Dual Gas Sensor Research Articles

CO and CO2 dual-gas detection based on mid-infrared wideband absorption spectroscopy

A dual-gas sensor system is developed for CO and CO2 detection using a single broadband light source, pyroelectric detectors and time-division multiplexing (TDM) technique. A stepper motor based rotating system and a single-reflection spherical optical mirror are designed and adopted for realizing and enhancing dual-gas detection. Detailed measurements under static detection mode (without rotation) and dynamic mode (with rotation) are performed to study the performance of the sensor system for the two gas samples. The detection period is 7.9 s in one round of detection by scanning the two detectors. Based on an Allan deviation analysis, the 1σ detection limits under static operation are 3.0 parts per million (ppm) in volume and 2.6 ppm for CO and CO2, respectively, and those under dynamic operation are 9.4 ppm and 10.8 ppm for CO and CO2, respectively. The reported sensor has potential applications in various fields requiring CO and CO2 detection such as in the coal mine.

Platinum Coating on an Ultrathin InN Epilayer as a Dual Gas Sensor for Selective Sensing of Ammonia and Acetone by Temperature Modulation for Liver Malfunction and Diabetes Applications

A platinum coating on an ultrathin InN resistive gas sensor was fabricated for the selective sensing of ammonia and acetone gas for liver malfunction and diabetes applications by using a temperature modulation technique. We use a cyclic temperature profile in the InN gas sensor heater, where the temperature varies from 200°C to 0°C and from 0°C to 200°C in increments of 50°C. Therefore, a different current variation response is measured on an InN epilayer for 5 ppm ammonia and 5 ppm acetone gas, respectively, because ammonia and acetone gas behave differently in the cyclic temperature profile. When ammonia and acetone gas are exposed in background air, the variation in the response of the current in different temperature regions is given as 2.5% for acetone gas and 7.85% for ammonia gas between 100°C to 150°C, and 12% for acetone gas and 8.85% for ammonia gas between 150°C to 200°C. Therefore, the temperature region 100°C to 150°C is suitable for selectively sensing ammonia gas for determining liver malfunction. The temperature range between 150°C to 200°C is suitable for selectively sensing acetone gas for the diabetes monitoring applications.

Silicon photonic dual-gas sensor for H2 and CO2 detection.

We report a silicon photonic dual-gas sensor based on a wavelength-multiplexed microring resonator array for simultaneous detection of H2 and CO2 gases. The sensor uses Pd as the sensing layer for H2 gas and a novel functional material based on the Polyhexamethylene Biguanide (PHMB) polymer for CO2 gas sensing. Gas sensing experiments showed that the PHMB-functionalized microring exhibited high sensitivity to CO2 gas and excellent selectivity against H2. However, the Pd-functionalized microring was found to exhibit sensitivity to both H2 and CO2 gases, rendering it ineffective for detecting H2 in a gas mixture containing CO2. We show that the dual-gas sensing scheme can allow for accurate measurement of H2 concentration in the presence of CO2 by accounting for the cross-sensitivity of Pd to the latter.

Molybdenum trioxide nanopaper as a dual gas sensor for detecting trimethylamine and hydrogen sulfide

The dual function of a free-standing, flexible, and semi-transparent MoO3nanopaper sensor to detect TMA and H2S in a highly selective manner.

Infrared Dual-Gas CH4/C2H6Sensor Using Two Continuous-Wave Interband Cascade Lasers

An infrared dual-gas sensor system for the simultaneous detection and monitoring of methane (CH 4 ) and ethane (C 2 H 6 ) at parts-per-billion by volume (ppbv) concentration levels was developed using two room temperature, distributed feedback interband cascade lasers, and two miniature multipass cells with an effective absorption length of 54.6 m. Laser direct absorption spectroscopy was used to detect CH 4 utilizing the 3038.5-cm -1 absorption line, and second-harmonic wavelength modulation spectroscopy method was used to detect C 2 H 6 using the 2996.88-cm -1 absorption line. The 1σ CH 4 detection limit is ~2.7 ppbv with a 1-s averaging time and exhibits a minimum value of ~1.7 ppbv for a 9-s averaging time; the 1σ C 2 H 6 detection limit is ~2.6 ppbv with a 3.4-s averaging time and shows an optimum averaging time of 65 s corresponding to a stability of ~0.36 ppbv. Using the dualgas sensor system, 24 h monitoring of the two atmospheric gases was performed in the Greater Houston area, TX, USA.

Mid-infrared dual-gas sensor for simultaneous detection of methane and ethane using a single continuous-wave interband cascade laser.

A continuous-wave (CW) interband cascade laser (ICL) based mid-infrared sensor system was demonstrated for simultaneous detection of atmospheric methane (CH4) and ethane (C2H6). A 3.337 µm CW ICL with an emitting wavenumber range of 2996.0-3001.5 cm-1 was used to simultaneously target two absorption lines, C2H6 at 2996.88 cm-1 and CH4 at 2999.06 cm-1, respectively. The sensor performance was first evaluated for single-gas detection by only targeting the absorption line of one gas species. Allan deviations of 11.2 parts per billion in volume (ppbv) for CH4 and 1.86 ppbv for C2H6 with an averaging time of 3.4 s were achieved for the detection of these two gases. Dual-gas detection was realized by using a long-term scan signal to target both CH4 and C2H6 lines. The Allan deviations increased slightly to 17.4 ppbv for CH4 and 2.4 ppbv for C2H6 with an averaging time of 4.6 s due to laser temperature and power drift caused by long-term wavelength scanning. Measurements for both indoor and outdoor concentration changes of CH4 and C2H6 were conducted. The reported single ICL based dual-gas sensor system has the advantages of reduced size and cost compared to two separate sensor systems.

A selective AQS system with artificial neural network in automobile

An air quality sensor (AQS) is one of very useful sensors among various sensor devices in automobile. An AQS, located near a fresh air inlet, serves to reduce the amount of pollution entering a vehicle cabin through the HVAC (heating, ventilating, and air conditioning) system by sending a signal to close the fresh air inlet door/ventilation flap when the vehicle enters a high-pollution area. One chip sensor module, which included a dual gas sensor, humidity sensor and temperature sensor, was developed for an AQS system in automobile. The dual gas sensor combined a reducing gas-sensing element with an oxidizing gas-sensing element on the same substrate to detect toxic oxidizing gases and reducing gases simultaneously. With this sensor module, a peripheral interface controller (PIC) microcontroller was designed with a back propagation neural network to reduce the detection error when the motor vehicles pass through an area with a complicated mixture of gases. The signal from the neural network was modified to give a control signal for the inlet of automobile and to display the outdoor gas environment on the driver's panel or to alert the driver of the dangerous situation.