MEASURING DEVICE FOR DETERMINING A DISTANCE IN A CONDUCTING STRUCTURE

Abstract

The invention relates to a distance-measuring device for determining a distance between a reflection body in a conducting structure and a coupling region for electromagnetic waves, which region is provided on an end section of the conducting structure, said measuring device comprising a transmitting and receiving device, and a conduction junction (1) provided on the coupling region, for coupling the transmitting and receiving device to the conducting structure containing a medium, in order to couple an electromagnetic wave into the conducting structure, and to decouple the electromagnetic wave, reflected on the reflection body, from the conducting structure. Said measuring device also comprises an evaluation device for determining the distance between the coupling region and the reflection body from the complex reflection coefficient between the coupled electromagnetic wave and the decoupled electromagnetic wave. The invention also relates to the corresponding method.

Claims

1. A distance measuring device for determining a distance between a reflection body in a conducting structure and a coupling region for electromagnetic waves, which region is provided on an end section of the conducting structure, a) comprising a transmitting and receiving device and a conduction junction (1) provided on the coupling region for coupling the transmitting and receiving device to the conducting structure containing a medium in order to couple an electromagnetic wave into the conducting structure and to decouple the electromagnetic wave reflected on the reflection body from the conducting structure, b) comprising an evaluation device for determining the distance between the coupling region and the reflection body from the complex reflection coefficient between the coupled electromagnetic wave and the decoupled electromagnetic wave.

2. The distance measuring device according to claim 1, characterised in that a measuring line (3) is provided for detecting the material properties of the medium in the region of coupling into the line structure for determining distance, the measuring line (3) preferably being a TEM line such as, for example, a coaxial line.

3. The distance measuring device according to claim 2, characterised in that the measuring line (3) for detecting material properties is operated in transmission and a) is connected to an HF transmitter (9) on the evaluation electronics by a coupling structure, and b) is connected to an HF receiver (10) on the evaluation electronics by a decoupling structure.

4. The distance measuring device according to claim 2, characterised in that the measuring line (3) for detecting material properties is operated in reflection and a) is connected to an HF transmitter (9) and an HF receiver (10) on the evaluation electronics by a directional coupler (8), and b) the reflection point of the measuring line (3) can be described analytically, such as for example as an open line end.

5. The distance measuring device according to claim 2, characterised in that by means of the HF receiver (10) and the HF transmitter (9) connected to the measuring line (3) the phase is measured which corresponds to the electrical length of the measuring line (3), including the electrical length of feed lines and any necessary passive components.

6. A method for determining a distance, in particular using a distance measuring device, between a reflection body in a conducting structure that has a medium and a coupling region for electromagnetic waves provided on an end section of the conducting structure, which comprises the following procedural steps: a) determining the relative permittivity of the medium in the conducting structure with the aid of a measuring line (3) for detecting the material properties of the medium, b) coupling an electromagnetic wave into the conducting structure by means of a conduction junction (1) in the coupling region, c) decoupling the electromagnetic wave reflected on the reflection body from the conducting structure by means of the conduction junction (1), and d) determining the distance between the coupling region and the reflection body from the phase difference between a number of frequencies and the corresponding electrical lengths in the conducting structure between the coupled and the decoupled electromagnetic wave.

7. A method for determining a distance between a reflection body in a conducting structure and a coupling region for electromagnetic waves provided on an end section of the conducting structure, comprising the procedural steps: a) coupling an electromagnetic wave into the conducting structure by means of a conduction junction in the coupling region, b) decoupling the electromagnetic wave reflected on the reflection body from the conducting structure by means of the conduction junction, c) measuring the phases and amplitude relationship with the evaluation unit and determining a complex reflection factor, d) determining the distance between the coupling region and the reflection body with the aid of the wavelengths in the dispersive line determined by means of the dielectric properties and the phase relationships of the extracted S-parameter block of the conducting structure taking into account the n*2*PI ambiguity of the phase.

8. The method according to claim 7, which further comprises the step: extracting with the complex reflection factor measured the S-parameter block that represents the measuring line for the distance measurement

9. The method according to claim 7, which further comprises the steps: determining the dielectric properties of the medium, in particular the relative permittivity from the dispersive frequency characteristics of the wavelength in the conducting structure that is dependent upon the dielectric properties with the aid of an extracted S-parameter block of the components before and in order to couple into the conducting structure and taking into account a phase of the extracted S-parameter block that is ambiguous by n*2*PI.

10. The method according to claim 6, which further comprises the steps: determining the relative permittivity of the medium in the conducting structure with the aid of a measuring line for detecting material properties.

11. The method according to claim 6, characterised in that when determining the distance with the aid of the phase difference between a number of frequencies, information on the phase difference, the distance and the dielectric properties is available as a reference value by means of a calibration measurement and using an additional measuring system.

