Occupancy sensors are often confused with motion sensors, but this is not the same thing. The latter are focused on motion detection, due to which an object that is in the field of action of the device is fixed. The human presence sensor responds to the location of people and large animals, regardless of whether they move or are motionless in place.
This is a very useful invention, which has found its application in many fields of human activity. The presence sensor is used to equip security systems and video surveillance systems, in “smart” houses as an energy management device, in toys with an interactive mode, in a taxi, etc. Moreover, such devices can respond to completely different parameters. The presence sensors can determine the location of a person by his weight, thermal energy, any sound and many other parameters.
For security systems, such devices are simply irreplaceable - they allow you to detect the presence of strangers in the protected area and take appropriate measures.
For the “smart home” system, these devices turn on and off the lighting devices, which not only allows you to not look for a switch in the dark, but also significantly save energy costs. At the same time, you should not think that presence sensors are the privilege of exclusively wealthy people, in fact, devices with this or similar principle of operation are installed in many entrances of high-rise buildings. They are used to reduce housing costs for electricity and usually respond to the sound of the steps of a walking person. Such devices are also popular in various taxi services - sensors help to monitor in real time and to separate free cars from cars with passengers.
It is very pleasing that from the point of view of ease of installation, such devices can be delivered to any person who is at least a little versed in technology. But presence sensors have one significant drawback - this is a false positive. Of course, for some areas of activity it is a completely harmless phenomenon and does not bring significant harm, for example, in interactive toys. However, for security or military purposes, this drawback is very significant.
Fortunately, the problem of false positives can be successfully combated, for this they use two different ways. The first method is to use several sensors that work separately from each other. These devices, in fact, duplicate each other, which is especially important in the presence of external interference. Another equally effective method is the use of sensors that record the presence of a person according to various parameters. For example, you can pair a device that responds to the electrical intensity of the human body, and a sensor that responds to heat.
These types of devices will be affected by different types of external interference, which means that the probability of false alarms of the entire system as a whole becomes negligible.