基于计算机的电容式湿敏元件测试系统及应用

介绍了一种基于计算机技术的新型智能电容式湿敏元件测试系统。该系统采用计算机及单片机技术,应用两次积分复数测量法测量湿敏元件的电容值和品质因数(Q)值。该系统实现了自动化测试,具有数据处理、分析计算、记忆、图表处理等多种功能,还可同时测量湿敏元件的灵敏度、湿滞、线性度等。电容值测试精度达到±0.1pF,Q值测量精度达到±5%。     

水热腐蚀铁钝化多孔硅的湿敏特性研究

采用水热腐蚀铁钝化法在单晶硅片上生长铁钝化多孔硅(IPS)薄膜,以IPS为感湿介质制成湿敏元件。在不同湿度环境以及测试频率下,测出其电容值,得到了IPS的湿敏特性曲线。研究发现,当相对湿度从11%RH逐渐增加到95%RH的过程中,在测试频率为100Hz时,IPS湿敏元件的电容值增大幅度达1500%,电容响应时间在升湿过程和脱湿过程分别为15s和5s,并且IPS湿敏元件的温度系数在15℃到35℃的范围内较小。结果表明:IPS湿敏元件的特性包括灵敏度、响应时间以及温度系数等均优于多孔硅(PS)湿敏元件的特性。     

基于硫化物系的湿敏元件的研究

研究了Zn、Cd、Sb等系列硫化物薄膜湿敏元件的感湿特性 ,发现金属硫化物元件具有较好的湿敏特性和稳定性 ,对元件的频率特性、湿滞特性、响应 -恢复时间、阻抗、以及稳定性进行了测试 ,并对其敏感机理进行了探讨     

ZrO2:TiO2复合纳米纤维湿度传感器的直、交流特性研究

利用ZrO2:TiO2复合纳米纤维制作了特性良好的电容型湿度传感器.该湿敏元件在100 Hz测量频率下灵敏度较高,线性度较好.其电容值在11％ ～98％相对湿度范围内从20 pF变化到1.5×105 pF.文中从直流特性(伏安特性、极性反转瞬时性)和交流特性(复阻抗)的角度分析了该湿敏元件的感湿机理.利用瞬时直流极性反...     

K2O-SnO2-LiZnVO4系湿敏陶瓷特性的研究

采用共沉淀法制备出K2O-SnO2-LiZnVO4系湿敏陶瓷材料,考察了液相掺杂K 对材料湿敏特性的影响,研究了材料的灵敏度、电容特性、阻抗特性等湿敏性能.实验结果表明: K 液相掺杂为10 mol%时可使材料具有低湿电阻小,灵敏度适中的特性.测试频率对试样的阻抗-相对湿度特性曲线影响较大,100 Hz时曲线的线性度最好.试样的电容在低频范围随相对湿度的升高而增大,但高频范围几乎不随相对湿度变化.     

用复阻抗法分析纳米钛酸钡湿敏元件感湿机理

用复阻抗方法对硅衬底纳米钛酸钡湿敏元件的感湿机理进行了分析。实验测量了湿敏元件在不同相对湿度下的复阻抗特性曲线及阻抗、电容等参数随频率的变化曲线。分析出相应的等效电路,推导了等效电路有关参数,分析讨论了纳米钛酸钡湿敏元件的感湿机理。低湿时,感湿材料本身颗粒电阻和电容及吸附的少量水分子共同起作用;高湿时,吸附的水分子电离和极化起主要作用。     

应用新型电容式湿度传感器与逻辑鉴宽器结合调节空气湿度

０　前　言由各种材料制成的阻抗式湿敏元件,虽然其灵敏度高,但温度系数也大,其阻抗对温度的函数关系复杂。这给湿度传感器带来温度补偿的困难。实践证明,采用阻抗式传感器来检测湿度,检测误差大,动态特性与静态特性都不太理想。对湿度控制系统来说,湿度检测是个难点,也是关键。笔者采用新型电容式湿度传感器与逻辑鉴宽器结合,能方便而可靠地调节湿度。１　电容式湿敏元件几何结构一定的电容器,其电容量与两极间介质的介电常数成正比。而介电常数又随空气湿度变化而变化。依此原理可制成电容式湿敏元件。专门用于检测湿度的电容介…     

