Rayk. I have a bit of experience with belt weighers. They are really sensitive for the belt installation. It must be absolutely straight. You must have at least 2 identical idlers on either side without loading point, without changes to the profile, etc.
Also, the load cells shouldnt be part of the idler frame itself, otherwise longitudional forces may be transferred to the loadcell (the manufacturer may claim that the loadcells are insensitive to longitudional forces, but I have found that to be false on several occasions). The loadcells must be installed so that the idler frame rests on the loadcell "freely" so to speak.
Shooter. I dont disagree, but the problem with compensation is mostly if you have long cables between loadcells and converter.
If using a classical converter I recommend to install it locally right next to the loadcells.