Abstract:
The inventive method employs the −/+ division for intensity norming but forms the quotient from the signal difference and the signal sum not from component signals (L 1 , L 2 ) generated by the sensor but—inventively —with signals (L 1 ′, L 2 ′) derived therefrom that exhibit periodically fluctuating intensity parts (I 1 ′AC, I 2 ′AC) of the same amplitude amount (|A|). The invention largely unites the advantages of −/+ division with those of AC/DC division.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a method for intensity norming of an optical sensor for measuring a periodically fluctuating electrical and/or magnetic field strength. 
     2. Description of the Related Art 
     A known example of an optical sensor for measuring electrical and magnetic fields is a two-channel, polarimetric optical alternating current and/or alternating voltage sensor. Such sensors proceed, for example, U.S. Pat. No. 4,564,754, German Patent Document DE-A-4 432 146 and U.S. Pat. No. 4,894,608. 
     Such a sensor utilizes the fact that, when polarized light is sent through an electrical and/or magnetic field, a modification of the polarization condition of the light which is dependent on the field strength of this field is produced due to specific physical effects (for example, Faraday effect, Pockels effect) and can be measured. 
     Alternating current and alternating voltage generate an electrical and/or magnetic field of periodically fluctuating field strength in their environment that generates a periodic fluctuation of the polarization condition of the polarized light sent through this field. 
     “Two-channel” in the known sensor means that the polarized light sent through the field is supplied to a polarization beam splitter that divides the supplied light into two light components of respectively fixed polarization conditions that, however, are different from one another, for example orthogonal relative to one another, whose intensities are dependent on the polarization condition of the light sent through the field and supplied to the divider. 
     Every light component generated in this way thus forms an intensity signal whose intensity is dependent on the field strength of the field. What is to be understood here as intensity signal is not only the light component itself but any other generated signal whose intensity, like the intensity of a light component varies dependent on the field strength of the field to be measured. An example is the electrical intensity signal generated by an opto-electrical transducer, for example a diode, from a light component. 
     Apart from attenuation losses, the intensities of the two light components that have arisen or of the intensity signals add up to the intensity of the light sent through the field and supplied to the polarization beam splitter. When the intensity of this supplied light is constant, the sum of the intensities of the two light components or intensity signals is also constant. 
     In order to eliminate influences of a non-constant intensity of the light sent through the field and supplied to the polarization beam splitter, an intensity norming is usually implemented. 
     A standard method for intensity norming of an optical sensor for measuring electrical and magnetic fields is the minus/plus division, i.e. a quantity is formed from the two light components or intensity signals that corresponds to a difference between the intensities of the two light components divided by the sum of the intensities of the two light components (see, for example, U.S. Pat. No. 4,564,754). 
     The minus/plus division is in the position to also compensate an intensity of the light sent through the field and supplied to the polarization beam splitter that fluctuates very rapidly. 
     Due to the periodically fluctuating polarization condition of the light sent through the field and supplied to the polarization beam splitter that is conditioned by the field strength, the intensities of the two light components or of both intensity signals generated by the splitter respectively exhibit a corresponding, periodic fluctuation, i.e. they are composed of a constant intensity part this is and of an intensity part periodically fluctuating dependent on the measured field strength. 
     The periodically fluctuating intensity parts of the intensities of the two light components generated by the splitter or of both intensity signals are in anti-phase relative to one another and, in the ideal case, exhibit an amplitude of the same amount, this resulting therein that the sum of the periodically fluctuating intensity parts of both light components or intensity signals is also constant in addition to the sum of the constant intensity parts when the intensity of the light sent through the field and supplied to the polarization beam splitter is constant. 
     In the real case, however, the sum of the intensities of the two light components generated by the splitter or of the two intensity signals is often not constant but fluctuates periodically even given a constant intensity of the light sent through the field and supplied to the polarization beam splitter. 
     This occurs, for example, when the intensity parts of the intensities of thetwo light components generated by the polarization beam splitter or of the two intensity signals that fluctuate periodically in anti-phase relative to one another exhibit amplitudes of an amount differing from one another. 
