| 摘要 |
PURPOSE: To select a real echo by providing an electric acoustic transducer, a transmitter and a receiver. CONSTITUTION: An interface 16 is provided for a transmitter 18 that transmits a pulse to an external ultrasonic wave transducer 20 and an interface 22 is provided for an A/D converter 24 that receives a feedback signal from the transducer 20 via a receiver 26 and a feedback signal from an external temperature sensor 28. A calculation means 12 forms a time-change threshold value file in accordance with a digital database file, compares both of the database files with each other and forms a comparison file of peak data of an echo profile. Before or during the comparison processing, at least one of the database files and the data in the time-change threshold value file are processed so that the possibility of being influenced by a false characteristic of the profile in the received signal is reduced when a real echo is recognized from the data in the comparison file.
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