Is Ice water a constant temperature?

scottiebabe over 2 years ago

Soft 404

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Andrew J over 2 years ago +3

Graphs always make results look rubbish. Look at the slope on that! The accuracy is great though - serendipitously, these were the thermistors I picked for my project. My bet is no, it isn't. I don't…
scottiebabe over 2 years ago in reply to Andrew J +3

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wolfgangfriedrich over 2 years ago +2

Ha, I also used ice water as an experiment when road-testing the Pico Datalogger with k-type thermocouples. It was far from constant, but all in plausible range. I did not think about stirring, but noticed…

0 scottiebabe over 2 years ago

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0 dougw over 2 years ago in reply to scottiebabe

I always wondered why ice cubes in water don't grow bigger. Maybe its because thermal conductivity of water is higher than ice.
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0 Andrew J over 2 years ago in reply to scottiebabe

Cool! Excuse the pun. Even in the flask, that lasted longer than I thought it would.
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0 scottiebabe over 2 years ago in reply to Andrew J

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0 scottiebabe over 2 years ago in reply to scottiebabe

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0 Andrew J over 2 years ago in reply to scottiebabe

If a pool noodle is what I think it is (it isn't a common expression in the UK!), foam-based floating support, then I'd think it would make an excellent insulator with all the air trapped in it. That was a good experiment and I'm surprised to see that ambient warms to such a degree - 1.34W seems like a lot. I know of some transistors that wouldn't hold up as well as that ice.
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0 scottiebabe over 2 years ago in reply to Andrew J

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0 Andrew J over 2 years ago in reply to scottiebabe

It's easy to forget that the air pockets make for a large surface area. Your graph, for the 4 degree point looks fairly linear - was it like that all the way? If not your thermal resistance is just a snapshot in time isn't it? There is another option: most domestic fridges are set at around 4 degrees (perhaps 5) but it may not be clear or exact (mine has a circular knob that can move between "cool" and "eco" but without degree C markings.) However, it should be constant as long as you don't keep opening the door. If you can measure from within there - e.g. stuff your DMM, thermistor and flask in the fridge then ambient would be controlled - you could also use a second thermistor to measure how constant that fridge ambient was (how much hysteresis does it exhibit?): you could verify that thermal resistance!

If nothing else, these are 'outside of the box' experiments with thermistors and good fun.
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0 scottiebabe over 2 years ago in reply to Andrew J

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0 Jan Cumps over 2 years ago in reply to scottiebabe

scottiebabe said:
LM399

Continuing on the tangent: I have a Keithley DMM6500 with an LT SL40057 reference. Rumours say it's an LM399 subset for (selected by) Keithley.

image: blurry photo from my device
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