Patent ID: 6843124

Claim:
A level measuring apparatus using electromagnetic waves for measuring the level of the material in a container, the material in the container fining a surface, the apparatus comprising: a two-wire process control loop; an electromagnetic wave antenna extending into the container; a level sensor located above the surface of the material for generating electromagnetic waves, for transmitting electromagnetic waves through said antenna toward the surface of the material and for receiving electromagnetic waves reflected from the surface of the material; a measuring circuit coupled to said level sensor for determining echo function representing amplitudes of electromagnetic waves received by said level sensor as a function of distance, determining the level of the material by evaluating the echo function, and transmitting a level signal representing the level of the material over said two-wire process control loop; and a power supply coupled to said two-wire process control loop for providing the sole source of power for said level sensor and said measuring circuit, wherein said measuring circuit includes a microcomputer that is operable to digitize and record the echo function.