FR2470387A1 - MEASUREMENT TRANSFORMER FOR MEASURING A MAGNETIC FIELD, PARTICULARLY GENERATED BY A MEASUREMENT CURRENT - Google Patents

Abstract

MAGNETIC FIELD MEASUREMENT TRANSFORMER. THIS MEASURING TRANSFORMER CONSISTS OF AT LEAST ONE MAGNETORESISTANT MAGNETIC FILM 1 ACTING THE ROLE OF MAGNETIC FIELD COMPARATOR, BY A MAGNETIC COIL 2 CONDUCTING A PRE-MAGNETIZATION CURRENT IN ALTERNATE DIRECTIONS AND BY A FLAT CONDUCTOR CONDUCTING A MEASURING CURRENT. THE RESISTANCE OF MAGNETIC FILM 1 VARIES Suddenly WHEN THE EXTERIOR MAGNETIC FIELD GOES THROUGH ZERO WHILE THE INSTANT AT WHICH THIS VARIATION IN RESISTANCE OCCURS REPRESENTS A MEASUREMENT OF THE MEASURING CURRENT. MAGNETIC FILM 1 IS ARRANGED ON A SEMI-CONDUCTIVE PLATE 5 WHICH REPRESENTS AN INTEGRATED MONOLITHIC CIRCUIT. THE MEASURING TRANSFORMER CAN BE MANUFACTURED IN SERIES BY A CLASSIC TECHNOLOGY OF MANUFACTURING OF INTEGRATED CIRCUITS. APPLICATION TO THE MEASUREMENT OF ELECTRICAL ENERGY.

Description

The present invention relates to a trans-

  measuring instrument for measuring a magnetic field

  that, especially generated by a measuring current,

  measuring transformer which has a magnetic coil

  genetics driving a current of premagnetization of

  alternate directions, and a magnetic field comparator

  consisting of at least one magnetic film

  anisotropic material of magneto-resistant ferromagnetic material

  that, connected to a power source and exposed to

  an external magnetic field which corresponds to the

  of the magnetic field to be measured and the field of

  magnetization generated by the current of premagnetization

  in such a way that the magnetic film is switched by the external field along its easy feed axis alternately in both directions of saturation and that approximately

  zero crossing of the external field, the electrical resistance

  the film of said film varies abruptly so

  that the moment at which this variation of

  is a measure of the absolute value and

  the sign of the magnetic field to be measured.

  A measuring transformer of this type is known from British Patent Application GB 2 000 873 A. In this document, it is mentioned that the preferential magnetic direction of the magnetic film, ie its axis of magnetization easy, may be parallel or perpendicular to the direction of the external magnetic field, or be inclined at an angle, for example 45, relative to this direction. As a magnetic coil capable of generating the field of premagnetization, it is provided in the aforementioned document cited a flat ribbon coil or

  in wire or a layer of spiral copper made

  in the manner of an engraved circuit board

  The object of the invention is to create a mountain

  measurement transformer, which can be realized by modern mass production processes and

  with low manufacturing costs.

  For this purpose, according to the invention, the

  magnetic field parser is arranged on a semiconductor wafer, which represents a circuit

monolithic integrated.

  The invention will be better understood by reading

  detailed description which follows and

  attached drawings which represent

  non-limiting examples, some forms of execution.

  In these drawings which are not drawn to scale: FIG. 1 is a basic representation of a measuring transformer; - Figures 2 and 3 each show in section a measuring transformer;

  FIG. 4 represents a transformation

  measuring transducer with measuring conductor; FIG. 5 is a block diagram of a static electricity meter comprising a measurement transformer; FIG. 6 is a sectional view of another measuring transformer, and FIG. 7 represents the transformer.

  measurement of Figure 6, seen from above.

  In FIG. 1, reference numeral 1 denotes a

  anisotropic magnetic film made of magnetic material

  ferromagnetic resistor, which forms a magnetic field comparator and is connected to a source of power not shown, which injects into the magnetic film 1 a current I0 passing in the longitudinal direction of said film. The easy magnetization axis EA of the magnetic film 1 makes, with the longitudinal direction and with an external magnetic field Ha applied in the longitudinal direction to the magnetic film, an angle P.

