Self-calibration of a polymer-based humidity sensor

A controller comprising;

• memory;
• and
• a processor coupled to the memory and configured to:
• calculate a rising temperature condition value as a function of a difference between a first temperature measurement and a second temperature measurement, the first and second temperature measurements taken by a temperature sensor while a heating element is operated;
• compare the temperature condition value to a threshold value;
• calculate a falling humidity condition value as a function of a difference between a first relative humidity measurement and a second relative humidity measurement, the first and second relative humidity measurements taken by a relative humidity sensor while the heating element is operated;
• determine a first offset value based on the rising temperature condition value and the falling humidity condition value;
• determine an operating voltage of the heating element;
• divide the first offset value by a divisor value according to the operating voltage to generate a second offset value;
• and
• calibrate the relative humidity sensor using the second offset value.

A system comprising:

• a relative humidity sensor formed over a semiconductor substrate;
• a temperature sensor formed over the semiconductor substrate;
• a heating element formed over the semiconductor substrate;
• and
• a controller coupled to the relative humidity sensor, the temperature sensor, and the heating element, the controller configured to:
• control operation of the heating element;
• receive first and second temperature measurements taken during a time interval of operating the heating element;
• calculate a rate of increase of temperature as a function of a difference between the first and second temperature measurements over the time interval;
• determine a first relative humidity measurement that was taken by the relative humidity sensor at a time when the rate of change increase of temperature is less than a threshold value;
• calculate a humidity falling slope value as a function of a difference between the first relative humidity measurement and a second relative humidity measurement over the time interval, the first and second relative humidity measurements taken while operating the heating element;
• determine a first offset value based on the rate of increase of temperature and the humidity falling slope value;
• determine an operating voltage of the heating element;
• divide the first offset value by a divisor value according to the operating voltage to generate a second offset value;
• and
• calibrate the relative humidity sensor using the second offset value.