     This, for example, can be based thereon that a light conductor conducting the one generated light component from the polarization beam splitter to, for example, an opto-electrical transducer for conversion of the intensity of this light component into a corresponding electrical intensity signal, for example an optical fiber, exhibits a different attenuation than a light conductor conducting the other generated light component to an opto-electrical transducer for conversion of the intensity of this other light component into a corresponding electrical intensity signal. 
     A standard method for intensity norming of an optical sensor for measuring electrical and magnetic fields that is different from the minus/plus division that is known as AC/DC division (see, for example, U.S. Pat. No. 4,894,608) can compensate light components generated by the polarization beam splitter and containing such intensity parts with amplitudes of a different amount which are periodically fluctuating relative to one another in anti-phase or, respectively, corresponding intensity signals. This method, however, fails given rapid fluctuations of the intensity of the light sent through the field. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the object of offering a method for intensity norming of an optical sensor referenced in greater detail above that can compensate both rapid fluctuations of the intensity of the light sent through the field as well as intensity parts which are periodically fluctuating in anti-phase with amplitudes of a different amount in the light components or intensity signals generated by the light sent through the field. 
     This and other objects of the invention are achieved by a method for intensity norming of an optical sensor for measuring an electrical and/or magnetic field with a periodically fluctuating field strength, given a sensor in which light is sent through the field; two intensity signals separated from one another comprising intensities containing intensity parts fluctuating periodically in anti-phase relative to one another dependent on the periodically fluctuating field strength are generated from this transmitted light and, for intensity norming, a quantity that corresponds to a quotient of a difference formed with the intensities of the two intensity signals and a sum formed with these intensities is derived from the two intensity signals, in that from the two intensity signals, two signals are acquired with signal intensities corresponding to intensities of the two intensity signals, whereby the signal intensities contain signal intensity parts which are periodically fluctuating in anti-phase relative to one another corresponding to the periodically fluctuating intensity parts of the intensities of the intensity signals such that the periodically fluctuating signal intensity parts of both acquired signals exhibit amplitudes of the essentially same amount; and the sum of the signal intensities of the two acquired signals is essentially constant; and in that the quantity is determined by the quotients from a difference of the signal intensities of the two acquired intensity signals and the sum of these signal intensities. 
     It is advantageously irrelevant in the inventive method whether the intensity parts of the two generated light components or intensity signals fluctuating periodically relative to one another in anti-phase exhibit amplitudes of the same or of a different amount, since correspondingly fluctuating signals whose amplitudes exhibit essentially the same amount are always available for the required formation of the quotient. 
     The inventive method advantageously unites most of the advantages of the minus-plus division with those of the AC/DC division. 
     The signals inventively that are derived from the intensities of the light components generated by the light sent through the field or of the two intensity signals are preferably and advantageously formed with the assistance of a correction factor selected such that the signal intensity parts fluctuating periodically anti-phase relative to one another of the signal acquired by multiplication with this correction factor and of the other derived signal exhibit an amplitude of essentially the same amount. It thereby suffices when the intensity of only of the light components generated by the light sent through the field or of the intensity signals that can be freely selected is multiplied by a correction factor but the intensity of the other light component or, respectively, intensity signal is not. Of the two acquired signals in this case, one represents the intensity of a light component or intensity signal multiplied by the correction factor and the other represents the unmodified intensity of the other light component or intensity signal. It could also be said that the correction factor of the other derived signal is equal to one. 
     Under certain circumstances, both acquired signals can respectively represent the intensity of the light component or, respectively, intensity signal allocated to it multiplied by a respective correction factor, so that each derived signal has arisen by multiplication with a respective correction factor differing from one. 
     A preferred and advantageous method for determining a correction factor is by formation of a quotient of the other intensity signal and the same amplitude-related, amount-oriented quantity of the one intensity signal to be multiplied by the correction factor. 
     A periodically fluctuating intensity part of an intensity signal required in this method can be acquired, for example, from a difference between the intensity of this intensity signal and a constant intensity part contained in this intensity signal the fundamental assumption that the periodically fluctuating intensity part of the intensity signal is composed essentially only of fluctuations cause only by the periodically fluctuating field strength on which essentially no noise fluctuations are superimposed, i.e. noise fluctuations that lie under a prescribable, allowable dimension with reference to the fluctuations caused by the field strength. 