退火对电容型硅纳米孔柱阵列湿度传感器性能的影响

基于硅纳米孔柱阵列(Si-NPA)制备电容型湿度传感元件,并在250℃、450℃和550℃三个温度下对元件进行退火处理。测试数据显示,在测试温度低于550℃时,Si-NPA湿敏元件灵敏度随退火温度的升高而增大,但响应时间略微延长,湿滞回差略微增大;550℃退火后,元件的灵敏度急剧降低。采用场发射扫描电镜(FE-SEM)对不同温度退火的硅纳米孔柱阵列表面形貌进行观察,发现550℃退火元件的微观多孔结构发生了明显变化,即多孔结构致密化。结果表明,通过合适温度退火可以显著提高Si-NPA湿敏元件灵敏度,同时仍然保持较快的响应速度和较小的湿滞回差。     

钛酸钡湿敏元件的介电特性

制备了电阻式纳米钛酸钡湿敏元件,测试了元件的阻抗、电容,以及介电损耗特性.测试频率对元件的阻抗-相对湿度特性曲线影响较大,特别是低湿范围.100 Hz时曲线的线性度最好.元件的电容在低频范围随相对湿度的升高而增大,但高频范围几乎不随相对湿度变化.在10～105 Hz频率范围内,湿敏元件在11%～98%RH范围都出现了介电损耗的极大值,而且随着相对湿度增大,介电损耗极大值向高频方向移动.分析实验结果,在环境水分子浓度变化时,不仅电阻式湿敏元件感湿材料的电阻发生变化,介电常数也发生变化,水分子的极化也同时存在,但是其电阻随相对湿度的变化最为明显.     

电容式高分子湿敏元件敏感材料的选择

阐述了衡量电容式湿敏元件性能的主要依据,分析了电容式湿敏元件的感湿机理,并从灵敏度、湿滞、响应时间、温度系数、长期稳定性等方面,提出了电容式高分子湿敏元件敏感材料的选择方法。     

Humidity sensing and electrical properties of a composite material of nano-sized SiO2 and poly(2-acrylamido-2-methylpropane sulfonate)

A composite material of nano-sized SiO₂ and poly(2-acrylamido-2-methylpropane sulfonate) (poly(AMPS)) was used to make a humidity sensor. The infrared (IR) spectra and microstructure of the material were analyzed, and the humidity sensing and electrical properties of the sensor were measured. The sensor well responded to humidity with a relative good linearity, though it depended on the applied frequency. The temperature influence between 15 and 35 °C was −0.71 and −0.15% RH/°C at 30 and 90% RH, respectively. The sensor showed a negligible hysteresis and fast response time upon humidification and desiccation. The stability of the sensor in a highly humid and alcoholic environment increased with increasing the SiO₂ content. The activation energy for conduction reduced with water adsorption. The different impedance plots observed at low and high relative humidity suggested different sensing mechanisms of the SiO₂/poly(AMPS) composite material.     

Humidity sensor based on LiCl-doped ZnO electrospun nanofibers

The humidity sensitive characteristics of sensors fabricated from pure ZnO nanofibers and LiCl-doped ZnO composite fibers by screen-printing on ceramic substrates with carbon interdigital electrodes have been investigated. The best result is obtained for 1.2 wt% LiCl-doped sample, which exhibits high humidity sensitivity, rapid response and recovery, small hysteresis, excellent linearity, and good reproducibility. The impedance of the sensor varies more than four orders of magnitude during the whole relative humidity (RH) from 11 to 95%. The response time and recovery time of the sensor is about 3 and 6 s, respectively. These results make our product a good candidate in fabricating high performance humidity sensors.     

