Pet Motions
Most companies that manufacture motion detectors also make motions which are pet immune up to various animal weights. Properly placed within the home, they work very well for their intended purpose, but even the best are not foolproof by any means. Many companies now use them as a "standard" motion in their installations even when there are no pets present, because they are generally of more expensive manufacture, and are more resistant to stray environmental issues that can inadvertently trip standard motions. Plus, any stray mice or birds won't trigger the alarm (especially useful in rural areas and in warehouse type environments).
From a homeowner's perspective, the type of animal and the weight of the animal are important issues to consider. There are two absolute "no-no's" in the placement of any pet immune motion. They must never be installed where an animal can climb to within six measured feet of the device (which will overpower it..), and they must never be installed facing stairs, where they will see an animal running quickly up the stairs. Failure to follow either of these placement rules will almost guarantee a false alarm regardless of the device used! It has been my experience that cats in the home generate more problems than dogs - even big ones - since cats love to climb on furniture.
The vast majority of standard pet motions use infrared technology, where the motion is looking for the infrared heat from a living creature moving across a number of set zones of coverage. In the pet variety, there can be two individual motions, both looking for the movement of infrared heat, but they are "wired" together such that when it sees the defined pattern in both lenses in a vertical format (such as a man walking), they trigger. However, if they see the pattern of movement in a horizontal plane, they define that as an animal, and ignore it. But if an animal moves quickly in a vertical plane up a set of stairs, it will generally fool the device ! Other more expensive devices use a combination of standard infrared detection coupled with a "check" by microwave technology, before triggering the alarm. These are generally much more tolerant of pets of larger sizes, but do cost considerably more to buy. But even they should follow the two rules of placement !!
If your alarm company has told you the reason for that false trigger was "a spider running across the lense of your motion detector", you can safely assume that they don't really know what caused the alarm. This is the standard industry "stock" answer for this kind of situation, and makes little real sense when you know how these devices "see" the world. Pet motion technology is not an exact science, and sometimes, no matter how well placed the device, a problem can occur. So when these motions are first installed, it is generally wise to have your alarm monitoring station put them on "test" for a couple of weeks just to be sure that no problems will occur. Have the station call you and your dealer but not dispatch on a motion alarm alone (but do dispatch if they see both a door or a window AND the motion trigger together)....after all, a cat or dog can't open a door !!
The pet motions that I have found work well in most situations are the Paradox Digiguard 75 dual lense infrared device (for animals up to 70 lbs), and the Detection System DT500, dual technology motion (for animals up to 100 lbs). I use the Paradox motion for ALL installations, and substitute the DT500 "moose proof" motion only when problems occur. Most companies make pet immune motions that work very well within their stated limits. These two just happen to be the two devices I have had the best luck with.
Pet motions of any make and model will work with all modern alarm panels regardless of the make and model. Most dealers "mix and match" based on their experience and satisfaction with the devices they choose..
NOTE: Many people complain that their motion detectors are not sensitive enough, and think that they are only operating properly when they trigger with an arm waved or some other slight motion. If they do activate this way, they are not operating properly, and are highly likely to false alarm at some point. Think of a cheap motion as a glass of water with the meniscus in a positive or "overfilled" mode. The slightest jar of the glass and water spills. However, a good motion will be like a glass of water with the meniscus in a negative mode. A slight jar won't spill anything. However, anyone moving in the room is like hitting the glass with a hammer and will always result in a trip of the motion.
You do NOT want motions that are too sensitive !