Just a quick question, are densitometer readings more stable (for lack of a better phrase) if the unit remains on for some period of time while calibrating it periodically it prior to use? This opposed to simply turgning it on, then waiting for a few minutes, then calibrating it prior to use.
How old is the denisitometer and what model? I wrote a post a few months back on the use of denisitometers which can be viewed here. Depending on your type of usage its wise to get them recalibrated every so often. Also do you have a step tablet that came with the unit to compare against?