High linearity, low offset interface for Hall effect devices

• US 6,392,400 B1
• Filed: 10/06/1999
• Issued: 05/21/2002
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: Itron Global Sarl (Itron, Inc.)
• Original Assignee: Schlumberger Resource Management Services Incorporated (Schlumberger NV)
• Inventors: Gervais, Michel, Lancaster, Andrew, Goodwin, Wendell, Kobbi, Farah, Heinz-Buethe, Karl
• Primary Examiner(s): Brown, Glenn W.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/413,616
• Time in Patent Office: 958 Days
• Field of Search: 324/117.H, 324/142, 324/117.R, 336/178, 338/32.H
• US Class Current: 324/117.00H
• CPC Class Codes: G01R 15/202 using Hall-effect devices Hall elements in arrangements for measuring electrical power G01R21/08
• CPC Class Codes: G01R 21/08 by using galvanomagnetic-effect devices, e.g. Hall-effect devices

Abstract

A Hall effect sensor or device may be used in a variety of embodiments, such as measuring current within an associated conductor by helping to measure flux density within a gap of a ferromagnetic power meter core, such as in a power meter. A high linearity interface for a Hall effect device is provided for minimizing offset effects without using complicated electronic circuits. First and second levels of modulation relative to line frequency are used to synchronize Hall effect device input switching circuits and feedback loops for improved elimination of offset signals or noise from the ultimate system output. The substrate of the Hall effect device may be connected electrically to an output pin of the Hall device or to a separate virtual ground to eliminate any effects caused by asymmetry of the voltage appearing in the channel relative to the substrate. The net effect of the high linearity interface is to eliminate any adverse effects to linearity of the system, especially at low magnetic flux levels where the output voltage of the Hall device would be relatively small compared to the offset voltage levels involved. The interface virtually eliminates adverse effects from operational amplifier input offset voltages, Hall effect device output offset voltages, and any common mode voltages.

Claims

1. A Hall effect sensor with improved output interface for high linearity and low offset performance, as associated with a given line voltage, comprising:

a Hall effect device of the type having a substrate, first and second device inputs and first and second device outputs;

an interconnection between said substrate and one of said device outputs;

a biasing current supplied to said device proportional to the line voltage with which said device and interface are associated;

plural pairs of inverting and non-inverting switch components connected between a given line voltage and said Hall effect device inputs, having controlled respective switching inputs commonly controlled by a modulation signal; and

modulation means operative with the associated line frequency for generating said modulation signal with reference to a line frequency, wherein said modulation means includes first modulation means directly associated with the line frequency, for providing respective outputs with reference thereto and second modulation means for fine tuning adjustment of the output of said first modulation means and for supplying said modulation signal to said switch components for controlling switching thereof.

2. A Hall effect sensor with improved output interface as in claim 1, further including a converter for outputting a single analog signal constituting the difference between said outputs of said Hall effect device.

3. A Hall effect sensor with improved output interface as in claim 2, further including a demodulator for demodulating said single analog signal from said converter based on one of said outputs of said first modulation means.

4. A Hall effect sensor with improved output interface as in claim 3, further including calibration means for selectively processing the output of said demodulator into a digitized signal of desired format and for forwarding such digitized signal to said second modulation means for synchronizing said second modulation means with said digitized signal.

5. A high linearity, low offset interface for a Hall effect device of the type having a device substrate, first and second device inputs and first and second device outputs, comprising:

switch means, responsive to switching control input thereto, for selectively switching line voltage, a parameter of which is to be sensed, to the inputs of a Hall effect device;

modulation means for controlling the switching characteristics of said switch means by providing said switching control input thereto;

output converter chip means for receiving the outputs of the Hall effect device and providing a selectively processed digitized output therefrom; and

biasing means for eliminating undesirable offset effects due to non-symmetries in the Hall effect device and for eliminating common mode voltages, wherein said biasing means includes said substrate electrically interconnected to one of said device outputs.

6. A high linearity, low offset interface for a Hall effect device as in claim 5, wherein said biasing means includes an interconnection between the Hall effect device substrate and one of the outputs of the device.

7. A high linearity, low offset interface for a Hall effect device as in claim 6, wherein said one of said Hall effect device outputs is interconnected to a virtual ground.

8. A high linearity, low offset interface for a Hall effect device as in claim 5, wherein said biasing means includes a differential drive circuit for inverting an input voltage appearing at one of the Hall effect device inputs and applying such inverted signal to the other of the Hall effect inputs.

9. A high linearity, low offset interface for a Hall effect device as in claim 5, wherein said biasing means includes an in-line connected biasing resistor for supplying to the Hall effect device bias current proportional to the line voltage.

10. A high linearity, low offset interface for a Hall effect device as in claim 5, wherein said switch means comprise a plurality of paired inverting and non-inverting switch components.

