The present invention relates to a method for the operation of a pressure measuring device for the measurement of the pressure in a system through which fluid flows, in particular in an extracorporeal circuit of a medical unit, with the pressure measuring device having a measuring chamber which is bounded by a flexible membrane, through which fluid flows in the operation of the system or which is filled with fluid and also having a pressure sensor connected to the membrane for the purpose of pressure measurement, with the method including the following steps not requiring any intervention of the staff: a. increasing the pressure in the measuring chamber (12) to a pressure value at which the membrane (13) is at least slightly outwardly curved relative to the measuring chamber (12) in the state not connected to the pressure sensor (14) or determining such a pressure value; b: separating the membrane (13) of the measuring chamber (12) from the pressure sensor (14); c. joining together the membrane (13) of the measuring chamber (12) and of the pressure sensor (14) such that the membrane (13) of the measuring chamber (12) contacts the pressure sensor (14); and d. repeating the steps a. to c. at predetermined intervals and/or on the occurrence of an error case.