Adjusting PIR Motion Sensor

I need to adjust the weight on the motion sensors in our home to account for the weight of our growing dog. How can I do that?
Thanks

Do you have the 2GIG-PIR1-345 motion detector?

If so there are two jumper pins on the inside of the detector near the battery tray. One jumper assigns sensitivity, one the pet immunity level, 35 or 55. You can access them by removing the bottom set screw on the detector housing and pulling off the back-plate.

Keep in mind the pet immunity is generalized for a pet of that rough size, not a specific weight limit, as it is more affected by the height of the animal.