Patent Publication Number: US-9903900-B2

Title: Electric leakage detecting apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an electric leakage detecting apparatus that detects electric leakage. 
     BACKGROUND ART 
     Electric leakage is that a current flows out of an electric wire connected from a power source to a load. The electric leakage is actually detected according to the difference between the current flowing from the power source to the load and the current returning from the load to the power source. A conventional electric leakage detecting apparatus is proposed as an apparatus configured to detect the variations in the impedance of a ring-shaped magnetic material by passing two electric wires communicating a power source with a load through the hole of the magnetic material (Patent Literature 1). 
     An electric leakage detecting apparatus  100  is schematically illustrated in  FIG. 24 . The electric leakage detecting apparatus  100  includes a ring-shaped magnetic material  101 , a magnetic impedance element  102  attached to the magnetic material  101 , and a detector  103  configured to detect the variations in the impedance. A pair of electric wires  110  and  111  (referred to as an electric wire A and an electric wire B) extending from a power source  115  to a load  116  pass through a hole  104  of the ring-shaped magnetic material  101 . 
     A magnetoresistive element of which resistance varies depending on the magnetic field is used as the magnetic impedance element  102 . The magnetoresistive element is placed in the magnetic field that the ring-shaped magnetic material  101  generates. For example, a part of the ring-shaped magnetic material  101  is removed to form a gap, and then the magnetoresistive element can be placed in the gap. Needless to say, another manner is acceptable. 
     The detector  103  can be any material as long as the material can detect the variations in the resistance of the magnetoresistive element. The detector  103 , for example, converts the variations in the resistance into a signal having a predetermined frequency, or reshapes a waveform using a filter circuit and an amplifier circuit, and then outputs the signal from a signal detection circuit to convert the signal into a main signal. 
     The operation of the electric leakage detecting apparatus  100  will be described. Without electric leakage, the current flowing in the electric wire A 110  has the same amount as the current flowing in the electric wire B 111  and the currents flow in the opposite directions. Thus, no magnetic flux arises in the ring-shaped magnetic material  101 . Consequently, the resistance of the magnetic impedance element  102  does not vary at that time. On the other hand, with electric leakage, the current flowing in the electric wire A 110  has a value different from the value of the current flowing in the electric wire B 111 . This generates magnetic flux in the ring-shaped magnetic material  101 . 
     The generated magnetic flux varies the impedance of the magnetic impedance element  102 . The detector  103  detects the generation of the electric leakage by detecting the variation. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 10-232259 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     The electric leakage detecting apparatus in Patent Literature 1, which has a simple configuration, can be miniaturized to some extent. However, the electric leakage detecting apparatus uses the ring-shaped magnetic material. This naturally limits the miniaturization. Additionally, it is necessary to pass the electric wire A and electric wire B extending from the power source through the hole of the ring. A thicker electric wire increases the size of the ring-shaped magnetic material  101 . Additionally, it is difficult to place the ring-shaped magnetic material  101  around the electric wires that have already been placed. For example, it is necessary to make a part of the ring-shaped magnetic material openable so as to put the electric wires from the opened part into the hole, and subsequently close the opened part again to form the closed paths of the magnetic flux, similarly to a clamp-on ammeter. 
     Additionally, it is necessary to simultaneously surround the two power source line patterns extending from the power source with the magnetic material while the miniaturization of the electric leakage detecting apparatus causes the integration of the circuit substrate. This makes it extremely difficult to attach the ring-shaped magnetic material  101  to the power source line patterns afterward. 
     Solution to Problem 
     The present invention has been developed in light of the foregoing. The present invention is an electric leakage detecting apparatus that is easy to install even on a circuit that has already been wired, and is capable of being miniaturized. More concretely, the electric leakage detecting apparatus according to the present invention is to be installed on a pair of power source lines connecting a power source and a load, and the electric leakage detecting apparatus includes: 
     a pair of holders configured to hold the pair of power source lines, respectively; 
     a fixing means configured to fix the pair of holders at a predetermined interval; 
     a pair of magnetic elements each placed on each of the holders while being parallel to the power source lines; 
     a detecting means configured to detect a difference between magneto-resistance effects of the pair of magnetic elements; and 
     a driving means configured to feed a drive current to the magnetic elements. 
     Advantageous Effects of Invention 
     The electric leakage detecting apparatus according to the present invention can readily be installed even on a circuit that has already been wired, taking advantage of a magnetoresistive element, for example, the non-contacting (principle), the easy installation (the extremely-compact and thin), and the energy conservation (the low energy consumption for measurement). Additionally, fixing the placed position of the magnetoresistive elements with regard to the electric wire A and the electric wire B can sufficiently suppress the effect of the magnetic field from the adjacent electric wire. This can stably detect an electric leakage. Providing a bias means on the magnetoresistive element also enables electric power measurement and current measurement. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1( a ) and 1( b )  are views of the structure of an electric leakage detecting apparatus according to the present invention. 
         FIG. 2  is an enlarged view of a magnetic element. 
         FIGS. 3( a ) and 3( b )  are explanatory views of the operation of the magnetic element. 
         FIG. 4  is a view of a (barber-pole) magnetic element with a stripe conductor pattern. 
         FIG. 5  is an explanatory view of the principle of electric power measurement using the magnetic element. 
         FIG. 6  is a cross-sectional view of the electric leakage detecting apparatus according to the present invention, taken along a plane perpendicular to the power source lines. 
         FIG. 7  is a view of the wire connection of the electric leakage detecting apparatus according to the present invention (with an independent power source). 
         FIG. 8  is a view of the wire connection of the electric leakage detecting apparatus according to the present invention (with a parasite power source). 
         FIG. 9  is a view of the wire connection of the electric leakage detecting apparatus according to the present invention and capable of measuring electric power and measuring electric current. 
         FIGS. 10( a ) and 10( b )  are the structure of the electric leakage detecting apparatus according to the present invention, and the structure which can reduce the effect of the magnetic field from the adjacent electric wire. 
         FIG. 11  is a cross-sectional view of the electric leakage detecting apparatus in  FIGS. 1( a ) and 1( b ) , taken along a plane perpendicular to the power source lines. 
         FIG. 12  is a cross-sectional view of the electric leakage detecting apparatus in  FIGS. 10( a ) and 10( b ) , taken along a plane perpendicular to the power source lines. 
         FIGS. 13( a ) and 13( b )  is a structure of the electric leakage detecting apparatus according to the present invention in which the magnetic element is placed at a place. 
         FIG. 14  is a view of the wire connection of the electric leakage detecting apparatus in  FIGS. 13( a ) and 13( b ) . 
         FIG. 15  is a view of the wire connection of the electric leakage detecting apparatus in  FIGS. 13( a ) and 13( b )  when a bias means is added to the magnetic element. 
         FIG. 16  is a view of the wire connection of the electric leakage detecting apparatus in  FIGS. 13( a ) and 13( b )  when one of the element terminals is grounded. 
         FIG. 17  is a view of the wire connection of the electric leakage detecting apparatus in  FIG. 16  when a bias means is added to the magnetic element. 
         FIG. 18  is a view of the wire connection of the electric leakage detecting apparatus (with a parasite power source) in  FIGS. 13( a ) and 13( b )  when the driving means is provided from the detected circuit. 
         FIG. 19  is a view of the wire connection of the electric leakage detecting apparatus in  FIG. 18  when a bias means is added to the magnetic element. 
         FIG. 20  is a view of the wire connection of the electric leakage detecting apparatus in  FIG. 18  when one of the element terminals are grounded. 
         FIG. 21  is a view of the wire connection of the electric leakage detecting apparatus in  FIG. 20  when a bias means is added to the magnetic element. 
         FIG. 22  is a view of the wire connection of the electric leakage detecting apparatus in  FIGS. 13( a ) and 13( b )  when the magnetic elements to which a bias means is added are placed as a straight line. 
         FIG. 23  is a view of the wire connection of the electric leakage detecting apparatus (with a parasite power source) in  FIG. 22  when the driving means is provided from the detected circuit. 
