Patent ID: 7358744

Claim:
A method for testing the serviceability of two-wire transducers in automation engineering that output a measurement signal as an injected DC loop current via a two-wire line, and whose active components are supplied with electrical power via the same two-wire line, wherein the DC loop current (I S ) is increased, independently of the measurement signal, from a minimum value towards a maximum value (I SM ), and an input voltage (U E ) across the internal resistance ( 110 , 120 ) of the transducer ( 100 ) is measured in the process the input voltage (U E ) is compared with a definable threshold value (U ES ) that is greater than a minimum input voltage (U EM ) required to maintain serviceability, and the DC loop current (I S ) is reduced until the input voltage (U E ) reaches at least the definable threshold value (U ES ), and a signal is given if the input voltage (U E ) falls below the threshold value (U ES ) before the DC loop current (I S ) has reached its maximum value (I SM ).