Endress U. Hauser Gmbh U. Co.

Andre Elle

Gunter Lange

Hartmut Schmidt

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.

Method and an arrangement for distance measurement using the pulse

The arrangement for the conversion of an electrical input quantity into an electrical DC signal proportional thereto comprises two digital pulse duration modulators of limited resolution. The first digital pulse duration modulator supplies a first periodic pulse sequence which is pulse duration modulated with a quantization value, corresponding to the limited resolution, of the input quantity neglecting the quantization remainder. The second digital pulse duration modulator supplies a second periodic pulse sequence which is pulse duration modulated with the sum of the quantization value and of the quantization remainder multiplied by a predetermined factor. A system is provided for selectively transmitting pulses of the first and second pulse sequences to an averaging circuit in such a manner that the raito of the number of transmitted pulses of the second pulse sequence to the total number of transmitted pulses is equal to the reciprocal of the predetermined factor. The averaging circuit forms the DC signal means value of the combined sequence of transmitted pulses, whereby the resolution is enhanced with respect to the limited resolution of the digital pulse duration modulators.

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Rummingen, Germany

Andre Elle