Process for standardising the intensity of optical sensors used for measuring periodically oscillating electric or magnetic field intensities

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 (L1, L2) generated by the sensor but--inventively --with signals (L1', L2') derived therefrom that exhibit periodically fluctuating intensity parts (I1'AC, I2'AC) of the same amplitude amount (.vertline.A.vertline.). The invention largely unites the advantages of -/+ division with those of AC/DC division.

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.

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 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.sub.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 L1 and L2 each having a
 fixed polarization condition p1 or, respectively p2, that differs from one
 another, whereby the polarization beam splitter 12 is set relative to the
 fixed polarity condition p.sub.0 ' of the light L supplied to it such that
 the intensities I1 and I2 of the two generated light components L1 and
 L2--in conformity with the periodically fluctuating polarization condition
 p' of the supplied light L--exhibit intensities I1 and I2 that are
 periodically fluctuating in anti-phase relative to one another, i.e. the
 intensity I1 of the light component L1 is composed of a constant intensity
 part I1DC on which a periodically fluctuating intensity part I1AC is
 superimposed and the intensity I2 of the light part L2 is composed of a
 constant intensity part I2DC on which a periodically fluctuating intensity
 part I2AC is superimposed, whereby the two periodically fluctuating
 intensity parts I1AC and I2AC are in anti-phase relative to one another.
 In the ideal, noise-free case, the amount .vertline.A1.vertline. of the
 amplitude A1 of the periodically fluctuating intensity part I1AC referred
 to the constant intensity part I1DC of the intensity I1 of the one light
 component L1 is essentially equal to the amount .vertline.A2.vertline. of
 the amplitude A2 of the periodically fluctuating intensity part I2AC
 referred to the constant intensity I2DC of the intensity I2 of the other
 light component L1, i.e. essentially
 .vertline.A1.vertline.=.vertline.A2.vertline.=.vertline.A.vertline.
 essentially applies.
 The intensities of the intensity signals I1 and I2 of the two generated
 light components L1 and L2--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 I1+I2
 of the intensities I1 and I2 of the two light components L1 and L2 is also
 constant.
 The light component L1 is supplied either directly or through an optical
 conductor ll.sub.1 to an opto-electrical transducer location 13.sub.1 in
 which the light component signal L1 is converted from the optical into the
 electrical form. Likewise, the light component L2 is supplied directly or
 through an optical conductor 11.sub.2 to an opto-electrical transducer
 location 13.sub.2 in which this component signal L2 is brought from the
 optical into the electrical form.
 The electrical component signal L1 is supplied to an acquisition means 2 of
 the inventive arrangement for intensity norming in an electrical conductor
 2.sub.1 and the electrical intensity signal L2 is supplied thereto in an
 electrical conductor 2.sub.2.
 When the two optical conductors 11.sub.1 and 11.sub.2 exhibit different
 attenuations relative to one another, the periodically fluctuating
 intensity parts I1AC or, respectively, I2AC of the component signals L1
 and L2 have amplitudes A1 or, respectively, A2 of an amount
 .vertline.A1.vertline..noteq..vertline.A2.vertline. differing from one
 another. The effect thereof is that the sum I1+I2 of the intensities I1
 and I2 of these two component signals L1 and L2 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.sub.2 is
 higher than that of the optical conductor 11.sub.1. In FIG. 2, the
 component signal L1 carried in the optical conductor 11.sub.1 is shown
 with a solid line and the intensity signal L2 conducted in the optical
 conductor 11.sub.2 is shown with a broken line. The intensity I1 of the
 intensity signal L1 is composed of the constant intensity part I1DC and of
 the intensity I1AC periodically fluctuating with reference to the level of
 this part I1DC and having the amplitude A1 with the amount
 .vertline.A1.vertline.. The intensity I2 of the intensity signal L2 is
 composed of the constant intensity part I2DC and the intensity I2AC
 periodically fluctuating with reference to the level of this part I2DC and
 having the amplitude A2 with the amount .vertline.A2.vertline.. Due to the
 higher attenuation in the optical conductor 11.sub.2 compared to the
 optical conductor 11.sub.1, the amount .vertline.A1.vertline. of the
 amplitude A1 of the periodically fluctuating intensity part I1AC with the
 intensity I1 of the intensity signal L1 conducted in the optical conductor
 11.sub.1 is greater than the amount .vertline.A2.vertline. of the
 amplitude A2 of the periodically fluctuating intensity part I2AC with the
 intensity I2 of the intensity signal L2 conducted in the optical conductor
 11.sub.2.
 For the sake of simplicity, the level of the constant intensity part I2DC
 of the intensity I2 of the intensity signal L2 conducted in the optical
 optical [sic] conductor 11.sub.2 in FIG. 2 is selected equal to the level
 of the constant intensity part I1DC of the intensity I1 of the intensity
 signal L1 conducted in the optical conductor 11.sub.1. Due to the
 relatively higher attenuation in the optical conductor 11.sub.2, the level
 of the constant intensity part I2DC is likewise lower in reality then the
 level of the constant intensity part I1DC. It is not the constant
 intensity parts I1DC and I2DC but only the periodically fluctuating
 intensity parts I1AC and I2AC that are responsible for the periodic
 fluctuation of the sum I1+I2.
