| 摘要 |
1. Apparatus for ultrasonic distance measurements comprising a converter 8 for converting an electrical signal into an acoustic signal and vice versa, a measuring reflector which can be moved, with respect to the converter, within a certain operating range, and a reference reflector positioned at a distance from the converter, an isotropic fluid being present in the area comprising the converter and the reflectors. Positioned at a predetermined distance 1R from the reference reflector is a second reference reflector 14. The first and second reference reflector are positioned outside the measuring reflector operating range, which extends between the first and the second reference reflector. The distance measurement method involves an acoustic signal being transmitted by a transmitter/converter, and a specific zero passage of an incoming signal received on a receiver/converter via a reflector being found by the incoming signal being compared with a positive and a negative reference level and a positive validation level. <IMAGE>
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