Secrecy sensor

A Secrecy Sensor is a type of Dark Detector. It is shaped like an ariel, but it is gold in color and very squiggly. It vibrates when it detects concealment and lies. "Professor Moody" (in reality Barty Crouch Jr) had one in his office during Harry's fourth year at Hogwarts. However, it was no use to him at the school because it was constatly humming, as students were always nearby teling lies about why they had not completed their homework assignments.