Enhanced offset compensation technique for thermal conductivity sensing of a gas concentration sensor

A gas concentration sensor configured to measure a gas concentration of a target gas, comprising:

• a reference chamber configured to contain a reference gas;
• a measurement chamber configured to contain the target gas that is different from the reference gas;
• and
• a measurement circuit configurable in a calibration mode and an operational mode, the measurement circuit comprising:
• a resistive bridge circuit comprising a plurality of resistive elements, including at least one first resistive element arranged in the reference chamber and at least one second resistive element arranged in the measurement chamber,
• wherein the resistive bridge circuit is configured to receive an input voltage and generate a measurement signal based on the input voltage,
• wherein, during the calibration mode, the input voltage has a first voltage value at which the resistive bridge circuit has a negligible sensitivity to thermal conductivity such that the measurement signal is representative of an offset,
• wherein, during the operational mode, the input voltage has a second voltage value at which the resistive bridge circuit is sensitive to thermal conductivity with an operational sensitivity such that the measurement signal is representative of a thermal conductivity of the target gas,
• wherein the measurement circuit is configured to, during the calibration mode, measure the offset based on the measurement signal, and
• wherein the measurement circuit is configured to, during the operational mode, subtract the offset from the measurement signal to generate a compensated measurement signal.

A method of calibrating an offset of a gas concentration sensor, the method comprising:

• configuring a measurement circuit of the gas concentration sensor in a calibration mode;
• applying, during the calibration mode, a first input voltage to a resistive bridge circuit of the gas concentration sensor to cause the resistive bridge circuit to generate a first measurement signal, wherein, based on the first input voltage, the resistive bridge circuit has a negligible sensitivity to thermal conductivity such that the first measurement signal is representative of the offset;
• configuring, during the calibration mode, a compensation component of the measurement circuit with the offset derived from the first measurement signal;
• configuring the measurement circuit of the gas concentration sensor in an operational mode;
• applying, during the operational mode, a second input voltage to the resistive bridge circuit of the gas concentration sensor to cause the resistive bridge circuit to generate a second measurement signal, wherein the second input voltage is greater than the first input voltage, and wherein, based on the second input voltage, the resistive bridge circuit is sensitive to thermal conductivity with an operational sensitivity such that the second measurement signal is representative of a thermal conductivity of a measurement gas;
• and
• subtracting, during the operational mode, the offset configured at the compensation component from the second measurement signal to generate a compensated measurement signal.