Abstract: A tool changer device for a robotic arm comprising a robot adapter (1) particularly adapted to be connected to a robotic arm (5) and to a tool (6). The robot adapter (1) comprises a pneumatic cylinder (117) inside which a piston (116) is slidably arranged for activating a coupling and uncoupling mechanism (120) of the robotic arm (5) to the tool (6). On one of the walls of the robot adapter (1) at least four through conduits (24, 25, 26, 27) are arranged, one end of which opens into the pneumatic cylinder (117) and another end of which opens outside of the pneumatic cylinder (117). The device further comprises a first differential pressure sensor (18) connected to at least two of the through conduits (24, 25), and a second differential pressure sensor (19) connected to another two of the through conduits (26, 27).