GB2345147A - Electric current sensors - Google Patents
Electric current sensors Download PDFInfo
- Publication number
- GB2345147A GB2345147A GB9828188A GB9828188A GB2345147A GB 2345147 A GB2345147 A GB 2345147A GB 9828188 A GB9828188 A GB 9828188A GB 9828188 A GB9828188 A GB 9828188A GB 2345147 A GB2345147 A GB 2345147A
- Authority
- GB
- United Kingdom
- Prior art keywords
- conductors
- magnetic field
- plane
- sensor
- current flowing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/146—Measuring arrangements for current not covered by other subgroups of G01R15/14, e.g. using current dividers, shunts, or measuring a voltage drop
- G01R15/148—Measuring arrangements for current not covered by other subgroups of G01R15/14, e.g. using current dividers, shunts, or measuring a voltage drop involving the measuring of a magnetic field or electric field
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
Abstract
The electric current flowing in three parallel conductors 1,2,3, is measured by measuring the associated magnetic fields using three Faraday-effect magnetic field sensors 7,8,9. The conductors 1,2,3 are located in a first plane, and the sensors 7,8,9 are located in a second, parallel plane at positions closest to the respective conductors. The distance between the sensors and the respective conductors is measured using three optical time-of-flight detectors 10,11,12. In a further embodiment, the cross-section of the three conductors forms an equilateral triangle, with the conductors positioned at the apices, and the sensors are positioned half-way along the sides of the triangle.
Description
2345147 ELECTRIC CURRENT SENSORS The present invention relates to
arrangements for measuring electric currents such as those flowing in transmission lines.
Electric current flowing in transmission lines can be measured by sensing the magnetic field associated with the current. However, one problem arising with such systems is that magnetic sensors will detect not only the magnetic field associated with the currents to be measured but also other stray magnetic fields. The problem is particularly acute when using magnetic field sensors to measure the electric current flowing in one or all of a group of conductors which are closely spaced, such as power transmission lines wherein three closely spaced conductors are used for transmitting three-phase electric current. Depending on the relative locations of the three conductors, it may not be possible to prevent a magnetic field sensor from being influenced by the electric current flowing in all three conductors.
In accordance with a first aspect of the present invention there is provided apparatus for measuring the electric current flowing in one of three substantially parallel elongate conductors, the apparatus comprising a magnetic field sensor positioned in relation to the conductors so as to maximise its sensitivity to the magnetic field associated with said one conductor and to minimise its sensitivity to the magnetic fields associated with the current flowing in the other two conductors.
It has been found that, when the separation between the sensor and its associated conductor is less than or equal to one half of the separation between adjacent conductors, the influence on that sensor of the current flowing in the other two conductors is small. When the sensor-conductor separation is substantially one fifth of the separation between adjacent conductors, the influence is even smaller.
In accordance with a second aspect of the present invention there is provided apparatus for measuring the electric current flowing in one of three substantially parallel elongate conductors lying substantially in a first plane, the apparatus comprising a sensor for measuring the magnetic field associated with the current flowing in said one
2 conductor, said sensor being positioned so as to measure the magnetic field within a second plane substantially parallel to said first plane, the sensor being located at the closest possible position within said second plane to said one conductor.
In accordance with a third aspect of the present invention there is provided apparatus for measuring the electric current flowing in one of three substantially parallel elongate non-coplanar conductors, the apparatus comprising a magnetic field sensor which is oriented so as to detect the magnetic field associated with the current flowing in said one conductor and positioned on a line passing through the other two of said three conductors.
The apparatus preferably further comprises means for measuring the distance between the or each magnetic field sensor and its associated electrical conductor. Such a means could comprise an electromagnetic radiation, e.g. optical, time- of-flight sensor.
In each of the above arrangements, the or each magnetic field sensor preferably comprises a sensor sensitive to the magnetic field direction, such as a magneto-optic sensor, e.g. a Faraday-effect sensor. With such a sensor, which involves a polarimetric, detection arrangement, there can be either a single-channel or a dual- channel detection scheme. In the single-channel scheme, the amount of light emerging from the Faraday effect material polarised in a given plane is measured, whereas, in the dual-channeI arrangement, the amount of light polarised in each of two orthogonal planes is measured, which enhances the detection sensitivity.
