| Humidity, as important environmental parameters, had a huge impact on industrial, agricultural and daily life. As the humidity measuring devices, humidity sensor was researched by people more and more interesting. The researchers committed to find high-performance humidity sensor that it was including high sensitivity, fast response time, small wet hysteresis, chemical and physical stability. After years of efforts, Humidity sensor was developing the new, integrated, multi-functional and intelligent.The humidity sensitive material of the traditional humidity sensor type was electrolyte, inorganic ceramic materials and organic polymer. With the development of nanotechnology, nanometer material with its unique physical and chemical performance was attracted more and more concern. Among numerous of nano-materials, TiO2 with its unique chemical stability, large specific surface area, had a broad application prospect in humidity sensitive sensing. In this paper, TiO2 as the research object, humidity sensor was was designed and fabricated. humidity measurement system was built. Through these works, some results were obtained.TiO2 nanorod array was grown directly between Au interdigital electrodes by the hydrothermal method. The nanorods were grown vertical along the lateral surface of Au electrodes to be prepared for humidity sensor. The nanorod array was a kind of loose and porous material, about 20nm in diameter,500nm in length. The resistance(R) and capacitance(C) changed range of the sensor had almost three orders of magnitude tested in humidity range of 6%RH-97%RH. The impedance (Z) changed range of the sensor had almost two orders of magnitude. The resistance response time and recovery time of the sensor was 1～3s and 5～6s, respectively. The capacitance response time and recovery time of the sensor was 21～23s and 1～3s, respectively. The article believed that the nanorod array structure had a lot of ordered channels of water vapor and was favorable to the entrance and exit of water molecule. Humidity sensor has good sensitivity and response speed.Nano-humidity sensor was used in humidity measurement system. Temperature and humidity information were real-time inspection, USB storage, query and other functions. Based on the electrical properties of the TiO2 nano-humidity sensor, RC oscillation circuit was applied in this paper to make the humidity signal changed to frequency signal. And then frequency was measured by equal precision frequency principle. The top of hardware architecture system was designed by SOPC Builder. By adding instruction, in NIOSⅡ environment for software design, realized the LCD display controll and USB storage controll.In this way, the problem of the resource consumption too much was solved in verilog progrom design. Transfer function of frequency-humidity was segmenting fitted by Matlab. Function was calculated in the NIOS II to get the humidity measurements.Measurement results show that, the humidity measurement system had good accuracy and stability in medial and high humidity. The USB storage was used in the humidity system that it was not limited to the upper computer. the humidity measurement system can freely move, convenient for field deterction. There was a big error in low humidity, and need to improve. In general, this system had realized the humidity real-time measurement, display, storage and query functions. The system could achieve the desired design goals. |
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