     However, considerable noise fluctuations can often occur that, for example, lie on the same order of magnitude as the fluctuations caused by the field strength and can have different causes. 
     For example, such considerable noise fluctuations can occur occasionally or regularly due to mechanical vibrations at the sensor and/or the optical channels carrying the intensity signals occurring for the greatest variety of reasons. 
     Such considerable noise fluctuations on both intensity signals can—dependent on the cause—be more or less equiphase or in anti-phase relative to one another and exhibit amplitudes of the same or of a different amount. 
     When the noise fluctuations exhibit a relatively small amount at all frequencies at which the fluctuations caused by field strength have a relatively large amount, the noise fluctuations—regardless of type—can be largely neutralized by filtering out all noise fluctuations lying at different frequencies with amplitudes of a relatively great amount, particularly when the amplitudes having a relatively small amount of the frequency components of the noise fluctuations lie below the prescribable allowable dimension. 
     A simple band-pass filtering with a band-pass filter often suffices. 
     Especially beneficial conditions are present when the fluctuations caused by field strength lie essentially at a single frequency, as is the case, for example, given periodically fluctuating field strength caused by alternating current or alternating voltage of a fixed frequency of, for example, 50 Hz or 60 Hz. It is rare here that noise fluctuations exhibit a frequency component with an amplitude of an adequately great amount exactly at this fixed frequency; on the contrary, this amount will usually be adequately small. A very narrow-band filter that essentially allows only the fixed frequency to pass but blocks at all other frequencies is then adequate for neutralizing the noise fluctuations. 
     Accordingly, the procedure in that a periodically fluctuating intensity part is acquired by filtering the intensity signal containing this intensity part has the considerable advantage that the inventive method can also be successfully applied given considerable noise fluctuations. 
     In the determination of the correction factor by formation of a quotient of the other intensity signal and the same amplitude-related, amount-oriented quantity of the one intensity signal to be multiplied by the correction factor, for example, the amount of an amplitude of the periodically fluctuating intensity part of an intensity signal or an effective value of this intensity part as well can be utilized as a specific amplitude-related quantity. It is more expedient, however, to employ a chronological average of the amounts of a plurality of amplitudes of the respective periodically fluctuating intensity part as the specific amplitude-related quantity, since the identified correction factor in this case is more independent of predetermined and/or arbitrary amplitude fluctuations. In any case, a division of zero by zero is avoided in the required formation of the quotient with the quantities determined in one of the ways described above. 
     An alternative embodiment of the method is characterized in that the intensity of one of the two intensity signals is multiplied by an adjustable, preliminary correction factor; an aggregate intensity is formed by summation of the intensity of the one intensity signal multiplied by the preliminary correction factor and the intensity of the other intensity signal not multiplied by a correction factor; a constant intensity part contained in the aggregate intensity is identified; a difference intensity is formed from the aggregate intensity and the constant intensity part contained therein; and the preliminary correction factor is set such to a final correction factor that the difference intensity is essentially equal to zero. The inventive method can be realized to an analog and/or digital components. 
     An arrangement for the implementation of the inventive method provides an acquisition means for acquiring two signals from the two intensity signals that comprise signal intensity parts periodically fluctuating anti-phase relative to one another corresponding to the intensity parts of the intensity signals such that the signal intensity parts of both acquired signals comprise amplitudes of essentially the same amount; and the sum of the intensities of the two acquired signals is essentially constant; and a means for forming a quotient from a difference of the two acquired signals and their sum. Preferred and advantageous embodiments of the arrangement provide that the acquisition means comprises a multiplication means for multiplying at least one of the two intensity signals by a correction factor selected such that the signal parts periodically fluctuating in anti-phase relative to one another of the derived signal acquired by multiplication of this one intensity signal by this correction factor and of the other derived signal exhibit amplitudes of essentially the same amount. A correction factor determination means for determining the correction factor by which an intensity signal is to be multiplied is preferably provided. The correction factor determination means has a means for acquiring the periodically fluctuating intensity part from the intensity signal that is to be multiplied by the correction factor; a means for deriving the periodically fluctuating intensity part from the other intensity signal; and a means for forming a quotient representing this coefficient from a specific, amplitude-related, amount-oriented quantity of the periodically fluctuating intensity part acquired from the other intensity signal and the same amplitude-related, amount-oriented quantity of the periodically fluctuating intensity part acquired from the one intensity signal. 
