CN205427017U - Accurate current sensor of interference formula - Google Patents

Abstract

An interferometric precise current sensor, comprising: a laser, an optical fiber beam splitter, a measured wire, an optical fiber coil, a polarization-maintaining optical fiber, an optical fiber beam combiner, an optical detector, and a signal processor, characterized in that the laser is a linearly polarized laser Or there is a polarizer at the output end, the light emitted by the laser is transmitted to the fiber beam splitter through the polarization maintaining fiber, and the fiber beam splitter is divided into four identical sub-beams, and the four sub-beams are respectively transmitted to a In the fiber optic coil, the four fiber optic coils are all wound on the wire to be tested. Except for the staggered positions, the winding methods and the number of turns of the four fiber optic coils are the same. The outer surface of the fiber of one of the fiber optic coils has an electromagnetic shielding layer, and each The output ends of the two fiber optic coils are connected to a fiber combiner, and the output ends of each fiber combiner are respectively connected to a photodetector through an optical fiber, and the output ends of the two photodetectors are connected to the same signal through a signal line. processor.

Description

Interferometric Accurate Current Sensors

technical field

The utility model relates to an optical fiber current sensor, in particular to an optical fiber current sensor with accurate measurement, which belongs to the field of current measurement.

Background technique

The rapid development of modern industry has put forward higher requirements for the transmission and detection of the power grid, and the traditional high-voltage and high-current measurement methods will face severe tests. With the development of optical fiber technology and material science, the optical fiber current sensor The system, because of its good insulation and anti-interference ability, high measurement accuracy, easy miniaturization, and no potential explosion hazard, has been widely valued by people. The main principle of the optical fiber current sensor is to use The Faraday effect of magneto-optic crystals. According to of=VBI, by measuring the Faraday rotation angle OF, the magnetic field strength generated by the current can be obtained, so that the current size can be calculated. Because the optical fiber has strong anti-electromagnetic interference ability and insulation performance Good and small signal attenuation, so in the research of Faraday current sensor, optical fiber is generally used as the transmission medium, and its working principle is shown in Figure 1.

The laser beam passes through the optical fiber, and generates polarized light through the polarizer, and shoots to the magneto-optic crystal through the self-focusing lens: under the action of the external magnetic field generated by the current, the polarization plane rotates by an angle of θF; through the analyzer and optical fiber, it enters the signal detection system, the current value is obtained by measuring θF.

When the angle between the light transmission axes of the two polarizers in the system is set to 45°, the outgoing light intensity after passing through the sensor system is:

I=(Io/2)(1+sin2θF)

In the formula, Io is the incident light intensity. By measuring the outgoing light intensity, θF can be obtained, so that the magnitude of the current can be measured.

However, there is a problem in the optical fiber current sensors in the prior art, that is, the accuracy is not high and the stability is poor. After our analysis, the reason for these problems is mainly due to the strong external interference. For example, when measuring in the field, due to changes in the measurement environment, such as wind, it will cause the vibration of the power line and the fiber coil. These vibrations, as well as other possible vibrations, may cause changes in the polarization state of the linearly polarized light in the fiber, that is, A rotation of the plane of polarization occurs, but the resulting rotation of the plane of polarization is not due to changes in the current intensity in the transmission line, but due to disturbances, but is reflected in the current in the measurement results, resulting in the measurement The result is an error.

The utility model is proposed aiming at the above problems to solve the problems of low measurement accuracy and poor stability of the optical fiber current sensor in the prior art.

Utility model content

The utility model provides a brand-new current sensor, which can accurately measure the amount of current transmitted in the wire, can completely overcome the defects in the prior art, and is not affected by environmental factors at all.

According to an embodiment of the present invention, an interferometric precise current sensor is provided, including: a laser, an optical fiber beam splitter, a measured wire, an optical fiber coil, a polarization-maintaining optical fiber, an optical fiber combiner, an optical detector, and signal processing The laser is characterized in that: the laser is a linearly polarized laser or has a polarizer at the output end, the light emitted by the laser is transmitted to the fiber beam splitter through a polarization-maintaining fiber, and is divided into four identical sub-beams by the fiber beam splitter, which The four sub-beams are respectively transmitted to an optical fiber coil through polarization-maintaining optical fiber. These four optical fiber coils are all wound on the wire to be tested. The four optical fiber coils have the same winding method and number of turns except for the staggered positions. One of the optical fiber coils The outer surface of the optical fiber has an electromagnetic shielding layer, wherein the output ends of every two optical fiber coils are connected to a fiber combiner, and the output ends of each fiber combiner are respectively connected to a photodetector through an optical fiber, and two photodetectors The outputs of the two are connected to the same signal processor via signal lines.