In accordance with a fourth aspect of the present invention there is provided a method of measuring the electric current flowing in one of three substantially parallel elongate conductors, the method comprising positioning a magnetic field sensor in relation to the conductors so as to maximise its sensitivity to the magnetic field associated with said one conductor and to minimise its sensitivity to the magnetic fields associated with the current flowing in the other two conductors.
In accordance with a fifth aspect of the present invention there is provided a method of measuring the electric current flowing in one of three substantially parallel 3 elongate conductors lying substantially in a first plane, the method comprising 0 positioning a magnetic field sensor so as to measure the magnetic field which is associated with the electric current flowing in said one conductor and which is directed within a second plane substantially parallel to said first plane, the sensor being located 5 at the closest possible position within said second plane to said one conductor.
The sensor is preferably located at a position along the line where the magnetic fields associated with the electric currents flowing in the other two conductors are substantially perpendicular to that associated with the electric current flowing in the conductor associated with that sensor. In this way, it is possible substantially to eliminate the influence of the electric currents flowing in the other two conductors.
Preferred embodiments of the present invention will now be described with reference to the accompanying drawings wherein:
Figure I illustrates apparatus in accordance with a first embodiment of the present invention; Figures 2(a), (b) and (c) are graphs illustrating the influence on a sensor output of electric currents flowing in the two conductors not associated with that sensor, in the first embodiment; Figure 3 illustrates apparatus in accordance with a second embodiment of the present invention; Figure 4(a) illustrates a circuit arrangement for measuring the distance between a magnetic field sensor and its associated electric conductor;
Figure 4(b) illustrates an alternative circuit configuration to that of Figure 4(a); and Figure 5 illustrates waveforms of signals generated in the circuit arrangemen of Figures 4(a) and 4(b), 4 Referring to Figure 1, three parallel current-carrying conductors 1,2,3 are arranged in a first plane with the centre conductor 2 position midway between the outer conductors 1,3, the spacing between adjacent conductors being denoted L. The electric currents flowing in the conductors have associated magnetic fields indicated by magnetic field lines 4,5,6. Arranged below the conductors 1,2,3 are respective Faraday effect magnetic field sensors 7,8,9 which measure the strength of the respective fields by sensing the change in the plane of polarisation of plane-polarised light passing through a respective transducer in each sensor. The separation d between each sensor 0 7,8,9 and its associated conductor 1,2,3 is substantially the same.
The magnetic field sensors 7,8,9 are positioned in a second plane parallel to the first plane at the closest position to the respective conductors 1,2,1 Each sensor is oriented within the second plane so as to be sensitive to the magnetic field associated with the current flowing in its respective conductor. In this way, each sensor is significantly more sensitive to the current flowing in its associated conductor than to the currents flowing in the other two conductors. This effect is enhanced when the distance d between each sensor 7,8,9 and its associated conductor 1,2,3 is small compared with L. For example, the ratio L/d may be set equal to 5. The distance d is measured by a respective distance sensor 10,11,12 to be described in greater detail below.
The magnetic field sensors 7,8,9 are mounted together with the distance sensors 10, 11, 12 on a support structure 13 which is mounted to the ground.
Although the magnetic field sensor 7 is intended to measure the electric current flowing in electric conductor 1, it will additionally be influenced by the electric current flowing in the other two conductors. The component of the output of the sensor 7 resulting from the current in the associated conductor 1 is proportional to the electric current 11 and inversely proportional to the distance d between the sensor and the conductor. Similarly, the component of the output of sensor 7 resulting from the current in the centre conductor 2 is proportional to that current 12 and inversely proportional to the distance between the sensor 7 and that conductor 2, which by Pythagoras's theorem i s (L 2 + d 2).
Furthermore, only that component of the magnetic field in the sensor direction will be measured, so that the current sensed is reduced by a factor of sin (arctan (d/L)). Similarly, the component of the output of sensor 7 resulting from the current in the furthest conductor 3 is proportional to that current 13, inversely proportional to the distance between the sensor 7 and that conductor 3, which is (4L 2 + d 2) and reduced by a factor sin (arctan (d/2L)).
