Method and apparatus for discriminating between liquids and gases

摘要

An apparatus and method for detecting a liquid/gas interface flowing in a transparent tube comprises directing light radially through the transparent tube orthogonal to its longitudinal axis such that the radially directed light passing through the tube when filled with liquid thereat will extend substantially within a predetermined zone and when filled with gas thereat will extend beyond the predetermined zone. Light is received at a position diametrically opposite to a position from which light is directed by receiving only light passing through the tube and extending beyond the predetermined zone. An output signal representative of liquid or gas in the tube is produced in response to the amount of light received. A second light receiver disposed outside the zone is used to determine the direction of flow.