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Quick Q about Thermometers

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  • slacker75@hotmail.com
    Hi, Just wondering... I have 2 12 long thermometers, and they both read temps. within about a degree of each other for most of the range, but when i put the
    Message 1 of 5 , Oct 2, 2001
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      Hi,
      Just wondering... I have 2 12" long thermometers, and they both
      read temps. within about a degree of each other for most of the
      range, but when i put the bulbs in boiling water, one reads 99C, the
      other 96C. I would have expected them to be a 1 degree or so out,
      but 96C? Does it matter how much of the thermometer is exposed to
      the air? I know its the CONSISTENCY that matters, but this test
      would seem to suggest that ONE of them ISN'T consistant.
      (Incedentally, the one that read 96C was more expensive than the one
      that reads 99C!)

      -Tone
    • slacker75@hotmail.com
      ... Just had a thought... (I know, I know, I m replying to my own posts again...!) But I live at about 250m above sea level. I assume I d need to take the
      Message 2 of 5 , Oct 2, 2001
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        >one reads 99C, the other 96C.

        Just had a thought... (I know, I know, I'm replying to my own posts
        again...!) But I live at about 250m above sea level. I assume I'd
        need to take the lower boiling point of water into account when I
        test the thermometers accuracy? How much lower will the BP of water
        be?

        Thanks
        -Tone
      • Ackland, Tony (CALNZAS)
        Tone - I doubt that its the cause, but a better factor rather than altitude is the barometric pressure at the time.. http://biggreenegg.com/boilingPoint.htm
        Message 3 of 5 , Oct 2, 2001
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          Tone - I doubt that its the cause, but a better factor rather than altitude
          is the barometric pressure at the time..

          http://biggreenegg.com/boilingPoint.htm


          Tony
        • Dick
          In message , slacker75@hotmail.com writes ... I ve just had a similar problem, the old faithfull thermometer (country of origin
          Message 4 of 5 , Oct 3, 2001
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            In message <9pdfvl+djik@...>, slacker75@... writes
            > Hi,
            >   Just wondering... I have 2 12" long thermometers, and they both
            > read temps. within about a degree of each other for most of the
            > range, but when i put the bulbs in boiling water, one reads 99C, the
            > other 96C.  I would have expected them to be a 1 degree or so out,
            > but 96C?  Does it matter how much of the thermometer is exposed to
            > the air?  I know its the CONSISTENCY that matters, but this test
            > would seem to suggest that ONE of them ISN'T consistant. 
            > (Incedentally, the one that read 96C was more expensive than the one
            > that reads 99C!)
            >
            I've just had a similar problem, the 'old faithfull' thermometer (country
            of origin unknown, accuracy unknown !) readings were up to 4-5 deg
            different from the digital thermometer (battery flat ?). Solution - go out to the
            local lab equipment supplier and buy a thermometer of known provenance,
            in my case BS1704 (British Standard), known UK manufacturer & marked
            accuracy - brand new & unused cost me £2 from his obsolete stock shelf. If
            you suspect a thermometer I suggest changing it for one with at least some
            form of national standard mark on it, all lab standard thermometers I looked
            at were also marked up with a range, accuracy and required immersion (e.g.
            G.P.105C/1.0/Total).

            For absolute accuracy the amount you immerse a thermometer in
            hot liquid/vapour can also effect the reading (I'm not sure by how much & if
            this applies to all types of thermometer) - some thermometers have a line
            marked round them to indicate how far you push them in.

            If still not happy then you can buy thermometers with a calibration
            chart - but it'll cost you !!!!!! Hope the info is of some use.
            --
            Dick
            Fra' Auld Reekie
          • slacker75@hotmail.com
            Dick, ... The one that read 96C (Made in France) says Total Immersion , whereas the other (made in England) just says Immersion . I m currently testing my
            Message 5 of 5 , Oct 4, 2001
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              Dick,

              > For absolute accuracy the amount you immerse a thermometer in
              > hot liquid/vapour can also effect the reading (I'm not sure by how
              > much & if this applies to all types of thermometer) - some
              > thermometers have a line marked round them to indicate how far you
              > push them in.

              The one that read 96C (Made in France) says 'Total Immersion',
              whereas the other (made in England) just says 'Immersion'. I'm
              currently testing my still, so if I find these two to be a problem,
              I'll take a leaf from your book and get a 'proper' one!

              -Tone
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