         FIG. 24  is a view of the structure of a conventional electric leakage detecting apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The electric leakage detecting apparatus according to the present invention will be described hereinafter with reference to the appended drawings. Note that each description below is an exemplary embodiment of the present invention. The present invention is not limited to the embodiments to be described below. The embodiments to be described below can be changed as long as the change does not depart from the gist of the present invention. 
     (First Embodiment) 
       FIG. 1  is a view of the appearance of an electric leakage detecting apparatus  1  according to the present embodiment.  FIG. 1( a )  illustrates the appearance of a part holding electric wires.  FIG. 1( b )  illustrates the structure of the connection relation with a to-be-detected circuit. With reference to  FIG. 1( b ) , the to-be-detected circuit  90  includes a power source  91 , a load  92 , and power source lines  93  connecting the power source  91  to the load  92 . The power source lines  93  include an electric wire A 93   a  and an electric wire B 93   b.    
     The electric leakage detecting apparatus  1  according to the present invention includes a pair of holders  11  configured to hold each of the pair of the power source lines  93 , a fixing means  12  configured to fix the interval between the holders  11 , magnetic elements  14  embedded in the holders  11 , and a detecting means  20  configured to detect the difference between the magneto-resistance effects of the magnetic elements  14 . The connection relation between the magnetic elements  14  and the detecting means  20  will be described in detail below. 
       FIG. 1( a )  illustrates the part including the holders  11 , the fixing means  12 , and the magnetic elements  14 , and  FIG. 1( a )  omits the detecting means  20 . 
     The power source lines  93  are a pair of electric wires (the electric wire A 93   a  and the electric wire B 93   b ) that supply electric power from the power source  91  to the load  92 . The power source  91  can be an alternating-current power source or a direct-current power source. The load  92  can have impedance without complex component or reactance (including capacitive and inductive) with complex component. 
     With reference to  FIG. 1( a ) , each of the holders  11  linearly fixes each of the electric wires (the electric wire A 93   a  and the electric wire B 93   b ) of the power source lines  93  over a predetermined length. Thus, the holders  11  are provided in a pair ( 11   a  and  11   b ). The shapes of the holders  11  are not especially limited while  FIG. 1  illustrates cylindrical holding members of which cross-sectional surfaces are partially chipped. Each of the holders  11  linearly fixes a part of each of the power source lines  93  over a predetermined length (L) as illustrated in  FIG. 1( b ) . 
     Tabular insertion means  13  are formed under the holders  11 . Magnetic elements  14  (A 14   a  and B 14   b ) are provided on the insertion means  13 , parallel to the fixed electric wire (A 93   a  and B 93   b ). Thus, when the holders  11  hold the electric wire (A 93   a  and B 93   b ), the magnetic elements  14  are placed parallel to the lengthwise direction of the electric wire (A 93   a  and B 93   b ). 
     The fixing means  12  fixes the interval between the holders  11  at a predetermined length. For example, the fixing means  12  can be a tubular member  12   a  on which a rail-shaped groove  12   b  is formed. Allowing the insertion means  13 , which are provided under the lower surfaces of the holders  11 , to be movably fitting along the groove  12   b  can make the distance between the holders  11  variable. Needless to say, when the distance between the holders  11  reaches a desired distance, the holders  11  can be fixed on the groove  12   b.    
     For the fixation, the insertion means  13  can be fastened on the fixing means  12 , for example, with a screw. The part configured to adjust the interval between the holders  11  described above is referred to as an interval adjuster. In the present embodiment, the interval adjuster is formed of the groove  12   b , the insertion means  13 , and a screw. However, the interval adjuster can be implemented in another method. 
     The magnetic elements  14  used in the present invention will be described hereinafter. With reference to  FIG. 2 , the magnetic elements  14  are obtained by forming a magnetic film  142  on a substrate  141  and forming element terminals (electrodes)  143  and  144  on both ends of the magnetic film  142 . The magnetic film  142  has a striped shape. The direction in which the element terminals  143  and  144  are formed is referred to as a longitudinal direction. It is preferable that a magnetization easy axis EA is induced on the magnetic film  142  in the longitudinal direction. 
     A current I 2  is applied to the magnetic element  14  from the detector power source  21 . The current I 2  flows in the magnetic film  142  in the longitudinal direction. Applying a magnetic field H from a direction perpendicular to the longitudinal direction at that time varies the electric resistance of the magnetic film  142 . This is referred to as a magneto-resistance effect. It is considered that the magneto-resistance effect is caused by the change of the directions of the current I 2  flowing in the magnetic film  142  and of the magnetization in the magnetic film  142 . 
       FIG. 3( a )  illustrates a plan view of the magnetic element  14  in  FIG. 2 .  FIG. 3( b )  illustrates the relationship between the external magnetic field H applied to the magnetic element  14  and a resistance value Rmr of the magnetic film  142 . The external magnetic field H applied to the magnetic film  142  is shown on the horizontal axis, and the resistance value (Ω) of the magnetic film  142  is shown on the vertical axis. It is considered that the difference between the direction of the current I 2  and that of the magnetization M causes the magneto-resistance effect. Thus, the resistance value of the magnetic film due to the applied external magnetic field H can be expressed as an even function. 
     However, when the external magnetic field H is applied from a state where the external magnetic field H is an intensity of zero, it is impossible to identify the direction of the external magnetic field H as the variation in the resistance value. In light of the foregoing, a bias magnetic field MF is applied in a direction perpendicular to the longitudinal direction. The bias magnetic field MF moves the operating point. Thus, the resistance value Rmr increases or decreases depending on the direction of the external magnetic field H.  FIG. 3( b )  illustrates that the external magnetic field H is applied when the resistance value is Rm 0  on the operating point, resulting in the variation of the resistance by +ΔRmr. Note that a reference sign MRC is a curve indicating the magneto-resistance effect. 
     A permanent magnet  149  can readily provides the bias magnetic field MF. Needless to say, the permanent magnet  149  can be an electric magnet. A material configured to provide the bias magnetic field MF to the magnetic element  14  as described above is referred to as a bias means  145 . The bias means  145  is not necessarily a material that directly generates a magnetic field. 
       FIG. 4  illustrates conductors  148  that are made of a highly conductive material, and are formed into a band-shaped stripe structure on the magnetic film  142 . In the stripe structure, the conductor  148  is formed into a band and inclined to the longitudinal direction of the magnetic film  142 . In such a structure, the current I 2  flows between the conductors  148  in a direction perpendicular to each band conductor  148 . Additionally, the magnetization easy axis EA is induced on the magnetic film  142  in the longitudinal direction of the magnetic element  14 . This causes the direction of the magnetization M to differ from the direction of the current I 2  even when the external magnetic field H has an intensity of zero. In other words, with regard to the magneto-resistance effect, it is possible to obtain a condition where the bias magnetic field is applied. 
     It is assumed that the external magnetic field H (a white arrow H) is applied to the magnetic element  14  having the structure described above from the upper side to the lower side of the drawing paper. The external magnetic field H rotates the magnetization M (a black arrow), which has been in a different direction from the current I 2  without the external magnetic field H, to the same direction as the current I 2 . This varies the resistance value as illustrated in  FIG. 3( b ) . 
     As described above, the bias means  145  herein includes a material that has the same effect as when the magnetic field is actually applied even if the material does not actually generate the magnetic field. The magnetic element  14  having the structure illustrated in  FIG. 4  is referred to as a barber-pole magnetic element. As another example, the magnetization easy axis EA introduced on the magnetic film  142  can be inclined from the longitudinal direction. This is because the direction in which the current originally flows (the longitudinal direction) is different from the direction of the magnetization even in such a case. 
       FIG. 5  illustrates the principle for an electric power meter using the barber-pole magnetic element  14 . The magnetic element  14  and the measuring resistance  22  are connected in series and are connected parallel to the load  92  connected to the power source  91  of a to-be-measured circuit  99 . The magnetic element  14  is placed next to and parallel to the electric wire A 93   a  connecting the power source  91  to the load  92 . In that case, the measuring resistance  22  has a value sufficiently larger than the resistance value Rmr of the magnetic element  14 . Meanwhile, the electric wire A 93   a  has a sufficiently small resistance. 
     First, the external magnetic field H applied to the magnetic element  14  is expressed an expression (1) if the power source  91  is a direct-current power source, the current flowing in the electric wire A 93   a  and the electric wire B 93   b  is I 1 , and the proportionality constant is α.
 
