| 摘要 |
In a field device comprising a signal processing unit (3) that generates a digital measurement, control or regulation signal (4), and comprising an output stage (5) that converts the digital measurement, control or regulation signal (4) into an analog voltage or current signal (I), a monitoring device (10) is provided which comprises - a measuring device (11) that detects the analog voltage or current signal (I) and converts the signal to a digital voltage or current measurement signal (13), - a first digital low-pass filter (15) for filtering the digital measurement, control or regulation signal (4), - a second digital low-pass filter (16) having the same cut-off frequency as that of the first digital low-pass filter (15), said second filter filtering the digital voltage or current measurement signal (13), - a comparator (19) downstream of the low-pass filters (15, 16), said comparator comparing the low-pass filtered digital signals (17, 18) with one another and - an evaluation device (22) that generates an error message (23) when the deviation between the compared signals (17, 18) exceeds a pre-determined level. |
