Development of integrated microsystem for hydrogen gas detection

摘要

A low-power microelectromechanical system-based metal-oxide gas sensor along with integrated signal conditioning unit is presented in this study to detect and quantify the variation of Hn₂ngas concentrations. The interface circuit controls the sensor operating temperature, measures the Hn₂ngas concentration, contributes a user-friendly interface and can be used with any suitable sensor network. A PIC16F877A microcontroller has been used for this purpose. The temperature of the sensors was stabilised by controlling the actuating voltage of the microheater. Temperatures of the microheater depend on the output voltage of the digital-to-analogue converter (DAC) and were measured by sampling the heater resistance through the use of a voltage divider and analogue-to-digital converters (ADCs). A microcontroller accordingly adjusts the output of DAC's in order to apply the appropriate steering voltage to the heaters. The method employed to measure the concentration of gases is to sample the voltage drop over the resistances of the sensors by ADCs. Alarming system for safety measure was also implemented in this design. The preventive action was taken by introducing an additional feature of wireless communication by sending short message service via global system for mobile modem to the designated emergency number.