A METHOD AND APPARATUS FOR DETERMINING LIQUID LEVELS IN VESSELS EMPLOYED IN STEAM GENERATING PLANTS AND PROCESS INDUSTRIES

摘要

The invention relates to a method and apparatus for determining liquid levels in vessels employed in steam generating plants and process industries, the liquids being water or chemical solutions and vapor produced from the liquid, the method comprising exciting a plurality of sensors mounted at different levels of the vessel, with an excitation source (103) providing square wave signal, conditioning the response signals from the sensors with a signal conditioner (105), comparing the output from the signal conditioner with the excitation signal using a Phase Comparator (106) and a Magnitude Comparator(107) to detect the time lag and the magnitude of the response signal, and logically interpreting the magnitude and the phase or time lag using a Logic Block (108) to identify at least four different statuses of the sensors, viz. Sensor in Liquid medium (109), Sensor in Vapor medium(110), Sensor system Short (11) and Sensor system Open (112).