H=αI 1   (1)
 
     As illustrated also in  FIG. 3( b ) , the variation ΔRmr in the electric resistance of the magnetic element  14  is proportional to the magnetic field H applied from the outside. The variation can be expressed as an expression (2) if the proportionality constant is β in consideration of the expression (1).
 
Δ Rmr=βH =β(α I   1 )  (2)
 
     An electric resistance R m  of the entire magnetic element  14  when the external magnetic field H is applied is expressed as an expression (3) if the electric resistance (on the operating point) is R m0  with no external magnetic field H applied to the magnetic film  142 .
 
 R   m   =R   m0   +ΔR   mr   =R   m0   +αβI   1   (3)
 
     In other words, the magnetic film  142 , which is placed next to the electric wire A 93   a  in which the current I 1  flows, has the electric resistance characteristic expressed in the expression (3). A voltage Vmr between the element terminals  143  and  144  of the magnetic element  14  is expressed as an expression (4) when the current I 2  flows between the element terminals  143  and  144 .
 
 V   mr   =R   m   I   2 =( R   m0   +ΔR   m ) I   2 =( R   m0   +αβI   1 ) I   2   (4)
 
     Next, an expression (5) holds when a voltage V in  is V 1 . This is because the power source  91  is a direct-current power source. Meanwhile, the resistance of the electric wire A 93   a  and electric wire B 93   b  is sufficiently small and the electric resistance R m  of the magnetic element  14  is also sufficiently smaller than the measuring resistance  22  (the value is R 2 ). The current I 1  flowing in the electric wire A 93   a  and the current I 2  flowing in the magnetic element  14  are expressed as an expression (6) and an expression (7), respectively, if the resistance of the load  92  is R 1 . 
     Consequently, voltage Vmr between the element terminals  143  and  144  of the magnetic element  14  is expressed as an expression (8). Note that the relationship of R m0 &lt;&lt;R 2  is used in the middle of the deformation in the expression (8). Additionally, K 1  is the proportionality constant. In other words, a voltage proportional to an electric power I 1 V 1  consumed in the load  92  can be obtained between the element terminals  143  and  144  of the magnetic elements  14 . 
     
       
         
           
             
               
                 
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     The relationships described above hold even when the power source  91  is an alternating-current power source. Next, a case in which the power source  91  is an alternating-current power source and the load  92  has reactance will be described. The relationships in the expression (1) to the expression (4) are described above. The power source  91  is an alternating-current power source. Thus, the voltage V in  is expressed as an expression (9) if the amplitude is V 1  and the angular frequency is ω. The load  92  has reactance in the to-be-measured circuit  99 . This causes a phase shift between the current I 1  flowing in the load  92  and the voltage V in  in the power source  91 . The phase shift is denoted with θ. On the other hand, the magnetic element  14  is in phase with the voltage V in  in the power source  91  because the magnetic element  14  has a normal resistance. Consequently, the currents I 1  and I 2  are expressed as expressions (10) and (11), respectively. 
     Substituting the expressions (10) and (11) into the expression (4) deforms the expression (4) as an expression (12). 
     
       
         
           
             
               
                 