According to another embodiment of the present utility model, the number of the optical fiber beam splitter is one, and the one optical fiber beam splitter directly divides the incident light beam into four equal parts.

According to another embodiment of the present utility model, the number of the optical fiber beam splitters is three.

According to another embodiment of the present utility model, the shielding layer is a metal coating layer with a thickness of several microns.

According to another embodiment of the present invention, the length of the polarization maintaining optical fiber is less than 10 cm.

According to an embodiment of the present invention, there is provided a method for measuring current by using a current sensor, which is characterized in that it includes the following steps: the laser beam emitted by the laser is transformed into four identical linearly polarized laser beams after passing through the fiber beam splitter These four beams of linearly polarized laser beams enter a fiber coil through polarization-maintaining fibers respectively, and the beams emitted by every two fiber coils are interfered, and then the light intensity after the interference is detected to obtain two detection results , the optical fiber of one of the four optical fiber coils is covered with an electromagnetic shielding layer, so that the electromagnetic field in the wire under test cannot affect the linearly polarized light in the optical fiber coil, and only environmental factors can affect the polarization state. The coherent action between the beam output by the fiber coil and the beam output by another fiber coil can be reflected in the result detected by the photodetector. After the interference, the change of light intensity is only the change caused by the current, and then the The light intensity measurement result is compared with the interference result of the output light of the other two fiber optic coils. The light intensity generated after the interference of the other two coils is used as the reference value. current value.

According to an embodiment of the present utility model, the number of turns of the optical fiber coil is 30 turns.

According to an embodiment of the present utility model, the signal processor is a PC or a single-chip microcomputer.

According to an embodiment of the present utility model, the thickness of the shielding layer is 2 microns.

Description of drawings

Accompanying drawing 1 is the schematic diagram of current sensor in the prior art;

Accompanying drawing 2 is the schematic diagram of the precise interferometric current sensor in the utility model.

In the above drawings, 1 represents the laser, 2 and 10 represent the fiber beam splitter, 3 represents the tested wire, 4 represents the fiber coil, 5 represents the polarization maintaining fiber, 6 represents the shielding layer, 7 represents the fiber combiner, 8 Represents a light intensity detector, 9 represents a signal processor.

detailed description

The embodiment of the present utility model will be described in detail below in conjunction with accompanying drawing 2 on the basis, in this embodiment, the electric current sensor of the present utility model comprises laser device 1, and this laser device emits linearly polarized laser beam, and the light that sends passes through polarization-maintaining optical fiber Transmit to the first optical fiber beam splitter 10, be divided into identical two beams of light by the first optical fiber beam splitter, be respectively the first beam of light and the second beam of light, then these two beams of light are transmitted to A 1:1 second optical fiber beam splitter 2, wherein the first beam of light becomes the same two beams after being split by the second optical fiber beam splitter 2, which are respectively the third beam and the fourth beam of light. Each of the three beams of light and the fourth beam of light is respectively transmitted to the first fiber coil and the second fiber coil 4 through the polarization-maintaining fiber 5, wherein the number of each fiber coil is at least one turn, and two fiber coils Wrapped around the conductor under test in an identical but staggered manner. One of the optical fibers in the first optical fiber coil and the second optical fiber coil 4 is covered with an electromagnetic shielding layer 6, such as a metal layer, and the output ends of the first optical fiber coil and the second optical fiber coil are respectively connected to the optical fiber bundle via a polarization-maintaining optical fiber. On the optical fiber combiner 7, the optical fiber combiner 7 is connected to the optical detector 8 via an optical fiber. After the second beam of light is split by another second optical fiber beam splitter 2, it also becomes the same two beams of light, namely the fifth beam of light and the sixth beam of light. Each of the fifth beam and the sixth beam of light is transmitted to the third fiber coil and the fourth fiber coil 4 respectively through the polarization-maintaining fiber 5, wherein the number of each fiber coil is at least one turn, and two fiber coils The coil is wound on the wire under test in the same way as the first and second fiber optic coils but the position is staggered, that is, the four fiber optic coils are wound in the same way except that the positions are staggered, and the number of turns of the four fiber optic coils It's the same. The output ends of the third fiber coil and the fourth fiber coil are respectively connected to another fiber combiner 7 via a polarization-maintaining fiber, and the fiber combiner 7 is connected to another photodetector 8 via a fiber. The two photodetectors are respectively connected to the signal processor 9 via signal lines, and the signal processor 9 processes the light intensity signals transmitted by the two photodetectors.

