Method and apparatus for pressure and level transmission and sensing

摘要

This invention provides a method and apparatus for transmitting and sensing liquid pressure (head) and liquid level (depth) in flow metering, tide gauge and liquid salinity or slurry density measurement applications. The invention essentially eliminates the effect of pressure sensor temperature variations and the effect of long-term pressure sensor signal drift on pressure sensing accuracy by resetting the zero and gain of the pressure sensor prior to pressure measurement. A variety of sources of a known differential pressure may be used to reset the gain of the differential pressure sensor by simultaneously exposing both sides of the differential pressure sensor to the known differential pressure. In one embodiment of the invention, the head loss through exhaust port of a spring-biased comparitor is the known pressure differential used to reset the pressure sensor gain. In another embodiment, a U-tube manometer is used to set a known differential pressure across an adjustable differential pressure regulator or an adjustable spring-biased comparitor and that pressure differential is used. The invention provides accurate bubbler pressure measurement under conditions of rapidly varying liquid head by means of a single calibration of a differential pressure sensor instead of sequential calibrations of a gauge pressure sensor. The present invention provides a compact and lightweight manifold-mounted pneumatic integrated circuit and a method for in situ recalibration of relatively inexpensive pressure sensors.