Method for checking the operability of measuring transducers

A method for checking an operability of two-wire measuring transducers in automation technology which output a measurement signal as an impressed loop direct current via a two-wire line and active assemblies of which are supplied with electrical energy via the two-wire line, the method comprising:

• measuring the loop direct current and an input voltage of the measuring transducer;
• increasing the loop direct current in a range from a minimum value to a maximum value independently of the measured value, while measuring the input voltage of the measuring transducer;
• storing the measured values of the input voltage at selected measuring points of the loop direct current as an individual signature of the measuring transducer;
• during ongoing operation, measuring the input voltage at connection terminals of the two-wire line via an internal resistance of the measuring transducer at a prevailing loop direct current and recursively comparing that with the signature at the same loop direct current;
• and
• triggering a predefined reaction of the measuring transducer as soon as the input voltage at the connection terminals of the two-wire line leaves a predefined tolerance via the internal resistance of the measuring transducer at a prevailing loop direct current.