howdy555@xxxxxxxxx wrote: >> It may be interesting to obtain the temperature from this sensor along with >> each reading, and to graph the temperature as well in order to identify a >> potential correlation. > If only there was a way of obtaining this info. (If it would Graeme needs to answer this - I'm not sure whether he is aware how to access the temperature sensor in the gadget he had mentioned. > be of any help: my room was approximately 23-24 degrees Celsius). Then we > could have a corelation and a possibility of > improving the results! I however think that it would be much easier to just > let it measure the same white spot (as the measurements are the fastest) and > wait until it stabilises. The only question is: how do we know that it has > actually stabilised. Hmm, is it really an option to wait until it has stabilized, if this takes about 1..2 hours? I think I would not be so patient :-) [And is it really worth to spend so much time if the drift in these 2 hours is only about 3%?] If one does not care about the accuracy of the absolute luminance, but more about the accuracy of the readings relative to monitor white, then I'd rather suggest to take a white reading after every N samples (or alternatively after every M seconds), compute a "current white" value as an exponential moving average of these interim white readings, and correct each reading by scaling it wrt. the "current white" level at the time when the reading is acquired. Such a procedure would also compensate a potential drift of the monitor's white luminance while it is being measured. > IS THERE ANYONE HERE WITH STATISTICS/METROLOGY BACKGROUND WHO WOULD BE ABLE > TO HELP??? I tried but I did not get any sensible results due to serious lack > of knowledge on this :) I was not thinking of some horribly complicated stuff, but the idea was simply to capture a 4-tuple [X,Y,Z,sensor_temperature] for each reading instead of only [X,Y,Z]. Then re-run you test again for a couple of hours and plot both, Y versus time, and temperature versus time, and compare the two curves. If there is a reasonable non-random relationship between the curves, I'm sure you'll see it intuitively. Prerequisite is certainly that the monitor is reasonably stable during the test, but since it was obviously pretty stable during the latter 7 of the 9 hours, I don't see any reason why it should not have been stable in the first two hours as well (particularly since it was already turned on for several hours before you started the test). [Finding a mathematical function which models the relation reasonably is a subsequent issue then - but first one would need to see the curves] Regards, Gerhard