Abstract: A transducer that combines a noncontacting displacement probe with a self-contained target. The target is held in position against a vibrating surface by a housing which also supports the noncontacting probe. The target vibrates with the surface and the probe senses the vibrations of the target.

Abstract: Automatic liquid volume compensation apparatus is disclosed having particular application to septic systems. The apparatus limits septic tank air volume to optimize bacterial decomposition of wastes and controls the flow rate from the inlet piping through the tank to the drain field to limit passage of unprocessed fluid and prevent backups in the inlet piping.In the first of two embodiments, a bladder within a settling tank inflates or deflates to accommodate changes in liquid volume while maintaining tank level within desired limits. In the second embodiment, an auxiliary tank stores excess liquid which is returned to the primary settling tank when settling tank liquid level has declined to a desired height.