Patent ID: 8441646

Claim:
A sensor device for detecting a turbidity of wash liquor, comprising: an optical transmitter including an LED for producing illumination responsive to a control signal; an optical receiver including a phototransistor for producing an output voltage responsive to illumination received from the transmitter, wherein the wash liquor to be tested flows between the optical transmitter and the optical receiver; and an electronic control and evaluation circuit for controlling the optical transmitter and receiving the output voltage from the optical receiver to (a) carry out a reference measurement by means of the optical transmitter and the optical receiver to determine a turbidity gradient by determining a change in output voltage of the receiver as a linear function of the luminosity emitted by the transmitter in order to determine a reference measured value of a turbidity gradient of a reference liquid; (b) carry out a turbidity measurement on the wash liquor to be measured by means of the optical transmitter and the optical receiver to determine a turbidity gradient by determining a change in output voltage of the receiver as a linear function of the luminosity emitted by the transmitter in order to determine a test measured value of the turbidity gradient of wash liquor; (c) relate the reference measured value to the test measured value as a function of the optical transmitter control signal and the voltage output from the optical receiver by calculating the ratio of reference turbidity to wash liquor turbidity; and (d) determine a characteristic value as a percentage of absolute level of turbidity for a determined turbidity of the wash liquor therefrom and transmit the characteristic value as a measurement signal.