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.