Endress+hauser Gmbh+co.

Endress + Hauser Gmbh + Co. Kg

Roland Muller

Sergej Lopatin

Igor Getman

Robert Lalla

Herbert Schroth

Peter Klofer

Winfried Maier

Bernd Strutt

Rolf Schwald

Stefan Cramer

Michael Sinz

A method which allows especially the extrapolation of the measured value at the upper and lower end of a measuring range where normally no direct measurement range where normally no direct measurement is possible by superposition of interfering signals, for example by reflection on a radar antenna. In the presence of strong interference signals, for example by reflection of a radar antenna. In the presence of strong interference signals, which are for example caused by the natural resonance of the container or neck in which the measuring device is mounted, the direct level indicator signal can be regularly used if it has a high amplitude caused by a superposition with the interfering signal lies between two interfering signals and does not extend beyond these, the level indicator value can be interpolated by the shift of the signals from the point of reflection. The inventive method automatically adapts itself to a prevailing measuring situation while according to known methods for the user has to decide between a measurement via a shift of EOL signal or a measurement via the direct level indicator echo.

Method for evaluating the measurement signals of a propagation-time based measurement device

Sensing the level of a liquid in a vessel by the pulse transit time technique is done by means of an ultrasonic transducer mounted above the highest-permissible level in the vessel which emits ultrasonic transmission pulses to the surface of the liquid and receives the ultrasonic echo pulses reflected from the liquid surface. The level in the vessel is established from the transit time of the ultrasonic pulses. To detect an overfill when the ultrasonic transducer is immersed in the liquid the decaying output signal of the ultrasonic transducer generated by the ringing of the ultrasonic transducer following the end of the each ultrasonic transmission pulse is analyzed. In this arrangement the fact is exploited that due to the better coupling of the ultrasonic transducer to the liquid than to air the ringing duration is shorter when the ultrasonic transducer is covered by the liquid.

Method and assembly for overfill detection in liquid level sensing in a

A level measuring device suitable for highly accurate measurements. A transmission pulse generator generates microwave pulses at a transmission repetition rate and transmits them through an antenna towards a material whose level is to be measured. Echo signal from the surface of the material are received by the antenna. A reference pulse generator generates reference pulses similar to the transmission pulses but at a reference repetition rate which differs from the transmission repetition rate by a small frequency difference. The echo signal and reference pulse are input to a first mixer which generates an intermediate frequency signal that, with respect to the echo signal, is slowed by a time dilation factor equal to the quotient of the transmission repetition rate and the frequency difference. A first subcircuit samples the intermediate frequency signal, the time interval between two successive samplings equaling a time unit. A differential signal generator generates a differential signal which changes with the frequency difference. A second subcircuit determines the period of the differential signal on the basis of the time unit. An evaluation unit determines an actual time interval between two points of the echo signal corresponding to the two sampling points.

Level measuring device operating with microwave

For measuring the level of a material in a vessel by a radar-based method an antenna arranged above the highest level anticipated radiates electromagnetic waves to the surface of the material contained in the vessel and receives reflected echo waves. The transit time of the wanted echo waves reflected by the material surface is measured from which the level is computed. Since this transit time corresponds to the group delay, for determining the reduction factor by which the group velocity of the electromagnetic waves differs from the velocity of propagation in the free space due to the geometry of the propagation space the phase difference of the wanted echo waves relative to a reference oscillation and the group delay are measured for various levels and the reduction factor is determined on the basis of the changes in the phase difference as a function of the group delay.

Radar-based method of measuring the level of a material in a vessel

For monitoring a predetermined level of a liquid in a container an ultrasonic transducer is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored. The ultrasonic transducer contains a piezoelectric element which generates, when excited by an alternating voltage pulse having a given transmission frequency, an ultrasonic transmission pulse which is transferred via a diaphragm to the container wall and which converts ultrasonic vibrations transferred from the container wall to the ultrasonic transducer into electrical reception signals. So that the piezoelectric element for given dimensions can be operated in a large frequency range, and so that a good adaptation to the diaphragm is achieved, the piezoelectric element consists of a porous piezoelectric ceramic having a type 3--3 connectivity.

Device for monitoring a predetermined level of a liquid in a container

For monitoring a predetermined level of a liquid in a container an ultrasonic sensor is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored, said sensor containing an ultrasonic transducer having a diaphragm in contact with the container wall. The components of the ultrasonic sensor including those of the ultrasonic transducer are grouped together in a sensor block which is releasably connected to an adapter secured to the container wall, this adapter being configured so that it can be secured in any way required to containers of differing shape and/or material.

For monitoring a predetermined level of a liquid in a container an ultrasonic transducer is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored. The ultrasonic transducer when excited by an alternating voltage pulse having a given transmission frequency which equals the thickness resonant frequency of the container wall, transfers an ultrasonic transmission pulse to the container wall and converts ultrasonic vibrations, generated by reflected echo pulses, into electrical reception signals that are transferred to an evaluation circuit. In the evaluation circuit, on the one hand the presence or absence of echo signals is detected, and, on the other, the ultrasonic vibrations generated by the after-vibration of the container wall at the end of the transmission pulse are evaluated. As a result of this it can be determined with high error detection reliability whether the measurement point is covered by the liquid or not and whether the measurement arrangement is working satisfactorily.

For monitoring a predetermined level of a liquid in a container an ultrasonic transducer is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored. The ultrasonic transducer contains a piezoelectric element which generates, when excited by an alternating voltage pulse having a given transmission frequency, an ultrasonic transmission pulse which is transferred via a diaphragm to the container wall and which converts ultrasonic vibrations transferred from the container wall to the ultrasonic transducer into electrical reception signals. The diaphragm comprises on the side facing the container wall protuberances which adjoin the container wall. Between the diaphragm and the container wall a coupling layer is arranged, the thickness of which is determined by the height of the protuberances. As a result of this the formation of a layer of air between the diaphragm and the container wall is prevented and a jump in impedance avoided so that a good acoustical coupling exists between the diapragm and the container wall.

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Steinen, Germany

Roland Muller