Method and device for the automatic calibration of measuring and indicating appliances for the determination of partial pressure of a gas

摘要

The method and the device based on it for the automatic calibration of measuring and indicating appliances used for the measurement and indication of the oxygen partial pressure in connection with polarographic sensors provide that a variable polarization voltage supplied by a polarization voltage generator (2), controlled by a central processor (4), is applied to a polarographic sensor (1). The resulting measuring signals of the sensor (1), after analog-digital conversion, are stored in a read-write memory (8). By comparing these with the desired current values stored in a read-only memory (7) the central processor (4) determines the theoretical residual current deviation from the zero value, which in turn is stored. The operating point is fixed at the point of the lowest slope within the operating range of the characteristic line. The theoretical value of the oxygen partial pressure is extrapolated to 100% relative humidity for the chosen sensor temperature with the aid of a signal proportional to the air pressure. The automatic calibration completely relieves the appliance user of the tedious and time-consuming calibration procedure.