Abstract: A device and method for remotely measuring movement between opposed walls in dangerous situations such as unstable mining excavations is described. A spring loaded telescopic pole which can be handled in its contracted form by a remote arm or gantry is placed in position and a holding pin securing the two halves of the pole is extracted so that the pole extends into engagement with the opposed walls of the excavation or other situation. A linear or rotary potentiometer is provided between the two halves of the pole to measure any extensive or compressive movement of the spring loaded poles and produce an output signal representative thereof. The output signal can be read at a safe distance using any convenient readout system.

Abstract: Apparatus for detecting or measuring movements in geological and other formations and capable of carrying out such measurements on a three-dimensional basis. The apparatus has a housing acting as a support and an elongated arm, e.g., a stiff measuring rod of adjustable length, projecting from the housing and acting as a movement following element. One end of the rod is secured within the housing by sliding and pivoting connections so that the remote end of the rod may move freely in three dimensions relative to the housing. Three movement sensors are positioned within the housing. A first one of the sensors measures translational motion of the rod in the axial direction. A second sensor measures rotation of the rod about the pivot in a first plane. A third sensor measures rotation of the rod about the pivot in a second plane which intersects the first plane at right angles. The first movement sensor is preferably a linear potentiometer and the second and third sensors are preferably rotary potentiometers.