You don't use ice as a reference. With ice water, the same principles apply that apply to boiling water. This is why these are convenient calibration check points.
Sent from mobile > On Jul 21, 2014, at 3:51 PM, jim s <[email protected]> wrote: > > >> On 7/21/2014 11:36 AM, Hal Murray wrote: >> [email protected] said: >>> >Ice water and boiling water coupled with altitude will give you two points. >> Has anybody used a good thermometer to measure air pressure? >> >> How much does the measured temperature vary between just barely boiling and a >> good roiling boil? Or in various locations within a pot of boiling water? > When you are dealing with water phase changes, you are dealing with both > temperature and heat. When you get up to a point like boiling, you have a > mass of water which is at the local boiling point and the only thing stopping > the water from going to steam phase is the amount of heat in the water. Once > a pot of water is at rolling boil all of the water in the pan should be at > and stay at the boiling point till it is all gone. > > Once you remove the heat, the boiling will slow and stop, and the temperature > will begin to fall as the water loses the heat. > > As long as you maintain a balance between having the sensor too close to the > point you are applying heat, and keeping it immersed in boiling water, you > should be able to assume the local boiling point. That boiling point has to > be adjusted for pressure, which affects the temp the most. Also assuming > only water, and no other contaminants as mentioned by another poster. > > The same sort of action occurs when water freezes, along with some other > oddball issues with the crystalization. You can arrive at the freezing > point, and you will dwell there for some time as the water loses its heat and > becomes solid. > > The thing that is different between freezing and boiling is that as long as > you have water and are boiling the temperature will remain at boiling, and no > higher. > > With freezing, if you are measuring water as you cool it and remove heat, it > will go thru freezing with a pause as it goes to ice, then it can continue to > cool as cold as you like. > > so when you are measuring by using ice as a reference, you should have frozen > the sensor or drilled it into the center of a block of ice, and let it come > to equilibrium in the ice w/o any freezing apparatus being active. It should > come to the freezing point till all of the ice melts. > > Jim > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