     A means for acquiring the periodically fluctuating intensity part from an intensity signal comprises a difference forming means for forming a difference between the intensity of this intensity signal and a constant intensity part of this intensity signal. The means for deriving the periodically fluctuating intensity part from an intensity signal comprises a filter means for filtering the periodically fluctuating intensity part from its intensity signal. The means for generating the specific, amplitude-related, amount-oriented quantity is in the form of a chronological average of the amount of the respective, acquired, periodically fluctuating intensity part. The acquisition means comprises a means for multiplying the intensity of one of the two intensity signals by an adjustable, preliminary correction factor; a means for forming an aggregate intensity by summation of the intensity of the one intensity signal multiplied by the preliminary correction factor and the intensity of the other intensity not multiplied by a correction factor; a means for determining a constant intensity part contained in the aggregate intensity; a means for forming a difference intensity from the aggregate intensity and the constant intensity part contained therein; and a means for setting the preliminary correction factor to a final correction factor such that the difference intensity is essentially equal to zero through 15. 
     Given the inventive method and the inventive arrangement, no information about the polarization condition of the constant light component of an optical signal supplied to a polarization beam splitter is lost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in greater detail in the following description with reference to the Figures. 
     FIG. 1 is a schematic illustration of an exemplary optical sensor for measuring a periodically fluctuating magnetic field strength together with an exemplary arrangement for the implementation of the inventive method shown in the fashion of a block circuit diagram; 
     FIG. 2 is a graph of exemplary intensity signals with intensity components fluctuating periodically anti-phase relative to one another shown on the time axis; 
     FIG. 3 signals derived from the intensity signals of FIG. 2 that exhibit signal intensities periodically fluctuating anti-phase relative to one another with amplitudes having essentially the same amount; 
     FIG. 4 is a block circuit diagram of an exemplary correction factor determination means of the arrangement according to FIG. 1; 
     FIG. 5 is a graph of an exemplary frequency spectrum with frequency components of the fluctuations caused by field strength and of noise fluctuation; 
     FIG. 6 is a block diagram of an alternative part of the correction factor determination means according to FIG. 4; and 
     FIG. 7 is a block diagram of an alternative embodiment of a derivation means contained in the arrangement according to claim  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, the exemplary optical sensor for measuring a periodically fluctuating electrical and/or magnetic field strength is referenced  1  and the exemplary arrangement for the inventive intensity norming of this sensor is referenced  1 ′. 
     Specifically and without limiting the universality of the invention, the exemplary sensor  1  is a two-channel polarmetric alternating current sensor that comprises an optical conductor  11  surrounding an electrical conductor  10  that carries the alternative current and proceeds, for example, perpendicular to the plane of the drawing, optical conductor  11  carrying polarized light L of a specific intensity I and a specific polarization condition p upon preservation of this polarization condition p. 
     For example, the optical conductor  11  can be composed of a fiber coil surrounding the conductor  10 . 
     The optical conductor  11  surrounding the electrical conductor  10  lies in the region of the magnetic field generated by the alternating current and surrounding the conductor  10  whose magnetic field strength {right arrow over (H)} which is constantly changing in direction is directed parallel to the plane of the drawing and perpendicular to the conductor  10 . 
     The light L having the specific intensity I and the specific polarization condition p is coupled into the optical conductor  11 . The light L that is coupled in experiences a modification of the polarization condition p when passing through the magnetic alternating field surrounding the electrical conductor  10  due to specific physical effects, for example the Faraday effect, such that a polarization condition p′ which is periodically fluctuating symmetrically around a specific, fixed polarization condition p 0 ′ corresponding to the alternating current arises. 
