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AssigneeEndress + Hauser GmbH + Co. KG
InventorBernhard Michalski
Estimating the term…
In distance measurement on the principle of pulse transit time in each measurement cycle in a transmitting phase a transmission pulse having a given transmission frequency is emitted and in a subsequent receiving phase the envelope of the received signals is formed to determine the transit time of the useful echo pulse. For suppressing the fixed target echoes a broken line of several segments surrounding the envelope of the fixed target echo is formed for each fixed target echo. For each segment, information as to the amplitude of the end point of the segment, as to the changing direction and slope of the segment, as well as for the first segment information as to the point in time of the start of the first segment in the measurement cycle are stored. In the course of the measurement cycle as of the point in time of the start of the first segment, for each segment, counting pulses having a repetition frequency dictated by the slope information are counted in a counting direction dictated by the direction information up to achieving a count dictated by the amplitude information. In the course of the measurement cycle each current count is used to control fixed target echo suppression.
A method for suppressing fixed target echoes when measuring a distance based on the principle of pulse transit time in which each measurement cycle of the distance measurement consists of a transmitting phase and a receiving phase, in the transmitting phase a transmission pulse having a given transmission frequency is emitted and in the subsequent receiving phase an envelope of the received signals with the given transmission frequency is formed to determine the transit time of an useful echo pulse and to compute therefrom the distance to be measured, and wherein, prior to the measurement cycle, information relating to the fixed target echoes is acquired and stored for use in each measurement cycle for suppressing the fixed target echoes, said method comprising the following steps:
An apparatus for distance measurement based on the principle of pulse transit time that suppresses fixed target echoes from fixed targets during a measurement cycle, comprising means for emitting a transmission pulse in a transmitting phase of each measurement cycle and a signal processing circuit for processing received signals received in a receiving phase following the transmitting phase of each measurement cycle, said signal processing circuit containing an analog subcircuit for amplifying and filtering the received signals and for forming an envelope of the received signals, and said signal processing circuit containing a distance counter, which during the measurement cycle, continuously counts the cycles of a clock signal to measure time elapsed since the commencement of the measurement cycle, wherein prior to the measurement cycle, information describing each fixed target echo is acquired and stored as a broken line consisting of a first segment and subsequent segments which surround the fixed target echo, said signal processing circuit includes, for each fixed target echo to be suppressed, a fixed target circuit containing a fixed target memory in which fixed target echo amplitude information, fixed target echo direction information and fixed target echo slope information are stored for all segments of the broken line in a table which contains a row for each segment, and each fixed target circuit contains a fixed target start register storing information as to the start time of the first segment in the measurement cycle, each fixed target circuit also contains a fixed target start comparator which continuously compares the information stored in the fixed target start register to the count of the distance counter and which on detecting equality activates row-by-row processing of the information stored in the fixed target memory.
Dependencies are inferred from the claim text.