Measurement shunt with compensation for induced error voltages

• US 4,494,068 A
• Filed: 04/27/1983
• Issued: 01/15/1985
• Est. Priority Date: 11/28/1979
• Status: Expired due to Term

• Current Assignee: Enertec SA (Vitec Group PLC)
• Original Assignee: Enertec SA (Vitec Group PLC)
• Inventors: Bazin, Alain, Allesch, Roland, Ley, Antony
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US06/488,522
• Time in Patent Office: 629 Days
• Field of Search: 324/126, 324/76 R, 338/49, 338/61, 338/62, 338/63, 328/165, 333/12, 307/89, 307/91
• US Class Current: 324/126
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: H01C 3/02 arranged or constructed for reducing self-induction, capacitance or variation with frequency

Abstract

A measurement shunt comprises a resistance provided with first and second voltage terminals and intended to provide a voltage representative of an electric current passing through it, and an inductance connected to at least the first of said voltage terminals to produce between first and second measurement terminals a voltage free of error voltages induced in said resistance, even in the presence of a variable magnetic field. The resistance is essentially constituted by a plate (12) of electrically conductive material, the first and second voltage terminals (26,28) are disposed on the same edge of the plate at spaced apart points thereon, and the inductance comprises at least one open loop (36a) at least partly formed from an electrically conductive material extending from its first and second ends respectively disposed in the vicinity of the first and second voltage terminals, towards the interior of the surface of the plate in a plane having, at least approximately the same direction as the plate.

Claims

1. A measurement shunt comprising:

a resistance formed from a plate of electrically conductive material, first and second current terminals and voltage terminal means connected to the plate, the voltage terminal means being disposed on a common edge of the plate at spaced apart points thereon, the resistance proving at the voltage terminal means a voltage representative of an electric current applied to the shunt at said current terminals and passing through the resistance; and

inductor means for developing a stray variable magnetic field induced voltage that is equal in magnitude and opposite in polarity to any stray variable magnetic field induced error voltage in said plate, the inductor means being formed from an electrically conductive material and having first and second ends disposed in the vicinity of the voltage terminal means, the inductor means extending from its first and second ends towards the interior of the surface of the plate in a plane substantially parallel to and adjacent the plate, electrical insulation means between said inductor means and said plate, the inductor means being connected electrically in series with a path in the plate via the voltage terminal means and between first and second measurement terminals, the inductor means providing, in the presence of a variable magnetic field, a voltage free of induced error voltage at the measurement terminals.

2. A shunt according to claim 1, wherein the voltage terminal means includes first and second voltage terminals and said inductance means comprises an open loop which forms an uninterrupted electrical path between its first and second ends, the first end of the loop is electrically connected to the first voltage terminal, and the first and second measurement terminals are respectively connected to the second voltage terminal and the second end of the loop.

3. A shunt according to claim 2, wherein the inductor means comprises two aligned U-shaped loops disposed on opposite faces of the plate, these two loops being physically connected by their respective first and second ends to form a one-piece rider.

4. A shunt according to claim 3, wherein the rider is made from an electrically conductive spring material and clips onto the plate.

5. A shunt according to claim 4, wherein said spring material is a bronze-beryllium alloy.

6. A shunt according to claim 1, wherein said voltage terminal means includes first and second voltage terminals, and wherein the inductor means is formed by two converging portions of two different electrical conductors which are insulated from each other, the first portion having one end electrically connected to the first voltage terminal, the second portion having one end electrically connected to the second voltage terminal, and the portions converging towards each other extend in a direction away from the ends connected to the voltage terminals.

7. A shunt according to claim 6, wherein said portions are disposed on the same side of the plate and meet at a common point near the edge of the plate opposite the edge on which the first and second voltage terminals are disposed, the conductors extend from this common point as a twisted pair, and said measurement terminals are constituted by respective ends of the twisted pair.

8. A shunt according to claim 1, wherein the plate is substantially rectangular.

9. A shunt according to claim 1, wherein said inductor means is bonded to one face of the plate by an adhesive.

10. A shunt according to claim 3 wherein the plate is substantially rectangular.

11. A measurement shunt comprising:

a resistance formed from a plate of electrically conductive material, first and second current terminals, and first and second voltage terminals disposed on a common edge of the plate at spaced apart points thereon, the resistance providing between the first and second voltage terminals a voltage representative of an electric current applied to the shunt at the current terminals and passing through the resistance; and

inductor means for developing a stray variable magnetic field induced voltage that is equal in magnitude and opposite in polarity to any stray variable magnetic field induced error voltage in said plate, the inductor means comprising at least one open loop formed of an electrically conductive material and having first and second ends disposed respectively in the vicinity of the first and second voltage terminals, the loop extending from its first and second ends toward the interior of the surface of the plate in a plane substantially parallel to and adjacent the plate, electrical insulation means between said inductor means and said plate, the inductor means being connected electrically in series with a path in the plate via said voltage terminals and between first and second measurement terminals, the inductor means providing, in the presence of a variable magnetic field, an induced voltage compensating for the voltage induced in the resistance by such magnetic field, such that a voltage free of induced error voltrage appears between the measurement terminals.