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. TO ACCURATELY ESTABLISH A TEMPERATURE, HOW MANY DEGREES OF FREEDOM MUST YOU FIX AND HOW MANY PHASES MUST BE PRESENT?) LN2 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 Kelvin. 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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