I previously posted on my first effort building the first complete sensor from OSBSS, a long-term battery powered temperature and relative humidity data logger (revision 09 30 2014), as well as about a week’s worth of data sampling at 1-minute intervals in my office and co-located next to an Onset HOBO U12. Just to test the battery life and clock drift, I’ve left it running since late September until yesterday (December 10, 2014), logging at 1-minute intervals in my office for a period of about 73 days. The sensor and data logger are still functioning normally even at this high resolution of data collection and powered only by AA batteries! The clock appears to have drifted minimally (maybe 5 seconds, although I can’t confirm that). See below!

My office, by the way, is in Alumni Memorial Hall, a 1946 Mies van der Rohe building, with large south-facing glazing (single glaze), steel frame, and brick wall. It has a radiator on which I can control the flow of steam, as well as a central forced air cooling system. You can see a huge fluctuation in both temperature in this relatively poorly controlled office — temperatures dropped as low as 15C (59F) and reached as high as 35C (95F). Similarly, RH has oscillated between 10% and 70% over the last 73 days, with a general downward trend that reflects trends in outdoor relative and absolute humidity.