Temperature measurement experiment by 2mo042


									              Experiment: Temperature Measurements
1.   Fabricate a thermocouple; acquire a 1N4148 silicon diode and 143-502LAG-RC1
     thermistor. For all measurements put the reference junction of the thermocouple in ice
     water at 0.0 C. (Where do you get ice?) In your writeup, state why you chose the
     thermocouple type you chose. Reference: the Omega Temperature Measurement and
     Control Handbook. It is claimed that the voltage required to source a fixed current through
     the 1N4148 diode is a very linear function of the temperature of the diode.

2.   Establish constant temperature baths at 0 C, -35.6 C, and -78 C. (To get good thermal
     contact between your bath and your reaction flask, the bath must contain a liquid phase.
     and water ice are available in the Department; dry ice you have to get from the Chemistry
     Stockroom. Each will require the use of a small Dewar, available in the OEML. Learn
     what you have to do to get set up for an account to purchase LN2. (Hint: start by
     requesting access from the Physics Department web site: http://www.physics.utah.edu/).

3.   Measure the voltages required to source 1 mA into the silicon diode at 0.0 C and -78 C.
     Fit the data to a straight line. Generate an equation for converting the voltage required to
     source 1 mA to temperature. Actually two equations: one for centigrade and one for

4.   Measure the thermocouple output voltages, thermistor resistances and silicon source
     voltages at -35.6 C, 77 K and the boiling point of water. Convert each to temperature.
     When possible, check with a mercury thermometer. Be careful not to break the
     thermometer. If you do, you must vacuum up all the larger pieces of mercury with the
     “vacuum cleaner” in JFB 331 and sequester the rest with sulfur powder.

5.   Measure the boiling point of water in Salt Lake City as many ways as you can. Calculate
     the boiling point of water in Salt Lake City. Determine the boiling point of nitrogen and
     helium in Salt Lake City.

6.   Write a report discussing what you learned about the accuracy, precision and utility of
     various thermometric techniques. Include a description of exactly how you go about
     purchasing the materials you need and how you dispose of them when you are finished.

7.   References:
     Omega Temperature Measurement and Control Handbook/Catalog
     Handout: Slush Bath Temperatures
     CRC Handbook of Physics and Chemistry

8.   What we give you:
     Dewar flasks and stirring sticks
     Thermocouple wire, welder and spaghetti
     Current supply and DVMs
     Chemical catalogs (Stockroom)
     Chemistry stockroom credit card and map to find it

9.   What you have to figure out or build for yourself:
     Weld up your own thermocouple with the TC welder
     Connect the various parts to source 1 mA into the diode and read the voltage required to do
     it. Start by figuring out which way the diode conducts.
     Where to order or otherwise obtain the chemicals you need make the slurry baths you need
     to establish the required temperatures. Explaining how to do the acquisition will be part of
     your writeup, but we will supply the actual chemicals except dry ice and... “wet ice”???
     frozen water, regular ice, plain old ice??? How do you distinguish plain old frozen water,
     H2O(s), from dry ice or any other kind?
     What liquid will you use to conduct heat and establish a uniform temperature at -78 C?
     Why did you choose this one?

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