I took delivery of another batch of 2xDS1822+PAR and 2xDS1822+ temperature sensors in the week, bringing to total up to eight. The parts are probably around £2 a piece from a specialist supplier. Maxim only quote price per thousand. I've wired them to the test rig, in parallel with the previous sensors and completed a three day test to check operation.  The sensors offer good resolution, but the precision of the parts does not seem to be fantastic, variations of almost a degree over the set (see chart below). It seems that humans can detect a one-degree difference - I know a system that hunts with a half a degree dead-band around target. A simple regression (over 86,856 points, approx 10,000 per part) should allow adequate calibration, i.e. determine a0 and a1 from tactual = a0 + a1*tsensor for each sensor. For tactual I will use the mean, I have no other reference :-(  Charting thanks to KDB Studio + kx Systems q evaluation. |