Field of the Invention The present invention relates to a system and a method for converting an input signal to an output signal, which system performs an digital conversion of the input signals into input digital data, which system performs digital conversion into the output signal, which system performs separate digital conversion of a plurality input signals.

Background of the Invention

DE4434553 Al concerns a field digital converter. The analogue signal is separately converted so that at first digitalization of the current is performed, and parallel to this process, digitalization of the voltage is performed. These two digital signals are then combined in an arithmetic logic circuit where a common signal is achieved which signal is then sent through a galvanic insulator before the signal is sent to a data communication system.

US 6329817 discloses a sensor for measuring a parameter includes at least one trans- ducer adapted to provide an analog transducer signal, and at least one converter adapted to convert the analog transducer signal into a digitized transducer signal, and a memory device associated with the converter capable of receiving the digitized transducer signal directly from the converter. The memory device is configured to provide a digitized output value from a memory location, the memory location being associated with or corresponding to the digitized transducer signal received by the memory device.

In the US 632917 there is not disclosed any galvanic isolation of the signals in that an analogue signal is transmitted parallelly to the digital signal for late to be combined in an analogue adder circuit. No galvanic isolation is performed during the analogue or digital communication line. A skilled man can therefore not get any information towards galvanic isolation.

Object of the Invention

It is the object of this pending application to achieve linear interpolation in multiple dimensions in the digital domain. A further object of the pending application is to achieve a very precise transmission of analogue signals by performing a transformation in the digital domain by using linear interpolation for compensating any linear and/or non linear effects on the analogue signal.

Description of the Invention

This can be achieved if the digital data segments representing the actual measured input signals which input signal are corrected in accordance with actual calculated cor- rection values, which correction values depends on the transfer function for the given input variables effect on the system, which digital data segments representing input signals is used to address stored correcting data sets, which correcting data sets are stored in at least one matrix of at least two dimensions, which addressed correcting data sets are continuously converted to an output signal.

Herby can be achieved that any electronic data set representing a plurality of parameters can be corrected by using each parameter as pointers in a multidimensional space, which multidimensional space comprises correction values stored in a multidimensional matrix. Data from this matrix can form a corrected output signal.

In a possible embodiment of the invention, the input is an analogue input signal and the output is an analogue output signal, which system performs an analogue to digital conversion of the input signals into input digital data, which system performs digital to analogue conversion into the analogue output signal, which system performs separate digital conversion of input current and input voltage , which digital data segments representing the actual measured input current is corrected in accordance with an actual calculated correction value, which correction value depends of a non linear load for the input current, which digital data segments representing input current and input voltage is used to address stored correcting data set, which correcting data set are stored in a matrix of at least two dimensions, which addressed correcting data set are continuously converted to an analogue output signal.

Hereby can be achieved that any un-linearity between voltage and current can be corrected in a nearly perfect way. This is very important if the metering signal is in fact a current signal and the voltage that is received has a value between wide voltage ranges, i.e. 6-35 volts. By such a high range of voltage that has to be accepted, there will always be some un-linearity in every system that is receiving this voltage. In many situations the signals are sent through a transformer for galvanic isolation. Therefore it is crucial to use a system that can correct the un-linearity so that a received current can be established at the output of the system. By using the correction a data set it is possi- ble to perform a correction of all known parameter that influence the measuring signal. Typically, differences in electronic components could have different influence on different circuits. In a system as the one described here where correction data sets are placed in a matrix, the contents of this matrix could in some situations be independent from unit to unit that is using the same components. In this way all tolerances of components could be corrected. A coding could be performed during a traditional test where, more or less automatically, the correcting data set is programmed into the matrix as a standard procedure in testing a unit.

The digital data segments representing input current and input voltage are used as pointers into the matrix. By using the data set from the two input channels as pointers for the matrix, a very fast operating system can be achieved which can operate at an extremely fast clock frequency. Therefore it should be possible to work with a rather high upper frequency for the received analogue signals that are being converted. The analogue input signal for current and voltage are converted independently of each other to digital data segments by an analogue to digital converter. In this way digitali- zation can be performed in a way that corresponds to the speeds of the pointers that are used in the system. The digital data segments generated by the analogue to digital converter are N-th Order modulated in a digital filter before the data is used for the pointers. Because of the number of bits that are generated by the analogue to digital conversion it is highly effi- cient that a digital filtration is performed which filtration can combine the digital values in a way by which the data contents is still mostly the same but the number of bits are reduced.

The correcting data set is converted in a first K-th order modulator. The data that has been picked up in the matrix is in the L-th order modulator also filtrated in a way where the numbers of bits are reduced without any reduction of the data contents.

The digital signal generated in the first K-th order modulator is further modulated in a second L-th order modulator. By performing a further filtration in the L-th order modulator a further reduction in the bit stream can be achieved and in a way by which the data leaving the L-th order modulator is in a form that can be used for a digital- analogue converter.

The digital signal generated in the second L-th order modulator is converted in a digital to analogue converter into the analogue output signal. Hereby an analogue current value is generated which is connected in a way by which the output current is mostly identical with the input current.

