A conductivity sensor includes a measuring circuit for measuring the electrical conductivity of a medium based upon a resistance measurement of the medium and the subsequent calculation with a factor that is referred to as a cell constant and results from the geometry of the conductivity sensor. Typically, the measuring circuits for a conductivity sensor are adjusted during the production. In the process, errors, such as amplification and zero point errors, are determined, and correction values, if any, are stored in the non-volatile memory. Such an adjustment usually occurs at room temperature, since a change in the temperature is difficult to implement during the adjustment. Such a conductivity sensor is operated at the customer's premises for a time period of many years and is there exposed to various environmental conditions, such as humidity and temperature fluctuations.
The correction values for the measuring circuit are determined at a point in time when defined environmental conditions, such as temperature, prevail. As a result of molding of the measuring circuit from, for example, epoxy resin, temperature fluctuations, or aging over a long period of operation, deviations in the measuring chain of the measuring circuit can occur. These deviations may possibly impair the specified measurement precision of the conductivity sensor.
USPTO Backgrounds
USPTO Backgrounds