thermometer suddenly lost ONE whole Celsius degree. I was processing at 19°C without knowing it (of course my negs were a bit thin).

    I had to check it against another tiny throwaway thermometer to realize what happened. Now I process my TRI-X at 21-sth and it seems to work.

    So YES, buy two identical thermometers and check one against the other regularly.

  5. #35
    greybeard's Avatar
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    Ummmmm....buy three. If you have two, they will probably never agree, and you won't know which one is wrong. If you have three, you can at least find the majority opinion

    Actually, if you have one unbroken, etched-stem liquid-filled thermometer, you are all set. There is practically nothing that you can do to one of these to change its inherent calibration more than a tiny fraction of a degree, and even the immersion depth correction is usually negligible.

    It is the type which has a cardboard scale glued to the thermometer inside a housing that are really problematic. If you are lucky, the cardboard falls off completely rather than shifting lengthwise slightly.

    Your reference thermometer doesn't even have to be all that accurate (in the sense of indicating temperature with respect to absolute zero) as long as the reading precision will let you see an error of a degree or so.

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