 The level of the constant intensity parts I1DC and I2DC of the intensities
 I1 and I2 of the component signals L1 and L2 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 I1DC and I2DC of
 the intensities I1 and I2 of the component signals L1 and L2 also
 fluctuate.
 Inventively, two signals L1' and L2' having signal intensities I1' or,
 respectively, I2' corresponding to the intensities I1 or, respectively, I2
 of the two component signals L1 and L2 are acquired from the two component
 signals L1 and L2 in the acquisition means 2, whereby the signal
 intensities I1' or, respectively, I2' contain signal intensity parts I1'AC
 or, respectively, I2'AC fluctuating periodically in anti-phase relative to
 one another corresponding to the periodically fluctuating intensity parts
 I1AC or, respectively, I2AC of the intensity I1 or, respectively, I2 of
 the component signals L1 or, respectively, L2 such that
 the periodically fluctuating signal intensity parts I1'AC or, respectively,
 I2'AC of both acquired signals L1' and L2' exhibit amplitudes A of
 essentially the same amount .vertline.A.vertline., and
 the sum I1'+I2' of the signal intensities I1' and I2' of both acquired
 signals L1' and L2' is essentially constant.
 FIG. 3 shows the signals L1' and L2' acquired in this way, whereby the
 acquired signal L1' is shown with a solid line and the acquired signal L2'
 is shown with a broken line. The signal intensity I1' of the acquired
 signal L1' is composed of the signal constant intensity part I1'DC and the
 signal intensity part I1'AC that is fluctuating periodically with
 reference to the level of this part I1'DC and having the amplitude A of
 the amount .vertline.A.vertline.. The signal intensity I2 of the acquired
 signal L2' is composed of the signal constant intensity part I2'DC and the
 signal intensity part I2'AC that is periodically fluctuating with
 reference to the level of this part I2'DC and having the amplitude A of
 the same amount .vertline.A.vertline.. For the sake of simplicity, the
 level of the signal constant intensity part I1'DC of the acquired signal
 L1' in FIG. 3 is likewise selected to be equal to the level of the signal
 constant intensity part I2'DC of the acquired signal I2'. This, however,
 is not required.
 Via, for example, electrical lines 2.sub.3 or 2.sub.4, the two acquired
 signals L1' and L2' are supplied to a means 3 for forming a quotient, in
 which, for example, the quotient P=(I1'-I2')/(I1'+I2') composed of the
 difference I1'-I2' between these two intensities I1'I2' and the sum
 I1'+I2' of these intensities I1' and I2' is formed from the intensities
 I1' and I2' of the two acquired signals L1' and L2' and is output for
 further-processing, for example at an electrical line 3.sub.1.
 The acquisition means 2 can modify both the component signal L1 as well as
 the component signal L2; 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 I1 of the component signal L1
 unmodified, so that this signal L1 is the acquired signal at the same
 time, i.e. L1=L1' applies; but the intensity I2 of the intensity signal L2
 is modified by contrast into the other I2' intensity of the acquired
 signal L2' for amplitude matching, so that I2.noteq.I2' applies. It could
 also be converse, i.e. such that the component signal L2 remains
 unmodified, i.e. L2=L2' applies, and the component signal L1 is converted
 into the acquired signal L1' which is different therefrom.
 The exemplary acquisition means 2 according to FIG. 1 comprises a
 multiplication means 20 for multiplying the intensity I2 of the intensity
 signal L2 by a correction factor k1.noteq.1 that is selected such that the
 periodically fluctuating intensity part I2AC'=k1.multidot.I2AC of the
 intensity k1.multidot.I2=I2' multiplied with this correction factor k1 of
 the acquired signal L2' thereby formed and the periodically fluctuating
 intensity part I1'AC of the intensity I1 left unmodified of the intensity
 signal L1 forming the acquired signal at the same time respectively
 exhibit the amplitude A of the same amount .vertline.A.vertline..
 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 I1 with a correction factor
 k2.noteq.1 selected such that the periodically fluctuating intensity part
 I1'AC=k2.multidot.I1AC of the intensity I1'=k2.multidot.I1 multiplied with
 this correction factor k2 of the acquired signal L1' thereby formed and
 the periodically fluctuating intensity part I2'AC of the intensity I2 left
 unmodified of the component signal L2 forming the acquire signal at the
 same time respectively exhibit the amplitude A having the same amount
 .vertline.A.vertline..
