INDUCTIVE SENSOR AND METHOD FOR THE OPERATION THEREOF

Abstract

An inductive sensor (10) has a substrate (20), on which multiple transmitter/receiver coils (31, 32, 33) are arranged side by side. It can be operated in such a way that the transmitter/receiver coils (31, 32, 33) are each stimulated independently of one another at a frequency of more than 100 MHz.

Claims

1. An Inductive sensor comprising a substrate on which multiple transmitter/receiver coils are arranged side by side.

2. The Inductive sensor according to claim 1, wherein at least two of the transmitter/receiver coils are connected to a common integrated circuit which has one oscillator per transmitter/receiver coil and at least one measuring element per transmitter/receiver coil.

3. The Inductive sensor according to claim 2, further wherein the integrated circuit is arranged on the substrate.

4. The Inductive sensor according to claim 3, further wherein the transmitter/receiver coils are arranged on the integrated circuit.

5. The Inductive sensor according to claim 1, further wherein the transmitter/receiver coils have the same dimensions.

6. The Inductive sensor according to claim 1, further wherein each transmitter/receiver coil has 1 to 4 windings.

7. The Inductive sensor according to claim 1, further wherein the substrate is circular and each transmitter/receiver coil has a diameter or a minor axis of at most 50% of the diameter of the substrate.

8. The Inductive sensor according to claim 1, further comprising a reference transmitter/receiver coil.

9. The Inductive sensor according to claim 8, further wherein the reference transmitter/receiver coil is one of the transmitter/receiver coils arranged side by side on the substrate.

10. The Inductive sensor according to claim 8, further wherein the reference transmitter/receiver coil is arranged together with a reference target on a substrate.

11. The Inductive sensor according to claim 1, further wherein the transmitter/receiver coils are each stimulated independently of one another at a frequency of more than 100 MHz.

12. The Inductive sensor according to claim 11, further wherein reception signals of several of the transmitter/receiver coils are combined to determine a lateral and axial position of a target.

13. The Inductive sensor according to claim 12, further wherein the combining of the reception signals takes place in an integrated circuit which controls the transmitter/receiver coils.

14. The Inductive sensor according to claim 11, further wherein the transmitter/receiver coils are stimulated simultaneously.

15. The inductive sensor according to claim 11, further wherein the transmitter/receiver coils are stimulated in succession.

16. The Inductive sensor according to claim 11, further wherein a time reference signal is generated by a reference transmitter/receiver coil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Exemplary embodiments of the invention are depicted in the drawings and are explained in more detail in the following description.

[0022] FIG. 1 shows a partially cut isometric depiction of an inductive sensor according to an exemplary embodiment of the invention.

[0023] FIG. 2 shows a schematic depiction of important components of an inductive sensor according to an exemplary embodiment of the invention.

[0024] FIGS. 3a to 3c show arrangements of reference transmitter/receiver coils on a circular substrate in different exemplary embodiments of the inductive sensor according to the invention.

[0025] FIG. 4 shows important components of an inductive sensor according to another exemplary embodiment of the invention.

[0026] FIGS. 5a to 5b show the arrangement of transmitter/receiver coils on a circular substrate in other exemplary embodiments according to the invention.

EXEMPLARY EMBODIMENTS OF THE INVENTION

[0027] An inductive sensor 10 according to a first exemplary embodiment of the invention has a housing 11, which consists of a metal. The housing 11 is substantially circular-cylindrical and has an opening on its front side which is closed by a plastic disc 12. Within the housing 11, a circular substrate 20 in the form of a printed circuit board is arranged directly behind the plastic disc 12. A further printed circuit board 21 is connected to the substrate 20 and extends along the longitudinal axis of the housing 11. It carries various electronic components of the inductive sensor 10. On the side of the substrate 20 facing the plastic disc 12, three circular transmitter/receiver coils 31, 32, 33 are arranged, which are designed as open coils and each have one winding.

