Communications – electrical: acoustic wave systems and devices – Echo systems – Distance or direction finding
Patent
1989-04-12
1990-11-20
Tarcza, Thomas H.
Communications, electrical: acoustic wave systems and devices
Echo systems
Distance or direction finding
367908, 342124, 73290V, G01S 1506
Patent
active
049723863
ABSTRACT:
The filling level meter for measuring the filling level in a container includes a transmitting and a receiving arrangement which directs sonic or ultrasonic pulses onto the filling material surface and receives the backscattered pulses reflected by the filling material surface and converts them to electrical reception signals. Connected to the transmitting and receiving arrangement is an evaluating circuit which in a signal processing path generates an envelope signal corresponding to the envelope of the reception signals, digitizes sampled values of the envelope signal, stores in a memory the digitized sampled values for creating a distance-dependent or travel-time-dependent amplitude profile of the measurement distance and evaluates the amplitude profile for determining the travel time of the most probable useful echo signal. Parallel to the signal processing path for generating the envelope signal, in the evaluating circuit a frequency detection of the echo signals is carried out by which echo signals having the transmission frequency of the sonic or ultrasonic pulses are determined. In dependence upon the result of the frequency detection the signal processing path is opened only for the echo signals having a frequency corresponding to the transmission frequency. As a result all the reception signals having a frequency not corresponding to the transmission frequency are excluded from the digitizing and further processing. Due to the Doppler frequency shift these include all the reception signals which are caused by reflections at moving obstacles. On the other hand, all reception signals having a frequency identical to the transmission frequency are passed on unchanged for the digitizing and further signal processing.
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Endress u. Hauser GmbH u. Co.
Swann Tod R.
Tarcza Thomas H.
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