I've been using digital thermometers to measure *film* developing chemistry for about 15 years. I have two "Tru Temp" thermometers that are supposed to be accurate to +/- 1 degree and are fast read (100ms refresh).
Anyhow I decided to treat myself and buy a Kintrex IR digital infrared thermometer for both photography and cooking (testing evenness of saute pans, etc). The IR thermometer is supposed to be extremely accurate (+/- 2 degrees). However, when I take an (opaque) cup of water and measure it with all three thermometers get THREE different readings. Even the two of the same brand with brand new batteries are degrees off. The IR thermometer is 5 degrees off from the mean difference of those two!
Anyhow, the question is- does anyone use IR thermometers for measuring chemistry- if so, how accurate have they been for you? Is it worth it? I don't want to screw the pooch on a spreadsheet I've been keeping for 10+ years with development times and temperatures. I understand analog thermometers could potentially be more accurate but they don't have the level of resolution I'm seeking (+/- a degree or two).