An improved magnetostrictive wire based position transducer that has applications in both liquid level measuring systems and in position indicating systems. A cylindrically structured and circularly polarized piezoelectric element directly measures the torsional acoustic waves in the magnetostrictive wire as they are received by the sensor. The cylindrical structure of the sensor eliminates many of the inadvertently detected acoustic and electrical pulses within the wire that are not indicative of the passage of the torsional wave of concern. The present system provides an improved sensor configuration which is selectively sensitive to torsional waves while being insensitive to vibrations in alternate planes. This improved piezoelectric sensor in combination with the electrical configuration allows placement of the magnetostrictive wire apart from the liquid whose level is being measured or from the indicator whose position is of concern. The system provides a means for transmitting the liquid level within a container to a sensor column outside of the container in a manner that improves access, maintenance, calibration, and installation. In the preferred embodiment, each of the above improvements is provided in a system that incorporates an instrumentation loop powered microprocessor based transmitter with low current requirements and increased sensitivity.
Howard S. Silvus, Jr.; Edward J. Miller, Jr.; J. Marion Matherne; Tony W. Harper