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AssigneeEndress u. Hauser GmbH u. Co.
InventorsAndre Elle, Hartmut Schmidt
Estimating the term…
For the measurement of distance using the pulse transit time principle the received signal produced after each transmission of a pulse is stored as an echo profile and the effective echo is determined from the stored echo profile. In order to suppress recurrent interfering signals a stationary threshold profile adapted to the measurement environment is formed and employed for each evaluation of a stored echo profile. In order to take into account fluctuations in the properties of the received echo profile rapidly without necessitating a modification in the stationary threshold profile for this, from a stored echo profile a floating threshold profile is generated in the form of a monotonously descending curve. From the mutually corresponding values of the floating threshold profile and of the stationary threshold profile the respectively larger value is utilized for the formation of a resulting threshold profile, which is employed for each evaluation of stored echo profiles.
A method for distance measurement using the pulse transit time principle, in which in consecutive measurement cycles in each case in a transmission phase a pulse is transmitted and in a receiving phase following the transmission phase the received signal is stored as an echo profile, in which further from at least one stored echo profile the effective echo reflected at the object to be measured is ascertained and the distance of the object is ascertained from the interval in time between the transmission of the pulse and the reception of the effective echo, and in which a stationary threshold profile is formed, which is adapted to the measurement environment for suppression of recurrent interfering signals and is employed in each evaluation of stored echo profiles, said method comprising the steps that from a stored echo profile a floating threshold profile is generated by freeing the echo profile of fluctuations by smoothing it in such a manner that the result is a curve that never increases in value, that of the mutually corresponding values of the floating threshold profile and of the stationary threshold profile the respectively larger value is utilized for forming a resulting threshold profile, and that the resulting threshold profile is employed for each evaluation of stored echo profiles.
An arrangement for distance measurement using the pulse transit time principle, comprising a transmitting and receiving device for transmitting a transmission pulse in each measurement cycle and for receiving the echo signals arriving as a result of each transmission pulse, and a signal processing circuit connected with the transmitting and receiving device, said signal processing circuit comprising an echo profile memory in which at least one echo profile is stored, which corresponds to the received signal supplied by the transmitting and receiving device in the course of a measurement cycle, an evaluation circuit which from the echo profile stored in the echo profile memory ascertains the effective echo reflected at the object to be measured and determines the distance of the object from the time interval between the transmission of the pulse and the reception of the effective echo, and a stationary threshold profile circuit in which a stationary threshold profile adapted to the measurement environment is stored, which renders possible the suppression of recurrent interfering signals on each evaluation of a stored echo profile by the evaluation circuit, said arrangement further comprising a floating threshold profile circuit with a device for generating and storing a smoothed and floating threshold profile that never increases in value from a stored each profile, and a combinatorial circuit for combining the floating threshold profile with the stationary threshold profile for forming and storing a resulting threshold profile, which is supplied to the evaluation circuit for the evaluation of the echo profile stored in the each profile memory.
Dependencies are inferred from the claim text.