[0028] Each of the transmitter/receiver coils 31, 32, 33 forms part of a measuring channel 41, 42, 43. In each of the measuring channels 41, 42, 43, the respective transmitter/receiver coil 31, 32, 33 is connected in parallel to a capacitor 411, 421, 431 and connected to an oscillator 412, 422, 432. Each oscillator 412, 422, 432 is connected to two measuring elements, namely to a measuring element 413, 423, 433 for measuring a frequency and a measuring element 414, 424, 434 for measuring an amplitude. The measuring elements 413, 423, 433 for measuring the frequency are designed as frequency counters. The capacitors 411, 421, 431, the oscillators 412, 422, 432 and the measuring elements 413, 414, 423, 424, 433, 434 are arranged in an integrated circuit 50. This circuit is located on the side of the substrate 20 opposite the transmitter/receiver coils 31, 32, 33. It is connected to a computing device 60 in the form of a microcontroller, which is arranged on the other circuit board 21. The computing device 60 has an integrated temperature sensor 61. An IO-link transceiver 62 serves as a sensor backend for the transmission of measurement data from the inductive sensor 10.

[0029] To measure the axial and lateral position of an object, two of the transmitter/receiver coils 31, 32 are stimulated by their oscillators 412, 422. A change in the frequency and amplitude of their magnetic fields is detected in their measuring elements 413, 414, 423, 424 and is first passed on to the integrated circuit 50 and then to the computing device 60. In this way, the transmitter/receiver coils 31, 32 are excited simultaneously or consecutively. The third transmitter/receiver coil 33 functions as a reference transmitter/receiver coil. For this purpose, it has a reference target which is not shown. A time reference signal is generated in the integrated circuit 50 by means of the reference transmitter/receiver coil 33. The measured frequency and amplitude values are calculated with the time reference signal and passed on to the calculator 60. Taking into account the data from the temperature sensor 61, the axial and lateral position of the object is calculated there.

[0030] FIG. 3a shows that the diameter d.sub.31 of the first coil 31, which also corresponds to the diameters of the other two equally sized transmitter/receiver coils 32, 33, is less than 45% of the diameter d.sub.20 of the substrate 20. In a second exemplary embodiment of the inductive sensor, however, the transmitter/receiver coils 31, 32, 33 are not circular but instead ellipsoidal, as shown in FIG. 3b. Each of the transmitter/receiver coils 31, 32, 33, which in turn are of the same size, has a minor axis a.sub.32 whose length is less than 45% of the diameter d.sub.20 of substrate 20. In a third exemplary embodiment of the inductive sensor, the three transmitter/receiver coils 31, 32, 33, as depicted in FIG. 3c, each have a boomerang shape.

[0031] FIG. 4 shows a fourth exemplary embodiment of the design sensor 10. In this exemplary embodiment, only two of the transmitter/receiver coils 31, 32 are arranged on the side of the substrate 20 facing the plastic disc 12. The third transmitter/receiver coil 33 is arranged together with a reference target inside the substrate 20, which is designed for this purpose as a multilayer printed circuit board. The third transmitter/receiver coil 33 can therefore function again as a reference transmitter/receiver coil. In contrast to the previous exemplary embodiments, each of the measuring channels 41, 42, 43 has its own integrated circuit 51, 52, 53. Otherwise, the structure of this exemplary embodiment of the inductive sensor corresponds to the first exemplary embodiment. The inductive sensor 10 according to the fourth exemplary embodiment enables a redundant measurement by means of its first measuring channel 41 and its second measuring channel 42. This makes is suitable for use in safety-relevant environments.

[0032] As depicted in FIG. 5a, the two transmitter/receiver coils 31, 32 in the fourth exemplary embodiment each have a circular shape. In a fifth exemplary embodiment, which is depicted in FIG. 5b, they are each ellipsoidal. In these two exemplary embodiments, the diameter and the length of the minor axis of each of the transmitter/receiver coils 31, 32 are also less than 45% of the diameter of the substrate 20.