Field device for process automation
First Claim
1. A field device for process automation, comprising:
- a signal processing device configured to generate a digital measurement, control or regulation signal;
an output stage configured to convert the digital measurement, control or regulation signal into a corresponding low-frequency analog voltage or current signal; and
a monitoring device comprising;
a measuring device configured to detect and convert the analog voltage or current signal into a digital voltage or current measurement signal;
a first digital low-pass filter configured to filter the digital measurement, control or regulation signal, a cut-off frequency of the low-pass filter being lower than the cut-off frequency of the output stage;
a second digital low-pass filter having a same cut-off frequency as the first digital low-pass filter and configured to filter the digital voltage or current measurement signal;
a comparator arranged downstream of the low-pass filters and configured to compare the low-pass-filtered digital measurement, control or regulation signal and the low-pass-filtered digital voltage or current measurement signal with one another; and
an evaluation device arranged downstream of the comparator and configured to generate an error message if a difference between the low-pass-filtered digital measurement, control or regulation signal and the low-pass-filtered digital voltage or current measurement signal exceeds a predefined amount.
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Accused Products
Abstract
A field device comprising a signal processing unit that generates a digital measurement, control or regulation signal, and comprises an output stage that converts the digital measurement, control or regulation signal into an analog voltage or current signal, The field device also includes a monitoring device which comprises a measuring device that detects the analog voltage or current signal and converts this signal into a digital voltage or current measurement signal, a first digital low-pass filter for filtering the digital measurement, control or regulation signal, a second digital low-pass filter having the same cut-off frequency as that of the first digital low-pass filter, a comparator downstream of the low-pass filters, and an evaluation device that generates an error message when the deviation between the compared signals exceeds a pre-determined level.
10 Citations
10 Claims
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1. A field device for process automation, comprising:
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a signal processing device configured to generate a digital measurement, control or regulation signal; an output stage configured to convert the digital measurement, control or regulation signal into a corresponding low-frequency analog voltage or current signal; and a monitoring device comprising; a measuring device configured to detect and convert the analog voltage or current signal into a digital voltage or current measurement signal; a first digital low-pass filter configured to filter the digital measurement, control or regulation signal, a cut-off frequency of the low-pass filter being lower than the cut-off frequency of the output stage; a second digital low-pass filter having a same cut-off frequency as the first digital low-pass filter and configured to filter the digital voltage or current measurement signal; a comparator arranged downstream of the low-pass filters and configured to compare the low-pass-filtered digital measurement, control or regulation signal and the low-pass-filtered digital voltage or current measurement signal with one another; and an evaluation device arranged downstream of the comparator and configured to generate an error message if a difference between the low-pass-filtered digital measurement, control or regulation signal and the low-pass-filtered digital voltage or current measurement signal exceeds a predefined amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification