Managing dynamic thermal exchanges in commercial semiconduting gas sensors

Thermal sensitivity of commercial gas sensors induces errors of several hundreds of ppm when used in the quantification of volatile compounds. We have quantified the effects of dynamic thermal exchanges which are very important because of the temperature dependence of the conductance of the sensor and non-linearity of the response. Even in manufactured electronic noses the simplistic approach of supplying the heater wire with a constant voltage is used for heating the sensor, because the lack of space for a temperature sensor inside the gas sensor. Thus, a new method was developed to measure the actual temperature. The use of temperature regulation resulted in an improvement of the temperature stability and reproducibility in real laboratory conditions (variation is within one degree). Use of PWM modulation for regulation allows high efficiency. Temperature regulation allows a very stable actual temperature, virtually independent of external parameters when temperature programming allows easy temperature setting, fast changes of the set point and fast temperature steps, sweeping or modulation within an experiment. Set point value is always reached in less than 3 s.