The sensor of the Xiaomi Automatic Soap Dispenser (Color Edition) is located below the foam spout in the black transparent area. This sensor is used to detect the presence of your hands. When the sensor detects that hands are near, it automatically dispenses the right amount of soap, allowing you to clean your hands without touching the device. To ensure optimal performance, make sure this area is not obstructed and keep it clean regularly. This design enhances convenience and reduces the risk of cross-contamination.