     The light L of this fluctuating polarization condition p′ is supplied in the optical conductor  11  to a polarization beam splitter  12  that divides this light L into two polarized light components L 1  and L 2  each having a fixed polarization condition p 1  or, respectively p 2 , that differs from one another, whereby the polarization beam splitter  12  is set relative to the fixed polarity condition p 0 ′ of the light L supplied to it such that the intensities I 1  and I 2  of the two generated light components L 1  and L 2 —in conformity with the periodically fluctuating polarization condition p′ of the supplied light L—exhibit intensities I 1  and I 2  that are periodically fluctuating in anti-phase relative to one another, i.e. the intensity I 1  of the light component L 1  is composed of a constant intensity part I 1 DC on which a periodically fluctuating intensity part I 1 AC is superimposed and the intensity I 2  of the light part L 2  is composed of a constant intensity part I 2 DC on which a periodically fluctuating intensity part I 2 AC is superimposed, whereby the two periodically fluctuating intensity parts I 1 AC and I 2 AC are in anti-phase relative to one another. 
     In the ideal, noise-free case, the amount |A 1 | of the amplitude A 1  of the periodically fluctuating intensity part I 1 AC referred to the constant intensity part I 1 DC of the intensity I 1  of the one light component L 1  is essentially equal to the amount |A 2 | of the amplitude A 2  of the periodically fluctuating intensity part I 2 AC referred to the constant intensity I 2 DC of the intensity I 2  of the other light component L 1 , i.e. essentially |A 1 |=|A 2 |=|A| essentially applies. 
     The intensities of the intensity signals I 1  and I 2  of the two generated light components L 1  and L 2 —apart from attenuation losses in the splitter  12 —supplement one another to, in other words, add up to the intensity I of the supplied light L. When this intensity I is constant, the sum I 1 +I 2  of the intensities I 1  and I 2  of the two light components L 1  and L 2  is also constant. 
     The light component L 1  is supplied either directly or through an optical conductor ll 1  to an opto-electrical transducer location  13   1  in which the light component signal L 1  is converted from the optical into the electrical form. Likewise, the light component L 2  is supplied directly or through an optical conductor  11   2  to an opto-electrical transducer location  13   2  in which this component signal L 2  is brought from the optical into the electrical form. 
     The electrical component signal L 1  is supplied to an acquisition means  2  of the inventive arrangement for intensity norming in an electrical conductor  2   1  and the electrical intensity signal L 2  is supplied thereto in an electrical conductor  2   2 . 
     When the two optical conductors  11   1  and  11   2  exhibit different attenuations relative to one another, the periodically fluctuating intensity parts I 1 AC or, respectively, I 2 AC of the component signals L 1  and L 2  have amplitudes A 1  or, respectively, A 2  of an amount |A 1 |≠|A 2 | differing from one another. The effect thereof is that the sum I 1 +I 2  of the intensities I 1  and I 2  of these two component signals L 1  and L 2  is also not constant but periodically fluctuates in time corresponding to the alternating current. 
     Let this be made clear by way of example on the basis of FIG. 2, given the assumption that the attenuation of the optical conductor  11   2  is higher than that of the optical conductor  11   1 . In FIG. 2, the component signal L 1  carried in the optical conductor  11   1  is shown with a solid line and the intensity signal L 2  conducted in the optical conductor  11   2  is shown with a broken line. The intensity I 1  of the intensity signal L 1  is composed of the constant intensity part I 1 DC and of the intensity I 1 AC periodically fluctuating with reference to the level of this part I 1 DC and having the amplitude A 1  with the amount |A 1 |. The intensity I 2  of the intensity signal L 2  is composed of the constant intensity part I 2 DC and the intensity I 2 AC periodically fluctuating with reference to the level of this part I 2 DC and having the amplitude A 2  with the amount |A 2 |. Due to the higher attenuation in the optical conductor  11   2  compared to the optical conductor  11   1 , the amount |A 1 | of the amplitude A 1  of the periodically fluctuating intensity part I 1 AC with the intensity I 1  of the intensity signal L 1  conducted in the optical conductor  11   1  is greater than the amount |A 2 | of the amplitude A 2  of the periodically fluctuating intensity part I 2 AC with the intensity I 2  of the intensity signal L 2  conducted in the optical conductor  11   2 . 