 A correction factor determination means 21 is provided for determining the
 correction k1 and/or k2 with which the appertaining intensity signal I2
 or, respectively, I1 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 k1
 and comprises a means 212 for acquiring the periodically fluctuating
 intensity part I2AC from the component signal L2 to be multiplied by this
 correction factor k1, a means 211 for acquiring the periodically
 fluctuating intensity part I1AC from the other component signal L1, and a
 means 213 for forming a specific quotient
 .vertline.I1AC.vertline./.vertline.I2AC.vertline. representing this
 coefficient k1 from a specific, amplitude-related, amount-oriented
 quantity .vertline.I1AC.vertline. of the periodically fluctuating
 intensity part I1AC acquired from the other intensity signal L1 and the
 same amplitude-related amount-oriented quantity .vertline.I2AC.vertline.
 of the periodically fluctuating intensity part I2AC acquired from the
 component signal L2.
 For forming the correction factor k2, the means 213 would have to be
 fashioned such that the quotient
 .vertline.I2AC.vertline./.vertline.I1AC.vertline. is formed.
 Each of the means 211 and 212 for acquiring the periodically fluctuating
 intensity part I1AC or, respectively, I2AC from the intensity signal L1
 or, respectively, L2 advantageously comprises a filter means 216 for
 filtering the periodically fluctuating intensity part I1AC or,
 respectively, I2AC from its component signal L1 or, respectively, L2. In
 the present case wherein the periodically fluctuating intensity parts I1AC
 and I2AC 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 L1 and L2 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 I1AC or, respectively, I2AC of the intensity
 signals L1 and L2 respectively lies at 50 Hz; the frequency spectrum of
 the noise fluctuations superimposed on the component signals L1 and L2 and
 caused, for example by mechanical vibrations is referenced S.
 A means 211 or, respectively, 212 for acquiring the periodically
 fluctuating intensity part I1AC or, respectively, I2AC from the
 appertaining component signals L1 or, respectively, L2 can also comprise a
 difference-forming means 215 (indicated in FIG. 6) for forming a
 difference I1-I1DC or, respectively, I2-I2DC between the intensity I1 or,
 rspectively, I2 of this intensity signal L1 or, respectively, L2 and the
 constant intensity part I1DC or, respectively, I2DC of this component
 signal L1 or, respectively, L2. This difference I1-I1DC or, respectively,
 I2-I2DC forms the periodically fluctuating intensity part I1AC or,
 respectively, I2AC of the appertaining component signal L1 or,
 respectively, L2.
 The amplitude-related, amount-oriented quantity is preferably a
 chronological average .vertline.I1AC.vertline. or, respectively,
 .vertline.I2AC.vertline. of the amount .vertline.I1AC.vertline. or,
 respectively, .vertline.I2AC.vertline.) [sic] of the respective, acquired,
 periodically fluctuating intensity part I1AC or, respectively I2AC of the
 appertaining intensity signal L1 or, respectively, L2. In this case, a
 means 217 is provided for generating the specific, amplitude-related,
 amount-oriented quantity in the form of the chronological average
 .vertline.I1AC.vertline. or, respectively, .vertline.I2AC.vertline. of the
 amount .vertline.I1AC.vertline., .vertline.I2AC.vertline. of the
 respective, acquired, periodically fluctuating intensity part I1AC or,
 respectively, I2AC.
 In an alternative embodiment of an inventive means, the acquisition means 2
 comprises
 a means 221 for multiplying the intensity I2 or, respectively, I1 of one L2
 or, respectively, L2 of the two intensity signals L1 and L2 with a
 variable, preliminary correction factor k1' or k2';
 a means 222 for forming an aggregate intensity k1'.multidot.I2+I1 or,
 respectively, k2'.multidot.I1+I2 by summation of the intensity
 k1'.multidot.I2 or, respectively, k2'.multidot.I1 of the one component
 signal L2 or, respectively, L1 multiplied by the preliminary correction
 factor k1' or, respectively, k2' and the intensity I1 or, respectively, I2
 of the other component signal L1 or, respectively, L2 that has been left
 unmodified;
 a means 223 for determining a constant intensity part
 (k1'.multidot.I2+I1).sub.DC or, respectively, (k2'.multidot.I1+I2).sub.DC
 containing in the aggregate intensity k1'.multidot.I2+I1 or, respectively,
 k2'.multidot.I1+I2;
 a means 224 for forming a difference intensity
 (k1'.multidot.I2+I1)-(k1'.multidot.I2+I1).sub.DC or, respectively,
 (k2'.multidot.I1+I2)-(k1'.multidot.I2+I1).sub.DC from the aggregate
 intensity k1'.multidot.I2+I1 or, respectively, k2'.multidot.I1+I2 and the
 constant intensity part thereof (k1'.multidot.I2+I1).sub.DC or,
 respectively (k2'.multidot.I1+I2).sub.DC ; and
 a means 225 for setting the preliminary correction factor k1' or,
 respectively, k2' to a final correction factor k1 or, respectively, k2
 such that the difference intensity
 (k1'.multidot.I2+I1)-(k1'.multidot.I2+I1).sub.DC or, respectively,
 (k12'.multidot.I1+I2)-(k1'.multidot.I2+I1).sub.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.