  In a plane parallel to the film

  1 is a magnetic coil 2, the conductive strip of which forms a rectangular spiral,

  the individual turns 3 of it, in the

  in which they are magnetically coupled

  with the magnetic film 1, extending perpendicularly

  the longitudinal direction of this last

  Niere. The magnetic coil 3 conducts a pre-magnetization current of alternating directions Iv, with a well-defined curve shape. This current of premagnetization

  Iv generates, in the longitudinal direction of the pel-

  Magnetic tip 1, a field of premagnetization. If, in addition, a magnetic field to be measured is applied

  in the longitudinal direction of the magnetic film

  tick 1, then it is created in the longitudinal direction

  dinal an external magnetic field Ha, which corresponds to

  is the sum of the magnetic field to be measured and the field of premagnetization. In the example shown,

  the magnetic field to be measured is generated by a

  Measuring electrode Im which passes in a flat conductor 4 perpendicular to the longitudinal direction of the magnetic film 1. The magnetization vector M is angularly offset from the angle α with respect to the axis

  of easy magnetization EA by the external field Hta.

  For Ha = 0, the magnetization vector M of the magnetic film I extends in the direction of the easy magnetization axis EA and, therefore, is

  angularly offset from the angle P with respect to the di-

  Longitudinal rection of the magnetic film 1. If the external magnetic field Ha believes negatively

  (ie in the opposite direction of the previous direction

  te), then the magnetization vector M is first of all

  again shifted angularly continuously tan-

  say that the angle has increased nuggetically. After having

  passed a point of stability, which can be determined from the known Stoner-W'ohlhahrts model, the vector

  magnetization I; continues to turn, but in a

  continuous, that is to say independently of the rate of change of the external field Ha, up to

  the magnetization axis difficult HA and takes very fast-

  a new equilibrium position shown in broken lines in FIG. 1. As a result, the magnetic film I changes ohmic resistance abruptly, which results in a voltage jump.

  abrupt and marked decreasing tension on the pel-

  magnetic pulse 1. This voltage jump can be easily

  detected and marks the zero crossing of the external field Ha with great precision. Discontinuous switching of magnetic film I, however, does not occur exactly at the zero crossing of the field

  outside Ha but for a field intensity of

  Hao, that is to say, there is a hysteresis 2 Hao. This hysteresis is minimal for 3 = 45 and also depends on the anisotropic field strength of the magneto-resistant material and what is called the

  demagnetization. Low demagnetization and, by

  a low hysteresis requires that the thickness of the magnetic film I be very small in front of

its width.

  If demagnetization is not neglected

  its influence can be largely compensated if, instead of the magnetic film 1, two identical magnetic films arranged in coincidence and separated by a thin insulating magnetic non-conductive layer are used, while in each of these films passes a current 1 / 2Io0 and

  while we choose preferably f = 0.

  According to FIG. 2, the magnetic film I is disposed on a semiconductor wafer 5, which forms a monolithic integrated circuit (IO) with

  the necessary electronic components of the transfor-

  measuring instrument. Between the magnetic film 1 and the semiconductor wafer 5 is a layer of

solely 6, for example SiO2.

  The longitudinal ends of the film

  magnetic circuit 1 are placed in contact with

  conductors 7, 8 for connecting the film

  magnetic circuit 1 to a DC power source

  denoting the current IO. The semiconductor wafer carries, inter alia, two transistors 9, 10, one of which

  is connected via the conductive band

  7, to the magnetic film 1 and injected into it the current I0, while the other is connected via a conductive strip 11 to the

  magnetic coil 2 and provides the current of premagnet-

Iv.

  Preferably, the magnetic coil 2 is

  a planar thin-film coil and is arranged,

  jointing with the magnetic film 1, on the

  In the example of FIG. 2, the magnetic coil 2 is disposed on the side-of the

  magnetic film 1 opposite the semiconductor wafer

  conductor 5 and is isolated from said film and

  conductive strips 7, 8 by an insulation layer 12.

  The magnetic film 1 is at a decent distance

  completed, for example a few microns, the coil

  magnetic field 2 at a location where the premagnetisation field

  is almost constant over the entire length

  magnetically active magnetic film 1.