     For the sake of simplicity, the level of the constant intensity part I 2 DC of the intensity I 2  of the intensity signal L 2  conducted in the optical optical [sic] conductor  11   2  in FIG. 2 is selected equal to the level of the constant intensity part I 1 DC of the intensity I 1  of the intensity signal L 1  conducted in the optical conductor  11   1 . Due to the relatively higher attenuation in the optical conductor  11   2 , the level of the constant intensity part I 2 DC is likewise lower in reality then the level of the constant intensity part I 1 DC. It is not the constant intensity parts I 1 DC and I 2 DC but only the periodically fluctuating intensity parts I 1 AC and I 2 AC that are responsible for the periodic fluctuation of the sum I 1 +I 2 . 
     The level of the constant intensity parts I 1 DC and I 2 DC of the intensities I 1  and I 2  of the component signals L 1  and L 2  are shown constant over time in FIG.  2 . This is only the case when the intensity I of the light L supplied to the polarization beam splitter  12  is constant. When this intensity I fluctuates, then the constant intensity parts I 1 DC and I 2 DC of the intensities I 1  and I 2  of the component signals L 1  and L 2  also fluctuate. 
     Inventively, two signals L 1 ′ and L 2 ′ having signal intensities I 1 ′ or, respectively, I 2 ′ corresponding to the intensities I 1  or, respectively, I 2  of the two component signals L 1  and L 2  are acquired from the two component signals L 1  and L 2  in the acquisition means  2 , whereby the signal intensities I 1 ′ or, respectively, I 2 ′ contain signal intensity parts I 1 ′AC or, respectively, I 2 ′AC fluctuating periodically in anti-phase relative to one another corresponding to the periodically fluctuating intensity parts I 1 AC or, respectively, I 2 AC of the intensity I 1  or, respectively, I 2  of the component signals L 1  or, respectively, L 2  such that 
     the periodically fluctuating signal intensity parts I 1 ′AC or, respectively, I 2 ′AC of both acquired signals L 1 ′ and L 2 ′ exhibit amplitudes A of essentially the same amount |A|, and 
     the sum I 1 ′+I 2 ′ of the signal intensities I 1 ′ and I 2 ′ of both acquired signals L 1 ′ and L 2 ′ is essentially constant. 
     FIG. 3 shows the signals L 1 ′ and L 2 ′ acquired in this way, whereby the acquired signal L 1 ′ is shown with a solid line and the acquired signal L 2 ′ is shown with a broken line. The signal intensity I 1 ′ of the acquired signal L 1 ′ is composed of the signal constant intensity part I 1 ′DC and the signal intensity part I 1 ′AC that is fluctuating periodically with reference to the level of this part I 1 ′DC and having the amplitude A of the amount |A|. The signal intensity I 2  of the acquired signal L 2 ′ is composed of the signal constant intensity part I 2 ′DC and the signal intensity part I 2 ′AC that is periodically fluctuating with reference to the level of this part I 2 ′DC and having the amplitude A of the same amount |A|. For the sake of simplicity, the level of the signal constant intensity part I 1 ′DC of the acquired signal L 1 ′ in FIG. 3 is likewise selected to be equal to the level of the signal constant intensity part I 2 ′DC of the acquired signal I 2 ′. This, however, is not required. 
     Via, for example, electrical lines  2   3  or  2   4 , the two acquired signals L 1 ′ and L 2 ′ are supplied to a means  3  for forming a quotient, in which, for example, the quotient P=(I 1 ′−I 2 ′)/(I 1 ′+I 2 ′) composed of the difference I 1 ′−I 2 ′ between these two intensities I 1 ′I 2 ′ and the sum I 1 ′+I 2 ′ of these intensities I 1 ′ and I 2 ′ is formed from the intensities I 1 ′ and I 2 ′ of the two acquired signals L 1 ′ and L 2 ′ and is output for further-processing, for example at an electrical line  3   1 . 
     The acquisition means  2  can modify both the component signal L 1  as well as the component signal L 2 ; however, both of these together are not required. The acquisition means  2  can be fashioned such that only one of the two component signals is modified relative to the other. 
