Device and method for capacitive determination of a proportion of a substance in a material

Abstract

A device and a method for capacitive determination of a proportion of a substance in a material. The device includes an oscillating circuit with a coil and a plate capacitor, wherein the oscillating circuit can be excited to oscillate at different frequencies or inductances. It is provided that the frequency response or resonant frequencies of the oscillating circuit are recorded and evaluated with regard to characteristic features. On the basis of the frequencies that can be assigned to these characteristic features, the proportion of a specific substance in the material to be measured can be determined. The method for capacitive determination of a proportion of a substance in a material is based in particular on the fact that the dielectric properties of the substance are used in the method in order to determine the proportion of the substance in the material to be measured.

Claims

1-13. (canceled)

14. A device for capacitive determination of a proportion of a substance in a material, the device comprising: an oscillating circuit with a coil and a plate capacitor, the plate capacitor fillable with the material as a dielectric, a frequency response of the dielectric being recorded and evaluated in order to determine the proportion of the substance in the material.

15. The device as recited in claim 14 wherein the determination of the proportion of the substance in the material takes place capacitively.

16. The device as recited in claim 14 further comprising a voltage source set up to excite the oscillating circuit to oscillate.

17. The device as recited in claim 14 further comprising a controller set up to record the frequency response of the dielectric.

18. The device as recited in claim 17 wherein the controller is also set up to apply different frequencies to the dielectric.

19. The device as recited in claim 18 wherein frequencies applied to the dielectric lie in a range from 0 to 1000 kHz.

20. The device as recited in claim 19 wherein the frequencies applied to the dielectric lie in a range from 10 to 800 kHz.

21. The device as recited in claim 20 wherein the frequencies applied to the dielectric lie in a range from 100 to 500 kHz.

22. The device as recited in claim 14 further comprising capacitance diodes for setting different frequencies in the oscillating circuit.

23. The device as recited in claim 22 wherein the capacitance diodes are connectable in series or in parallel to the plate capacitor of the oscillating circuit.

24. The device as recited in claim 14 further comprising a relay, an analog switch or a gyrator circuit for setting different frequencies in the oscillating circuit.

25. A method for capacitive determination of a proportion of a substance in a material, the method comprising the following steps: a) providing the device as recited in claim 14; b) filling the plate capacitor with the material, wherein the proportion of the substance in the material is to be determined; c) setting different frequencies or inductances in an oscillating circuit of the device; d) recording a frequency response or resonant frequencies of the material; e) evaluating the frequency response or the resonant frequencies by searching for characteristic features; f) determining the proportion of the substance using characteristic frequencies assignable to the characteristic features.

26. The method as recited in claim 25 wherein dielectric properties of the substance are used to determine the proportion of the substance in the material.

27. The method as recited in claim 25 wherein changes in frequencies are brought about by setting the different inductances, the inductances describing properties of a coil of the oscillating circuit.

28. The method as recited in claim 25 wherein changes in the frequencies are brought about by setting different capacitances, the capacitances describing properties of capacitance diodes or of the plate capacitor of the oscillating circuit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In the figures, identical and similar components are denoted by the same reference signs. In the figures:

[0066] FIG. 1 shows a schematic representation of a preferred embodiment of the device; and

[0067] FIGS. 2a and 2b show a plot of the recorded voltage against different frequencies that can be set in the oscillating circuit for determining the wanted proportion of a substance.

DETAILED DESCRIPTION

[0068] FIG. 1 shows a schematic representation of a preferred embodiment of the device 1. The device 1 comprises an electromagnetic oscillating circuit 2, which in turn comprises a coil L and a capacitor C. The capacitor C is formed as a plate capacitor. It preferably has two plates between which there is an electric field. A material, such as for example dust, can be filled into the volume that is formed between the plates of the plate capacitor. For the purposes of the invention, it is preferred that this material is to be examined for its constituent substances, as well as their proportions in the material.

[0069] Different frequencies can be applied to the oscillating circuit 2. The corresponding oscillations are excited by a voltage source 3. The voltage source 3 may preferably be formed as a frequency generator or a sine-wave generator. For the purposes of the invention, it may also be preferred that the control unit 4 and the voltage source 3 form a unit.

[0070] Furthermore, the device 1 may comprise a control unit 4, which is preferably formed as a microcontroller. For the purposes of the invention, it is preferred that the control unit 4 is set up to record the frequencies in the oscillating circuit 2 and its quality. In addition, the control unit 4 may be set up to electrically set or “loop in” the capacitances and inductances of the oscillating circuit 2. A relay, an analog switch and/or a gyrator circuit shown schematically as SW can also set different frequencies in the oscillating circuit 2. For the purposes of the invention, it is preferred that the control unit 4 comprises a device for voltage measurement, which may be formed for example as an oscilloscope with an integrated option for performing a Fast Fourier transformation. For the purposes of the invention, it is particularly preferred that the control unit 4 is intended in particular to carry out frequency measurements.

[0071] The oscilloscope is preferably set up to record an amplitude of the frequency falling across the capacitor C. For the purposes of the invention, it is preferred that the amplitude of the frequency falling across the capacitor C represents the measured variable in the method. For the purposes of the invention, it is particularly preferred that the amplitude is recorded over the sinusoidal frequency. This preferably means the excitation of the electromagnetic oscillating circuit 2 with a preferably sinusoidal excitation signal, which can be generated by a frequency generator. The peak values of the voltage of the empty capacitor C are then compared with the peak values of the capacitor C filled with dust containing quartz. The resonant frequencies can be determined by the position of the peaks in the frequency-inductance diagrams or the voltage-frequency diagrams.

[0072] FIGS. 2a and 2b show a plot of the recorded voltage against different frequencies that can be set in the oscillating circuit 2 for determining the wanted proportion of a substance. FIG. 2a shows a voltage-frequency diagram for a quartz-free dust, while FIG. 2b shows a voltage-frequency diagram for a quartz-containing dust. In other words, the material to be measured in FIG. 2a is quartz-free dust and the material to be measured in FIG. 2b is quartz-containing dust. On the x-axis of the voltage-frequency diagram, the frequency or the resonant frequency f of the oscillating circuit is plotted in the unit kilohertz (kHz), while on the y-axis of the voltage-frequency diagram the voltage U recorded by the control unit 4 is plotted in the unit volt (V). The diagrams shown in FIGS. 2a and 2b allow the frequency response to be evaluated by searching for characteristic features, as according to the first evaluation method using voltage-frequency diagrams. The proportion of the substance is determined in particular using characteristic frequencies fc, which can be assigned to the characteristic features.

[0073] FIG. 2b clearly shows the characteristic frequencies fc1 and fc2, which are at frequencies of approximately 150 kHz and 250 kHz. The position of these characteristic frequencies fc1 and fc2 suggests that quartz is present in the examined dust with which the plate capacitor C of the device 1 is filled. In the example of the invention shown in FIGS. 2a and 2b, quartz is the substance of which the proportion in the material to be measured, here dust, is to be determined.

LIST OF REFERENCE SIGNS

[0074] 1 Device [0075] 2 Oscillating circuit [0076] 3 Voltage source [0077] 4 Control unit [0078] L Coil [0079] C Capacitor [0080] SW Relay, Analog Switch and/or a Gyrator Circuit