Temperature based rapid SAW humidity sensor

This paper investigates the effect of temperature on the sensitivity of a thin-film Polyvinyl alcohol (PVA) based SAW humidity sensor. A PVA coated 433.92 MHz SAW resonator-based humidity sensor was fabricated and tested with different levels of humidity (0.5 to 95% RH) at different operating temperatures (10°C to 70°C). The sensor response was recorded through in-house developed data acquisition software and it was observed that PVA thin film coated SAW sensor shows the maximum sensitivity for trace level moisture detection at a lower temperature (≤10 °C). The sensor sensitivity has been recorded >400Hz/% RH for trace level detection (0.5–30% RH). It has been observed that sensor sensitivity deteriorates when temperature increased to 40 °C from 10 °C. The sensor has a fast response (~1s) and recovery time (<3s) for trace level humidity detection. The proposed sensor can be used in many applications, including fabrication of electronic devices, IC fabrication, pharmaceutical, textile industries, food processing, semiconductor device fabrication, and packaging

Health monitoring of pavement systems using smart sensing technologies

Pavement undergoes a process of deterioration resulting from repeated traffic and/or environmental loading. By detecting pavement distress and damage early enough, it is possible for transportation agencies to develop more effective pavement maintenance and rehabilitation programs and thereby produce significant cost and time saving. Structural Health Monitoring (SHM) has been conceived as a systematic method for assessing the structural state of pavement infrastructure systems and documenting their condition. Over the past several years, this process has traditionally been accomplished through the use of wired sensors embedded in bridge and highway pavement. However, the use of wired sensors has limitations for long-term SHM and presents other associated cost and safety concerns. Recently, Micro-Electromechanical Systems (MEMS) and Nano-Electromechanical Systems (NEMS) have emerged as advanced/smart-sensing technologies with potential for cost-effective and long-term SHM. To this effect, a study has thus been initiated to evaluate the off-the-shelf MEMS sensors and wireless sensors, identify their limitations, and demonstrate how the acquired sensor data can be utilized to monitor and assess concrete pavement behavior. The feasibility of implementing a wireless communication system into a MEMS sensor was also investigated. Off-the-shelf MEMS sensors and wireless sensors were deployed in a newly constructed concrete highway pavement. During the monitoring period, the temperature, moisture, and strain profiles were obtained and analyzed. The monitored data captured the effects of daily and seasonal weather changes on concrete pavement, especially, early-age curling and warping behavior of concrete pavement. These sensors, however, presented issues for long-term operation, so to improve performance, a ZigBee protocol-based wireless communication system was implemented for the MEMS sensors. By synthesizing knowledge and experience gained from literature review, field demonstrations, and implementation of wireless systems, issues associated with sensor selection, sensor installation, sensor packaging to prevent damage from road construction, and monitoring for concrete pavement SHM are summarized. The requirements for achieving Smart Pavement SHM are then explored to develop a conceptual design of smart health monitoring of both highway and airport pavement systems for next-generation pavement SHM. A cost evaluation was also performed for traditional as well as MEMS sensors and other potential smart technologies for SHM