Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
2000-10-02
2002-05-21
Young, Brian (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C341S118000, C341S126000
Reexamination Certificate
active
06392583
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method and a configuration for processing at least one analog signal containing a number of frequency ranges.
In particular, the invention relates to a method and a configuration for processing output quantities of an optical transducer.
An optical transducer for acquiring an electrical quantity to be measured is known. This applies especially to the optical measurement of an electric current by utilizing the Faraday effect and also to the optical measurement of an electric voltage by utilizing the Pockels effect. A polarized light signal, the polarization of which changes under the influence of the electrical quantity to be measured, is launched into a sensor element (for example Faraday element or Pockels element) which is under the influence of the electrical quantity to be measured. The change in polarization is thus a measure of the quantity to be measured. Furthermore, an embodiment is known in which two polarized light signals having opposite directions of travel are launched into the sensor element. To analyze the change in polarization, each light signal is supplied to a (polarization) analyzer after passing at least once through the sensor element. The analyzer can divide the associated light signal either into two linearly polarized partial light signals having different planes of polarization which are generally perpendicular to one another (two-channel analysis) or pass only one light component projected onto a predetermined direction of polarization (single-channel analysis). From the light intensities of the two partial light signals or of the light component, corresponding electrical signals are generated, for example with the aid of photodiodes, from which a polarization signal is derived. The polarization signal is a measure of the change in polarization of the light signal in the sensor element under the influence of the alternating electrical quantity to be measured.
International Patent disclosure WO 95/10046 and German Patent DE 196 01 727 C1 disclose in the example of a magneto-optical current transducer how the polarization signal described can be calculated from two partial light signals LT
1
and LT
2
or, respectively, from the electrical (intensity) signals I
1
and I
2
determined from these. The polarization signal P is formed as quotient from a difference and the sum of the two electrical signals I
1
and I
2
as follows:
P
=
(
I1
-
I2
)
(
I1
+
I2
)
(
1
)
Neglecting interference, the polarization signal P is equal to:
P
=sin (2&rgr;)=sin (2
·N·V·I
) (2)
where &rgr; is the so-called Faraday angle of rotation. The Faraday angle of rotation &rgr; then corresponds to the angle through which the polarization of the light signal is rotated in the Faraday element due to the electrical current I to be detected. According to the relation:
&rgr;=2
·N·V·I
(3)
it is essentially directly proportional to the amplitude of the current I to be measured. In addition, in equation (3) N is the number of rotations of the light signal around a current conductor through which the current I to be measured flows, and V is the so-called Verdet constant V. The Verdet constant V is a parameter of the Faraday element which is generally dependent on the material and the temperature.
A limiting factor of the optical transducer described is the periodicity of the polarization dependent on the quantity to be measured. In the case of the Faraday effect, for example, the state of polarization is repeated after a 180° rotation of the linear input polarization. This initially results in a limited single-valued measuring range for the alternating electrical quantity to be detected.
If the sensitivity of the sensor is reduced in order to be able to map the largest possible signal amplitudes of the alternating electrical quantity within the limited measuring range, this is at the cost of smaller signal amplitudes which can then no longer be extracted from the noise. Conversely, an increase in sensitivity to achieve better acquisition of relatively small signal amplitudes has a negative effect on the maximum signal amplitude that can be mapped within the limited measuring range.
In the field of public electricity supply, a potential field of application of optical test methods inter alia due to the inherent high electromagnetic compatibility, it must be possible to cover a wide dynamic range of the alternating electrical quantity to be detected, especially of the electrical current. The demand for maximum measurement accuracy at low current amplitude is a prerequisite from the metering for invoicing. On the other hand, it must also be possible to reliably detect a very high current amplitude for the purpose of short-circuit current detection.
To meet the above requirements, a method has been developed which has a measuring range that is mainly extended upward. Published, European Patent Application EP 0 613 015 A1 discloses an electro-optical voltage transducer, the measuring range of which extends beyond the single-valued range of the first period. In this configuration two optical light signals are analyzed which are sent through a Pockels element with a predetermined offset phase. A signal reconstruction of the electrical voltage to be measured is done via a special counting method that evaluates the zero crossings of polarization signals derived from the two light signals. In principle, therefore, the measuring range of this electro-optical voltage transducer is no longer limited at the top.
Furthermore, a magneto-optical current transducer which generates two electrical signals which are in each case multi-valued functions of the current to be measured and are phase shifted by an angle of 90° with respect to one another is known from European Patent EP 0 208 593 B1. By comparing the signs and the absolute values, a single-valued measurement signal is assembled from these two multi-valued signals. In principal, therefore, the measuring range of this magneto-optical current transducer is also no longer limited at the top.
German Patent DE 196 01 727 C1 discloses a magneto-optical current transducer having an extended measuring range, which supplies a polarization signal which is similar to the function tan (&rgr;) of the Faraday angle of rotation &rgr;. In this case, the polarization signal calculated in the analyzing unit is only analyzed within the range of single-valueness of the tan (&rgr;) function. Compared with the usual embodiment which only supplies a polarization signal proportional to sin (2&rgr;) according to the above equation (2), this provides a measuring range which is virtually twice as large.
After passing through the sensor element, electrical signals are generated from the partial light signals via photo-electrical transducer units. In deriving the polarization signal from the electrical signals, the configurations disclosed in German Patent DE 196 01 727 C1 and in International Patent Disclosure WO 95/10046 initially use analog circuit technology. However, there are also indications that the analysis can be carried out digitally in a corresponding manner. A digital analysis of an optical current transducer is also disclosed in the report titled “Vergleichende Darstellung verschiedener magneto-optischer Stromwandlerkonzepte” (Comparative Representation of Various Magneto-Optical Current Transducer Concepts) by T. Bosselmann,
113
th
PTB Seminar
“Unkonventionelle Me&bgr;wandler für Hochspannungsnetze” (Unconventional Measurement Transducers for High-Voltage Systems), Braunschweig, Nov. 15-16, 1993. In this report, the electrical signals at the output of the photo-electric transducer units are initially digitized via analog/digital (A/D) converters and are then processed further in a digital calculating unit which can contain, for example, a digital signal processor. This digital form of signal processing is very useful especially if it is intended to eliminate disturbances such as, for example, temperature influences, or the characteristic,
Bosselmann Thomas
Menke Peter
Mohr Stephan
Willsch Michael
Wollenhaupt Mario
Greenberg Laurence A.
Lerner Herbert L.
Nguyen John
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Method and configuration for processing at least one analog... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and configuration for processing at least one analog..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and configuration for processing at least one analog... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905835