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Subject: Re: Calibrated Thermometers




"Pieter Litchfield" wrote

> If I put the thermometer in a glass of water full of ice cubes, should it
> not read 32 degees F (or 0 degrees C)?

No.
Try it.

Read:
http://www.its-90.com/wtpguide.html

The short form is:

o The ice is melting in the water so the water must be
above freezing.

Ergo, the water is > 32F

o The ice that has not melted is below freezing. If
cold enough it will freeze the water. For water to freeze
it must be supercooled.

Ergo, the water is < 32F

At some time in the process the water may pass through 32F.

When demonstrated by the 7th grade science teacher cold ice
(<32F) is added to the mix as the teacher stirs and peers at
the thermometer. When enough ice has been added for the
thermometer to pass through 32F the teacher promptly announces
success and tosses the mixture in the sink. If the teacher
had kept going and the the water was pure enough and well
polished with no air in it and the ice cold enough the water
can get as cold as -40F/C.

> I can't use boiling water. Are there any other useful points? I would
> think that if there is a way of setting the calibration near 68 degrees F
> to 75 degreesF

To do this you need a known good thermometer to know that the
water bath is at 68F so the questionable thermometer can be read
to determine it's error.



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