Title of Invention

A MEASURING DEVICE FOR AN ELECTRICITY METER

Abstract

A measuring device (1) for connection to a ~tI measurement circuit of an electricity meter (2), the I device comprising a shunt provided with first and second I voltage terminals (6, 7) disposed on a side of the shunt (5) to supply a voltage that is an image of the electrical current flowing through the shunt, the portion of the shunt between said two terminals (6, 7) being essentially flat, the device being characterized by the fact that it comprises a ribbon cable (11) that is I substantially flat and rectangular in shape, incorporating first and second connection wires (19, 20) and disposed substantially parallel to the flat surface of the shunt, the inlet terminals of the connection wires being disposed on one of the edges of the ribbon cable (11) and being connected to the voltage terminals (6, 7) of the shunt, and the outlet terminals of the connection wires (19, 20) being disposed on a second edge of the ribbon cable (11) to be connected to a measurement circuit of a meter. I

Full Text

A MEASURING DEVICE FOR AN ELECTRICITY METER The present invention relates to a measuring device for connection to a measurement circuit of an electricity meter, the device comprising a shunt provided with first and second voltage terminals disposed on one side of the shunt to supply a voltage that is an image of the electrical current flowing through the shunt, the portion of the shunt between said two terminals being essentially flat. In the field of electricity metering, the replacement of electromechanical meters by electronic meters has given rise to several techniques for extracting a signal representative of current and suitable for use in calculating the electrical power consumed, including the use of Hall effect cells, measurement transformers, and shunts. The first patent which describes an electricity meter using a shunt as its measuring element is the French patent granted under the No. 2391474 in the name of Schlumberger Industries S.A. That patent states various fundamental principles, including the use of a measurement circuit operating at the voltage of a phase, together with a shunt having first and second electrical terminals for delivering a voltage representative of the current in that phase. The shunt is also provided with a third terminal suitable for supplying power supply current to the measurement circuit. An example of the physical structure of a shunt is described in the European patent granted under the No. 0030186 in the name of Schlumberger Industries S.A. The shunt described in that patent includes a compensation loop for compensating measurement errors induced by the magnetic field of the shunt. That device has certain advantages over the devices in existence at that time. Nevertheless, relatively complex assembly is required in the connections between the voltage terminals of the shunt and the measurement circuit of the meter. In this context, the object of the present invention is to propose a measuring device constituted by a shunt that is simple in structure, that is suitable for mass production at relatively low cost, and that does not possess the drawbacks of known devices. Accordingly the present invention relates to a measuring device for connection to a measurement circuit of an electricity meter, the device comprising a shunt provided with first and second voltage terminals disposed on one side of the shunt to supply a voltage that is an image of the electrical current flowing through the shunt, the portion of the shunt between said two terminals being essentially flat, the device being characterized by the fact that it includes a ribbon cable that is substantially flat and rectangular in shape, incorporating first and second connection wires and disposed substantially parallel to the flat surface of the shunt, the inlet terminals of the connection wires being disposed on one of the edges of the ribbon cable and being connected to the voltage terminals of the shunt, and the outlet terminals of the connection wires being disposed on a second edge of the ribbon cable to be connected to a measurement circuit of a meter. Preferably, the shunt is provided with a third voltage terminal suitable for supplying a power supply voltage, which terminal is disposed on the same edge of the shunt as the first and second voltage terminals, the ribbon cable likewise being provided with a third connection wire having an inlet terminal disposed on the first edge of the ribbon cable and connected to the third voltage terminal, and an outlet terminal placed on the second edge of the ribbon cable and suitable for connection to the measurement circuit to deliver power thereto. In an embodiment, a portion of the shunt between the first and second terminals is made of a material that has relatively high resistance, voltage measurement being performed relative to the current flowing through said portion of the shunt. For example, this portion of the shunt may be made of a material such as manganin. Given the high cost of this material, and for reasons of heating, it is preferable for only the portion of the shunt which is used for current measurement to be made out of this material, with the other portions of the shunt being made of a material that is less expensive, for example copper. The bonding between the measurement portion and the other portions of the shunt may be performed by electron bombardment. In an embodiment, the voltage terminals of the shunt are placed on the portions of the shunt having lower resistance on either side of the measurement portion. This embodiment possesses the advantage that defects in the connection between the