Pressure transducer

• US 4,352,085 A
• Filed: 03/27/1981
• Issued: 09/28/1982
• Est. Priority Date: 04/10/1980
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Herden, Werner
• Primary Examiner(s): Albritton, C. L.
• Application Number:
  US06/248,433
• Time in Patent Office: 550 Days
• Field of Search: 338/32 H, 338/32 R, 338/42, 323/368, 73/728, 73/727, 73/722, 73/721, 73/DIG. 3, 324/251, 324/252
• US Class Current: 338/42
• CPC Class Codes: G01L 9/0041 Transmitting or indicating the displacement of flexible diaphragms
• CPC Class Codes: G01L 9/0082 Transmitting or indicating the displacement of capsules by electric, electromechanical, magnetic, or electromechanical means G01L9/0008 takes precedence
• CPC Class Codes: G01L 9/14 involving the displacement of magnets, e.g. electromagnets

Abstract

Two permanent magnets at an adjustably fixed distance from each other face each other with like poles and are mounted on the moveable portion of a pressure-sensitive membrane, with one magnet near the membrane, and the other one at some distance away, while a Hall-effect sensor of fixed position is located between the magnets. The null point of the output scale and the scope of the transducer characteristic can be set either by adjusting the position of the magnets or by adjusting the amount of their magnetization.

Claims

1. A transducer for measuring pressure comprising a membrane mounted so as to be at least in part displaced by pressure to which it is exposed, a Hall-effect device for producing an electrical signal dependent upon the magnetic field in which it is located, a first permanent magnet mounted for producing a magnetic field such as to provide output of said Hall-effect device which is proportional to the pressure to which said membrane is exposed, a second permanent magnet on the opposite side of said Hall-effect device from which said first permanent magnet, said first and second magnets facing each other with like magnetic poles, and further comprising the improvement which consists in that:

said first and second magnet are connected together and to a pressure-displaceable portion of said membrane by rigid structure so that the relative position of said magnets remains fixed and both may be displaced by said membrane relative to the Hall-effect device located between them.

2. A transducer as defined in claim 1, in which an adjustable bracket (30) is provided for rigidly connecting said first and second magnet (7, 9), said bracket being adjustable at least for adjusting the spacing between said brackets.

3. A transducer as defined in claim 1, in which said first permanent magnet (7) is mounted on said membrane (17) so as to be located between said membrane and said Hall-effect device.

4. A transducer as defined in claim 2, in which said first permanent magnet (7) is mounted on said membrane (17) so as to be located between said membrane and said Hall-effect device.

5. A transducer as defined in claim 1, in which the magnetization of said magnets (7, 9) is adjusted so to provide a specified zero point and slope in the electrical signal provided by said Hall-effect device in response to changes in pressure to which said membrane is exposed.

6. A transducer as defined in claim 1, 2, 3, 4 or 5, in which said magnets (7, 9) consist of a cobalt-samarium compound.