US Patent 10408641 Measurement system

A system for determining the location of a movable element within a container is provided in which a linear variable differential transformer (“LVDT”) is formed with the container and the movable element therein. The LVDT includes a coil assembly including a primary or excitation winding, a secondary or output winding, and a movable element or core that is magnetically permeable. Measurement of an output signals allows for precise determination of the movable element location relative to the container. The system can be utilized to determine fluid volumes in accumulators used for controlling subsea equipment by monitoring the location of a movable element, e.g., a piston, within a hydraulic fluid accumulator.