     It is assumed by way of example given the example of FIG. 1 that the acquisition means  2  leaves the intensity I 1  of the component signal L 1  unmodified, so that this signal L 1  is the acquired signal at the same time, i.e. L 1 =L 1 ′ applies; but the intensity I 2  of the intensity signal L 2  is modified by contrast into the other I 2 ′ intensity of the acquired signal L 2 ′ for amplitude matching, so that I 2 ≠I 2 ′ applies. It could also be converse, i.e. such that the component signal L 2  remains unmodified, i.e. L 2 =L 2 ′ applies, and the component signal L 1  is converted into the acquired signal L 1 ′ which is different therefrom. 
     The exemplary acquisition means  2  according to FIG. 1 comprises a multiplication means  20  for multiplying the intensity I 2  of the intensity signal L 2  by a correction factor k 1 ≠1 that is selected such that the periodically fluctuating intensity part I 2 AC′=k 1 ·I 2 AC of the intensity k 1 ·I 2 =I 2 ′ multiplied with this correction factor k 1  of the acquired signal L 2 ′ thereby formed and the periodically fluctuating intensity part I 1 ′AC of the intensity I 1  left unmodified of the intensity signal L 1  forming the acquired signal at the same time respectively exhibit the amplitude A of the same amount |A|. 
     Instead of the multiplication means  20  or in addition thereto, a multiplication means  22  (indicated with broken lines) could also be provided for multiplying the intensity signal I 1  with a correction factor k 2 ≠1 selected such that the periodically fluctuating intensity part I 1 ′AC=k 2 ·I 1 AC of the intensity I 1 ′=k 2 ·I 1  multiplied with this correction factor k 2  of the acquired signal L 1 ′ thereby formed and the periodically fluctuating intensity part I 2 ′AC of the intensity I 2  left unmodified of the component signal L 2  forming the acquire signal at the same time respectively exhibit the amplitude A having the same amount |A|. 
     A correction factor determination means  21  is provided for determining the correction k 1  and/or k 2  with which the appertaining intensity signal I 2  or, respectively, I 1  is to be multiplied. 
     An example of such a correction factor determination means is shown in FIG.  4 . This exemplary means  21  serves for determining the correction factor k 1  and comprises a means  212  for acquiring the periodically fluctuating intensity part I 2 AC from the component signal L 2  to be multiplied by this correction factor k 1 , a means  211  for acquiring the periodically fluctuating intensity part I 1 AC from the other component signal L 1 , and a means  213  for forming a specific quotient |{overscore (I 1 AC)}|/|{overscore (I 2 AC)}| representing this coefficient k 1  from a specific, amplitude-related, amount-oriented quantity |{overscore (I 1 AC)}| of the periodically fluctuating intensity part I 1 AC acquired from the other intensity signal L 1  and the same amplitude-related amount-oriented quantity |{overscore (I 2 AC)}| of the periodically fluctuating intensity part I 2 AC acquired from the component signal L 2 . 
     For forming the correction factor k 2 , the means  213  would have to be fashioned such that the quotient |{overscore (I 2 AC)}|/|{overscore (I 1 AC)}| is formed. 
     Each of the means  211  and  212  for acquiring the periodically fluctuating intensity part I 1 AC or, respectively, I 2 AC from the intensity signal L 1  or, respectively, L 2  advantageously comprises a filter means  216  for filtering the periodically fluctuating intensity part I 1 AC or, respectively, I 2 AC from its component signal L 1  or, respectively, L 2 . In the present case wherein the periodically fluctuating intensity parts I 1 AC and I 2 AC lie at only a fixed frequency, the alternating current frequency of, for example 50 Hz or 60 Hz, this filter means  216  is composed of a narrow-band filter that only allows this one frequency to pass but blocks all other frequencies. As a result thereof, all noise fluctuations that do not exhibit an amplitude of an adequately great amount at this fixed frequency can be neutralized. 
