CN102565725B - Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum - Google Patents
Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum Download PDFInfo
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- CN102565725B CN102565725B CN 201210072950 CN201210072950A CN102565725B CN 102565725 B CN102565725 B CN 102565725B CN 201210072950 CN201210072950 CN 201210072950 CN 201210072950 A CN201210072950 A CN 201210072950A CN 102565725 B CN102565725 B CN 102565725B
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Abstract
The invention relates to a device and a method for measuring an alternating Faraday magnetic declination angle by using a signal spectrum. The method comprises the following steps of: theoretically calculating a one-to-one corresponding relation curve between ratios of signal amplitude values at the base frequency to signal amplitude values at the dual frequency and amplitude values of Faraday magnetic declination angles; supplying a fixed optical rotary angle by using an output of an alternating Faraday coil through a standard optical rotary pipe, acquiring a changed optical signal subjected to photoelectric conversion after a fixed angle change is produced, performing spectrum analysis on the acquired signal, and calculating the ratio of the signal amplitude value at the base frequency to the signal amplitude value at the dual frequency; searching an amplitude value of the corresponding Faraday magnetic declination angle on the determined relation curve according to the determined ratio, and precisely determining the Faraday magnetic declination angle. The device has a simple structure; and according to the method, one-time positioning is realized, and repeated adjustment for a mechanical structure is not required. The alternating Faraday magnetic declination angle can be measured in real time, the measurement range is large, influence of high-frequency harmonic on a measurement result is eliminated completely, and a possibility is supplied to development of a novel current sensor.
Description
Technical field
The present invention relates to a kind of measuring technique, particularly a kind of device and method that utilizes signal frequency spectrum measuring alternation faraday magnetic declination.
Background technology
Faraday effect proposes nearly 1 and is widely used in half a century, especially in current sensor, optoisolator and the fields such as magneto-optic modulator, chemical composition analysis.In its application, the measurement of faraday's magnetic declination is core and the basis of technology always.
When a branch of linearly polarized light, during through the magneto-optic material in a magnetic field, its polarization direction can deflect, and its yawing moment is only relevant with magnetic direction and have nothing to do with the direction of propagation of light, and the size of deflection angle is calculated by Faraday effect:
, wherein Φ is faraday's magnetic declination, and V is the Field constant, and B is magnetic field intensity, and L is the effective length that light is propagated along magnetic direction in medium.
So far, the method for measuring faraday's magnetic declination mainly contains 3 kinds, is respectively angle compensation method, method of approximation and double beam interferometry.The angle compensation method is simple in structure, but measuring accuracy is low, affected by mechanical running accuracy larger; The method of approximation measurement range is little, is only applicable to small angle measurement, and limitation is large, fully the impact of Eliminate highter harmonic; The double beam interferometry complex structure, cost is high, high to the light path accuracy requirement.
Summary of the invention
The method precision that the present invention be directed to current measurement faraday magnetic declination is low, and the problem that measurement range is little has proposed a kind of device and method that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, from a new angle, realizes the measurement to faraday's magnetic declination.To faraday's magnetic declination of alternation, by the frequency spectrum of analytic signal, the relation between binding signal frequency spectrum and faraday's magnetic declination, reach the purpose of measuring faraday's magnetic declination.The method is simple in structure, and measuring accuracy is high, and measurement range is large, has eliminated the error that high-frequency harmonic causes measurement result fully.
Technical scheme of the present invention is: a kind of device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, comprise successively light source, the polarizer, faraday's coil, standard polarization tube, analyzer, photodetector, amplifier, signals collecting and signal processing unit, display, the optical axis of the polarizer and analyzer is adjusted to mutually orthogonal position, and the alternating current that faraday's coil is ω by frequency drives.
Described light source is semiconductor laser light resource.
