Do Cats Set Off Motion Detectors?

No, cats will not set off motion detectors, provided that the motion detectors in question offer pet-immunity and they are installed correctly. But if a motion detector is installed in a poor location, or if it does not have pet-immunity, then it's likely a cat will set the device off.

It's important for users to understand how pet-immune motion detectors work. A pet-immune motion sensor isn't able to just magically ignore small animals. Instead, these devices look for the motion of a person walking up-right, while ignoring the movement of a pet that is closer to the ground. But if a motion detector is installed in a poor location, then a few things can go wrong with this setup.

First, if a pet-immune motion sensor is installed at too low a height or at an improper angle, then it might still detect the motion of a cat walking on the ground. That is why it is important to install pet-immune motion sensors high enough up so that they aren't triggered by pets walking by. But remember, installing a motion detector too high might cause it to miss the movement of a human intruder. The optimal installation height for a pet-immune motion sensor is usually between 7.5 and 8 feet high.

Second, if a cat is able to get up high enough, it could set off a pet-immune motion sensor, even if it is installed at a proper mounting height. This could be because the cat climbed on top of a piece of furniture or because the motion sensor was facing a stairwell. This is why mounting location is very important with motion sensors. Users must make sure that their motion sensors are not facing any obstacles that their pets could climb or jump on to trigger the device.

Remember, "pet-immune" does not mean that it's impossible for pets to set off the device. If a cat is able to get directly in front of a motion sensor, it will still activate, regardless of any pet-immunity rating. But by installing a motion sensor in a proper location and at a proper height, it will be nearly impossible for this to happen. For more information, please review this FAQ on where to install motion sensors.