Survey of liquid-level detection devices used in safeguards and their performance values

摘要

Liquid-level detection devices commonly used in safeguards for measuring the liquid volume in a tank were investigated. The study addressed physical models, limitations and advantages, measurement uncertainties, and measurement control techniques. Volume measurements are necessary to determine the amounts of material in liquids in process tanks. To calculate the volume, a calibration curve is used to relate volume to liquid height. Calibration curves depend on the geometric shape of the tank. For a closed process tank, the distance from the bottom of the tank to the liquid surface (i.e., height) in general cannot be measured directly. Level measurement devices can be grouped according to four measurement points of reference. These are: tip of probe, length of submerged probe, top of tank, and liquid surface. Level detection techniques corresponding to these measurement points are pressure, electrical characteristics of the probe, sonic reflections, and visual scales.