The pending patent application further concerns a method for correcting signal be- tween an input signal and an output signal which method concerns the following sequence of steps: a: perform digital conversion of the input signal into a number of digital data set (x-bit) representing the parameters of the input signal,

b: perform a high order modulation of the datasets representing parameters of the input signal into a reduced data set for pointers, c: Use the pointers for selecting data field of a matrix of a correction data sets, d: use the further pointers for selecting datasets,

e: transmit the data segment (15) selected by pointers (a bit) into a further high order modulator and perform the high order modulation into a second data sets (c bit), f: further perform a low order modulation of the data segments (c bit) into third data segments ( d bit), g: perform a digital to conversion of the third data sets for generating the output (6).

In a preferred method the method concerns the following sequence of steps: a: perform analogue to digital conversion of the input current signal into a first digital data set (X-bit) representing the input current, b: perform analogue to digital conversion of the input voltage signal into a second digital data set (Z-bit) representing the input voltage, d: perform a N-th order modulation of the first data set representing the input current into (V-bit) to a first pointer, e: perform M-th order modulation of the second dataset representing the input voltage into (Y-bit) to a second pointer, f: Use the first pointer for selecting a row in a matrix of a correction data sets, g: use the second pointer for selecting a column in the matrix of the correction data set, h: transmit the data segment (15) selected by the first and second pointer (a bit) into a K-th order modulator and perform the K-th order modulation into a second data set (c bit), i: further perform a L-th order modulation of the second data segment (c bit) into a third data segment ( d bit), j : perform a digital to analogue conversion for generating the analogue output (6). By the method it can be achieved that analogue signals received, which comprise a measuring current as that of the actual data set but with different voltages, and that the current signal is corrected so any unlinearity of the input side of a system is corrected by correcting the data sets in accordance with both current and voltage with correction values, which correction values are sent through different kinds of digital filtration be- fore they are converted into an analogue value. Hereby it is achieved that an analogue current value can be transmitted through this system in a very precise manner, without any information being changed.

Description of the Drawing

Fig. 1 shows a possible embodiment for a system for analogue to digital conversion and back to an analogue signal.

Fig. 2 shows a preferred embodiment for the same invention as for fig. 1.

Detailed Description of the Invention

Fig. 1 shows a system 2 which system concerns an analogue input 4 and an analogue output. The system comprises a voltage input 8 and a current input 10. Both these two input signals are sent through analogue to digital converters 24. These analogue digital converters are in a preferred embodiment, but not limited hereto, SAR converters. The analogue digital converters deliver a digital data set 12 and 13 which both data sets independent of each other are sent through digital filters 25 which digital filters perform an N-th order modulation of the voltage signals and an M-th order modulation of the data set representing the current. An output is performed as V-bit and Y-bit. The V-bit output from the N-th order modulator 25 is used for controlling a pointer 20 and the Y-bit generated by the M-th order modulator 25 is used for controlling a pointer 22. These two pointers 20 and 22 are continuously moved in dependence of the actual voltage and the actual current. A matrix 14 comprises correction values for the current. The pointers 20 and 22 are pointing one of the data segments in the matrix, for example the data segment 15. This data segment is then transmitted as an A-bit into a first digital filtration 23. Here is a data stream defined as B-bit sent into a K-th order modulator 27. A C-bit is afterwards transmitted to an L-th order modulator 28. Further, a D- bit data stream is sent to a digital analogue converter 26. This analogue signal is then sent to an analogue filter 30, before the current signal 6 is leaving the system. The B-bit signal is further sent through an additional arithmetic unit 32, and an E-bit signal is sent through an UART 34. Hereby is achieved that a data signal 36 represents the current. This data stream can be used for transmitting the measured date segments representing the current further in a system.

In operation can a current input 10 represent a measured value. In many situations a signal has to pass through a galvanic isolation, such as a transformer. Transformers are non linear so that frequency or voltage has influence of the impedance and as such of the relation between input and output current. Therefore has the current representing a measured value to be corrected after passing a transformer.. This can be achieved if the voltage, frequency or current signal are independently converted into a digital data stream in the analogue digital converters. These bit streams can be sent through a digital filter of a high order in order to reduce the number of bits, but without reducing the actual data contents in the data stream. These two separate data streams are then used for input through pointers in a matrix where the pointers are selecting one correction value 15 placed somewhere in the matrix. This value is then immediately sent through the output to the digital filtration and further in reduction of the bits into a data stream of further bits, before the signal is sent through the digital analogue converter. Hereaf- ter, the signals are again filtrated, but at this time in an analogue filter of a second order. Parallel to that is generated a digital output value that is representing the corrected current value used for the input. This digital output can then be used for further data processing. Fig. 2 shows a system mostly equal to the system shown at fig. 1, but the system 102 has a double input 104 for a voltage and a current and an output 106. The input terminal for the voltage 108 and the input terminal 110 for the current are sent into two analogue digital converters 124 which are 10 bit converters. These two analogue digital converters are producing 10 bit digital segments 112 and 113 which data is sent through a first order modulator 125. Here the 10 bits are reduced into 4 bits. These 4 bits are then used for the matrix 114 where pointers 120 and 122 are selecting one data segment 115 which can be a 16 bit data segment that are transmitted through the first order modulator 127. Here are the 16 bit data segment changed into a 8 bit data segment which is transmitted to a second order modulator 128. The 128 second order modulator converts the 8 bit words into a 1 bit data stream which is sent for a digital analogue converter 126. Afterwards the signals are sent through an analogue filter of second order 130 in order to filter out all higher frequencies which end up in an output current 106.