Does the sensor work without power?
There is a built-in battery in the device so that the sensor can work after charging. This usually takes 6-8 hours. When the voltage is below 3.8V which is indicated in the APP, it is recommended to recharge the battery.The sensor is designed to protect itself from overcharging.
How does the Door/Window sensor work?
The Door/Window sensor includes two parts: inductor and magnet,they are placed on the door/window and doorframe/window-frame, and inductor detects the distance to the magnet to find whether the door/window is opened or closed.
At what distance does the inductor need to be from the magnet to no longer detect closed status?
When the inductor and magnet are within 2cm of one another, the door/window sensor indicates closed status. If they are further apart it indicates open status.