| 摘要 |
Acoustic level sensing apparatus is provided, in which pulses of acoustic energy are transmitted by an electrically energized transducer towards a surface to be sensed, and the electrical output from the transducer following the pulse received by a receiver is digitized and analyzed by a programmed microprocessor to detect a return echo from the surface, so as to produce a digitized echo profile. The digitized echo profile is enhanced by removing narrow peaks likely to correspond with certain types of spurious echo and narrow valleys which may represent fragmentation of a wanted echo. Echoes are identified by comparing the profile with a time varying threshold generated derived from a linear regression performed on part of the echo profile various different types of comparison being performed and their results combined prior to selecting the most likely true echo on the basis of the combined results. |