The described method of utilizing signal frequency spectrum measuring alternation faraday magnetic declination, comprise the device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, specifically comprises the steps:
1) amplitude that theory calculates the ratio of fundamental frequency and two frequency multiplication place signal amplitudes and faraday's magnetic declination is relation curve one to one, the opening relationships curve map;
2) utilize in the device of signal frequency spectrum measuring alternation faraday magnetic declination, the linearly polarized light of the fixedly direction of vibration obtained after the polarizer, under the modulation of faraday's coil, the direction of vibration of linearly polarized light produces and swings, through a standard polarization tube, obtain the light signal of an alternation after analyzer again;
The light signal of the alternation obtained 3) step 2) becomes the electric signal of alternation through photodetector, after the electric signal of alternation amplifies signal through amplifier again, by signals collecting and signal processing unit collection and carry out Fourier transform (FFT), obtain the frequency spectrum of signal, and calculate the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places;
4) according to the ratio of step 3) gained amplitude, at ratio A and faraday's magnetic declination Φ of the signal amplitude of fundamental frequency shown in step 1) and two frequencys multiplication
0graph of a relation in, find the faraday magnetic declination Φ corresponding with the ratio of this amplitude
0, realize the measurement of faraday's magnetic declination.
Described step 2) the standard polarization tube in can make to rotate fixed angle α=6.46 degree by the polarization direction of the linearly polarized light of faraday's coil outgoing.
Beneficial effect of the present invention is: the present invention utilizes the device and method of signal frequency spectrum measuring alternation faraday magnetic declination, technology by digital signal processing improves measuring accuracy, eliminated the error that high-frequency harmonic causes measurement result fully, measuring method is simple in structure, and measurement range is large.
The accompanying drawing explanation
Fig. 1 is the schematic diagram of device that the present invention utilizes signal frequency spectrum measuring alternation faraday magnetic declination;
Fig. 2 is that fundamental frequency of the present invention and two frequency-doubled signal amplitudes are than A and faraday's magnetic declination φ
0graph of relation;
Fig. 3 is that the present invention utilizes signal spectral analysis to measure electric signal analogous diagram in the device of alternation faraday magnetic declination;
Fig. 4 is that the present invention utilizes signal spectral analysis to measure the spectrogram of simulate signal in the device of alternation faraday magnetic declination.
Embodiment
Utilize as shown in Figure 1 the schematic diagram of device of signal frequency spectrum measuring alternation faraday magnetic declination, device comprises light source 1, the polarizer 2, faraday's coil 4, standard polarization tube 5, analyzer 6, photodetector 7, amplifier 8, signals collecting and signal processing unit 9, display 10 successively.Light source is semiconductor laser light resource.The optical axis of the polarizer 2 and analyzer 6 is adjusted to mutually orthogonal position.The alternating current 3 that faraday's coil 4 is ω by frequency drives.Standard polarization tube 5 can make the polarization direction rotation alpha of the linearly polarized light that wavelength is 534nm=6.46 degree.
In this device, the magnetic declination that faraday's coil produces can be expressed as:
Φ wherein
0for the maximum magnetic flux drift angle.From Malus law, when the deflection angle that departs from quadrature position when the polarizer and analyzer is θ, emergent light I light intensity is:
I wherein
0for the light intensity by before analyzer.
In this device, the light signal of output can be expressed as:
This signal is carried out to the FFT conversion, obtain the spectrogram of signal shown in formula (3), calculate the ratio of the signal amplitude of its fundamental frequency and two frequencys multiplication, the signal ratio A that ω/2 Π and 2 ω/(2 Π) locates.Different Φ in theory
0corresponding different A values, Φ
0and the relation curve between A as shown in Figure 2.Photodetector 7 is converted to electric signal by light signal, and electric signal is gathered by signals collecting and signal processing unit 9.Figure 3 shows that the analogous diagram of the electric signal that system acquisition arrives, simulate signal in Fig. 3 is carried out to the spectrogram (as shown in Figure 4) that spectrum analysis obtains this signal, calculate the ratio of the signal amplitude of fundamental frequency and two frequencys multiplication in signal spectrum, then in Fig. 2, find faraday's magnetic declination Φ corresponding to ratio of this amplitude
0, realize the measurement of faraday's magnetic declination.
A kind of method of utilizing signal spectral analysis to measure alternation faraday magnetic declination, the amplitude of the at first theoretical ratio that calculates fundamental frequency and two frequency multiplication place signal amplitudes and faraday's magnetic declination is relation curve one to one; By opto-electronic conversion, light signal is converted to electric signal, gather electric signal and signal is carried out to spectrum analysis, try to achieve the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places; According to the definite ratio obtained, find the amplitude of corresponding faraday's magnetic declination on definite relation curve.
