Patent ID: 7334470

Claim:
A level measurement apparatus for measuring a distance to a material having a surface, said level measurement apparatus comprising: a transducer for emitting energy pulses and detecting energy pulses reflected by the surface of the material, said transducer having an operating frequency; a controller operating under stored program control; a transmitter, said transmitter being operatively coupled to said controller; a receiver interface, said receiver interface being operatively coupled to said controller; said stored program including a receive signal processing module; said transducer being operatively coupled to said transmitter and responsive to said transmitter for emitting said energy pulses, and said receiver interface being operatively coupled to said transducer for receiving reflected energy pulses coupled by the transducer; a converter coupled to said receiver interface, said converter being responsive to said receive signal processing module for converting said reflected energy pulses into digital samples and storing said digital samples in memory, said memory being accessible by said controller, and said digital samples providing a digitized echo signal; said receive signal processing module including a processing component for calculating the distance to the surface of material based on said digitized echo signal, said receive signal processing module comprising a low pass filtering program component, said low pass filtering program component operating to low pass filter a plurality of said digital samples; said receive signal processing module including a bandpass filtering program component, said bandpass filtering program component operating to apply a band pass filter to a plurality of said digital samples, said band pass filter having a center frequency corresponding to said operating frequency; and, wherein said receive signal processing module includes an envelope detection program component, said envelope detection program component operating to determine an envelope for said digitized echo signal.