Data processing: measuring – calibrating – or testing – Measurement system – Measured signal processing
Patent
1997-08-22
1998-11-10
Barlow, Jr., John E.
Data processing: measuring, calibrating, or testing
Measurement system
Measured signal processing
702190, 364724011, 36474501, G06F 704
Patent
active
058358870
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to the problem that in a digital device which acquires and digitizes analog measured values, the digital processing unit has a smaller binary word length than the measured values to be processed. This problem occurs in particular if a cost-effective microprocessor with a small bus length has to be used as a digital processing unit.
BACKGROUND OF THE INVENTION
In digital measuring and process automation technology it is often necessary to acquire and further process analog values from a technical process under memory-programmable control. To this end, these analog measured values are sampled by so-called analog-value input assemblies with a fixed timing pattern, which is frequently referred to as a sampling cycle, and are then subjected to analog-to-digital conversion. In such cases, the measured values occur with a binary word length, for example of 16 to 32 bits, which is determined by the binary word length at the output of the analog-to-digital converter used and by the respective accuracy requirements. German Patent No. 32 10 571 describes an analog-to-digital converter device with an adaptation device for the analog signal fed to the analog-to-digital converter, with which adaptation device said signal can be amplified or attenuated by one level. In this way, the analog input signal is adjusted to the prescribed working range of the analog-to-digital converter used. Finally, a relationship is established between the resultant digital output signal and a digital signal which is simultaneously conditioned by means of a calibration device, as a result of which the amplification or attenuation of the analog input signal is corrected in terms of a measured range adaptation.
German Patent No. 38 20 144 describes a high-resolution A/D and D/A converter in which an amplifier with programmed amplification is connected upstream of the analog-to-digital converter. By appropriately selecting the amplifier stages, the maximum signal without reaching an overdrive level can be fed to the analog-to-digital converter. The input signal which is amplified by a specific factor in this way is multiplied, after conversion into a digital word, by the digital reciprocal value of the factor, so that the word length of the converted signal is increased. To this end, a corresponding number of amplifiers are connected in cascade and an A/D converter is connected to each amplifier output. The output signal of the amplifier which supplies the maximum signal without overdriving is fed by a selection switch to a multiplier. Finally the reciprocal value of the amplification of the amplifier chain which is connected upstream of the selected converter is fed to the multiplier.
For conditioning and further processing said measured values in digital measuring-technology systems, for reasons of cost processors are often used which have, in terms of hardware, only restricted word lengths. The binary word lengths of such processors are, as a rule, only 4, 8 or, at most, 16 bits. Thus, the problem arises that processing values, for example digital measured values which have been sampled from a technical process and have a binary word length of, for example, 16 bits, have to be further processed by a microprocessor which, in comparison, has a restricted binary word length, for example an internal data bus with only an 8-bit word length.
Such processing must therefore be carried out sequentially by the, for example, 16-bit "long" digital processing value being further processed in fragments by using a plurality of cycles of the processor. In offline systems, this computing time-intensive processing in blocks of "excess length" processing values is, as a rule, uncritical. However, propagation time problems occur in so-called online systems in which analog measured values, for example temperatures, pressures, displacement values and angular values, and much more, have to be acquired from a technical process, digitized and further processed, under certain circumstances, at a high sampli
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H.B. Bemmann et al., Anwendung adaptiver Analog-Digital-Umsetzer ini der MeBtechnik, Nachrichtentech., Elektron, Berlin 37 (1987), pp. 10-11. Y Dec. 82.
Barlow Jr. John E.
Miller Craig Steven
Siemens Aktiengesellschaft
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