  The conductive strips 7, 8 and 11 and the magnetic coil 2 may be, for example, gold, copper or aluminum and may be deposited by

  photolithographic processes known in the art.

  integrated circuits, on the isolation layer,

  6 or 12. The deposition of the insulation layers 6 and 12 can also be carried out by conventional methods in the manufacture of integrated circuits. In addition, it is possible to combine the formation of the conductive strips 7, 8 and 11, the magnetic coil 2, as well as the insulating layers 6 and 12, with operations of establishing contact or isolation during the manufacture of the integrated circuit, so that, compared to conventional manufacturing of integrated circuits, it is sufficient to build the transformer

  described, to add as an additional operation

  silence the deposit of the magnetic film 1.

  The measuring transformer of FIG. 3 differs from that of FIG. 2 essentially in that the magnetic coil 2 is arranged between the semiconductor wafer 5 and the film

  1. Although the individual layers

  Figure 3 partially shows a shape slightly different from that of Figure 2, designated on

  Figure 3, for the sake of clarity, the elements that

  the same functions as in Figure 2 by the

  same numerical references as on this one.

  The semiconductor wafer 5, carrying the magnetic film 1 and the magnetic coil 2, can be provided in the conventional manner of connections

  electric and can be encapsulated in a housing.

  In this case, the flat conductor 4 (FIG.

  the way of the cooling plate of a transistor

  tor power, form a part of the boot.

  Advantageously, the flat conductor 4, as shown in FIG.

  4, can be bent in a U-shape and the semiconductor wafer 5 can be arranged between the branches of the flat conductor 4, while the electrical connections 13 protrude laterally outwards between the branches. The magnetic field

  generated by the measuring current Im is maximum

  Be the branches of the flat conductor 4 and virtually zero outside thereof. By depositing a weakly magnetic layer on the outer surface of the

  conductor 4, magnetic shielding can be

that extra.

  Circuit diagram of principle of the cir-

  embedded cooking constituted by the semiconductor wafer 5 is shown with the magnetic film 1 and the magnetic coil 2 in FIG. 5 inside a

  interrupted frame symbolizing a montage 14.

  The assembly 14 comprises an oscillator 15, a source

  pre-magnetizing current 16, a source of

  continuous current 17, an alternating current amplifier

  tif 18, a threshold switch 19, a multiplier 20 or other analog or digital signal processing element and, in addition; a supply voltage stabilizer 21, the magnetic film 1 with the conductive strips 7, 8 and the magnetic coil 2 which,

  in the example of Figure 5, is a coil spira-

double.

  The oscillator 15 generates a train of

  pulses of constant frequency by which the source

  This pre-magnetizing current 16 supplying the premagnetization current Iv is excited. Source

  direct current 17 applies the current 1 to the pel-

  1. The alternating voltage component

  decreasing voltage on the magnetic film

  1 is amplified in the AC amplifier 18 and reaches the threshold switch 19, which generates a pulse approximately at each zero crossing of the external field Ha. For a well defined curve shape of the premagnetization current

  of alternate meanings Iv, the moments at which these impulses

  appear are a measure of

  their instantaneyet of the sign of the magnetic field

  to the measuring transformer or the current passing

  in the flat conductor 4. In the multiplier or

  signal processing element 20, a signal

  logical or numerical value representing the instantaneous

  born of the current can be formed from these instants.

  The measuring transformer describes

  comes particularly well for energy measurement

  electric. For this purpose, the alternating current

  surer is directly applied to the flat conductor 4 and, as can be seen in FIG.

  to be measured U is transmitted, for example via

  voltage divider 22, multiplier 20, the output of which is connected to a counter 23.

  multiplier 20 forms the product of the instantaneous value

  from the alternating current obtained by means of

  measurement meter and the instantaneous value of the

  alternating voltage and the counter 23 forms the integra-

the time of this product.

  To feed the assembly shown in the rectangle 14, the alternating voltage U is converted, by means of a transformer 24, a rectifier 25 and a capacitor 26, into a low DC voltage and this is applied to the voltage stabilizer

Power supply 21.

