The invention provides a signal sensor. The signal sensor comprises a housing, having a connector and a display unit; a tuner, configured to receive a cable signal; a microcontroller unit (MCU), electrically connected with the tuner and the display unit; a scanning switch, electrically connected with the MCU; a power supply, configured to supply a power to the MCU, the tuner and the white LED; and a power switch, electrically connected with the MCU.