Claims (3)
1. a method of utilizing signal frequency spectrum measuring alternation faraday magnetic declination, it is characterized in that, comprise the device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, device comprises light source (1) successively, the polarizer (2), faraday's coil (4), standard polarization tube (5), analyzer (6), photodetector (7), amplifier (8), signals collecting and signal processing unit (9), display (10), the optical axis of the polarizer (2) and analyzer (6) is adjusted to mutually orthogonal position, the alternating current (3) that faraday's coil (4) is ω by frequency drives, the measuring method concrete steps are as follows:
1) amplitude that theory calculates the ratio of fundamental frequency and two frequency multiplication place signal amplitudes and faraday's magnetic declination is relation curve one to one, the opening relationships curve map;
2) utilize in the device of signal frequency spectrum measuring alternation faraday magnetic declination, the linearly polarized light of the fixedly direction of vibration obtained after the polarizer (2), under the modulation of faraday's coil (4), the direction of vibration of linearly polarized light produces and swings, through a standard polarization tube (5), obtain the light signal of an alternation after analyzer (6) again;
The light signal of the alternation obtained 3) step 2) becomes light signal the electric signal of alternation through photodetector (7), after the electric signal of alternation amplifies signal through amplifier again, gathered by signals collecting and signal processing unit (9) and carry out Fourier transform, obtain the frequency spectrum of signal, and calculate the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places;
4) according to the ratio of step 3) gained amplitude, at ratio A and faraday's magnetic declination Φ of the signal amplitude of fundamental frequency shown in step 1) and two frequencys multiplication
0graph of a relation in, find the faraday magnetic declination Φ corresponding with the ratio of this amplitude
0, realize the measurement of faraday's magnetic declination.
2. utilize according to claim 1 the method for signal frequency spectrum measuring alternation faraday magnetic declination, it is characterized in that, described light source (1) is semiconductor laser light resource.
3. utilize according to claim 1 the method for signal frequency spectrum measuring alternation faraday magnetic declination, it is characterized in that described step 2) in standard polarization tube (5) can make the polarization direction rotation fixed angle α of the linearly polarized light by faraday's coil (4) outgoing=6.46 degree.
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| CN 201210072950 CN102565725B (en) | 2012-03-20 | 2012-03-20 | Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum |
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| CN 201210072950 CN102565725B (en) | 2012-03-20 | 2012-03-20 | Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum |
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| CN106052594B (en) * | 2016-05-10 | 2018-05-22 | 河南师范大学 | A kind of method that optical fiber containing magneto-optic measures angle of rotation using fiber grating laser beat frequency |
| CN107643438A (en) * | 2017-09-14 | 2018-01-30 | 重庆大学 | Optical current sensor and its current measuring method based on Faraday magnetooptical effect |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN200993639Y (en) * | 2006-12-19 | 2007-12-19 | 中国海洋大学 | Faraday effect measuring instrument |
| WO2008065196A3 (en) * | 2006-11-30 | 2008-12-11 | North Sensor As | Faraday effect current sensor |
| CN102158284A (en) * | 2011-03-17 | 2011-08-17 | 电子科技大学 | Light signal polarization direction determination and power equalization system |
| CN102253350A (en) * | 2011-05-03 | 2011-11-23 | 西安交通大学 | Switching arc magnetic field measurement device and method based on magneto-optic imaging |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008065196A3 (en) * | 2006-11-30 | 2008-12-11 | North Sensor As | Faraday effect current sensor |
| CN200993639Y (en) * | 2006-12-19 | 2007-12-19 | 中国海洋大学 | Faraday effect measuring instrument |
| CN102158284A (en) * | 2011-03-17 | 2011-08-17 | 电子科技大学 | Light signal polarization direction determination and power equalization system |
| CN102253350A (en) * | 2011-05-03 | 2011-11-23 | 西安交通大学 | Switching arc magnetic field measurement device and method based on magneto-optic imaging |
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