Method for determining a measured value of a measurement quantity in process
automation technology in a liquid or gaseous medium by means of an optical sensor, which has at least one
transmitter (17.1) for sending
transmitted light with at least two wavelengths (1-7), and a
receiver (17.2) associated with the
transmitter (17.1) for receiving received light, comprising the steps: - Taking a sample (13) of the medium (15), - Mixing the sample (13) with one or more reagents (16), - Applying an
excitation signal to the
transmitter (17.1) to generate the
transmitted light, wherein the
transmitted light is converted into the received light by interaction, in particular by absorption, with the mixed sample (13) depending on the
measured quantity, - Generating a
receiver signal using the
receiver (17.2) from the converted received light, - Determining the measured value based on the receiver
signal and a
calibration function, characterized by the fact that The aging of the reagents is taken into account when determining the measured value. In particular, the
calibration function includes a term that accounts for aging. the reagents taken into account, where the
calibration function is created using a
kernel method, where the
kernel method is the
Support Vector Machine or the Kernel Fisher
discriminant, where the measured value c(x) is given by c ( x ) = a 0 + ∑ i = 1 N ai ⋅ k ( x , xi ) is calculated using the kernel function k ( x , xi ) = exp ( − μ | | xi − x | | 2 ) , with x a
data vector comprising the receiver
signal of at least two wavelengths, x i Support vectors, a0, ai coefficients, µ is a kernel parameter, and N is the number of support vectors as a natural number, in particular between 50 and 300.