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     With reference to the expression (12), the last term expresses that the effective electric power consumed in the load  92  is a direct-current component. In other words, the direct-current voltage obtained by passing the output between the element terminals  143  and  144  through a low-pass filter is proportional to the effective electric power consumed in the load  92 . Depending on the method of connecting the magnetic element  14 , not only the current flowing in the power source lines  93  but also the electric power consumed in the load  92  connected to the power source can be measured using the magnetic element  14  as described above. 
     Based on the preparation described above, the electric leakage detecting apparatus  1  in  FIG. 1  will further be described.  FIG. 6  is a schematic cross-sectional view of the magnetic elements  14  placed along the electric wires A 93   a  and B 93   b  of the power source lines  93 . The electric wire A 93   a  is on the left side and the electric wire B 93   b  is on the right side. The magnetic element  14  placed on the electric wire A 93   a  is defined as a magnetic element A 14   a  and the magnetic element  14  placed on the electric wire B 93   b  is defined as the magnetic element B 14   b . The power source lines  93  connect the power source  91  and the load  92  (see  FIGS. 1( a ) and 1( b ) ). Thus, the currents flow necessarily in the opposite directions in the right and left power source lines. Consequently, it is assumed that the current in the left electric wire A 93   a  flows from the rear surface to the front surface of the drawing paper, and that the current in the right electric wire B 93   b  flows from the front surface to the rear surface of the drawing paper. 
     At that time, magnetic fields arise around the electric wires. The magnetic field around the electric wire A 93   a  arises in the counterclockwise (the dashed line) on the drawing paper. The magnetic field around the electric wire B 93   b  arises in the clockwise (the alternate long and two short dashes line) on the drawing paper. Then, a magnetic field Ha is applied to the magnetic element A 14   a  from the left side to the right side of the drawing paper, and a magnetic field Hb is applied to the magnetic element B 14   b  from the right side to the left side of the drawing paper. This means that the magnetic fields are applied from the outside of the magnetic film in a direction which is an in-plane direction of the magnetic film  142  and is perpendicular to the longitudinal directions of the magnetic elements  14 . 
     Note that, in that case, the two magnetic elements A 14   a  and B 14   b  are configured to have the same magneto-resistance effect when the same magnetic fields are applied to the two magnetic elements. Manufacturing the magnetic elements such that the magnetic films  142  have the same dimensions in thickness, length, and width, and the same composition under the same manufacturing conditions can provide the same magneto-resistance effect to the magnetic elements  14 . 
     Furthermore, the intensity of the magnetic field applied to each of the magnetic elements  14  at that time is inversely proportional to the square of the distance from each of the electric wires A 93   a  and B 93   b  to each of the magnetic elements A 14   a  and B 14   b . Thus, the two magnetic elements A 14   a  and B 14   b  have the same resistance value if the magnetic elements are placed at the same distances away from the electric wires A 93   a  and B 93   b , respectively, and no current leaks. This is because the same current flows in the electric wires A 93   a  and B 93   b.    
     On the other hand, when the current leaks from the circuit formed of the power source  91  and the load  92  (the to-be-detected circuit  90 ), the current flowing in the electric wire A 93   a  from the power source  91  to the load  92  differs from the current returning through the electric wire B 93   b  from the load  92  to the power source  91 . Concretely, the current flowing in the electric wire A 93   a  is not the same as the current flowing in the electric wire B 93   b  in  FIG. 6 . Thus, the resistance value of the magnetic element A 14   a  differs from the resistance value of the magnetic element B 14   b.    
     Consequently, by configuring a circuit, as the electric leakage detecting apparatus, to output the difference between the resistance value of the magnetic element A 14   a  and the resistance value of the magnetic element B 14   b , it is possible to determine that no current leaks have occurred when the difference between the resistance values of the magnetic element A 14   a  and B 14   b  is zero, and that the current leaks have occurred when a difference having a predetermined value or more is detected. 
     Note that the placement of the magnetic element A 14   a  and the magnetic element B 14   b  is not especially limited as long as the magnetic element A 14   a  and the magnetic element B 14   b  are placed at the same distances away from the electric wire A 93   a  and the electric wire B 93   b  that are adjacently placed, respectively. In  FIG. 6 , the magnetic element A 14   a  and the magnetic element B 14   b  are placed on the same plane. 
       FIG. 7  is a view of the wire connection when the electric leakage detecting apparatus  1  according to the present embodiment is installed on the to-be-detected circuit  90  formed of the power source  91  and the load  92 . The power source  91  can be an alternating-current power source or a direct-current power source. Additionally, the load  92  can have either impedance without complex numbers or reactance with complex numbers. The two power source lines  93 , which extend from the power source  91 , are referred to as the electric wire A 93   a  and the electric wire B 93   b . A part of each of the electric wires A 93   a  and B 93   b  is held with each of the holders  11  illustrated in  FIGS. 1( a ) and 1( b ) . 
     Each of the electric wires A 93   a  and B 93   b  is preferably held at a part as close to the power source  91  as possible. This is because an electric leakage may fail to be detected unfortunately in a direct-current power source  91  if the current leaks from a part nearer to the power source  91  than the position at which the detection have occurred, whereas an electric leakage can be detected at any position on the electric wires A 93   a  and B 93   b  in an alternating-current power source  91 . 
     The part held with the holders  11  is surrounded with a dashed line in  FIG. 7 . The electric wire A 93   a  is adjacent to the magnetic element A 14   a , and the electric wire B 93   b  is adjacent to the magnetic element B 14   b  at the part. A first terminal element  143   a  of the magnetic element A 14   a  is connected to a first terminal element  143   b  of the magnetic element B 14   b . A first terminal of the measuring resistance A 22   a  is connected to a second terminal element  144   a  of the magnetic element A 14   a  in series. A first terminal of the measuring resistance B 22   b  is connected to a second terminal element  144   b  of the magnetic element B 14   b  in series. 
     Second terminals of the measuring resistances A 22   a  and B 22   b  are connected to each other. Furthermore, the magnetic elements A 14   a  and B 14   b  are connected to a first electrode of the detector power source  21 , and the second terminals of the measuring resistances A 22   a  and B 22   b  are connected to a second electrode of the detector power source  21 . Thus, the magnetic element A 14   a  and the measuring resistance A 22   a  are connected to each other and form a branch. The magnetic element B 14   b  and the measuring resistance B 22   b  are connected to each other and form a branch. Connecting the two branches in parallel forms a bridge circuit  30 . 
     The detector power source  21 , which feeds a drive current to the magnetic elements A 14   a  and B 14   b , is a driving means. In  FIG. 7 , the detector power source  21  and the power source  91  of the to-be-detected circuit  90  are formed as separate circuits. This can be said that the power sources are independent from each other. 
     The connecting point of the magnetic element A 14   a  and the measuring resistance A 22   a , and the connecting point of the magnetic element B 14   b  and the measuring resistance B 22   b  are named as measuring terminals  23  ( 23   a  and  23   b ), respectively. The measuring terminals  23  are connected with inputs of the amplifier  24  so as to amplify the voltage between the measuring terminals  23 . The display means  26  is connected to the output from the amplifier  24 . The display means  26  is not especially limited to as long as the display means  26  can display the output from the amplifier  24 . For example, the display means  26  can display the output from the amplifier  24  without any change. Alternatively, a threshold used to round off predetermined noise levels can be provided such that the display means  26  can display a signal indicating the presence of an electric leakage when the output from the amplifier  24  is higher than the threshold. 
     Note that the detecting means  20  includes the detector power source  21  that is a driving means, the measuring resistances  22   a  and  22   b , the amplifier  24 , and the display means  26 . When the power source  91  of the to-be-detected circuit  90  is also used as the driving means as described below, the detecting means does not include a driving means. 
