In connection with SIGRIST instruments, linearization describes the piecewise linear approximation between the value measured and the value displayed. During factory calibration (calibration (turbidity)), a linearization table is provided in the measuring instruments, which describes the connection between the value measured and the concentration of the primary standard (e.g. formazine). Analogously to the internal linearization table (calibration (turbidity)), further linearization curves can be provided which display the concentration of the primary standard as customized values. This allows the measurement to be adapted to process specific applications.