Abstract: Angle measuring apparatus including a disc having a circular track of marks on one surface concentric with the disc, such disc being rotated about its axis. A mark sensor located adjacent the disc surface detects each mark and generates a signal as it passes thereby. A pair of angle-input means are located adjacent the disc for defining the angle to be measured. Reference means rotate with the disc and interact with each input-means to generate a reference signal each time the reference means passes thereby. Control circuitry counts the number of mark signals occurring between selected reference signals and from such count, the defined angle can be accurately computed.

Abstract: A water level recorder for use with pressure-sensitive chart paper and having a framework with a lead screw rotatably mounted in the framework. A pulley is secured to the lead screw. The pulley is driven by a tape which is positioned by a float that is adapted to rest upon the surface of the water. A lead screw nut is mounted on the lead screw for movement longitudinally of the lead screw as the lead screw is rotated. A marking member for marking the chart paper is carried by the lead screw nut. A drum is secured to the lead screw for rotation with the lead screw. A helix for marking the chart paper is formed on the drum. Chart paper drive means is provided for advancing the chart paper over the helix and the marking member.