Thus the total output S, from sensor 7 is: 10 S, (x I i/d + 12 - sin (arctan (d/L)) / (4L 2 + d 2) + 13. sin (arctan (d/2L)) / (4L 2 + d 2) = li/d + 12.d / (L2 + d 2) + 13.d / (4L2 + d 2) Thus, for d U2: 15 S, 11 + 0.200 12 + 0.059 13 For d = U5:
S, (x I, + 0.038 12 + 0.010 13 For d = L/10:
S] Cell +0.01012+0.00213 25 Figures 2(a)-(c) are graphs illustrating both the theoretical output signal of the sensor 7 and an actual sinusoidal current 11 flowing in the associated conductor 1, for different values of d/L. As can be seen, the effect on the output signal of the currents 12 and 13 is not significant when d = U5 and negligible when d = L/10. 30 Referring now to Figure 3, a second embodiment of the present invention concerns the measurement of electric current flowing in three parallel conductors 21,22,23 which are arranged such that the spacing between any two conductors is the 6 same. The cross-section of the conductors thus represents the apices of an equilateral triangle. The magnetic fields 24,25,26, associated with the electric currents are measured using three respective Faraday-effect sensors, 27,28,29, as in the first embodiment, the sensor associated with each conductor being positioned half-way 5 between the other two conductors.
The magnetic field sensors 27,28,29 are sensitive only to magnetic field lines passing in one direction through the sensor and are oriented so as to detect the magnetic field associated with the electric current flowing in the associated conductor. However, the positioning of each sensor half-way between two conductors ensures that that sensor cannot detect the magnetic fields associated with currents flowing in those two conductors, since the magnetic fields are directed at right angles to the direction of sensitivity of the sensor.
Three distance sensors 30,31,32 are mounted on the magnetic field sensors
27,28,29 and are positioned so as to measure the distance between the adjacent magnetic field sensor, e.g. 28, and its associated electric conductor 21.
The distance sensors are shown in greater detail in Figure 4(a).
The sensor 42 comprises a light source 43, such as a light-emitting diode, a laser or a laser diode. The light source 43 is supplied with a squarewave signal SW from a square-wave signal generator 44. The square-wave signal SW is also supplied to a phase shifter 45, the output SW of which is supplied to the first input of a phase- sensitive detector 46. Light reflected from the current-carrying conductor 2 is received by a photodetector 47, such as a photodiode, the output signal SW of which is supplied to the second input of the phase- sensitive detector 16. The phase-sensitive detector 46 generates an output signal the magnitude of which is proportional to the phase difference between the signals SW and SW supplied to the first and second inputs respectively. The output signal is fed back to a control input of the phase shifter 45 which introduces a phase shift into the square-wave signal SW which is dependent on the magnitude of the output signal, thus forming a phase-locked loop 48. The output signal from the phase-locked loop 48 is supplied via an electrical filter 49 to an 7 amplifier 50, the output signal of which is a measure of the distance between the corresponding magnetic sensor and the current-carrying conductor.
Z> In an alternative arrangement, as shown in Figure 4(b), both signals SW and SWare supplied to the respective inputs of the phase shifter 45, and the feedback path is eliminated. In this case, the signal SW is the output signal from the detector after amplification in an amplifier 5 1.
Typical waveforms of the two signals supplied to the first and second inputs of the phase-sensitive detector 46 are illustrated in Figure 5. It can be seen that the photodetector output signal SW lags in relation to the square-wave generator output signal SW by an amount to, which is the time taken for the light from the light source 43 3 to reach the light detector 47 after reflection at the current-carrying conductor. The distance r is then given by:
r = c - to 12, where c is the speed of light. From a knowledge of the distance r, it is possible to calculate the current flowing in the electrical conductor.
ZZ> 8
Claims (28)
1 Apparatus for measuring the electric current flowing in one of three substantially parallel elongate conductors, the apparatus comprising a magnetic field sensor positioned in relation to the conductors so as to maximise its sensitivity to the magnetic field associated with said one conductor and to minimise its sensitivity to the magnetic fields associated with the current flowing in the other two conductors.
