I made a homemade psychrometer to try to figure out the humidity in the classroom. I got instructions here but wasn’t 100% sure of a few details so to try to get a little more data I used two different sets of thermometers. The results? Indeterminate. Each one gave me different readings. It was a little hard to get readings at all because the scale provided with the directions did not include temperatures as high as those in my classroom (it was over 105 Fahrenheit in the only spot in the room where I could plug in the fan, set up the clipboard, etc.), so I had to turn to an on-line calculator that could go higher. It’s possible that one of my two hygrometers was actually correct, as it was reading around 40% (the other one’s needle is clearly broken; it now swings freely), which, while vastly different most days from the humidity for the zip code provided by the Weather Underground, wasn’t that far from some of my psychrometer results. Could my room really be that much less humid than the outside air, as a result of the way we are heated and other factors? Anyway, FOSS is sending me two new ones so we’ll see what happens when those arrive (cross your fingers that it’s soon).