METAL FACE INDUCTIVE PROXIMITY SENSOR

• US 20090189600A1
• Filed: 11/14/2008
• Published: 07/30/2009
• Est. Priority Date: 01/26/2008
• Status: Active Grant

• Current Assignee: Pepperl + Fuchs GmbH
• Original Assignee: Pepperl+Fuchs, Inc. (Pepperl+Fuchs Se)
• Inventors: Kurkovskiy, Igor
• Granted Patent: US 8,154,278 B2
• Time in Patent Office: Days
• US Class Current: 324/207.160
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: H03K 17/9505 Constructional details
• CPC Class Codes: H03K 17/9545 with variable frequency

Abstract

Metal face inductive proximity sensors and methods are presented for sensing the presence or absence of a target object in a target sensing area in which a coil system is operated to generate a magnetic field extending outward from the sensing face at a frequency in a range that maximizes a relative target effect for the sensing face area, material, and thickness, and a target material from which the target object is made to allow the protective advantages of metal sensing face materials while enhancing sensing distance by optimizing the ratio of the target energy loss to the energy loss in the metal face.

Claims

1. An inductive proximity sensor for sensing the presence or absence of a target object in a target sensing area, the sensor comprising:

a body with a housing and a sensing face extending across a sensing surface facing a target sensing area, the sensing face formed of a metallic material of a given thickness;

a coil system with a coil provided with alternating current to generate an alternating magnetic field extending outward from the sensing face in the target sensing area at a frequency in a frequency range that includes a frequency value that maximizes a relative target effect for the sensing face area, material, and thickness, and a target material from which the target object is made; and

a sensing system operative to sense an impedance of the coil and to provide a signal indicative of the presence or absence of objects in the target sensing area based at least partially on the sensed impedance.

2. The sensor of claim 1, wherein the alternating current is provided to the coil at a frequency value in a range for which the relative target effect is within about 20 percent of the global or relative maximum.

3. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.2 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 8 mm, wherein the target material is aluminum, and wherein the frequency value is about 3,443 Hz or more and about 9,919 Hz or less.

4. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.2 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 8 mm, wherein the target material is stainless steel, and wherein the frequency value is about 15,860 Hz or more and about 66,174 Hz or less.

5. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.2 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 8 mm, wherein the target material is steel, and wherein the frequency value is about 20,156 Hz or more and about 91,093 Hz or less.

6. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 12 mm, wherein the target material is aluminum, and wherein the frequency value is about 1,839 Hz or more and about 4748 Hz or less.

7. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 12 mm, wherein the target material is stainless steel, and wherein the frequency value is about 6,514 Hz or more and about 19,896 Hz or less.

8. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 12 mm, wherein the target material is steel, and wherein the frequency value is about 7,616 Hz or more and about 52,846 Hz or less.

9. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 18 mm, wherein the target material is aluminum, and wherein the frequency value is about 1,039 Hz or more and about 2,711 Hz or less.

10. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 18 mm, wherein the target material is stainless steel, and wherein the frequency value is about 4,071 Hz or more and about 15,603 Hz or less.

11. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 18 mm, wherein the target material is steel, and wherein the frequency value is about 4,746 Hz or more and about 17,217 Hz or less.

12. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 30 mm, wherein the target material is aluminum, and wherein the frequency value is about 700 Hz or more and about 1,798 Hz or less.

13. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 30 mm, wherein the target material is stainless steel, and wherein the frequency value is about 2,896 Hz or more and about 11,632 Hz or less.

14. The sensor of claim 1, wherein the sensing face is formed of a stainless steel metallic material of a thickness of about 0.3 mm or more and about 1.0 mm or less, wherein the sensing face is circular with a diameter of about 30 mm, wherein the target material is steel, and wherein the frequency value is about 3,134 Hz or more and about 19,835 Hz or less.

15. A method for sensing the presence or absence of a target object in a target sensing area, the method comprising:

providing an inductive proximity sensor having a body with a housing and a sensing face formed of a metallic material of a given thickness extending across a sensing surface facing the target sensing area, and a coil;

providing alternating current to the coil to generate an alternating magnetic field extending outward from the sensing face in the target sensing area at a frequency in a frequency range that includes a frequency value that maximizes a relative target effect for the sensing face area, material, and thickness, and a target material from which the target object is made;

sensing an impedance of the coil; and

providing a signal indicative of the presence or absence of objects in the target sensing area based at least partially on the sensed impedance.

16. The method of claim 15, wherein the alternating current is provided to the coil at a frequency value in a range for which the relative target effect is within about 20 percent of the global or relative maximum.