2. Apparatus for measuring the electric current flowing in one of three substantially parallel elongate conductors lying substantially in a first plane, the apparatus comprising a sensor for measuring the magnetic field associated with the current flowing in said one conductor, said sensor being positioned so as to measure the magnetic field within a second plane substantially parallel to said first plane, the sensor being located at the closest possible position within said second plane to said one conductor.
3. Apparatus for measuring the respective electric currents flowing in three substantially parallel elongate conductors lying substantially in a first plane, the apparatus comprising three magnetic field sensors for measuring the magnetic field associated with the current flowing in the three conductors, each of said sensors being disposed substantially within either a second or a third plane substantially parallel to said first plane, said first plane lying substantially midway between said second and said third planes, each sensor being arranged so as to measure the magnetic field which is associated with the current flowing in a respective one of said conductors and which is directed within said second plane or said third plane respectively, each sensor being located at the closest possible position within said second plane or said third plane to its associated conductor.
4. Apparatus as claimed in Claim 3, wherein said sensors all lie in the same plane.
9
5. Apparatus as claimed in Claim 3 or Claim 4, wherein the three sensors are positioned such that the three respective components of the magnetic field sensed thereby lie in the same line.
6. Apparatus as claimed in any preceding claim, wherein the centre conductor is located substantially midway between the outer two conductors.
7. Apparatus as claimed in any preceding claim, wherein the separation between the or each sensor and its associated conductor is less than or equal to one half of the separation between adjacent conductors.
8. Apparatus as claimed in Claim 7, wherein the separation between the or each sensor and its respective conductor is substantially one fifth of the separation between adjacent conductors.
9. Apparatus for measuring the electric current flowing in one of three substantially parallel elongate non-coplanar conductors, the apparatus comprising a magnetic field sensor which is oriented so as to detect the magnetic field associated with the current flowing in said one conductor and positioned on a line passing through the other two of said three conductors.
10. Apparatus for measuring the respective electric currents flowing in three substantially parallel elongate non-coplanar conductors, the apparatus comprising three respective magnetic field sensors each of which is oriented so as to detect the magnetic field associated with the current flowing in a respective one of said three conductors and positioned on a line passing through the other two conductors.
11. Apparatus as claimed in Claim 10, wherein the three sensors are positioned within a plane substantially perpendicular to the axes of the conductors.
12. Apparatus as claimed in any one of Claims 9 to 11, wherein the or each sensor is located at a position along a said line where the magnetic fields associated with 1 the electric current flowing in said other two conductors is substantially perpendicular to that associated with the electric current flowing in the conductor associated with that sensor.
1 Apparatus as claimed in any one of Claims 9 to 12, wherein the or each sensor is located at a position on a said line between said other two conductors.
14. Apparatus as claimed in any one of Claims 9 to 13, wherein said conductors are equally spaced from each other.
15. Apparatus as claimed in any preceding claim, wherein the or each magnetic field sensor comprises a sensor sensitive to the magnetic field direction.
16. Apparatus as claimed in any preceding claim, wherein the or each magnetic field sensor comprises a magneto-optic sensor.
17. Apparatus as claimed in Claim 16, wherein the or each magnetic field sensor comprises a Faraday-effect sensor.
18. Apparatus as claimed in Claim 17, wherein said Faraday-effect sensor comprises a polarimetric detection scheme involving a single channel.
19. Apparatus as claimed in Claim 17, wherein said Faraday-effect sensor comprises a polarimetric detection scheme involving two channels.
20. Apparatus as claimed in any preceding claim, further comprising means for measuring the distance between the or each magnetic field sensor and its associated electrical conductor.
21. Apparatus as claimed in Claim 20, wherein said distance-measuring means comprises an electromagnetic radiation time-offlight sensor.
CI
22. A method of measuring the electric current flowing in one of three substantially parallel elongate conductors, the method comprising positioning a magnetic field sensor in relation to the conductors so as to maximise its sensitivity to the magnetic field associated with said one conductor and to minimise its sensitivity to the magnetic fields associated with the current flowing in the other two conductors.
