Why use ultrasonic sensors:
Ultrasonic occupancy sensors are an ideal way to save electricity. The function of an occupancy sensor is to switch off unwanted lights and other electrical appliances that may be left on by mistake. Occupancy sensors also light up the area where they are installed when someone enters it. These sensors help reduce light pollution as they reduce unnecessary outdoor lighting.
When ultrasonic sensors should be utilized:
Ultrasonic occupancy sensors are ideal for any area that is occupied intermittently. They are, therefore, used in hospitals, schools, restrooms, storage areas, etc. Occupancy sensors are also being used in new construction sites to save energy. In business units, almost 40% of the power bill is for lighting. The use of ultrasonic occupancy sensors can help reduce this drastically and can save up to 70% of the lighting energy that is used.
How ultrasonic sensors work:
Ultrasonic sensors work by generating a high-frequency ultrasonic signal. Using the Doppler principle, the sensor measures the strength of the reflected signal. A change in the magnitude of the reflected signal is interpreted as motion in the given space. The pitch of a signal that is being bounced back changes into pitch as soon as a person walks within the range of the sensor. The audio frequency of the wave is higher than what is perceptible by the human ear, rendering it inaudible to humans.
The benefit of using ultrasonic sensors:
The advantage of using an ultrasonic sensor is that it can detect movement even around corners. This means that the sensor does not require a direct line of sight to identify a person entering the room. These sensors are, however, more suited to detecting movement towards the sensor rather than detecting movement across the path of the sensor. Ultrasonic sensors are better than infrared sensors as they can detect arm and upper torso movement up to a range of 40 feet, which is comparatively 10 feet longer than the average passive infrared (
PIR) sensor.
The disadvantages of using ultrasonic sensors:
One of the disadvantages of occupancy sensors is false triggering, which can occur due to a person walking by in an adjacent place. This, however, usually happens if the sensor is positioned poorly, causing part of the signal to bleed through the doorway into the adjacent room. Electrical or other objects that usually get heated up by a heater of a HVAC can also lead the system to act undesirably. Similarly, direct sunlight falling on a sensor can also trigger it. The above mentioned reasons make this sensor inappropriate for covering a selective area or partitioned rooms. This sensor is also unsuitable for rooms that have high ceilings or areas where there is a significant amount of vibration in the airflow. An ideal ultrasonic system should have an automatic switch on for public areas while private and semi-private areas should have a manual override.