     Next, the operation of the electric leakage detecting apparatus  1  will be described. When no current leaks in the to-be-detected circuit  90  including the power source  91  and the load  92 , the same current flows in the electric wire A 93   a  and the electric wire B 93   b . At that time, the resistance values of the magnetic element A 14   a  and magnetic element B 14   b  affected by the magneto-resistance effects are the same. Thus, the voltages are the same on the measuring terminals  23   a  and  23   b  in the bridge circuit  30  including the magnetic element A 14   a , the measuring resistance A 22   a , the magnetic element B 14   b , and the measuring resistance B 22   b . Consequently, the output from the amplifier  24  is zero. 
     On the other hand, when the current leaks from the to-be-detected circuit  90  including the power source  91  and the load  92 , the current flowing in the electric wire A 93   a  is not the same as the current flowing in the electric wire B 93   b . Consequently, the electric resistance of the magnetic element A 14   a  has a value different from the electric resistance of the magnetic element B 14   b . In other words, the voltage difference corresponding to the difference of the electric resistances between the magnetic element A 14   a  and the magnetic element B 14   b  arises between the measuring terminals  23   a  and  23   b . The voltage difference is amplified with the amplifier  24  and is displayed on the display means  26 . 
     Note that, in the case of the electric leakage, the output from the amplifier  24  is a direct-current output if the power source  91  is a direct-current power source. Alternatively, if the power source  91  is an alternating-current power source, the output from the amplifier  24  is also an alternating-current output. Thus, when the power source  91  is an alternating-current power source, a rectifier (not illustrated in the drawings) can be placed between the amplifier  24  and the display means  26 . 
     The detector power source  21  is independent from the to-be-detected circuit  90  in the electric leakage detecting apparatus  1  according to the present embodiment. Thus, only fixing the electric wire A 93   a  and electric wire B 93   b  in the already-formed to-be-detected circuit  90  with the holders  11  can install the electric leakage detecting apparatus  1  on the detected circuit. Additionally, the difference between the measuring terminals  23   a  and  23   b  is amplified with the amplifier  24 . Thus, an electric leakage can be detected even when the voltage of the detector power source  21  drops. However, the drop in the electric power supplied to the amplifier  24  sometimes may reduce the voltage output from the amplifier  24 . 
     Note that each of the magnetic elements A 14   a  and B 14   b  does not necessarily include the bias means  145  in the electric leakage detecting apparatus  1  according to the present embodiment. It is only required to find the difference between the magneto-resistance effects on the magnetic element A 14   a  and B 14   b  by monitoring the voltages on the measuring terminals  23   a  and  23   b  in the bridge circuit  30 . Needless to say, the magnetic elements A 14   a  and B 14   b  each can be magnetic elements  14  including a bias means  145 . In other words, the electric leakage detecting apparatus  1  according to the present embodiment detects the difference between the currents flowing in the electric wire A 93   a  and electric wire B 93   b.    
     Second Embodiment 
       FIG. 8  illustrates the wire connection when an electric leakage detecting apparatus  1   b  according to the present embodiment is installed on a to-be-detected circuit  90 . Electric wires A 93   a  and B 93   b  are held in the same manner as in  FIGS. 1( a ) and 1( b ) . In the present embodiment, a power source  91  of the to-be-detected circuit  90  is used also as the power source for a bridge circuit  30 , namely, as the detector power source. 
     Similarly to the embodiment 1, a magnetic element A 14   a , a measuring resistance A 22   a , a magnetic element B 14   b , and a measuring resistance B 22   b  form the bridge circuit  30 . Current is supplied to the bridge circuit  30  through a circuit of which first end is connected to the electric wire A 93   a  and of which second end is connected to the electric wire B 93   b . In other words, the driving means is the power source  91  of the to-be-detected circuit  90 . Such a configuration is described as that the detector power source is parasite in the to-be-detected circuit  90 . 
     In the electric leakage detecting apparatus  1   b  according to the present embodiment, the magnetic element A 14   a  and the measuring resistance A 22   a  are connected to the power source  91  of the to-be-detected circuit  90  parallel to the load  92 . In other words, the voltage between element terminals  143   a  and  144   a  of the magnetic element A 14   a  provides an output proportional to the electric power consumed in the load  92 . The magnetic element B 14   b  and the measuring resistance B 22   b  are also connected to the power source  91  of the to-be-detected circuit  90  parallel to the load  92 . Thus, the voltage between both ends of the magnetic element B 14   b  also provides an output proportional to the electric power consumed in the load  92 . In other words, what is monitored between the measuring terminals  23   a  and  23   b  is equivalent to the difference between the consumed power value in the load  92  measured on the electric wire A 93   a  and the consumed power value in the load  92  measured on the electric wire B 93   b . Both of the values are obtained from the same electric power consumed in the load  92 . 
     When no current leaks from the to-be-detected circuit  90 , the power consumed in the load  92  seen from the power source  91  measured on the electric wire A 93   a  is the same as that measured on the electric wire B 93   b . On the other hand, when the current leaks from the to-be-detected circuit  90 , the power consumed in the load  92  measured on the electric wire A 93   a  is different from that measured on the electric wire B 93   b . Consequently, the difference of the voltages on the measuring terminals  23   a  and  23   b  is not zero. The voltage difference between the measuring terminals  23   a  and  23   b  is generated, which causes the amplifier  24  to provide the output voltage proportional to the voltage between the measuring terminals  23   a  and  23   b.    
     As a result, the electric leakage can be confirmed on the display means  26 . The electric leakage detecting apparatus  1   b  in the present embodiment detects the electric power consumed in the load  92  as described above. Note that it is preferable that the electric leakage detecting apparatus  1   b  be previously embedded in the to-be-detected circuit  90  because the electric leakage detecting apparatus  1   b  uses the power source  91  of the to-be-detected circuit  90  as the driving means. 
     In the detection of the electric leakage, when the power source  91  is a direct-current power source, the output from the amplifier  24  is a direct-current output. When the power source  91  is an alternating-current power source, the output from the amplifier  24  is an alternating-current output. When the power source  91  is an alternating-current power source, it is only required to monitor the direct-current components in the output from the amplifier  24 . Thus, when the power source  91  is an alternating-current power source, placing a low-pass filter between the amplifier  24  and the display means  26  enables the display means  26  to receive the direct-current output. 
     Third Embodiment 
       FIG. 9  illustrates the wire connection when an electric leakage detecting apparatus  1   c  according to the present embodiment is installed on a to-be-detected circuit  90 . Power source lines  93  are held and fixed in the same manner as in  FIGS. 1( a ) and 1( b ) . Additionally, the method of installing the electric leakage detecting apparatus  1   c  on the to-be-detected circuit  90  is the same as in the second embodiment. In other words, the power source  91  of the to-be-detected circuit  90  is used also as the driving means for the bridge circuit  30 . 
     The difference between the present embodiment and the second embodiment is that the present embodiment uses barber-pole magnetic elements as magnetic elements  14 , and that the present embodiment is provided with a power detecting amplifier  32 , and that a terminal element  143   b  of the magnetic element B 14   b  includes a switch  36 , the power detecting amplifier  32  being configured to output the voltage between the element terminals  143   a  and  144   a  of a first magnetic element A 14   a , the switch  36  being configured to switch whether the terminal element  143   b  is connected to the to-be-detected circuit  90  or independent to be connected to a circuit  33  in which current flows from a constant current source  35  which is different from the power source  91  of the to-be-detected circuit  90 . A current detecting amplifier  34  is connected to the circuit  33  parallel to the constant-current power source  35 . 
