Sensor for locating metallic objects and method for evaluating measurement signal of such a sensor

• US 7,759,939 B2
• Filed: 07/25/2005
• Issued: 07/20/2010
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Renz, Kai, Skultety-Betz, Uwe, Haase, Bjoern
• Primary Examiner(s): Whittington; Kenneth J
• Application Number:
  US11/573,572
• Publication Number:
  US 20080303517A1
• Time in Patent Office: 1,821 Days
• Field of Search: 324/67, 324/228, 324/239, 324/242, 324/243, 324/326, 324/329
• US Class Current: 324/326
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: H05K 2201/10151 Sensor

Abstract

A sensor for locating metallic objects, in particular a metal sensor for building materials, includes at least one transmission coil and at least one reception conductor loop system that are inductively coupled to one another. The reception conductor loop system is made up of conductor structures on a printed circuit board. A second reception conductor loop system can be provided, which is situated coaxial to the first reception conductor loop system in a common first plane with it on the printed circuit board. The sensor preferably operates in a frequency range between 1 kHz and 10 kHz.

Claims

1. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) for inducing a flux and at least one reception conductor loop system (112, 212) for receiving said flux modified by a metallic object, wherein said at least one transmission coil (116, 216) and said at least one reception conductor loop system (112, 212) are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a second reception conductor loop system (114, 214) is provided for receiving said flux, wherein said second reception conductor loop system (114, 214) is situated coaxial to the first reception conductor loop system (112, 212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), so that a presence of a metallic object is determined when changes in inductive properties caused by the metallic object are registered by said first and second reception conductor loop systems, and

wherein the sensor operates in a frequency range between 1 kHz and 10 kHz.

2. The sensor as recited in claim 1, wherein an electric shielding electrode (242, 244) is provided between the at least one transmission coil (116, 216) and at least one reception conductor loop system (112, 114, 212, 214), and the electric shielding electrode (242, 244) is embodied on the printed circuit board (100, 200).

3. The sensor as recited in claim 1, wherein a shunt resistor (246) connected in series with at least one transmission coil (116, 216) is provided, which is embodied as a conductor path structure on a printed circuit board (100, 200).

4. The sensor as recited in claim 1, wherein at least one transmission coil (116, 216) is mounted on a winding body and the winding body is fastened to a printed circuit board (100, 200).

5. The sensor as recited in claim 1, wherein at least one transmission coil (116, 216) is situated vertically offset from the plane (126, 226) of the printed circuit board (100, 200).

6. The sensor as recited in claim 5, wherein additional compensation conductor loops (130, 132, 230, 232) of at least one reception conductor loop system (112, 114, 212, 214) are provided in the vicinity of at least one transmission coil (116, 216) on the printed circuit board (100, 200).

7. The sensor as recited in claim 6, wherein the compensation conductor loops (130, 132, 230, 232) are embodied in the form of conductor structures on the printed circuit board (100, 200).

8. The sensor as recited in claim 7, wherein the compensation conductor loops (130, 132, 230, 232) are provided on two opposite sides (201, 202) of the printed circuit board (200).

9. The sensor as recited in claim 8, wherein the compensation conductor loops (130, 132, 230, 232) are oriented in opposite directions while having virtually the same geometry.

10. The sensor as recited in claim 6, wherein the compensation conductor loops (130, 132, 230, 232) are embodied in the form of conductor structures on superposed inner layers of an at least two-layered printed circuit board.

11. The sensor as recited in claim 5, wherein additional compensation conductor loops (130, 132, 230, 232) of at least one reception conductor loop system (112, 114, 212, 214) are provided beneath the at least one transmission coil (116, 216) on the printed circuit board (100, 200).

12. The sensor as recited in claim 1, wherein at least one tuning conductor loop (241) is provided on the printed circuit board (100, 200) and is connectable to the reception conductor loop system (112, 114, 212, 214) via switching means (240).

13. The sensor as recited in claim 12, wherein semiconductor switches, in particular field effect transistors, are used as the switching means (240).

14. A measuring device (500), in particular a hand-held locating device, having at least one sensor as recited in claim 1.

15. The sensor according to claim 1, wherein the sensor operates in a frequency range between 4 to 6 kHz.

16. A method for evaluating the measurement signal of a sensor comprising:

providing a sensor as recited in claim 1; and

digitizing the measurement signals.

17. The method as recited in claim 16, wherein a narrow-band digital filtration is carried out in order to reduce the noise bandwidth by means of digital generation of an excitation signal of the frequency f and phase-synchronous analog/digital conversion of a measuring amplifier output signal of an evaluation circuit of the sensor.

18. The method as recited in claim 17, wherein the phase-synchronous analog/digital conversion of the measuring amplifier output signal occurs with the frequency f_d=4 n f, i.e. at a frequency 4f four times the frequency of the excitation field or an integral multiple n of this frequency.

19. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) for inducing a flux and at least one reception conductor loop system (112, 212) for receiving said flux modified by a metallic object, wherein said at least one transmission coil (116, 216) and said at least one reception conductor loop system (112, 212) are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a second reception conductor loop system (114, 214) is provided for receiving said flux, wherein said second reception conductor loop system (114, 214) is situated coaxial to the first reception conductor loop system (112, 212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), and

wherein a shunt resistor (246) connected in series with at least one transmission coil (116, 216) is provided, which is embodied as a conductor path structure on a printed circuit board (100, 200) so that a presence of a metallic object is determined when changes in inductive properties caused by the metallic object are registered by said first and second reception conductor loop systems.

20. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) for inducing a flux and at least one reception conductor loop system (112, 212) for receiving said flux modified by a metallic object, wherein said at least one transmission coil (116, 216) and said at least one reception conductor loop system (112, 212) are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a shunt resistor (246) connected in series with at least one transmission coil (116, 216) is provided, which is embodied as a conductor path structure on a printed circuit board (100, 200),

further comprising an evaluation circuit (260), which is connectable with both the shunt resistor (246) and at least one reception conductor loop system (112, 114, 212, 214) via switching means (248), wherein the evaluation circuit (260) has at least one bipolar input stage so that a presence of a metallic object is determined when changes in inductive properties caused by the metallic object are registered by said reception conductor loop system.

21. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) and at least one reception conductor loop system (112, 212) that are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a second reception conductor loop system (114, 214) is provided, which is situated coaxial to the first reception conductor loop system (112, 212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), and

wherein the sensor operates in a frequency range between 1 kHz and 10 kHz wherein an electric shielding electrode (242, 244) is provided between the at least one transmission coil (116, 216) and at least one reception conductor loop system (112, 114, 212, 214), and the electric shielding electrode (242, 244) is embodied on the printed circuit board (100, 200).

22. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) and at least one reception conductor loop system (112, 212) that are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a second reception conductor loop system (114, 214) is provided, which is situated coaxial to the first reception conductor loop system (112, 212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), and

wherein the sensor operates in a frequency range between 1 kHz and 10 kHz, and

wherein at least one transmission coil (116, 216) is situated vertically offset from the plane (126, 226) of the printed circuit board (100, 200), and

wherein additional compensation conductor loops (130, 132, 230, 232) of at least one reception conductor loop system (112, 114, 212, 214) are provided in the vicinity of at least one transmission coil (116, 216) on the printed circuit board (100, 200).

23. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) and at least one reception conductor loop system (112, 212) that are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100, 200),

wherein a second reception conductor loop system (114, 214) is provided, which is situated coaxial to the first reception conductor loop system (112, 212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), and

wherein the sensor operates in a frequency range between 1 kHz and 10 kHz, and

wherein at least one transmission coil (116, 216) is situated vertically offset from the plane (126, 226) of the printed circuit board (100, 200), and

wherein additional compensation conductor loops (130, 132, 230, 232) of at least one reception conductor loop system (112, 114, 212, 214) are provided beneath the at least one transmission coil (116, 216) on the printed circuit board (100, 200).

24. A sensor for locating metallic objects, in particular a metal sensor for building materials, having at least one transmission coil (116, 216) for inducting a flux and at least one reception conductor loop system (112, 212) for receiving said flux modified by a metallic object, wherein said at least one transmission coil (112, 216) and said at least one reception conductor loop system (112, 212) are inductively coupled to one another,

wherein the reception conductor loop system (112, 212) is comprised of conductor structures on a printed circuit board (100,200),

wherein a second reception conductor loop system (114, 214) is provided for receiving said flux, wherein said second reception conductor loop system (114, 214)) is situated coaxial to the first reception conductor loop system (112,212), in a common first plane (126, 226) with it on the printed circuit board (100, 200), so that a presence of a metallic object is determined when changes in inductive properties caused by the metallic object are registered by said first and second reception conductor loop systems,

wherein the sensor operates in a frequency range between 1 kHz and 10 kHz, and

wherein a shunt resistor (246) connected in series with at least one transmission coil (116, 216) is provided, which is embodied as a conductor path structure on a printed circuit board (100, 200).

25. The sensor as recited in claim 24, having an evaluation circuit (260), which is connectable with both the shunt resistor (246) and at least one reception conductor loop system (112, 114, 212, 214) via switching means (248).

26. The sensor as recited in claim 24, wherein semiconductor switches, in particular field effect transistors, are used as the switching means (248), and the switching means are situated on the printed circuit board (100, 200).

27. The sensor as recited in claim 25, wherein the evaluation circuit (260) has at least one bipolar input stage.