Tags: labview · lego · temperature · thermometer
We set out to put the new Dexter Industries Thermometers through trials. How accurate is it? How quickly does it respond to temperature changes? What kind of resolution do we get with it? Just how good is the thermometer?
First, Brian Davis wrote a great blog entry about the Lego thermometers and a really nice analysis of their performance. His entry gives a great baseline for comparison of the hardware already on the market . . .
For most of the experiments, we used water . . . it cools with ice cubes and heats on a hotplate. It also offers a pretty even temperature throughout the beaker it’s in. But we wanted to test the thermometer through a larger range of temperatures, above boiling point, to determine how it behaves. So past about 80 Celsius, we switched to oil as a heating medium. We always used a stirbar to keep the liquid the same temperature throughout (no thermal pockets or temperature gradients). In the accuracy experiments, we checked our accuracy with a mercury thermometer. The mercury thermometer gives a precision of about 0.5 Degrees C.
In NXT-G, the average delta, or error, was -0.28 C. In Labview, the average error was about -0.498.
Resolution: How precise can we be? We went about calculating resolution in two ways: theoretical and experimental. Because of the nature of the thermomister in the thermometers, the resolution varies over the range of measured temperatures. The thermometer should become more precise in the middle (higher resolution), between 0 C and 100 C, and begin to lose resolution outside that range.
Room for Improvement:
While the analog thermometers are reasonably accurate for work between 0 and 100 Celsius, at the edges of this range, it becomes less precise. What can we do about it?
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