When plugged in, your Canary Flex will operate in the same manner as the Canary All in One, in which it uses "computer vision" to determine if motion is happening. It's basically just looking at changes in the pixels on the screen. Any pixels changing is registered as motion. Canary's computer vision algorithms then try to filter out repetitive motion from things like ceiling fans, or background motion like lights and shadows to provide you with intelligent notifications.
When operating unplugged, Canary Flex uses a low-power standby state. Your Canary Flex will only detect motion using its passive infrared (PIR) sensor. The PIR sensor is located on the front of the Flex in the middle of the LED ring. This sensor will blast the area with rays of passive infrared, which will detect heat signatures. When something with a different heat signature than the surrounding environment passes through those rays, it "trips" the sensor, wakes up your device from its low power state and your Canary Flex begins to record.
If you believe your device is not capturing enough motion here are a few suggestions.
Adjust the PIR sensitivity
You can change your range of detection within the Canary app. Adjusting the sensitivity range of your device to a 'near range' can help conserve power, allowing your Canary Flex to record for even longer on a single battery charge. The drawback here is the PIR sensor would require a fairly large heat signature in order to wake the device. Adjusting the sensitivity range of your device to a 'long range' will help capture additional motion, but you sacrifice battery life.
Note: To learn more, visit How can I adjust the recording range of my Canary Flex?.
We recommend placing Canary Flex at a maximum height of 8 feet. Above this height, people will have to come quite close to the device before they are detected. Additionally you will want to place your device at such an angle where the intended target would come across the field of view of the devices 116° wide angle lens rather than walk directly towards the device. By having an object come across the field of view you increase your chances of detection and account for the extra second of time it requires for the device to wake up from its low power state.
Canary Flex devices are not intended to be placed behind glass. Glass is not as transparent to infrared light as it is to visible light. Therefore when using PIR the Flex will be unable to detect motion if placed behind a window. Additionally you may encounter a glare that will blind the view of the Canary when night vision is activated.
Note: To learn more, visit Will Canary detect motion through glass?