Abstract: This invention concerns a device for checking the depth reached by operation of a digging machine including a digging implement (11) arranged on an arm (8) pivotably supported relative to the machine. The device comprises a fluid-filled conduit (13) associated with the arm (8) and extending between a location (14) thereon and a location (15) on the machine separated from the arm. The conduit is associated with a pressure sensor (17) for delivering information corresponding to the height of the fluid column between the locations. On the arm (8), there is provided, in addition to the first mentioned sensor (17), a second sensor (18) adapted to deliver information as to the inclination of the arm. In this way, the pressure sensor (17) may be provided at an arbitrary location on the arm 8.