measurement portion and the other portions of the shunt are detected during the calibration stage. Nevertheless, in another embodiment, the voltage terminals may be formed directly on the measurement portion. In another preferred embodiment, the ribbon cable is disposed in a vertical plane substantially parallel to the plane of the surface of the shunt, the first connection wire being disposed substantially vertically and perpendicularly to the direction of the current flowing through the shunt, the second wire being disposed diagonally relative to the first wire to pass through the portion of the ribbon cable situated immediately above the measuring portion of the shunt. This disposition of the connection wires possesses advantages, particularly with respect to compensating currents induced in the wires by the magnetic field of the shunt, and also external magnetic fields. Other embodiments without compensation are also possible, for example when the second wire is also in vertical alignment, perpendicular to the direction of current flowing in the shunt. However, such embodiments are liable to measurement error due to the currents induced in the wires. In a particular embodiment, the shunt is cut out from a metal strip to form a U*shape, the limbs of the shunt which define its inlet and outlet being curved after being cut out so as to be substantially perpendicular to the plane of the measuring portion of the shunt. This embodiment makes it possible to manufacture the shunt at relatively low cost and it makes it easier to install the shunt on the surface of an electronic circuit card. Preferably, the ribbon cable includes a fourth connection wire suitable for connecting the measurement circuit to the neutral wire, the inlet and outlet terminals of the fourth wire being disposed on the second edge of the ribbon cable to connect the measurement circuit to a neutral wire jumper disposed beneath the shunt. The shunt and the jumper may also be received in a plastics support before being installed on an electronic circuit card. An embodiment of the invention is described below by way of non-limiting example with reference to the accompanying drawings, in which: • Figure 1 is a perspective view of a measuring device of the present invention; • Figure 2 is a perspective view of the Figure 1 ribbon; and • Figure 3 is a perspective view showing the hidden side of the Figure 1 device. With reference to Figure 1, the measuring device 1 of the present invention comprises a shunt 2 having an inlet 3 and an outlet 4, first and second voltage terminals 6 and 7 disposed at opposite ends of a measuring portion 5, and a third voltage terminal 8. The shunt 2 is received in a plastics support which also contains a measuring jumper 10 connected to the neutral wire of the power supply. The measuring device also has a ribbon cable 11 fixed to the shunt and to the voltage terminals. The shunt 2 is cut out in a strip of metal made up of two metals, manganin and copper, the measurement portion 5 of the shunt being made of manganin while the other portions are made of copper. Manganin is the preferred choice because of its stability in the face of temperature changes. Nevertheless, other materials could be used, for example constantln. The copper could also be replaced by cuprofor. The shunt Is cut Into a U-shape, and the limbs 3 and 4 of the shunt are then curved so as to extend perpendicularly to the measuring portion. The portions made of manganln and of copper may be bonded together by electron bombardment. The shunt 2 Is used as a component In an electronic type electricity meter and It Is connected In series with a live wire of the power supply network. The current flowing In the wire causes a voltage drop proportional to said current to appear between the first and second voltage terminals 6 and 7. The voltage representing current Is applied to the measurement circuit of the meter as a data signal for processing thereby. The conductor powering the circuit is connected to the power supply terminal 8 of the shunt located upstream from the voltage texminals 6 and 7 so as to ensure that the current used by the circuit does not flow through the measurement portion and consequently does not affect the power supply voltage applied to the circuit. The signal at the power supply terminal is also processed by the measurement circuit to determine the voltage of the live wire of the network. The connection between the shunt and the measurement circuit, which is not shown but which is located beneath the measuring device, is provided by the ribbon cable 11 whose structure is as shown in detail in Figure 2. The ribbon cable 11 is made of plastic and it incorporates first and second connection wires 15 and 16 connected to the first and second voltage terminals 6 and 7 of the shunt, a third connection wire 17 which is connected to the power supply terminal 8 of the shunt, and a fourth connection wire 18 which is connected to the neutral wire jumper 10. The connection wires 15 to 18 are connected to the voltage terminals of the shunt and to the neutral wire jumper via inlet terminals 19 to 22. The measurement circuit of the meter is connected via terminals 23 to 26 which are received in an electronic circuit card that carries the components of the measurement circuit. The inlet terminals 19 to 22 are bonded to the shunt and the neutral wire jumper by ultrasound. In other embodiments, bonding may be performed by soldering. The shunt and the jumper are disposed on a power supply line and the ribbon cable is positioned underneath. Once bonding has been performed, the shunt and the jumper are then housed in the plastics support. The portion of the ribbon cable