A Low-Cost Electronic Interface for Electrochemical and Semiconductor Gas Sensors

Abstract

A low-cost interface circuit, suitable for both electrochemical and semiconductor sensors for gas detection, is described. The proposed solution offers a wide range of measurement, as well as high sampling rate, on the order of 25 ms, thus facilitating the monitoring of the sensor behavior in the presence of fast transients. The presented front end has a 3.3 V single-supply and a time-coded digital signal output; thus, it is suitable to be directly interfaced to, or integrated with, a microcontroller for the management of the measurement process. Experimental results, conducted using a discrete component prototype and sample resistors emulating the sensor, have shown a maximum linearity error in the estimation of the sensor current or resistance of about 5 % over a measurement range of seven decades, with a maximum measurement time of 25 ms. Further tests with real sensors have confirmed the capability of the front end of acquiring fast sensor transients, thus demonstrating the validity of the proposed approach.