23. A method of measuring the electric current flowing in one of three substantially parallel elongate conductors lying substantially in a first plane, the method comprising positioning a magnetic field sensor so as to measure the magnetic field which is associated with the electric current flowing in said one conductor and which is directed within a second plane substantially parallel to said first plane, the sensor being located at the closest possible position within said second plane to said one conductor.
24. A method of measuring the electric current flowing in three substantially parallel elongate conductors lying substantially in a first plane, the method comprising positioning each of three magnetic field sensors within either a second or a third plane substantially parallel to said first plane, said first plane lying substantially midway between said second plane and said third plane, so as to measure the magnetic field which is associated with the current flowing in a respective one of said three conductors and which is directed within said second plane or said third plane respectively, each sensor being positioned at the closest possible position within said second plane or third plane to its associated conductor.
25. A method of measuring the electric current flowing in one of three substantially parallel elongate non-coplanar conductors, the method comprising orienting a magnetic field sensor so as to measure the magnetic field associated with the current flowing in said one conductor and positioned on a line passing through the other two of said three conductors.
26. A method of measuring the respective electric currents flowing in three substantially parallel elongate non-coplanar conductors, the method comprising 12 orienting each of three magnetic field sensors so as to measure the magnetic field associated with the current flowing in a respective one of said three conductors and positioning each of said three sensors on a line passing through the other two conductors.
27. Apparatus for measuring the electric current flowing in one of three substantially parallel elongate conductors substantially as hereinbefore described with reference to the accompanying drawings.
W
28. A method of measuring the electric current flowing in one of three substantially parallel elongate conductors substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9828188A GB2345147A (en) | 1998-12-21 | 1998-12-21 | Electric current sensors |
| AU17917/00A AU1791700A (en) | 1998-12-21 | 1999-12-21 | Electric current sensors |
| PCT/IB1999/002078 WO2000037947A1 (en) | 1998-12-21 | 1999-12-21 | Electric current sensors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9828188A GB2345147A (en) | 1998-12-21 | 1998-12-21 | Electric current sensors |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9828188D0 GB9828188D0 (en) | 1999-02-17 |
| GB2345147A true GB2345147A (en) | 2000-06-28 |
Family
ID=10844696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9828188A Withdrawn GB2345147A (en) | 1998-12-21 | 1998-12-21 | Electric current sensors |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1791700A (en) |
| GB (1) | GB2345147A (en) |
| WO (1) | WO2000037947A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102016210970A1 (en) * | 2016-06-20 | 2017-12-21 | Siemens Aktiengesellschaft | Apparatus and method for measuring the current strength of a single conductor of a multi-conductor system |
| WO2020258895A1 (en) * | 2019-06-28 | 2020-12-30 | 苏州大学 | Magnetic flux leakage detection probe with high sensitivity |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111771128B (en) * | 2018-03-01 | 2023-03-31 | 横河电机株式会社 | Current measuring device, current measuring method, and computer-readable non-transitory recording medium |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4578639A (en) * | 1984-03-02 | 1986-03-25 | Westinghouse Electric Corp. | Metering system for measuring parameters of high AC electric energy flowing in an electric conductor |
| JPH01142265A (en) * | 1987-11-28 | 1989-06-05 | Mitsuba Electric Mfg Co Ltd | Rotor for magneto and manufacture thereof |
| US5159561A (en) * | 1989-04-05 | 1992-10-27 | Mitsubishi Denki Kabushiki Kaisha | Zero-phase sequence current detector |
| US5250894A (en) * | 1992-03-31 | 1993-10-05 | Bridges Electric, Inc. | Current sensing system having electronic compensation circuits for conditioning the outputs of current sensors |
