There are three popular types of electronic pet door sensors on the market today and they all are designed for the same purpose: To release the pet door when the pet wants to enter or exit the house.
1. Ultra Sonic
An ultra sonic sensor receives a signal from a transmitter fitted to the pet’s collar. The level of the sound is above the range of human ears so they can’t hear it. Ultra sonic sensors work very well but you may encounter two possible faults. The first is that although humans cannot hear the signal, the pet sometimes can. This can be distressing for the pet and puzzling for the owner who doesn’t always realize what the problem is.
The second problem is that the signal will release the pet door as soon as the pet is close enough, even if the pet does not intend to approach the door. This can leave an open invitation for other animals to enter the house. Older designs of ultra sonic pet doors would operate even if the pet was lying in front of the door. This wasn’t always a problem but the solenoids that retracted the bolts from the doors could get hot and become a fire hazard. Always check to make sure that the pet door you are looking at does not release the door indefinitely. Modern ultra sonic doors can detect the direction in which the pet is moving and whether it is stationary. They won’t release the door until the pet is near enough to enter.
2. Infra Red
An infra red sensor reacts to an infra red beam from an attachment on the pet’s collar. These work well but can also have a couple of minor problems. The first is that the attachment to the collar can get twisted behind the pet’s neck preventing the infra red beam from reaching the sensor. The second problem is rare but some insects are attracted to infra red light and can be a nuisance. Infra red sensors don’t work at a great distance so the pet has to be close to the door before it is released.
Magnetic sensors react to a very low-strength magnetic field surrounding a magnet attached to the pet’s collar. The magnets can even have a mild therapeutic effect on the pet. Although the magnets can sometimes be set so that every magnetic collar will not release the door, the number of variations available is quite small compared with ultra sonic and infra red sensors.
Ultra sonic and infra red sensors can be set to receive a coded series of pulses so that only one collar will release the pet door. There are enough variations to make it fairly safe to assume that your pet will be wearing a uniquely coded transmitter for your sensor installation.
Electronic pet doors deliver a level of security that standard pet doors cannot. But all electronic pet doors operate on the mains power to operate. If the mains are cut, the pet door will not work. It is possible to have a battery back-up system if power outages are a common occurrence in your area.