The measurement method and the effect of the current sensor of the present invention will be described below. According to the current sensor of the present invention, the linearly polarized laser beam sent by the laser becomes Four identical linearly polarized laser beams, these four linearly polarized laser beams respectively pass through the polarization-maintaining fiber and enter an optical fiber coil with the same number of turns wound on the wire under test, and the beams emitted by each two optical fiber coils Interference, and then detect the light intensity after the interference, so as to obtain two detection results, and then compare the two detection results to obtain the magnitude of the current in the wire. An optical fiber in the four optical fiber coils is coated with an electromagnetic shielding layer, such as a metal layer. Since the optical fiber of the optical fiber coil is coated with an electromagnetic shielding layer, the electromagnetic field in the wire to be tested cannot be linearly polarized in the optical fiber coil. Light has an impact, and only the environmental factors can have an impact. In this way, the coherent effect between the beam output by the optical fiber coil and the beam output by another optical fiber coil can be reflected in the results detected by the optical detector, that is, The change of light intensity after interference is only the change caused by the current, and the change caused by environmental factors is the same for the two fiber coils, so this factor is eliminated after the interference of the two beams of light, and then the The light intensity measurement results are compared with the interference results of the output light of the other two fiber optic coils. Since the other two fiber optic coils are not equipped with electromagnetic shielding layers, the light intensity generated by the interference of the other two coils is the reference value. Therefore, according to the simple By comparison, the rotation angle of the polarization plane can be obtained, and then the current value in the wire can be obtained.

Wherein, in order to make the measurement result as accurate as possible, the length of the polarization-maintaining fiber used between each two devices should be as short as possible, for example, it can be set below 10 cm, and the shorter one can be set below 5 cm.

In summary, the method of the utility model can simply eliminate the influence of environmental factors, thereby obtaining accurate measurement results.

The electromagnetic shielding layer can be a metal layer that is simply coated, such as an aluminum layer or a copper layer, as long as the electromagnetic shielding effect can be realized. The thickness of the shielding layer can be set to several microns, for example, 2 microns.

The number of turns of the fiber optic coil can be set a little more to further improve the measurement accuracy, for example, it can be set to 30 turns.

The signal processor can be any device capable of data processing in the prior art, such as a PC, a single-chip microcomputer and the like.

The laser may not be a linearly polarized laser, and a polarizer may be added outside the laser to achieve linear polarization of the laser beam.

It should be noted that the above descriptions are all based on specific implementations, but this should not be interpreted as a limitation of the present utility model. For those skilled in the art, various known methods based on the above disclosure Deformation and improvement are all within the protection scope of the present utility model.

Claims (5)

1. null1. interfere formula precision current sensor for one kind，Including: laser instrument，Fiber optic splitter，Tested wire，Fiber optic coils，Polarization maintaining optical fibre，Optical-fiber bundling device，Photo-detector，Signal processor，It is characterized in that: laser instrument is linearly polarized laser device or outfan has polaroid，The light that this laser instrument is launched is transferred to fiber optic splitter through polarization maintaining optical fibre，It is divided into the beamlet that four bundles are identical by fiber optic splitter，This four bundles beamlet is transferred in a fiber optic coils respectively through polarization maintaining optical fibre，These four fiber optic coils are all wrapped on tested wire，Four fiber optic coils are in addition to staggering in position，Canoe and the number of turn are the most identical，The fiber outer surface of one of them fiber optic coils has electro-magnetic screen layer，Wherein the outfan of each two fiber optic coils is connected to an optical-fiber bundling device，The outfan of each optical-fiber bundling device is connected to a photo-detector by optical fiber respectively，The outfan of two photo-detectors is connected to same signal processor via holding wire.
2. Current sensor the most according to claim 1, it is characterised in that: the quantity of described fiber optic splitter is one, and incident beam is directly divided into four parts of equalization by this fiber optic splitter.
3. Current sensor the most according to claim 1, it is characterised in that: the quantity of described fiber optic splitter is three.
4. Current sensor the most according to claim 1, it is characterised in that: described screen layer is metal coat, and thickness is several micron.
5. Current sensor the most according to claim 1, it is characterised in that: a length of below the 10cm of described polarization maintaining optical fibre.