SimpliSafe's motion sensor guide says motion sensors detect movement within 35 feet in a 90-degree field of view, and the Gen 2 has Pet Mode to distinguish people from pets. The pets article says to position the sensor correctly and adjust settings for a pet's weight and body heat, and that the Gen 1 has a dome about one inch across while the Gen 2's is about an inch and a half.
The checks in more detail
If it misses movement, check it is mounted at the recommended height and angle, has a fresh CR123A battery, is online and is armed in Away mode, since Home mode leaves motion sensors off. Adjust sensitivity and Pet Mode in Device Settings. Keep it away from heat sources such as radiators, direct sun and vents, and away from windows that catch sun and moving branches. If you get false alarms from a pet, enable Pet Mode and check placement so the pet cannot get close.
Test it in Test Mode by walking across its field, and the Base Station should announce the sensor. If it goes offline, replace the battery, move it closer to the Base Station and remove and re-add it if needed. Motion sensors are also useful for triggering cameras. Check the sensor's tamper switch is closed. Walk the route an intruder would take and listen for the announcement, since a test from one direction says little about the others.
Check again at a different time of day, since sun and heat change what triggers. Adjust sensitivity in small steps. A motion sensor near a return air vent sees warm air as movement, so moving it a meter often removes a mystery false alarm. Pet Mode tells pets from people by size and heat, so a very small child or a very large dog may confuse it, and testing with a household member is the honest way to check.
Differential
Likely causes of “SimpliSafe sensors, Keypad and accessories misses motion or records too many events”, and how to tell them apart
- 1
Home mode
What separates it Motion is not detected because the system is in Home mode, which leaves motion sensors off
How to confirm Use Away mode when you want motion sensors armed, or arm them specifically as needed
- 2
Pets
What separates it You get false alarms from pets because Pet Mode is off or the sensor points at where they walk
How to confirm Enable Pet Mode on the Gen 2 sensor, and adjust the placement so that it points above where pets go
- 3
Heat or sun
What separates it You get false triggers because the sensor sees heat or sunlight from a window or vent
How to confirm Move the sensor away from heat sources, direct sun and vents, which can look like movement
- 4
A weak battery
What separates it Movement is missed at times because the battery in the sensor is weak
How to confirm Replace the battery with a fresh CR123A cell, then test the sensor again in Test Mode
- 5
A poor angle
What separates it Some areas are not covered because the sensor is mounted at a poor angle
How to confirm Adjust the mounting height and angle so that the sensor views the area you want covered
Before you touch a setting
Record this first — changing settings destroys the evidence
- Which mode the system was in when motion was missed
- Whether it is the Gen 1 or the Gen 2 sensor
- The height and place where the sensor is mounted
- How old the sensor battery is
Try in this order
0 of 7 completedUse Away mode
ReversibleUse Away mode when you need motion sensors armed, since Home mode leaves them switched off.
Check the battery
ReversibleCheck the battery, which is one CR123A cell in the Gen 2 sensor, and replace it if it is old.
Adjust placement
ReversibleAdjust the placement, meaning the height and angle, so the sensor covers the area you need.
Enable Pet Mode
ReversibleEnable Pet Mode if you have pets, so that the Gen 2 sensor can tell them apart from people.
Test in Test Mode
ReversibleTest in Test Mode by walking across the sensor's view, and watch that the Keypad reports the motion.
Move from heat and sun
ReversibleMove the sensor away from heat and direct sun, which can cause false triggers when they change.
Contact SimpliSafe
ReversibleContact SimpliSafe if it still fails, and tell them the mode, the placement and the battery age.
Model-specific
What is true of this model and not of its siblings
- Gen 1
- Has a dome about one inch across.
- Gen 2
- Has a larger dome and Pet Mode.
Stop boundary
When this stops being a self-service repair
- !If it never triggers after checks, contact SimpliSafe support
- !If pets keep causing alarms, adjust Pet Mode and the placement of the sensor
- !If it is offline, follow the offline steps
Evidence ledger
Sources behind this answer
Motion sensor range and Pet Mode.
Motion sensors and pets.
Test Mode.
Battery types and lives for every device.
The company and its products.
Exact questions
Common questions
How far does it detect?+
It detects movement up to 35 feet away, within its field of view in front of the sensor.
What is its field of view?+
Its field of view is 90 degrees, so it covers a wedge of the room and not the whole space.
Does Home mode use motion?+
No, Home mode leaves motion sensors off, so it will not catch movement inside the home.
Which battery?+
It uses one CR123A battery, so keep a spare of that type ready for when it runs down.
How do I test a sensor?+
Test a sensor with Test Mode from the Keypad, which lets you trigger it and see whether the Base Station hears it.
Where do I find Device Settings?+
Find Device Settings in the SimpliSafe app under My System, where each device has its own settings page.
How far from wireless devices should sensors sit?+
Keep sensors at least three to five feet from other wireless devices, which can interfere with their radio signal.
What is the Smoke and CO Detector battery life?+
The Smoke and CO Detector runs about two years on two CR123A cells before the batteries need replacing.
What batteries does the CO Detector use?+
The CO Detector uses three AA lithium cells, which are not the same as the alkaline cells other devices use.