Process and system for the operation of a resistive moisture sensor

A system for operating a resistive moisture sensor on a subject to be cleaned, suitable for operation on a windshield of a motor vehicle, the system providing for application of a pulsed electric signal to the sensor wherein pulses provide for sudden changes in the electric signal, the system providing for repetitive measurements of the conductivity of the moisture sensor shortly after such sudden change of signal, the system providing also for an extraction of data from the repetitive measurements as to the nature and degree of a dirtying of the subject;

• wherein the system comprises:
• a current measurement resistor connected in series with the moisture sensor;
• a computer having an analog-to-digital converter for receiving an analog signal;
• means controlled by the computer for applying a voltage across the series combination of sensor and current measurement resistor resulting in a voltage drop across the measurement resistor;
• and
• an amplifier for feeding the voltage drop as the analog signal to an analog input port of said converter;
• wherein the computer is operated by a program to detect said measurements, to establish a threshold, and to compare said measurements with the threshold.

A method for operating a resistive moisture sensor on a subject to be cleaned of material on the subject, suitable for operating a moisture sensor on a windshield of a motor vehicle, comprising the steps of:

• applying a measurement pulse comprising a voltage pulse of predetermined duration repetitively across terminals of the sensor;
• measuring the conductivity of the moisture sensor at at least two successive measurement times within said pulse duration to obtain a first conductivity measurement and a second conductivity measurement in a sequence of measurement times providing at least two measurements of a sequence of measurements;
• establishing a threshold based on a value of one of said measurements and on a difference between at least one pair of measurements in said sequence of measurements;
• adjusting a value of the threshold based on subsequent values of said measurements;
• and
• verifying that a last measurement of said measurement sequence exceeds said threshold;
• and
• wherein a verification that said last measurement of said measurement sequence exceeds said threshold is indicative of a presence of sufficient moisture on the subject to warrant a wiping of the moisture.

A method of operating a resistor moisture sensor on a subject to be wiped, the method being suitable for operating a resistive moisture sensor on the windshield of a motor vehicle, the method comprising steps of:

• feeding an electric pulsed signal to the sensor;
• performing a first measurement and a second measurement of conductivity of the sensor during a pulse of the signal, the second measurement following the first measurement;
• comparing one of said measurements with a threshold to obtain a comparison;
• outputting a drive signal based on a value of said comparison, said drive signal being suitable for actuation of a windshield cleaning system;
• establishing a relation of threshold adjustment factor based on one of said measurements and a difference between said first and said second measurements;
• and
• adjusting a value of said threshold by use of said adjustment factor.