| EP0597404A2 (en) * | 1992-11-13 | 1994-05-18 | ABBPATENT GmbH | Method and device for determining lead currents of a polyphase system |
| US5438256A (en) * | 1992-07-06 | 1995-08-01 | Gec Alsthom T & D Sa | Apparatus and method for measurement from the ground for high voltage overhead lines |
| US5615075A (en) * | 1995-05-30 | 1997-03-25 | General Electric Company | AC/DC current sensor for a circuit breaker |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62163976A (en) * | 1986-01-16 | 1987-07-20 | Toshiba Corp | Photocurrent transformer |
| US5202812A (en) * | 1988-09-21 | 1993-04-13 | Ngk Insulators, Ltd. | Apparatus for detecting faults on power transmission lines |
-
1998
- 1998-12-21 GB GB9828188A patent/GB2345147A/en not_active Withdrawn
-
1999
- 1999-12-21 WO PCT/IB1999/002078 patent/WO2000037947A1/en active Application Filing
- 1999-12-21 AU AU17917/00A patent/AU1791700A/en not_active Abandoned
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4578639A (en) * | 1984-03-02 | 1986-03-25 | Westinghouse Electric Corp. | Metering system for measuring parameters of high AC electric energy flowing in an electric conductor |
| JPH01142265A (en) * | 1987-11-28 | 1989-06-05 | Mitsuba Electric Mfg Co Ltd | Rotor for magneto and manufacture thereof |
| US5159561A (en) * | 1989-04-05 | 1992-10-27 | Mitsubishi Denki Kabushiki Kaisha | Zero-phase sequence current detector |
| US5250894A (en) * | 1992-03-31 | 1993-10-05 | Bridges Electric, Inc. | Current sensing system having electronic compensation circuits for conditioning the outputs of current sensors |
| US5438256A (en) * | 1992-07-06 | 1995-08-01 | Gec Alsthom T & D Sa | Apparatus and method for measurement from the ground for high voltage overhead lines |
| EP0597404A2 (en) * | 1992-11-13 | 1994-05-18 | ABBPATENT GmbH | Method and device for determining lead currents of a polyphase system |
| US5615075A (en) * | 1995-05-30 | 1997-03-25 | General Electric Company | AC/DC current sensor for a circuit breaker |
Non-Patent Citations (1)
| Title |
|---|
| WPI Abstract No. 98-366381 & JP 01 142 265 A * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102016210970A1 (en) * | 2016-06-20 | 2017-12-21 | Siemens Aktiengesellschaft | Apparatus and method for measuring the current strength of a single conductor of a multi-conductor system |
| WO2020258895A1 (en) * | 2019-06-28 | 2020-12-30 | 苏州大学 | Magnetic flux leakage detection probe with high sensitivity |
Also Published As
| Publication number | Publication date |
|---|---|
| AU1791700A (en) | 2000-07-12 |
| GB9828188D0 (en) | 1999-02-17 |
| WO2000037947A1 (en) | 2000-06-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5933003A (en) | Magnetoresistive wheatstone bridge with compensating current conductor for measuring an electric current | |
| US6492800B1 (en) | Electro-optic voltage sensor with beam splitting | |
| US6122415A (en) | In-line electro-optic voltage sensor | |
| US8841905B2 (en) | System and method for fiber magneto-optic detection | |
| CN104569544B (en) | Faradic currents sensor and faraday's temperature sensor | |
| US5834933A (en) | Method for magnetooptic current measurement and magnetooptic current-measuring device | |
| US20210285987A1 (en) | Reflective current and magnetic sensors based on optical sensing with integrated temperature sensing | |
| CA2295047A1 (en) | Position detector | |
| US6166816A (en) | Combination fiber optic current/voltage sensor | |
| US8773119B2 (en) | System for fiber DC magneto-optic detection and method thereof | |
| US4232264A (en) | Arrangement for the magneto-optical measurement of currents | |
| JP2574694B2 (en) | Metal detector | |
| GB2345147A (en) | Electric current sensors | |
| JP3035724B2 (en) | Metal detection method | |
| JP2958796B2 (en) | Zero-phase current measurement sensor | |
| JPS6224165A (en) | Orientation system of transmission and distribution wire failure section | |
| JPS60138480A (en) | Optical magnetic field sensor | |
| JPH07306095A (en) | Polarization-analysis evaluation method of polarization modulation optical signal | |
| GB2345148A (en) | Electric current sensors | |
| WO2000037953A1 (en) | Optical sensors | |
| JP2624977B2 (en) | Optical magnetic field measurement method | |
| JPH0797116B2 (en) | Fiber optic current sensor | |
| JPH03242559A (en) | Method for measuring current by photo-magnetic field sensor | |
| SU1068742A2 (en) | Device for measuring forces | |
| JPS6184571A (en) | Optical fiber magnetometer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |