Just added a large dog to our family. He's 70 lbs .. should we adjust or remove the motion detector?

Hey everyone .. We've had our Digital Life system about a month. So far no problems that I couldn't figure out and fix. We had 2 chihuahua's, each averaging about 15 lbs when we had the system installed. This past weekend we rescued a new dog. He's a large shepherd mix, about 70 lbs right now and will probably get a little bigger as he grows and fills out. The guys that installed our system said that our chihuahua's wouldn't set the motion detector off because they were under 30 lbs. What do I do about it now that we have a bigger dog? Is there a setting somewhere I can't find to set for the size/weight of our pets or do I need to call AT&T about changing or removing the motion detector? Until we figure this out we're not going to use the "away" setting on the alarm. Help!!