Very good information on resistors. I already knew most of it, but there were a couple that I haven't heard of. One thing I didn't see was Positive Temperature Coefficients vs Negative Temperature Coefficients, or PTC vs NTC. It turns out, you can use both for a sensor to carefully to compensate for temperature changes over a fairly large temperature range.
Also as sensors, resistors, and other components age, they tend to change. This is why a good manual or automatic calibration is important to have.