A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer

In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm−1), a low detection limit (0.2 ppm) and a rapid response time (35 s)

Home-made Detection Device for a Mixture of Ethanol and Acetone

A device for the detection and determination of ethanol and acetone wasconstructed, consisting of a packed column, a chamber with a sensor head, 2 dc powersupplies, a multimeter and a computer. A commercially available TGS 822 detector head(Figaro Company Limited) was used as the sensor head. The TGS 822 detector consists of aSnO2 thick film deposited on the surface of an alumina ceramic tube which contains aheating element inside. An analytical column was coupled with the setup to enhance theseparation of ethanol and acetone before they reached the sensor head. Optimum systemconditions for detection of ethanol and acetone were achieved by varying the flow rate of thecarrier gas, voltage of the heating coil (VH), voltage of the circuit sensor (VC), loadresistance of the circuit sensor (RL) and the injector port temperature. The flow of the carriergas was 15 mL/min; the circuit conditions were VH = 5.5 V, VC = 20 V, RL = 68 k ; and theinjection port temperature was 150°C. Under these conditions the retention times (tR) forethanol and acetone were 1.95 and 0.57 minutes, respectively. Calibration graphs wereobtained for ethanol and acetone over the concentration range of 10 to 160 mg/L. The limitsof detection (LOD) for ethanol and acetone were 9.25 mg/L and 4.41 mg/L respectively

Home-made Detection Device for a Mixture of Ethanol and Acetone

A device for the detection and determination of ethanol and acetone wasconstructed, consisting of a packed column, a chamber with a sensor head, 2 dc powersupplies, a multimeter and a computer. A commercially available TGS 822 detector head(Figaro Company Limited) was used as the sensor head. The TGS 822 detector consists of aSnO2 thick film deposited on the surface of an alumina ceramic tube which contains aheating element inside. An analytical column was coupled with the setup to enhance theseparation of ethanol and acetone before they reached the sensor head. Optimum systemconditions for detection of ethanol and acetone were achieved by varying the flow rate of thecarrier gas, voltage of the heating coil (VH), voltage of the circuit sensor (VC), loadresistance of the circuit sensor (RL) and the injector port temperature. The flow of the carriergas was 15 mL/min; the circuit conditions were VH = 5.5 V, VC = 20 V, RL = 68 k ; and theinjection port temperature was 150°C. Under these conditions the retention times (tR) forethanol and acetone were 1.95 and 0.57 minutes, respectively. Calibration graphs wereobtained for ethanol and acetone over the concentration range of 10 to 160 mg/L. The limitsof detection (LOD) for ethanol and acetone were 9.25 mg/L and 4.41 mg/L respectively