11. A high linearity, low offset interface for a Hall effect device of the type having a device substrate, first and second device inputs and first and second device outputs, comprising:

switch means, responsive to switching control input thereto, for selectively switching line voltage, a parameter of which is to be sensed, to the inputs of a Hall effect device;

modulation means for controlling the switching characteristics of said switch means by providing said switching control input thereto;

output converter chip means for receiving the outputs of the Hall effect device and providing a selectively processed digitized output therefrom;

biasing means for eliminating undesirable offset effects due to non-symmetries in the Hall effect device and for eliminating common mode voltages; and

wherein said modulation means includes first modulation means for providing two respective outputs synchronized relative to the line frequency and second modulation means, responsive to one of said first modulation means outputs and to said selectively processed digitized signal from said output converter chip means, for providing said switching control input to said switch means, synchronized with the line frequency and adjusted by said converter chip means digitized output.

12. A high linearity, low offset interface for a Hall effect device as in claim 11, wherein said output converter chip means includes:

converter means for converting the outputs of the Hall effect device to a single analog signal based on the difference between the two device outputs;

demodulation means for demodulating said converter means single analog signal based on a demodulation signal from one of the outputs of said first modulation means; and

calibration means processing the output of said demodulation means into a digitized signal of a desired format.

13. A power meter arrangement, comprising:

a laminated ferromagnetic power meter core having a designated region thereof defining a core gap;

a Hall effect sensor residing in said core gap of said power meter core for sensing magnetic flux from which power consumption data may be derived concerning current flow through an associated conductor line, said Hall effect sensor including a Hall effect device of the type having a substrate, first and second device inputs and first and second device outputs, said sensor further including interface means for providing a high linearity low offset sensor output signal and a biasing circuit including said substrate, wherein said substrate is electrically interconnected to one of said device outputs;

switch means, responsive to switching control input thereto, for selectively switching line voltage, a parameter of which is to be sensed, to the inputs of a Hall effect device;

modulation means for controlling the switching characteristics of said switch means by providing said switching control input thereto;

output converter chip means for receiving the outputs of the Hall effect device and providing a selectively processed digitized output therefrom;

an interconnection between said Hall effect device substrate and one of said outputs of said device;

an interconnection between said one of said Hall effect device outputs and a virtual ground;

a differential drive circuit for inverting an input voltage appearing at one of said Hall effect device inputs and applying such inverted signal to the other of said Hall effect inputs; and

an in-line connected biasing resistor for applying to the Hall effect device a bias current proportional to the associated line voltage.

14. A power meter arrangement, comprising:

a laminated ferromagnetic power meter core having a designated region thereof defining a core gap;

a Hall effect sensor residing in said core gap of said power meter core for sensing magnetic flux from which power consumption data may be derived concerning current flow through an associated conductor line, said Hall effect sensor including a Hall effect device of the type having a substrate, first and second device inputs and first and second device outputs, said sensor further including interface means for providing a high linearity low offset sensor output signal and a biasing circuit including said substrate, wherein said substrate is electrically interconnected to one of said device outputs;

switch means, responsive to switching control input thereto, for selectively switching line voltage, a parameter of which is to be sensed, to the inputs of a Hall effect device;

modulation means for controlling the switching characteristics of said switch means by providing said switching control input thereto;

output converter chip means for receiving the outputs of the Hall effect device and providing a selectively processed digitized output therefrom; and

wherein said switch means comprise a plurality of paired inverting and non-inverting switch components.

15. A power meter arrangement, comprising:

a laminated ferromagnetic power meter core having a designated region thereof defining a core gap;

a Hall effect sensor residing in said core gap of said power meter core for sensing magnetic flux from which power consumption data may be derived concerning current flow through an associated conductor line, said Hall effect sensor including a Hall effect device of the type having a substrate, first and second device inputs and first and second device outputs, and said sensor further including interface means for providing a high linearity low offset sensor output signal;

said interface means comprising switch means, responsive to said switching control input thereto, for selectively switching line voltage, a parameter of which is to be sensed, to the inputs of a Hall effect device, modulation means for controlling the switching characteristics of said switch means by providing said switching control input thereto and output converter chip means for receiving the outputs of the Hall effect device and providing a selectively processed digitized output therefrom; and

wherein said modulation means includes first modulation means for providing two respective outputs synchronized relative to the line frequency and second modulation means, responsive to one of said first modulation means outputs and to said selectively processed digitized signal from said output converter chip means, for providing said switching control input to said switch means, synchronized with the line frequency and adjusted by said converter chip means digitized output.

16. A power meter arrangement as in claim 15,wherein said output converter chip means includes:

converter means for converting the outputs of the Hall effect device to a single analog signal based on the difference between the two device outputs;

demodulation means for demodulating said converter means single analog signal based on a demodulation signal from one of the outputs of said first modulation means; and

calibration means processing the output of said demodulation means into a digitized signal of a desired format.