favorite temp sensors

Apr 12, 2013 125 Replies

ot a propellor-on-a-shaft type stirrer, you can stir the contents of your D ewar flask easily enough, but most places I've been rely on Teflon coated m agnets spun by an external magnetic field, and those are hard to get spinni ng in a Dewar flask.

beaker lasts for quite a while.

My probe is 'open to the elements', in direct contact with the water.

George H.

The last tap water I measure had a conductivity of 300 usiemens/cm, which i s high enough to be signifcant.

De-ionised water is a couple of orders of magnitude better, but atmospheric CO2 dissolves in it to give you more ions than you'd expect from a pH of 7 .

I don't know how much the dissolved salts in tap-water lower the melting po int.

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includes a discussion of more subtle influences, such as atmospheric pressu re and isotope levels.

Bill Sloman, Sydney

:

is high enough to be significant.

ic CO2 dissolves in it to give you more ions than you'd expect from a pH of 7.

point.

It looks as if freezing point depression in water is about -1.86K per mole.

Tap water seems to have anything from 0.001 to 0.003 moles of dissolved sal ts - mostly magnesium and calcium carbonates - which would depress the free zing point by between 2 and 5mK.

Bill Sloman, Sydney

:

is high enough to be signifcant.

ic CO2 dissolves in it to give you more ions than you'd expect from a pH of 7.

point.

sure and isotope levels.

Yeah I was thinking that maybe if I poured some liquid nitrogen into a dewar with DI water in the bottom, that I could make a DI ice/water bath. Hmm maybe just supermarket distilled water would work.

George H.

Volume of a liquid with indication amplification by a capillary tube. Differential expansion of two solid materials bonded together, often amplified with a spiral construction. Differential densities of specific gas-liquid volumes in slightly deformable envelopes "floated" in another liquid.

Any of these jog any memories?

?-)

Johnson Noise Thermometer

Bragg reflector fiber - grating line spacing varies with temperature.

Quartz Thermometer

There are many. What problem are you solving?

Joe Gwinn

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