     Barber-pole magnetic elements are used as the magnetic elements  14  in order to cause the electric leakage detecting apparatus to also work as a current sensor and an electric power sensor using at least one of the barber-pole magnetic elements  14  utilizing the bias means  145  structurally included in the barber-pole magnetic elements. Thus, a bias means  145  other than the bias means included in the barber-pole magnetic element can also be used. 
     To use the electric leakage detecting apparatus as an electric leakage detecting apparatus, the switch  36  is switched such that first terminals  143   a  and  143   b  of the two magnetic elements A 14   a  and B 14   b  are connected to the to-be-detected circuit  90 . When no current leaks, the voltage difference between the measuring terminals  23   a  and  23   b  in the bridge circuit  30  is zero. When the current leaks, a predetermined pressure arises between the measuring terminals  23   a  and  23   b . This is the same as in the second embodiment. 
     In that case, the bias means  145  are provided to the magnetic elements A 14   a  and B 14   b  in the opposite directions to each other. In other words, the conductor patterns in the magnetic elements A 14   a  and B 14   b  are inclined in the different directions. Concretely, each of the bias means  145  is provided so as to give a bias magnetic field extending toward the center  11   c  between the holders  11   a  and  11   b  in  FIGS. 1( a ) and 1( b )  or a bias magnetic field extending from the center between the holders  11   a  and  11   b  toward both outer sides. The conductors  148  that have a stripe structure and that are the bias means  145  of the magnetic elements A 14   a  and B 14   b  are inclined to the center  11   c  in such barber-pole magnetic elements in  FIG. 9 . Since a current I 1 a flows in the electric wire A 93   a  in the opposite direction to the direction in which a current I 1 b flows in the electric wires B 93   b , the same magneto-resistance effects is generated when the currents flow in the opposite directions to each other. 
     The generation of the same magneto-resistance effects means that the magnetic elements A 14   a  and B 14   b  vary in the same direction from the operating point on the curve MRC indicating the magneto-resistance effect (see  FIG. 3( b ) ). In  FIG. 9 , the magnetic field caused by each of the currents I 1 a and I 1 b changes the direction of the magnetization in each of the magnetic elements A 14   a  and B 14   b  to the direction away from the direction in which the current flows in the magnetic film. 
     In the configuration described above, the currents I 1 a and I 1 b having the same value reduce both of the resistance values of the magnetic elements A 14   a  and B 14   b  from the resistance values on the operating point. Additionally, when the magnetic elements A 14   a  and B 14   b  have the magneto-resistance effects showing the same curve MRC, the resistance values are reduced to the same resistance value. Thus, when no current leaks, no voltage arises between the measuring terminals  23   a  and  23   b  in the bridge circuit  30 . 
     On the other hand, when the current leaks, the resistance value of one of the magnetic elements  14  varies. This generates a voltage corresponding to the difference between the resistance values of the magnetic elements A 14   a  and B 14   b  between the measuring terminals  23   a  and  23   b  in the bridge circuit  30 . Amplifying the voltage in the amplifier  24  and displaying the amplified voltage on the display means  26  enable the user to detect the generation of the electric leakage. 
     The electric leakage detecting apparatus  1   c  according to the present embodiment can be used not only to detect an electric leakage described above but also as an electric power sensor and a current sensor. Concretely, measuring the voltage between the element terminals  143   a  and  144   a  of the magnetic element A 14   a  can find the voltage proportional to the electric power consumed in the load  92  of the to-be-detected circuit  90  from the power detecting amplifier  32 . Note that, when an alternating current flows in the to-be-detected circuit  90 , the power detecting amplifier  32  can provide the voltage output of which direct-current component is proportional to the effective electric power consumed in the load. To extract the direct-current component, for example, a low-pass filter  25  may be connected to the output from the amplifier  24 . 
     By switching the switch  36 , a terminal  143   b  of the magnetic element B 14   b  is connected to the external circuit  33 . The switching causes a current to flow to the magnetic element B 14   b  from a constant-current power source  35  that is different from the to-be-detected circuit  90 . Then, the voltage between the element terminals  143   b  and  144   b  is measured. This can detect the voltage proportional to the current flowing in the to-be-detected circuit  90 . When the power source  91  of the to-be-detected circuit  90  is an alternating-current power source, the output of the current detecting amplifier  34  is also an alternating-current output. 
     As described above, the electric leakage detecting apparatus  1   c  according to the present embodiment can work also as a current sensor and an electric power sensor using one of the magnetic elements A 14   a  and B 14   b.    
     Fourth Embodiment 
       FIG. 10( a )  is a perspective view of a part including holders  11 , insertion means  13 , and a fixing means  16  in an electric leakage detecting apparatus  2   a  according to the present embodiment. The holders  11 , the insertion means  13 , and the fixing means  16  in  FIG. 10( a )  are similar to the holders  11 , the insertion means  13 , and the fixing means  12  illustrated in  FIGS. 1( a ) and 1( b ) . However, the fixing means  16  includes inclined surfaces  16   a   1  and  16   a   2  forming a predetermined angle from a predetermined position  16   c  of the fixing means toward both ends. In other words, the inclined surface  16   a   1  and the inclined surface  16   a   2  abut against each other at an angle  16 θ. 
       FIG. 11  is a cross-sectional view of power source lines  93 . As described above with reference to  FIG. 6 , the magnetic elements A 14   a  and B 14   b  are affected by the magnetic field generated from the electric wires A 93   a  and B 93   b , and the magneto-resistance effects change the electric resistances. Considering the magnetic fields further away from the electric wires A 93   a  and B 93   b , the magnetic field from the electric wire A 93   a  (the dashed line) affects also the magnetic element B 14   b  placed under the electric wire B 93   b . Similarly, the magnetic field from the electric wire B 93   b  (the alternate long and two short dashes line) affects also the magnetic element A 14   a  placed under the electric wire A 93   a.    
     The magnetic fields work so as to reduce the magnetic fields that the magnetic elements A 14   a  and B 14   b  receive from the electric wires A 93   a  and B 93   b . This leads to the decrease in the sensitivity of the magnetic elements A 14   a  and B 14   b  for detecting an electric leakage. 
       FIG. 12  is a cross-sectional view when the magnetic elements A 14   a  and B 14   b  are inclined at a predetermined angle as illustrated in  FIGS. 10( a )  and  10  ( b ). Providing the magnetic elements A 14   a  and B 14   b  each inclined at a predetermined angle to the electric wires A 93   a  and B 93   b  can create the circumstances under which only the components that are perpendicular to the magnetic films of the magnetic elements A 14   a  and B 14   b  in the magnetic fields from the electric wires A 93   a  and B 93   b  are applied to the magnetic elements A 14   a  and B 14   b . Concretely, the magnetic element A 14   a  is placed on the tangent from the center of the electric wire B 93   b  to the electric wire A 93   a . The magnetic element B 14   b  is placed on the tangent from the center of the electric wire A 93   a  to the electric wire B 93   b.    
     Under such placement, the magnetic field from each of the adjacent electric wires affects the magnetic film of each of the magnetic elements A 14   a  and B 14   b  only in the perpendicular direction. The magnetic film in each of the magnetic elements  14  is much thinner than the magnetic element in width. Thus, the magnetic field in the perpendicular direction to the magnetic film affects the development of the magneto-resistance effect very slightly. Consequently, each of the magnetic elements A 14   a  and B 14   b  exerts the magneto-resistance effect by being affected only by the magnetic field generated from the electric wire A 93   a  or B 93   b  provided on the magnetic element without significantly being affected by the electric wire B 93   b  or A 93   a  adjacent to its own electric wire. 
     This gives the effects of error reduction and stable operation. Note that the angle  14 θ between the magnetic elements A 14   a  and B 14   b  is expressed by an expression (13) with reference to  FIG. 12  that is a line diagram. Thus, the angle  14 θ formed of the magnetic element A 14   a  and B 14   b  can be an angle  14 θ obtained from the expression (13) or an angle near the angle  14 θ. Note that “a” denotes the distance between the electric wires B 93   b  and A 93   a , and “r” denotes the radius of each of the electric wires. 
     
