A process for setting the transmission frequency of a distance measuring instrument operating according to the echo-sounding principle

摘要

PCT No. PCT/EP93/02630 Sec. 371 Date Jun. 1, 1994 Sec. 102(e) Date Jun. 1, 1994 PCT Filed Sep. 28, 1993 PCT Pub. No. WO94/08252 PCT Pub. Date Apr. 14, 1994.In order to set a range finding instrument operating according to the echo-sounding principle using sonic or ultrasonic pulses to an optimum transmission frequency, the transmission frequency is altered stepwise within a predetermined frequency range. During each reception spell following on the transmission of a sonic or ultrasonic pulse an amplitude-time-profile of the received signals is formed and integrated. The integration values obtained for the various transmission frequencies are stored, and an optimum transmission frequency is set to that frequency at which the maximum integrated value is obtained. In order to eliminate the effects of background noise on the determination of the optimum transmission frequency a mean noise amplitude of the received signals is determined and subtracted from the amplitude-time-profile of the received signals before integration.