  For the measurement of electrical energy in

  a three-phase current network, it is advantageous to use

  for each phase a measuring transformer of the type described, while the formation of the product for each phase can be carried out in the multiplier 20 of the assembly represented by the rectangle 14 of the phase concerned, or in a common microcomputer

at all phases.

  The turns of the magnetic coil 2 are

  in the form of a thin-film coil can

  wind, as described previously, extend in a common plane. It is also possible to arrange the individual turns of the thin-film coil, in a known manner, one above the other in coincidence and to isolate them two by two by a

intermediate isolation layer.

  Another advantageous embodiment of a thin-film coil is described below in

  reference to Figures 6 and 7, on which

  numerical ferences identical to those of the figures

  previous examples indicate elements with the same function

  only on these. In the transformer of

  In FIGS. 6 and 7, the thin-film coil is

  constituted by a first group of conductive bands

  these parallels 27 extending in a first plane and by a second group of parallel conductive strips

  28 extending in a second plane. The conductive strips

  27 are found below the protective film.

  1, on the insulating layer 6 deposited on the semiconductor wafer 5, and are isolated from the

  magnetic film 1 by the insulation layer 12.

  Above the magnetic film 1 are arranged, on an insulation layer 29, the conductive strips 28. The insulation layers 12 and 29 do not completely cover the conductive strips 27 but leave the ends of the latter freely accessible. . The

  two ends of conductive strips 28 are

  in the shape of Z and are each connected with one

  ends of two conductive strips 27 succes-

  sive. With respect to the plane magnetic coil 2, the

  magnetic coil constituted by the conductive strips

  these 27, 28 presents, for the same number of turns,

  a driver length several laws lower.

REVEIDICATIONS

  1) Measuring transformer for measurement

  re of a magnetic field, in particular generated by a measurement current, a measurement transformer comprising a magnetic coil conducting a pre-magnetizing current of alternating directions and a comparator

  of magnetic fields, consisting of at least one pel-

  Anisotropic Magnetic Anisotropic Material

  both ferromagnetic, connected to a source of cou-

  rant and exposed to an external magnetic field which corresponds to the sum of the magnetic field to be measured and the premagnetization field generated by the pre-magnetization current, such that the magnetic film is switched by the external field along its axis of easy magnetization alternately in both directions of saturation and that approximately to

  each zero crossing of the external field, the resistance

  electrical resistance of said film varies abruptly

  foolish than the moment at which this variation occurs

  resistance represents a measure of the absolute value and the sign of the magnetic field to be measured, said measuring transformer being characterized in that

  that the magnetic field comparator (1) is dis-

  placed on a semiconductor wafer (5), which

  presents a monolithic integrated circuit (14).

  2) Transformer measuring according to the

  claim 1, characterized in that the magnetic spool

  gnetic (2, 27, 28) is a thin film

  placed on the semiconductor wafer (5) and extends

in a greater number of plans.

  3) Measuring transformer according to one

  claims 1 and 2, characterized in that the

  circuit (14) comprises a power source of prema-

  it gnetting (16), the current source (17) connected

  the magnetic field comparator (1), an amplification

  (18), a threshold switch (19) and / or a

  digital or analog signal processing element

  cal. 4) Measuring transformer according to claim 3, characterized in that the element of

  signal processing is a multiplier (20).

  Measuring transformer according to Claim 4, characterized in that the measuring current (I1) is an alternating current, in that the

  circuit (14) comprises a multiplier (20) for

  of the product of the instantaneous value of the measurement current (La) obtained by means of the transformer of

  measurement and the instantaneous value of a voltage

  ternative (U) and that after the multiplier

  (20) is mounted a counter (23) for forming the in-

time of the product.

  6) Measuring transformer according to one

  Claims 1 to 5, characterized in that the

  semiconductor wafer (5) is arranged between the branches of a U-shaped curved flat conductor (4) which conducts the measuring current (Im) * 7) Measuring transformer according to one

  Claims 2 to 6, characterized in that

  magnetic field consists of two groups of

  parallel conductive strips (27, 28) extending

  in one plane, the conductive strips (27) of

  one of the groups being arranged below the pel-

  magnets (1) and conductive strips (28) of the other group above the magnetic film

  (1), while both ends of the conductive strips

  two of the groups are each connected to one end of two conductive strips (27).

different from the other group.