I recently came across an excellent little illustration of this on page 7 of the Keller-Druck Brochure : http://flipflashpages.uniflip.com/2/52802/96120/pub/#page7.
From a signal processing point of view the key points from this diagram are :
1/ When the measurements are very precise (as shown in diagram A) then accuracy can be improved by removing the offset via subtraction of the average of the samples.
2/ When measurements are more accurate but there is a larger deviation (as shown in diagram B) then the deviation can be reduced by oversampling and averaging the results.
If you have found this solution useful then please do hit the Google (+1) button so that others may be able to find it as well.
Numerix-DSP Libraries : http://www.numerix-dsp.com/eval/