       
         
           
             
               
                 
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                   13 
                   ) 
                 
               
             
           
         
       
     
     With reference to  FIG. 10( a )  again, the predetermined angle  16 θ between the inclined surfaces  16   a   1  and  16   a   2  of the fixing means  16  that abut against each other is the angle formed of the surfaces inclined at the predetermined angle  14 θ illustrated in  FIG. 12  or at the angle obtained by adjusting the angle  14 θ. In other words, the inclined surfaces  16   a   1  and  16   a   2  are inclined at a predetermined angle to the midpoint  16   c  of the holders  11 . 
       FIG. 10 ( b )  illustrates that the electric wires A 93   a  and B 93   b  in the to-be-detected circuit  90  are held on the part including the holders  11 , the fitting means  13 , and, the fixing means  16  illustrated in  FIG. 10( a ) . The configuration illustrated in  FIGS. 10( a ) and 10( b )  is the same as the configuration illustrated in  FIGS. 1( a ) and 1( b )  except that the fixing means  16  includes the inclined surfaces  16   a   1  and  16   a   2 . Thus, the fixing means  16  in  FIG. 10( a )  can be used instead of the fixing means  12  described in the first to third embodiments. Note that a groove  16   b  is formed on the fixing means  16 , similarly to the groove  16   b  on the fixing means  12  in  FIGS. 1( a ) and 1( b ) . The insertion means  13  is movably inserted in the groove  16   b , similarly to the case in  FIGS. 1( a ) and 1( b ) . 
     More concretely, what is obtained by wiring the fixing means  16  in  FIG. 10( a )  as illustrated in  FIG. 10( b )  is an electric leakage detecting apparatus  2   a . This corresponds to the first embodiment. What is obtained by wiring the fixing means  16  in  FIG. 10( a )  as illustrated in  FIG. 8  is an electric leakage detecting apparatus  2   b . This corresponds to the second embodiment. What is obtained by wiring the fixing means  16  in  FIG. 10( a )  as illustrated in  FIG. 9  is an electric leakage detecting apparatus  2   c . This corresponds to the third embodiment. 
     Fifth Embodiment 
       FIGS. 13( a ) and 13( b )  illustrate holders  11  and the like in an electric leakage detecting apparatus  3  according to the present embodiment. The holders  11  according to the present embodiment include a magnetic element  14  only in one place. Even if a plurality of magnetic elements  14  are used, the magnetic elements  14  are placed as a straight line. The holders  11  are integrated in a fixing means  17 . In  FIG. 13( a ) , the interval between a holder  11   a  and a holder  11   b  is fixed. However, the interval can also be variable. The magnetic element  14  is held between the holders  11   a  and  11   b . The magnetic element  14  is fixed in a direction in which the magnetic fields from electric wires A 93   a  and B 93   b  held in the holders  11   a  and  11   b  affect the inside of the plane of the magnetic element  14 . The magnetic element  14  used in the fixing means  17  is denoted with a reference sign  14   s.    
       FIG. 13( b )  illustrates the wire connection in the electric leakage detecting apparatus  3   a  according to the present embodiment. In the electric leakage detecting apparatus  3   a , one of the electric wire A 93   a  and the electric wire B 93   b  is held in the holder  11  after being twisted once. In other words, one of the electric wires is twisted such that currents I 1 a and I 1 b flow in the same direction at the fixing means  17  in the electric wires A 93   a  and B 93   b  held with the pair of holders  11   a  and  11   b . In other words, a loop is formed on the electric wire B 93   b  before the electric wire B 93   b  is held with the holder  11 . Forming the loop causes the magnetic field to be zero at the magnetic element  14   s  when no current leaks and the currents having the same amount flow in the electric wires A 93   a  and B 93   b . This is because the magnetic fields of the electric wires A 93   a  and B 93   b  cancel each other. 
     If the currents flow in the opposite directions at the fixing means  17  in the electric wire A 93   a  and the electric wire B 93   b , the sum of the magnetic fields generated by the currents flowing in the electric wires A 93   a  and B 93   b  is applied to the magnetic element  14   s . In such a case, it fails to be determined whether both of the currents flowing in the electric wires A 93   a  and B 93   b  have increased or decreased, or only one of the currents flowing in the electric wires A 93   a  and B 93   b  has increased or decreased. Making the currents I 1 a and I 1 b flow in the same direction at the fixing means  17  as illustrated in  FIG. 13( b )  can detect only the case in which there is a difference between the currents flowing in both of the electric wires A 93   a  and B 93   b.    
       FIG. 14  illustrates the wire connection in  FIG. 13( b ) . The electric leakage detecting apparatus using the fixing means  17  in  FIGS. 13( a ) and 13( b )  and the wire connection in  FIG. 14  is the electric leakage detecting apparatus  3   a . The electric leakage detecting apparatus  3   a  includes a detector power source  21 , a magnetic element  14   s , a measuring resistance  22 , a measuring terminals  23   a  and  23   b , an amplifier  24 , and a display means  26 . The part surrounded with a dashed line is the electric wires A 93   a  and B 93   b  held with the holder  17 . 
     The detector power source  21  that is a driving means, the magnetic element  14   s , and a measuring resistance  22  connected in series to the magnetic element  14   s  form a circuit in the electric leakage detecting apparatus  3   a . The detector power source  21  is independent from a power source  91  of a to-be-detected circuit  90 . This makes it easy to install the electric leakage detecting apparatus  3   a  on the already-established to-be-detected circuit  90  afterward. Additionally, an objective of the detector power source  90  and the measuring resistance  22  is to feed a predetermined constant current to the magnetic element  14   s . Thus, a constant-current power source can be used instead of the detector power source and the measuring resistance. The amplifier  24  and the display means  26  are connected between element terminals  143   s  and  144   s  of the magnetic element  14   s . Thus, the voltage at the element terminal  143   s  is the same as that at the measuring terminal  23   a , and the voltage at the element terminal  144   s  is the same as that at the measuring terminal  23   b  in the electric leakage detecting apparatus  3   a.    
     The operation of the electric leakage detecting apparatus  3   a  according to the present embodiment will be described. The power source  91  is connected to the load  92  through the power source lines  93  (the electric wire A 93   a  and the electric wire B 93   b ) in the to-be-detected circuit  90 . The currents I 1 a and I 1 b flow in the same direction at the fixing means  17  in the electric wires A 93   a  and B 93   b  because the electric wire B 93   b  returning from the load  92  to the power source  91  is twisted once halfway. 
     The magnetic element  14   s  placed at the center of the holders  11   a  and  11   b  receives the magnetic fields from the electric wires A 93   a  and B 93   b . However, the magnetic fields cancel each other. Thus, when no current leaks, no voltage arises between the element terminals  143   s  and  144   s  in the magnetic element  14   s . On the other hands, when the current leaks, the current flowing in the electric wire A 93   a  differs from the current flowing in the electric wire B 93   b . Consequently, an external magnetic field is applied to the magnetic element  14   s.    
     In other words, the resistance value of the magnetic element  14   s  varies due to the magneto-resistance effect. The detector power source  21  feeds a predetermined current to the magnetic element  14   s . This generates a voltage between the element terminals  143   s  and  144   s  in the magnetic element  14   s . Amplifying the voltage in the amplifier  24  and displaying the amplified voltage on the display means  26  can notify the user of the generation of the electric leakage. 
     Note that, when the current leaks, it is necessary in the electric leakage detecting apparatus  3   a  in  FIG. 14  to detect the variation in the resistance value from the resistance value without the electric leakage in the magnetic element  14   s . Thus, it is necessary to record the output from the amplifier  24  when there is no electric leakage so as to sequentially compare the recorded value with the output from the amplifier  24 . Thus, a memory and comparing means  40  is preferably placed for the output from the amplifier  24 . 
     The configuration of the memory and comparing means is not especially limited as long as the memory and comparing means  40  has a function for recording the output from the amplifier  24  when no current leaks as an initial value to compare the output from the amplifier  24  after the start of the detection of an electric leakage with the default value, and sending a signal to the display means  26  when the output has varied. 
     When the power source  91  is a direct-current power source, the output from the amplifier  24  is also a direct-current output. When the power source  91  is an alternating-current power source, the output from the amplifier  24  is also an alternating-current output. In the electric leakage detecting apparatus  3   a , the value of the current flowing in the to-be-detected circuit  90  is detected at the magnetic element  14   s . Thus, when the power source  91  is an alternating-current power source, the amplitude of the output from the amplifier  24  corresponds to the variation to be detected in the current. Thus, it is preferable to insert a rectifier (not illustrated in the drawings) between the amplifier  24  and the memory and comparing means  40  so as to process a signal with direct current when the power source  91  is an alternating-current power source. 
     Note that any magnetic element  14   s  including the bias means  145  can determine also from which electric wire A 93   a  or B 93   b  the current leaks according to the direction of the voltage variation in the amplifier  24  (the positive or negative direction).  FIG. 15  illustrates the wire connection in an electric leakage detecting apparatus  3   av  including a barber-pole bias means  145 . The electric leakage detecting apparatus  3   av  is the same as the electric leakage detecting apparatus  3   a  in  FIG. 14  except that the magnetic element  14   s  is a barber-pole magnetic element. 
     Sixth Embodiment 
       FIG. 16  illustrates the wire connection of an electric leakage detecting apparatus  3   b  according to the present embodiment and relative to a to-be-detected circuit  90 . The appearance including a fixing means  17  and the like is the same as the case in  FIGS. 13( a ) and 13( b ) . The difference between the present embodiment and the fifth embodiment is that a second terminal  144   s  (on the side connected to a first terminal of a measuring resistance  22 ) of a magnetic element  14   s  is grounded, and measuring terminals  23  are provided between a first terminal  143   s  of the magnetic element  14   s  and a second terminal of the measuring resistance  22  in the present embodiment. 
     The measuring resistance  22  is configured so that it has a resistance value equal to the resistance value of the magnetic element  14   s . As described above, the magnetic element  14   s  and the measuring resistance  22  have the same resistance value, and the connecting point is grounded. This can cause the outputs on both ends of the magnetic element  14   s  and the measuring resistance  22  to be zero when no current leaks. Therefore, generation of the electric leakage can be detected from a predetermined voltage generated in the output from the amplifier  24 . 
     Note that, when the power source  91  is a direct-current power source, the output from the amplifier  24  is also a direct-current output. When the power source  91  is an alternating-current power source, the output from the amplifier  24  is also an alternating-current output. Thus, a rectifier is preferably provided between the amplifier  24  and the display means  26  when the power source  91  is an alternating-current power source. 
       FIG. 17  illustrates the wire connection of an electric leakage detecting apparatus  3   bv  in which a magnetic element  14   s  includes a bias means  145 . The electric leakage detecting apparatus  3   bv  is the same as the electric leakage detecting apparatus in  FIG. 16  except for the magnetic element  14   s . Providing the bias means  145  can determine from which electric wire A 93   a  or B 93   b  the current leaks. 
     Seventh Embodiment 
       FIG. 18  illustrates the wire connection of an electric leakage detecting apparatus  3   c  according to the present embodiment and relative to a to-be-detected circuit  90 . The appearance including a fixing means  17  and the like is the same as the case in  FIGS. 13( a ) and 13( b ) . The magnetic element  14   s  is connected in series to the measuring resistance  22 . The magnetic element  14   s  and the measuring resistance  22  are connected to a power source  91  of the to-be-detected circuit  90  parallel to the load  92 . An electric wire B 93   b  is held on a holder  11   c  after being twisted once so as to feed currents I 1 a and I 1 b in the same direction at the fixing means  17 . An amplifier  24  is connected to element terminals  143   s  and  144   s  of the magnetic element  14   s . A display means  26  is connected to the output from the amplifier  24 . 