     In a diagram, FIG. 5 shows an example of such a frequency spectrum. In this diagram, the amount of the amplitude of the component signals L 1  and L 2  as well as that of noise fluctuations dependent on the frequency f entered on the abscissa is entered on the ordinate. The frequency of the periodically fluctuating intensity parts I 1 AC or, respectively, I 2 AC of the intensity signals L 1  and L 2  respectively lies at 50 Hz; the frequency spectrum of the noise fluctuations superimposed on the component signals L 1  and L 2  and caused, for example by mechanical vibrations is referenced S. 
     A means  211  or, respectively,  212  for acquiring the periodically fluctuating intensity part I 1 AC or, respectively, I 2 AC from the appertaining component signals L 1  or, respectively, L 2  can also comprise a difference-forming means  215  (indicated in FIG. 6) for forming a difference I 1 -I 1 DC or, respectively, I 2 -I 2 DC between the intensity I 1  or, rspectively, I 2  of this intensity signal L 1  or, respectively, L 2  and the constant intensity part I 1 DC or, respectively, I 2 DC of this component signal L 1  or, respectively, L 2 . This difference I 1 -I 1 DC or, respectively, I 2 -I 2 DC forms the periodically fluctuating intensity part I 1 AC or, respectively, I 2 AC of the appertaining component signal L 1  or, respectively, L 2 . 
     The amplitude-related, amount-oriented quantity is preferably a chronological average |{overscore (I 1 AC)}| or, respectively, |{overscore (I 2 AC)}| of the amount |I 1 AC| or, respectively, |I 2 AC|) [sic] of the respective, acquired, periodically fluctuating intensity part I 1 AC or, respectively I 2 AC of the appertaining intensity signal L 1  or, respectively, L 2 . In this case, a means  217  is provided for generating the specific, amplitude-related, amount-oriented quantity in the form of the chronological average |{overscore (I 1 AC)}| or, respectively, |{overscore (I 2 AC)}| of the amount |I 1 AC|, |I 2 AC| of the respective, acquired, periodically fluctuating intensity part I 1 AC or, respectively, I 2 AC. 
     In an alternative embodiment of an inventive means, the acquisition means  2  comprises 
     a means  221  for multiplying the intensity I 2  or, respectively, I 1  of one L 2  or, respectively, L 2  of the two intensity signals L 1  and L 2  with a variable, preliminary correction factor k 1 ′ or k 2 ′; 
     a means  222  for forming an aggregate intensity k 1 ′·I 2 +I 1  or, respectively, k 2 ′·I 1 +I 2  by summation of the intensity k 1 ′·I 2  or, respectively, k 2 ′·I 1  of the one component signal L 2  or, respectively, L 1  multiplied by the preliminary correction factor k 1 ′ or, respectively, k 2 ′ and the intensity I 1  or, respectively, I 2  of the other component signal L 1  or, respectively, L 2  that has been left unmodified; 
     a means  223  for determining a constant intensity part (k 1 ′·I 2 +I 1 ) DC  or, respectively, (k 2 ′·I 1 +I 2 ) DC  containing in the aggregate intensity k 1 ′·I 2 +I 1  or, respectively, k 2 ′·I 1 +I 2 ; 
     a means  224  for forming a difference intensity (k 1 ′·I 2 +I 1 )−(k 1 ′·I 2 +I 1 ) DC  or, respectively, (k 2 ′·I 1 +I 2 )−(k 1 ′·I 2 +I 1 ) DC  from the aggregate intensity k 1 ′·I 2 +I 1  or, respectively, k 2 ′·I 1 +I 2  and the constant intensity part thereof (k 1 ′·I 2 +I 1 ) DC  or, respectively (k 2 ′·I 1 +I 2 ) DC ; and 
     a means  225  for setting the preliminary correction factor k 1 ′ or, respectively, k 2 ′ to a final correction factor k 1  or, respectively, k 2  such that the difference intensity (k 1 ′·I 2 +I 1 )−(k 1 ′·I 2 +I 1 ) DC  or, respectively, (k 12 ′·I 1 +I 2 )−(k 1 ′·I 2 +I 1 ) DC  is essentially equal to zero. 
     The means  225  is preferably a regulating means. 
     The invention is not limited to the alternating current sensor  1  described by way of example but can be generally applied given any sensor, particularly given alternating voltage sensors as well. 
     Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.