Abstract
Metal oxide (MOX) gas sensors show a resistive value varying in a wide range, from hundreds of kilohms up to tens of gigohms. For this reason, oscillating circuits are often used to interface these sensors. Simple oscillators need a measuring time which is directly proportional to the resistive value; when large resistive value (gigohms) occur, the output updating time is on the order of seconds. In addition, the sensor is excited with a square wave, but the variable frequency can affect the measurement accuracy. In this paper, we propose a new oscillating circuit having a limited oscillating time regardless the resistive value. This behavior is obtained by means of self-moving thresholds, the slower limiting the maximum measuring time. The proposed circuit has been simulated and experimentally tested with commercial resistors (values between 1 MΩ and 100 GΩ).
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Depari, A. et al. (2010). A New Fast-Readout Front-End for High Resistive Chemical Sensor Applications. In: Malcovati, P., Baschirotto, A., d'Amico, A., Natale, C. (eds) Sensors and Microsystems. Lecture Notes in Electrical Engineering, vol 54. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-3606-3_53
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DOI: https://doi.org/10.1007/978-90-481-3606-3_53
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