The type of sensor you install, and the way you install it, can make a big difference in the performance and the longevity of the door. You need one set of sensors to open the door reliably, and you may need another set of sensors to close the door safely. For opening the door, the main point is to sense an approaching vehicle early enough so that the door is
open enough to avoid damage by the time the vehicle reaches it. Calculate the appropriate distance between the sensor and the door by using the door opening speed and the maximum expected vehicle speed. For example, consider a door that opens at the rate of eight feet per second. It is used by forklift trucks that require a vertical clearance of eight feet. Therefore, the door requires an opening time of one second to provide adequate clearance. If the maximum expected speed of the truck is ten feet per second (about seven miles per hour), then the sensor must start opening the door while
the truck is at least ten feet from the door. For closing the door safely, you need additional sensors that verify the absence of objects in the door safety zone. For example, an induction loop cannot sense a person standing underneath an open door. To keep the door from closing on the person, you need sensors that will detect anything within the door area itself.
In general, you can use any type or combination of sensors with any type of door. The sensor installation may be entirely separate from the door assembly. It’s up to you to select a sensor that will work reliably in your application. The types used most commonly with quick-acting doors are: