Tunnel Ingress Illuminance Detector is a precision instrument for monitoring brightness inside tunnels. It converts measured values into 485 signals for the tunnel control system based on the changes in interior illumination, coordinating with lighting equipment for intelligent control. During use, it is installed on the walls at the entrance, transition, or middle sections of the tunnel, around 3 meters in height, accurately reflecting road surface illumination and ensuring safety. It is typically used in conjunction with an exterior height detector. The instrument uses high-precision silicon photovoltaic cells as sensing elements, with light signals passing through a professionally designed cosine corrector and a special high-efficiency filter before being converted into electrical signals by the sensing elements. These signals are then processed by a high-integration circuit and output as 485 signals.