How Do Pet Immune Motion Detectors Work? (Simple Explanation)

How many times have you heard someone complain about their pet tripping the motion sensor? It’s so common to see pet owners complain about how they’d have to turn off the sensors because of false alarms. Thankfully, pet immune motion detectors exist to help save us from this mess.

Though the idea behind these sensors is great, a frequent question we’ve received for them is – how do pet immune motion detectors work? Before we discuss how these motion sensors work, let’s discuss what pet immune sensors are in the first place.

What are Pet Immune Motion Detectors?

Pet immune motion detectors are specialized sensors with the ability to detect pets and avoid triggering alarms. They use a combination of algorithms and datasets of weight, height, speeds, and movement to identify pets. Once these are ruled out, the sensor triggers on everything but pets.

Though pet immune sensors are great, they’re only going to help if mounted properly. Manufacturers generally send manuals on how to mount these sensors such that they’re great against pets. If you’re unaware of how to mount your pet immune detector, fret not – we’ll discuss this soon.

How Do Pet Immune Motion Detectors Work?

Pet immune motion detectors work by neglecting motion signals from anything behaving like a pet. These sensors generally use weight as the main indicator to differentiate pets from humans. If the weight of the pet is below 80 pounds, the motion detector doesn’t trip.

Motion detectors for pets use the same lens as a typical motion sensor. They pick up heat signals along with motion patterns from their field of view to detect objects. However, the calibration, sensitivity, and detection capabilities of a pet immune sensor is a bit different.

Though features vary by manufacturer, most of these sensors can neglect a pet weighing between 40 and 80 pounds. Anything above it is considered a human and trips the sensor. We’ll discuss what you can do if your pet doesn’t fit this weight limit.

Moreover, the average height of small pets is used as a low sensitivity zone for the motion detector. If an object (which matches the weight and other indicators) is in that zone, the sensor doesn’t trip. It’s why mounting the pet immune sensor correctly is fairly important.

Pet immune sensors aren’t immune to pets by nature but they need special care during installation. If not mounted properly, you’d still be facing hundreds of false alarms, frowns from your neighbors, and even a fine if it continues for longer periods. 

You might be wondering:

Would the pet immune sensor detect someone who attempts to crawl past the sensor?

It will, considering the weight of an average human is far greater than a cat or a small dog.

But, weight isn’t the only indicator of detection for pet immune sensors. These detectors use a variety of indicators such as height, movement patterns, and speeds along with specialized algorithms to pick apart pets from humans.

A human attempting to crawl past the sensor won’t succeed as many indicators would fail to meet.

Will Larger Pets Trigger the Pet Immune Motion Detector?

Larger pets might trigger the pet immune sensor as their height and weight won’t meet the sensor’s requirements. Most pet immune sensors are able to avoid pets below 80 pounds. If your pet weighs above it, it might cause the sensor to trigger.

Though you can reduce the sensitivity of the motion sensor to avoid detecting large pets, it’d be inefficient against humans. Let’s not forget the primary aspect of the sensor – to detect criminals from entering your property. Pet immune sensors already feature a trade-off – mostly between detecting humans very well versus detecting humans and avoiding pets. 

It’d be better to replace the motion sensor with something more efficient in your case – maybe 

even a glass break detector. A trained pet is very less likely to break through glass, than a criminal trying to enter your residence.

Tips on Installing a Pet Immune Motion Detector

In order to ensure your pet immune motion detector works as intended, you must follow the manufacturer’s guide. However, there are a few tips that generally apply to every installation of a motion sensor.

Here are a few tips from our experts: 

Optimum Height

Pet immune sensors should be installed at an optimal height of 7.5 to 8 feet. If it is installed at a height below this, the pet might not fall under the lower sensitivity area of the lens and trigger the sensor.

One more reason why stairways are a bad place to install the motion sensor. If the pet comes crawling up, it might intrude the field of view of the sensor. 


Pet immune sensors should be low in sensitivity to avoid detecting pets.

Motion sensors use pulse counts to identify area coverage and sensitivity. Higher pulse counts would indicate a larger being such as a human which covers a larger region. On the contrary, a lower pulse count would cover a much smaller region (a category a pet would fall in).

Use low pulse counts on your pet immune sensor so pets don’t trigger it. If you suspect the sensitivity is way too low, you can switch it to medium and then configure a setting which works well for you.

Mount Point, Angle, and Position

If your motion sensor uses infrared radiations (PIR), make sure there are less sources of heat around the sensor. Radiators, sunlight, and lighting might cause the sensor to false trigger. Pick a place where the sensor doesn’t have as much interference from other objects or devices.

Secondly, make sure the angle of the sensor isn’t too low as it would shorten its field of view. Ultimately, the low sensitivity region of the sensor would also be too short for it to avoid pets.

Thirdly, make sure the position of the sensor is far away from your pets reach. If the pet were to climb to it or attempt to walk on their hind legs, it would trigger the sensor as well.

A good position would be at the optimal height, covering angles which only humans might pass through, and far away from a pet’s reach.

Frequently Asked Questions on How Pet Immune Motion Detectors Work

Let’s switch to our very own ask-me-anything session. We’ve shortlisted some of the best community-asked questions on how pet immune motion detectors work. Here are our answers to them:

Will pets set off motion detectors?

Pets can set off motion detectors if not mounted properly or at low heights. Most PIR sensors can pick motion signals from pets. To avoid a pet from setting off a motion detector, you can use a pet immune variant which uses weight filters to avoid detecting pets.
Pet immune motion detectors aren’t expensive motion sensors. They cost the same as a typical sensor with maybe a few bucks added on top of it for additional features. Generally, it’s their sensitivity which is calibrated to match high sensitivity zones and avoid detecting small moving objects.

How do movement sensors ignore small animals?

Movement sensors don’t ignore small animals by default. However, most PIR sensors allow you to configure the sensitivity to ignore certain regions, heights, temperatures, or weights. Calibrate your motion sensor’s sensitivity such that it can ignore small animals below a certain height.
Since a pet immune sensor can only filter out smaller animals, larger animals will still trigger the sensor. These pets are bulkier in weight and their heights exceed that of the low sensitivity region. It’s easier to install and configure other devices of security if you’re concerned about frequent false triggers.

How does a motion sensor work?

Passive infrared motion sensors work by detecting heat signals or movement across their field of view. If detected, they trigger an alarm. On the contrary, active motion sensors work by emitting waves of several kinds to detect objects within their field of view, eventually triggering alarms. 
Both motion sensor types have flaws which can be bypassed by using a combination of the two. Passive infrared sensors only rely on heat signals, whereas active sensors would trigger on anything capable of reflecting waves. A dual sensor would trigger only if both the sensors trigger. 

In conclusion, pet immune motion detectors are great security devices if mounted and configured properly. Frequent false triggers can get you in hot waters fairly quickly. These devices can, at the very least, ensure your pets don’t cause those triggers.

All set? Your sensor should now be ready to use its sixth sense to detect malicious activity around your residence!