Highly sensitive humidity sensor at low humidity based on the quaternized polypyrrole composite film

Polypyrrole composite was fabricated by using chemical polymerization at room temperature, which was further quaternized with 1,4-bromobutane to prepare the humidity sensitive material. The electrical properties of the sensor were measured. The results showed that the quaternized polypyrrole composite film exhibited low impedance at very low humidity; the impedance value was about 780 kΩ at 11% RH and the impedance changed from 10⁶ to 10³ Ω between 11% and 95% RH, which was suitable for detection of low humidity. Moreover, the logarithm of impedance of the polypyrrole composite film varied linearly (R² = 0.9916) with relative humidity in the range of 11–95% RH. Surface and cross-sectional morphology of the films, response–recovery time and hysteresis were also measured and estimated. The sensing mechanism of the sensor was also investigated.     

Properties of humidity sensing ZnO nanorods-base sensor fabricated by screen-printing

The humidity sensitive characteristics of a sensor fabricated from flower-like ZnO nanorods by screen-printing on a ceramic substrate with Ag–Pd interdigital electrodes have been investigated. The sensor shows high humidity sensitivity, rapid response and recovery, small hysteresis, and good stability. It is found that the impedance of the sensor decreases by about five orders of magnitude with increasing relative humidity (RH) from 11 to 95%. The response and recovery time of the sensor is about 5 and 10 s, respectively. These results indicate that the flower-like ZnO nanorods can be used in fabricating high-performance humidity sensors.     

基于LabVIEW的湿度传感器的特性测试与分析

以上海仪器仪表研究所生产的ZL5型智能ICR测量仪为硬件基础,采用Agilent公司生产的82350A GPIB接口卡和GPIB电缆将测试仪与PC机连接起来,在LabVIEW开发平台下,编制了功能强大的通信、测试与处理软件,组成了一套湿度传感器的自动测试系统.该系统可以对湿敏元件的响应恢复特性、湿敏特性、频率特性、电容特性和复阻抗特性等进行实时测量,极大地提高了测试效率,减少了实验数据处理过程中主观误差.     

Humidity sensing properties of mesoporous iron oxide/silica composite prepared via hydrothermal process

Mesoporous Fe₂O₃/SiO₂ composites with various Fe/Si molar ratios were synthesized via hydrothermal route and then studied as humidity sensor materials. The best result is obtained for the sample with a Fe/Si molar ratio of 0.5, which exhibits high humidity sensitivity, rapid response and recovery, small hysteresis and excellent linearity. The impedance of the sensor varies more than four orders of magnitude during the whole relative humidity (RH) from 11 to 95%. The response time and recovery time of the sensor is about 20 and 40 s, respectively. These results make our product a good candidate in fabricating high performance humidity sensors.     

High-performance capacitive humidity sensor with novel electrode and polyimide layer based on MEMS technology

A high-performance capacitive humidity sensor based on a newly designed electrode and a polyimide (PI) layer is presented in this paper. The humidity sensor consists of a substrate with a cavity, a bottom electrode, a PI sensing layer, and a comb-shaped top electrode with branches. The cavity structure of the substrate was formed to protect the top electrode. In order to enhance the performance of the sensor, the coated PI layer was etched by using an O₂ plasma asher in accordance with the top electrode passivation. After the PI etching, the humidity sensor showed a high sensitivity of 506 fF/% RH and a fast response time of less than 6 s, which is attributed to the increased contact area between the PI layer and moisture, and shortened moisture absorption path into the PI layer. Further characterizations were carried out to measure the effect of temperature, hysteresis, and stability. The humidity sensor showed a hysteresis of 2.05% RH, little temperature dependence, and stable capacitance value with maximum 0.28% error rate for 24 h.