A Very Large Dynamic Range Integrated Interface Circuit for Heterogeneous Resistive Gas Sensors Matrix Read-Out

In this chapter we present a low-cost multiplexed interface circuit based on a resistance-to-time converter suitable for the complete read-out of a 5x5 gas sensors matrix. The front-end circuit includes a bias branch, a continuous time integrator, a couple of discriminators, a control logic and 20 sets of analog multiplexers. Low-cost feature is achieved by means of the fact that the interface circuit is shared between different read-out configurations and that no calibration or bulky auto-ranging are mandatory. The worst case linearity error that is about 0.3%, when using a single fixed integrating capacitor. The presented read-out circuit performance satisfies the requirements of most environmental gas monitoring applications for which a precision better than 1% is enough in order to be sure to detect every gas type of interest with adequate accuracy. © 2012 Springer Science+Business Media, LLC.