Motion Alarm Versus The Dog

Many people have pets.  Many people want the extra security that a sensory detector can give them.  Unfortunately, many people want both, and sometime having a dog (or a cat, but lets focus on the dog this time) can make you worry about getting a motion sensing alarm.  You might wonder, "What if my pet sets it off while I'm not home?"

Well, it might not be as big of a deal as you might think it is.

There are a couple different kinds of motion sensors. The two main categories are active sensors and passive sensors.

Active sensors are called active because they continuously send off some kind of signal. Some of them send off a beam of light, while others send off sonar waves. With all of them, there is some kind of sensor to measure changes in the light or sonar waves. If a large change is found, the sensor activates. The most well-known version of this is the "laser beam" security that is seen in movies and TV shows all the time. If something breaks the beam, the alarm goes off... or in the case of grocery stores that employ the same technology, it just makes a bell ring to let the employees know that a customer has arrived. However, the most visible of these devices on a day-to-day basis is probably the motion detectors used for automatic doors. These use sonar to continuously scan a small area in front of the door. If the sonar waves suddenly bounce back to the sensor at a significantly different rate, it triggers the sensor and the doors open.

Passive sensors do not send anything out into the environment, they only sense what is already there.  These sensors almost always take a continuous reading of the levels of infrared in the area.  Since humans naturally emit a significant amount of infrared light due to the heat that escapes from our bodies, these sensors can tell when a human body enters its field of vision.  However, the human body only emits certain wavelengths of infrared light, so these sensors are designed to sense that range.

Furthermore, these sensors only activate when there is a fast change in the level of infrared, so a person that is just standing there will not activate it, but a person that is moving will.  That is why they are known as motion detectors instead of heat detectors, and it makes them more practical for conserving energy on outdoor lighting.

The simplest solution is to set the motion detector high enough that the dogs movements won't trigger it.  The problems start if you have a dog that likes to jump... especially if they like to jump HIGH!

If you have a dog that likes to jump, you might be able to turn down the sensitivity of the sensor.  This might prove especially useful if you have a smaller dog that produces significantly less body heat than a human does.  This does require a detector that allows you to adjust sensitivity, though, so you might want to think about this while you're actually shopping for the sensor.

If all else fails, you might have to restrict the pet's access to the areas that have a motion detector.  For example, if you keep most of your valuables in your bedroom, you can install the motion detector there and simply keep the door shut so that the dog can't trigger it.  This is probably the most annoying of the solutions, though, because it limits where you can put the sensor, and if you forget to close the door one day it could easily result in a false alarm.  Hopefully you won't have a large dog that likes to jump as high as the one in the picture!

If you would like to know more about why you might want a sensory detector alarm in the first place, visit Total Home Security's page on Sensory Detectors.