Accurate temperature control of thick film metal oxide gas sensors

To facilitate an improvement in sensor accuracy the operating temperature of a range of metal oxide gas sensors has been elevated to 300-600 degrees C utilising an accurately controlled resistive heating element. This has provided a performance enhancement as a result of the direct relationship which exists between sensor operating temperature, sensor sensitivity and specificity. This paper discusses the design and implementation of a novel controller used for the thermal control of a thick film Taguchi metal oxide gas sensor. A system model was derived and then utilised to develop and implement a suitable temperature controller in hardware. The technique was subsequently extended to an 8-element array and a comparison made between controlled and uncontrolled operation in open environments. Clearly, the implications for low power operation of multisensor metal oxide arrays and the subsequent increase in portability and sensor repeat ability may be significant.