which is connected to the neutral wire is curved to allow the jumper to be installed in the support, as shown by portion 27 of Figure 3. As shown in Figure 2, the inlet terminals 19 to 21 of the connection wires 15 to 17 are disposed on one of the edges of the ribbon cable and the outlet terminals 23 to 25 on the other edge. However, the inlet terminal 22 and the outlet terminal 26 of the connection wire 18 are both disposed on the same edge to enable the jumper to be located beneath the shunt. With reference to Figures 2 and 3, it can be seen that the ribbon 11 is disposed in a plane that is substantially parallel to the plane extending vertically to the surface of the shunt. The first wire 19 is located substantially vertically relative to the measurement portion and perpendicularly to the direction of the current flowing in the shunt. The second wire 20 is disposed diagonally relative to the first wire 19 and passes through the portion of the ribbon that is situated immediately above the measuring portion of the shunt. This disposition of the connection wires neutralizes the effects of the magnetic field of the shunt, and in particular the magnetic field existing around the measuring portion of the shunt, and also the effects of external magnetic fields. Figure 3 also shows connection tabs 30 of the device for connecting the power supplying wires and the power consuming wires to the elements of the measuring device. The measuring device shown in Figures 1 to 3 has the advantage of being suitable for flow soldering to the measurement circuit because this component is a component having through leads, i.e. a component whose output terminals pass through the printed circuit card of the measurement circuit. WE CLAIM 1/ A measuring device for connection to a measurement circuit of an electricity meter, the device comprising a shunt provided with first and second voltage terminals disposed on one side of the shunt to supply a voltage that is an Image of the electrical current flowing through the shunt, the portion of the shunt between said two terminals being essentially flat, the device being characterized by the fact that It Includes a ribbon cable that Is substantially flat and rectangular In shape. Incorporating first and second connection wires and disposed substantially parallel to the flat surface of the shunt, the Inlet terminals of the connection wires being disposed on one of the edges of the ribbon cable and being connected to the voltage terminals of the shunt, and the outlet terminals of the connection wires being disposed on a second edge of the ribbon cable to be connected to a measurement circuit of a meter. 2/ A measuring device according to claim 1, in which the shunt is provided with a third voltage terminal suitable for supplying a power supply voltage, which terminal is disposed on the same edge of the shunt as the first and second voltage terminals, the ribbon cable likewise being provided with a third connection wire having an inlet terminal disposed on the first edge of the ribbon cable and connected to the third voltage terminal, and an outlet terminal placed on the second edge of the ribbon cable and suitable for connection to the measurement circuit to deliver power thereto. 3/ A measuring device according to claim 1 or 2, in which a portion of the shunt between the first and second terminals is made of a material that has relatively high resistance, voltage measurement being performed relative to the current flowing through said portion of the shunt. 4/ A measuring device according to claim 3, in which the shunt Includes a measuring portion of high resistance disposed between two portions of lower resistance, the first and second voltage terminals being disposed on the two portions on either side of the measuring portion. 5/ A measuring device according to any one of claims 1 to 4, in which the ribbon cable is disposed in a vertical plane substantially parallel to the plane of the surface of the shunt, the first connection wire being disposed substantially vertically and perpendicularly to the direction of the current flowing through the shunt, the second wire being disposed diagonally relative to the first wire to pass through the portion of the ribbon cable situated immediately above the measuring portion of the shunt. 6/ A measuring device according to any one of claims 1 to 5, in which the shunt is cut out from a metal strip to form a U-shape, the limbs of the shunt which define its inlet and outlet being curved after being cut out so as to be substantially perpendicular to the plane of the measuring portion of the shunt. 7/ A measuring device according to any one of claims 1 to 6, in which the ribbon cable Includes a fourth connection wire suitable for connecting the measurement circuit to the neutral wire, the inlet and outlet terminals of the fourth wire being disposed on the second edge of the ribbon cable to connect the measurement circuit to a neutral wire jumper disposed beneath the shunt. 8/ A measuring device according to any one of claims 1 to 7, in which the shunt and the neutral wire jumper, are housed in a plastics support. 9. A measuring device for connection to a measurement circuit of an electricity meter, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

2827-mas-1997-abstract.pdf

2827-mas-1997-claims duplicate.pdf

2827-mas-1997-claims original.pdf

2827-mas-1997-correspondence others.pdf

2827-mas-1997-correspondence po.pdf

2827-mas-1997-description complete duplicate.pdf

2827-mas-1997-description complete original.pdf

2827-mas-1997-drawings.pdf

2827-mas-1997-form 1.pdf

2827-mas-1997-form 26.pdf

2827-mas-1997-form 3.pdf

2827-mas-1997-form 4.pdf

abs-2827-mas-1997.jpg