Motion Sensors vs. Presence Sensors
These two sensors get confused for each other constantly, but they do different jobs. A motion sensor's role is to open the door — it watches for someone approaching and triggers the swing or slide. A presence sensor's role is to keep the door from closing on someone who is already in its path. One starts the cycle; the other interrupts it.
That distinction matters because a door can have a perfectly good motion sensor and still close on someone if the presence sensor isn't doing its job. The motion sensor already did its work when it opened the door. From that point forward, it's the presence sensor's responsibility to hold things open until the doorway is clear.
The Hard Case: Someone Standing Still
A person walking through a doorway is the easy scenario — movement is exactly what most detection technology is built to notice. The hard case is the opposite: someone standing motionless in the door's path. Think of a person in a wheelchair pausing to adjust a bag, an employee holding a loaded cart while waiting for someone else, a parent bent over picking up a dropped item, or a shopper who stopped mid-doorway to check a phone.
None of those people are moving, but all of them are occupying space the door needs to stay clear of. A presence sensor has to recognize that someone is there even when there's no motion to react to — which is a fundamentally harder detection problem than simply noticing someone walking toward a door.
Common Blind Spots
Presence sensors can miss people or objects for a number of reasons, and most facility staff never notice until something gets caught. Common blind spots include:
- Low-profile objects near the floor — wheelchair footrests, walker legs, pet carriers, or rolling luggage that sit below the main detection zone
- The far edges of the door's swing or slide path, where coverage can taper off
- A sensor lens that's dirty, fogged, or partially obstructed by a sticker, sign, or decoration
- A sensor that's been bumped, misaligned, or mounted at the wrong height for that particular door and ceiling
- Flooring or lighting changes (new tile, added signage, a relocated display) that alter how the sensor reads the space beneath it
Any one of these can turn a working sensor into one that's technically on but not actually covering the doorway the way it should.
Never Disable a "Nuisance" Sensor
When a presence sensor keeps holding the door open longer than staff expect — because of steady foot traffic, a drafty entrance, or a sensor that's a little too sensitive — the quick fix some facilities reach for is to cover it, unplug it, or have someone disable it. We understand the frustration, but this is the one shortcut we'd ask you never to take on your own.
A presence sensor that's firing too often is telling you something is out of adjustment, not that it should be ignored. Disabling it removes the one piece of the system whose entire job is to stop a door from closing on a person, a cart, or a pet. The sensor isn't the problem to eliminate — it's the symptom pointing to a problem that needs a proper diagnosis.
Force, timing, and sensor sensitivity on a commercial automatic door are safety-critical settings, and getting them right takes testing equipment and training most facilities don't keep on hand. That kind of adjustment belongs to a certified AAADM technician who can bring the sensor and door back within the manufacturer's limits — not to trial and error with a sensor cover or a disconnected wire.
Keeping Accessible Entrances Working the Way They Should
Entrances that serve the public every day — retail storefronts, clinic lobbies, hotel entries, office buildings — depend on presence sensors doing quiet, reliable work in the background. When a sensor starts acting up or you're not confident it's catching everything it should, that's worth a second look before it becomes a bigger problem.
CSC Automatic Doors has been serving businesses across central Arkansas since 1976, with AAADM-certified technicians covering Conway, Little Rock, North Little Rock, Benton, Bryant, Maumelle, Jacksonville, Searcy, Russellville, Cabot, Sherwood, and Hot Springs. If a presence sensor at your entrance is holding too long, missing people, or just acting unpredictable, give us a call at 501-548-2374 and we'll get a technician out to take a look.
Frequently asked questions
What's the difference between a motion sensor and a presence sensor on an automatic door?
A motion sensor detects someone approaching and triggers the door to open. A presence sensor's job starts after that — it keeps the door from closing while someone or something is still in its path, whether they're moving or standing still.
Why would an automatic door close on someone who isn't moving?
Some detection zones and sensor setups are better at picking up motion than stillness. A person standing in the doorway without moving can fall into a blind spot or a gap in coverage, which is why presence sensor placement and adjustment matter so much.
Our door's sensor seems overly sensitive and holds too long — can we just turn it down ourselves?
Sensitivity, timing, and force are safety-critical settings that take testing equipment to adjust correctly. Rather than disabling or adjusting the sensor yourself, have a certified AAADM technician diagnose why it's over-triggering and bring it back within the manufacturer's limits.