Slaved pressure transducer

• US 4,077,262 A
• Filed: 11/01/1976
• Issued: 03/07/1978
• Est. Priority Date: 11/04/1975
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cholet, Jean
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US05/737,459
• Time in Patent Office: 491 Days
• Field of Search: 73/398 R, 73/410, 73/406, 73/386, 73/387, 318/645, 318/653
• US Class Current: 73/701
• CPC Class Codes: G01L 11/008 electrostatic or electromagnetic counterbalancing forces
• CPC Class Codes: G01L 9/0085 using variations in inductance

Abstract

Servo pressure pickup comprising a sealed housing having a pressure inlet and in which is mounted an anaroid capsule one wall of which is mechanically linked to an electrical displacement measuring device. The current feed of an electromagnet is controlled by the measuring device. The electromagnet includes a movable core interposed between the capsule and the displacement measuring device. The electromagnet is designed to generate a force in opposition to that produced by the expansion of the capsule and proportional to the feed current of the electromagnet from the measuring device. The displacement measuring device may be amplified and used to generate an analog or a digital pressure measurement output signal.

Claims

1. Servo pressure pickup apparatus comprising a sealed housing having pressure inlet means, aneroid capsule means mounted in said housing in communication with said inlet means;

electromagnet means in said housing;

physical displacement measuring means disposed in said housing for generating an electrical displacement signal corresponding to the pressure being measured;

electronic circuit means in said housing for electrically coupling said displacement signal to said electromagnet means;

said electromagnet means including core member means coupled to a wall of said capsule means and to said displacement measuring means for movement thereof in one sense in response to movement of said wall of said capsule means to cause said displacement measuring means to generate a displacement signal coupled by said electronic circuit to said electromagnet means for generation of a force causing movement of said core member means in an opposite sense;

wherein said displacement measuring means comprises a Hall-effect differential device located in an air gap defined between two pole pieces of permanent magnet means in said housing, said wall movement of said capsule means causing relative displacement between said differential device and said pole pieces.

2. Pickup apparatus according to claim 1, wherein the permanent magnet means is coupled to said core member means;

and wherein said differential device is mounted fixedly in said housing.

3. Pickup apparatus according to claim 1, wherein said housing includes a partition between said electromagnet means and said Hall-effect differential device.

4. Pickup apparatus according to claim 1, wherein said Hall-effect differential device comprises two Hall-effect cells having feed terminals connected in parallel and having outputs connected in opposition.

5. Pickup apparatus according to claim 4, wherein said Hall-effect cells comprise doped impurity regions in a semiconductor body.

6. Pickup apparatus according to claim 5, wherein said Hall-effect cells and said electronic circuit are embodied in a common integrated circuit.

7. Pickup apparatus according to claim 1, wherein said electronic circuit means includes an operational amplifier having inputs connected to outputs of said Hall-effect differential device and having an output connected to a power transistor stage having a collector-emitter circuit connected to feed a winding of said electromagnet means and connected in series with an adjustable load resistor means for producing an analog pressure measurement signal.

8. Pickup apparatus according to claim 1, wherein said electronic circuit means includes a comparator having inputs connected to outputs of said Hall-effect differential device and having an output connected to an input of an up-down counter;

digital-analog converter means connected between digital outputs of said up-down counter and a power transistor stage having a collector-emitter path connected to feed a winding of said electromagnet means;

said counter output providing a digital pressure measurement signal.

9. Pickup apparatus according to claim 1, including zero adjustment means comprising a movable member mounted in a wall of said housing and bearing on a wall of said aneroid capsule means opposite said wall to which said core member means of said electromagnet is coupled.

10. Servo pressure pickup apparatus comprising a sealed housing having pressure inlet means, aneroid capsule means mounted in said housing in communication with said inlet means;

electromagnet means in said housing;

physical displacement measuring means comprising a Hall-effect differential device located in an air gap defined between pole pieces of permanent magnet means in said housing for generating an electrical displacement signal corresponding to the pressure being measured;

semiconductor integrated electronic circuit means in said housing for electrically coupling said displacement signal to said electromagnet means;

said electromagnet means including core member means coupled to a wall of said capsule means and to said Hall-effect differential device for movement thereof in one sense in response to movement of said wall of said capsule means to cause relative displacement between said Hall-effect differential device and said pole pieces to generate a displacement signal coupled by said electronic circuit to said electromagnet means for generation of a force causing movement of said core member means in an opposite sense; and

wherein said Hall-effect differential device comprises two Hall-effect cells comprising doped impurity regions in said integrated circuit structure;

said Hall-effect cells having feed terminals connected in parallel and having outputs connected in opposition to provide respective inputs to said electronic circuit.

11. Pickup apparatus according to claim 10, wherein said electronic circuit means further includes means for producing an analog pressure measurement signal.

12. Pickup apparatus according to claim 10, wherein said electronic circuit means further includes means for producing a digital pressure measurement signal.