12. The method according to claim 6, characterised in that the relative permittivity with greater than or equal to a frequency is determined by the time or frequency duplex method and is specified by averaging the results with different frequencies.

13. The method according to claim 6, characterised in that the measuring line (3) is decoupled for the respectively initiated frequencies from the conducting structure in order to measure a distance.

14. The method according to claim 6, characterised in that the S-parameter block is determined by a parameter search with the aid of error minimisation by modelling an ideal measuring line for the distance measurement, the distance reference information and the measured values of the evaluation unit of the complex reflection factor for greater than or equal to 2 measuring positions and greater than or equal to 2 frequencies.

Description

[0054] Further advantages, features and possible applications of the present invention emerge from the following description of preferred exemplary embodiments in connection with the drawings. The latter show as follows:

[0055] FIG. 1 a perspective illustration of an embodiment of the distance measuring device with a conduction junction on a conducting structure made in the form of a cylinder;

[0056] FIG. 2 a perspective illustration of an embodiment of the distance measuring device with a conduction junction on a cylinder and additionally a line for detecting material properties with a coupling and decoupling point;

[0057] FIG. 3 the high frequency equivalent circuit diagram of an embodiment of the distance measuring device with the essential components before the conduction junction which must be de-embedded for determining permittivity and measuring a distance; and

[0058] FIG. 4 the high frequency equivalent circuit diagram of an embodiment of the distance measuring device with the essential components before the conduction junction including the components for coupling the line for the material detection (FIGS. 1 and 2) that must be de-embedded for determining permittivity and measuring a distance.

[0059] FIG. 1 shows a perspective simplified illustration of an embodiment of the distance measuring device with a conduction junction, in a coupling region CR, as a mode transformer 1 for the coupling of the coaxial wave into a waveguide wave in the E01 mode into the dispersive conducting structure made in the form of a cylinder 4. Also illustrated is a mechanical piston stop 7 that in particular protects the mode transformer 1 from colliding with the piston 5, actuated here by the piston rod 6

[0060] FIG. 2 shows a perspective simplified illustration of an embodiment of the end section of a cylinder of the distance measuring device with a conduction junction, in a coupling region CR, as a mode transformer 1 for coupling the coaxial wave into a waveguide wave in the E01 mode into the dispersive conducting structure or cylinder 4 and a measuring transmission line for detecting material 3 operated in transmission. The piston 5 reflects waves coupled into the cylinder 4, and therefore behaves as a reflection body. The wave guided in the line for detecting material is fed via the coupling and decoupling points 2. A high degree of coupling of the two different coupling structures 1, 3 is guaranteed by the embodiment and the positioning of the line for detecting material 3.

[0061] FIG. 3 shows the high frequency equivalent circuit diagram of an embodiment of the distance measuring device with the essential components before the conduction junction 15. Shown here is the entire signal path of the signal generation in the HF transmitter 9, the connections on the circuit board 14, a directional coupler 8 for transmitting the energy via other connections 14 to the coupling point of the distance measuring device 15. After coupling into the conducting structure 16 the wave propagation takes place in the dispersive conducting structure and the reflection in the piston in a conducting structure.

[0062] Furthermore, the reflected wave is conveyed further with the coupling structure for mode transformation 15 via a connection 14 to the directional coupler 8, where it is conveyed on to the HF receiver 10. The complex reflection factor is measured here at the HF receiver 10 by a phase synchronisation by means of an Lo line 11 of the HF transmitter 9.

[0063] For the extraction of the dielectric properties and of the distance measurement in changing environmental conditions described in the invention, in this connection the electrical lengths and reflection factors of the components 8 (directional coupler), 9 (HF transmitter), 10 (HF receiver), 14 (connection), 15 (coupling structure for the mode transformation) of the complex reflection factor measured, measured at the output of the receiver 13, are to be de-embedded. This de-embedded complex reflection factor describes the electrical characteristics of the conducting structure 16 for the distance measurement and is drawn upon in the method described in the invention for determining permittivity and distance according to claim 13. The different frequencies are set here by a control signal 12 to the HF transmitter.

[0064] FIG. 4 shows the high frequency equivalent circuit diagram of an embodiment of the distance measuring device equivalent to FIG. 3, but extended by the components which are required for use of the line in order to detect material properties. For the implementation of a transmission line for detecting material properties, in this connection the signal path starting from a second HF transmitter 9 via connections 14 for coupling to the transmission line in the region of the coupling point for the distance measuring device 17 is shown.

[0065] After decoupling the line for detecting material a second HF receiver 10 is connected.

[0066] All of the technical features disclosed in the present documents are claimed as essential to the invention.