In this research, a highly sensitive and selective hydrogen gas sensor was developed based on Cu-doped SnO2. Sensing characteristics were compared based on SnO2 doped with different concentrations of Cu, and the highest sensitivity and fastest response time were shown when 3% Cu was contained. A 3D structure was formed using a polystyrene to increase the surface-to-volume ratio, which allows more oxygen molecules to bond with the surface of the SnO2 sensing material. Extremely increased sensitivity was observed as compared to the planar structure. A temperature sensor and micro-heater were integrated into the sensor, and the surface temperature was maintained constant regardless of external influences. In addition, an electronic sensor interface was developed for the efficient analysis of real-time data. The developed sensor was wire-bonded to the flexible printed circuit board (FPCB) cable and connected with the sensor interface. Sensitivity and linearity measured based on the developed sensor and interface system were analyzed as 0.286%/ppm and 0.98, respectively, which were almost similar to the results observed by a digital multimeter (DMM). This indicates that our developed sensor system can be a very promising candidate for real-time measurement and can be applied in various fields. The enhanced sensitivity of 3% doped SnO2 toward hydrogen is attributed to the huge number of oxygen vacancies in the doped sample.

Reduced graphene oxide and molybdenum disulfide (rGO:MoS 2 ) are the most representative two-dimensional materials, which are promising for a humidity sensor owing to its high surface area, a large number of active sites, and excellent mechanical flexibility. Herein, we introduced a highly sensitive and stable rGO:MoS 2 -based humidity sensor integrated with a lowpower in-plane microheater and a temperature sensor, directly insertable to transformer insulating oil, and analyzed by a newly developed customized sensor interface electronics to monitor the sensor's output variations in terms of relative humidity (RH) concentration. rGO:MoS 2 sensing materials were synthesized by simple ultrasonication without using any additives or additional heating and selectively deposited on titanium/platinum (Ti/Pt) interdigitated electrodes on a SiO 2 substrate using the drop-casting method. The significant sensing capability of p−n heterojunction formation between rGO and MoS 2 was observed both in the air and transformer insulating oil environment. In air testing, the sensor exhibited an immense sensitivity of 0.973 kΩ/%RH and excellent linearity of ∼0.98 with a change of humidity from 30 to 73 %RH, and a constant resistance deviation with an inaccuracy rate of 0.13% over 400 h of continual measurements. In oil, the sensor showed a high sensitivity of 1.596 kΩ/%RH and stable repeatability for an RH concentration range between 34 and 63 %RH. The obtained results via the sensor interface were very similar to those measured with a digital multimeter, denoting that our developed total sensor system is a very promising candidate for realtime monitoring of the operational status of power transformers.

cause significant damage to humans. ≈4%-75% of the hydrogen content in air is combustible, therefore real-time monitoring of hydrogen leakages is essential to prevent potentially catastrophic events in practical applications. As previously reported in the literature, the hydrogen is generated in transformer insulating oil due to local heating, corona, and arcing. [1][2][3] Gas chromatography and photoacoustic spectroscopy are the typically used methods to measure the concentration of hydrogen leaking out through a ultrafine porous filter from the insulating oil near the drain of a transformer, but the sensor systems involved are bulky, too complex, expensive, and a significant amount of time is required to obtain the final results. Various types of hydrogen sensors have been reported in the literature with different operation mechanisms and sensing materials, including resistance type, [4][5] optical fiber, [6][7][8] electrochemical-based type, [9] and methods using surface acoustic wave (SAW) technology. [10][11][12][13] Most available resistive types of hydrogen sensors usually operate at high temperatures which precludes their commercialization. The high operating temperature of resistive based hydrogen sensors can also lead to the explosive hazards and energy consumption. Among various types of gas sensors, in particular, SAW-based hydrogen gas sensors have drawn attention owing to their high sensitivity, room temperature operation, stability, and low minimum detection level. The sensing mechanism of the SAW sensor is based on the adsorption of target gas molecules on the surface of sensing materials which induces changes in the mass (mass loading), conductivity (electric loading), and elasticity (elastic loading) of sensing film deposited in the propagation path. Any changes, such as mass, resistance, and elastic properties of sensing material lead to modification of SAW propagation properties, resulting in a frequency shift of SAW sensors. Previous studies have shown that mass, electric, and elastic loading are the three factors likely to contribute to the frequency shift of SAW-based sensors. [14] Moreover, several factors may concurrently contribute to the frequency shift of SAW-based sensors. Therefore, it is important to study the contribution of each factor to better understand the detection mechanism for the production of high performance SAW A surface acoustic wave (SAW)-based hydrogen sensor and its corresponding interface electronics have been developed to measure the hydrogen concentration in air at room temperature. Two SAW delay lines with center frequencies of 284 and 284.3 MHz are employed for the sensor system to eliminate any environmental disturbances emerging from temperature and humidity variations on a sensor output. A beehive-configured and Cu-doped SnO 2 nanostructure is used as a hydrogen-sensitive material to have a high surface to volume ratio, high sensitivity, and selectivity for the target hydrogen. The smallest frequency difference detectable in our sensor system including oscil...

No abstract

No abstract