     The operation of the electric leakage detecting apparatus  3   c  according to the present embodiment will be described. When no current leaks, the magnetic fields applied to the magnetic element  14   s  from the electric wire A 93   a  and the electric wire B 93   b  cancel each other, and no magnetic field is applied to the magnetic element  14   s . In other words, when the electric power consumed in the load viewed from the power source  91  is measured on the electric wire A 93   a  side and on the electric wire B 93   b  side, there is no difference between the two. 
     On the other hand, when the current leaks, the current in one of the electric wires  93  is smaller than that in the other thereof, and thus, an external magnetic field is applied to the magnetic elements  14   s . The magnetic field causes the magnetic element  14   s  to generate a magneto-resistance effect. The effect changes the voltage between the element terminals  143   s  and  144   s . Consequently, displaying the generated voltage on the display means  26  through the amplifier  24  enables the user to detect the generation of the electric leakage. 
     Note that a memory and comparing means  40  is preferably provided between the amplifier  24  and the display means  26 , similarly to the case in  FIG. 14  described in the fifth embodiment. This is because the electric leakage detecting apparatus  3   c  according to the present embodiment observes the variations in the resistance value of the magnetic element  14   s  as the variations in the voltage. 
     Note that, when the power source  91  of the to-be-detected circuit  90  is an alternating-current power source, the direct-current component in the output from the amplifier  24  can be extracted as the voltage proportional to the electric power consumed in the load  92 . Thus, by providing a low-pass filter  25  on the output end of the amplifier  24 , it is possible to detect an electric leakage either in a direct-current power source  91  or in an alternating-current power source  91 . 
     An electric leakage detecting apparatus  3   cv  in which a magnetic element  14   s  includes a bias means  145  will be described with reference to  FIG. 19 . The electric leakage detecting apparatus  3   cv  is the same as that in  FIG. 18  except that the magnetic element  14   s  includes the bias means  145 . By providing the bias means  145  to the magnetic element  14   s , it is possible to determine from which electric wire A 93   a  or B 93   b  the current leaks. Note that the implement of the bias means  145  is not limited to a barber-pole magnetic element  14   s  as illustrated in  FIG. 19 . 
     Eighth Embodiment 
       FIG. 20  illustrates the wire connection of an electric leakage detecting apparatus  3   d  according to the present embodiment. The appearance including a fixing means  17  and the like is the same as the case in  FIGS. 13 ( a ) and 13( b ) . In the electric leakage detecting apparatus  3   d , a part between the magnetic element  14   s  and the measuring resistance  22  that are connected in series to each other is grounded, and the magnetic element  14   s  and the measuring resistance  22  are configured to have the same resistance value when no external magnetic field is applied. Additionally, both ends of the magnetic element  14   s  and measuring resistance  22  are measuring terminals  23   a  and  23   b . This can cause the voltage between the measuring terminals  23   a  and  23   b  to be zero. Thus, when no current leaks, the output from the amplifier  24  is zero. The generation of an output from the amplifier  24  can be used to detect the generation of the electric leakage. 
     Note that, when the power source  91  of the to-be-detected circuit  90  is an alternating-current power source, the direct-current component in the output from the amplifier  24  can be extracted as the voltage proportional to the electric power consumed in the load  92 . Thus, by providing a low-pass filter  25  on the output end of the amplifier  24 , it is possible to detect an electric leakage either in a direct-current power source  91  or in an alternating-current power source  91 . 
     An electric leakage detecting apparatus  3   dv  in which a magnetic element  14   s  includes a bias means  145  will be described with reference to  FIG. 21 . By providing the bias means  145  to the magnetic element  14   s , it is possible to determine from which of the electric wires the current leaks. Note that the implement of the bias means  145  is not limited to a barber-pole magnetic element  14   s  as illustrated in  FIG. 21 . 
     Ninth Embodiment 
       FIG. 22  illustrates the wire connection of an electric leakage detecting apparatus  3   e  according to the present embodiment and relative to a to-be-detected circuit  90 . The appearance including a fixing means  17  and the like is the same as the case in  FIGS. 10( a ) and 10( b ) . The magnetic element  14   s  is provided with two magnetic elements  14  each including a bias means  145 . At least parts of the electric wires A 93   a  and B 93   b  at which the magnetic elements A 14   a  and B 14   b  are placed in the same direction are held linearly. 
     In  FIG. 22 , the barber-pole magnetic elements having a center tap  14   c  are connected to a pair of measuring resistances  22   a  and  22   b  so as to form a bridge circuit  30   e . A pair of lines each formed of the measuring resistance  22  and magnetic element  14  connected in series is prepared, and then, the lines are connected in parallel each other to form the circuit. In other words, a pair of barber-pole magnetic elements  14  is prepared and then the barber-pole magnetic elements  14  can be placed as a straight line. Note that the bias means  145  of the magnetic elements  14  are formed or placed in the opposite directions at that time. A detector power source  21  supplies current between a node  22   j  which couples the measuring resistances  22   a  and  22   b  and a node  14   c  (the center tap means) which couples the magnetic elements A 14   a  and B 14   b.    
     The electric wires A 93   a  and B 93   b  are placed in parallel to the pair of the magnetic elements A 14   a  and B 14   b  placed in the same direction, respectively. Needless to say, the electric wire B 93   b  is held with a holder  11   b  after being twisted once. In the bridge circuit  30   e , the node which couples the measuring resistances  22   a  and the magnetic element  14  is named as a measuring terminal  23   a , and the node which couples the measuring resistance  22   b  and the magnetic element  14  is named as a measuring terminal  23   b . A display means  26  is connected to the output from the amplifier  24 . 
     The operation of the electric leakage detecting apparatus  3   e  according to the present embodiment will be described. The magnetic elements  14  each include a bias means  145 , which is in the opposite direction to each of the magnetic fields generated from the electric wires A 93   a  and B 93   b . For example, in  FIG. 22 , the current in the magnetic film flows from the center of the magnetic element  14  to the left side on the terminal element  143  side from the center tap  14   c  of the magnetic element  14 , and the current flows from the center of the magnetic element  14  to the right side on the terminal element  144  side from the center tap  14   c  of the magnetic element  14 . 
     When no current leaks, the magnetic fields generated from the electric wires A 93   a  and B 93   b  cancel each other at the magnetic elements  14 . Thus, the output from the bridge circuit  30   e  is zero. In other words, when the output from the amplifier  24  is zero, no current leaks. 
     On the other hand, when the current leaks, the amount of the current flowing in the electric wire A 93   a  differs from the amount of the current flowing in the electric wire B 93   b . This generates a magnetic field at the magnetic element  14 . The magnetic field inclines the magnetization of the magnetic element  14  in a direction. However, the current flows in the different directions above and below the center tap  14   c . Thus, the magnetization of the magnetic film is close to the current direction on one side, and the magnetization of the magnetic film is away from the current direction on the other side. In other words, the opposite magneto-resistance effects arise above and below the center tap  14   c . The resistance value increase on one side, and the resistance value decreases on the other side. A potential difference is generated by the imbalance between the currents flowing in the paths in the bridge circuit  30   e . Consequently, the potential difference can be extracted in the amplifier. 
     As described above, the magnetic elements  14  having the bias means  145  in the opposite directions are placed as a straight line in the electric leakage detecting apparatus  3   e  according to the present embodiment. This can further allow the variation in the magnetization of the magnetic film to be amplified and output the variation, thereby increasing the sensitivity of the electric leakage detecting apparatus. 
     Note that, when the power source  91  of the to-be-detected circuit  90  is an alternating-current power source in the electric leakage detecting apparatus  3   e  according to the present embodiment, the output from the amplifier  24  can also be obtained as an alternating-current output. 
     Tenth Embodiment 
       FIG. 23  illustrates the wire connection of an electric leakage detecting apparatus  3   f  according to the present embodiment and relative to a to-be-detected circuit  90 . The appearance including a fixing means  17  and the like is the same as the case in  FIGS. 13( a ) and 13( b ) . In the present embodiment, a bridge circuit  30   e  including combinations each of the magnetic element  14  and measuring resistance  22  having the same structure as the embodiment 9 is connected to a power source  91  of the to-be-detected circuit  90  parallel to a load  92 . More concretely, a part  22   j  at which the measuring resistances  22  of the bridge circuit  30   e  are connected to each other is connected to a first terminal of the power source  91 , and a center tap  14   c  of the magnetic elements  14  is connected to a second terminal of the power source  91 . 
     The connecting points of the magnetic element  14  and the measuring resistance  22  are named as measuring terminals  23   a  and  23   b , and an amplifier  24  is connected to the connecting points. This is the same as the embodiment 9. 
     Next, the operation of the electric leakage detecting apparatus  3   f  according to the present embodiment will be described. When no current leaks, the magnetic fields generated from the electric wires A 93   a  and B 93   b  cancel each other at the magnetic elements  14 . In other words, no imbalance between the resistance values of the magnetic elements  14  occurs. Thus, the output from the bridge circuit  30   e  is zero. In other words, when the output from the amplifier  24  is zero, no current leaks. 
     On the other hand, when the current leaks, the resistance value varies above and below the center tap  14   c  of the magnetic element  14 . A voltage difference is generated between the measuring terminals  23   a  and  23   b  due to the imbalance between the currents flowing in the branches in the bridge circuit  30   e . Thus, the amplifier  24  generates an output voltage. In other words, when the output from the amplifier  24  can indicate the generation of an electric leakage. 
     Note that, when the power source  91  of the to-be-detected circuit  90  is an alternating-current power source in the present embodiment, the direct-current component in the output from the amplifier  24  is used to detect the electric power consumed by an electric leakage. Thus, by placing a low-pass filter to the output from the amplifier  24 , it is possible to monitor the effective consumed electric power when the power source  91  of the to-be-detected circuit  90  is an alternating-current power source. Needless to say, when the power source  91  of the to-be-detected circuit  90  is a direct-current power source, the output from the amplifier  24  is also a direct-current output. 
     INDUSTRIAL APPLICABILITY 
     The present invention can widely be used to detect an electric leakage in the fields, for example, of home electric appliances, automobiles, and industrial equipment. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  1   b ,  1   c ,  2 ,  3 ,  3   a ,  3   b ,  3   c ,  3   d ,  3   e ,  3   f  Electric leakage detecting apparatus 
           11  Holder 
           12 ,  16 ,  17  Fixing means 
           13  Insertion means 
           14  Magnetic element 
           20  Detecting means 
           21  Detector power source 
           22  Measuring resistance 
           23  Measuring terminal 
           24  Amplifier 
           25  Low-pass filter 
           26  Display means 
           30  Bridge circuit 
           32  Power detecting amplifier 
           34  Current detecting amplifier 
           35  Constant-current power source 
           36  Switch 
           40  Memory and comparing means 
           90  To-be-detected circuit 
           91  Power source 
           92  Load 
           93  Power source line 
           93   a  Electric wire A 
           93   b  Electric wire B 
           141  Substrate 
           142  Magnetic film 
           143 ,  144  Terminal element 
           145  Bias means 
           148  Conductor 
           149  Permanent magnet