Font Size: a A A

Study On The Ambient Effects On The High-Performance Mems Wind Sensors

Posted on:2017-05-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:B ChenFull Text:PDF
GTID:1108330491964070Subject:Microelectronics and Solid State Electronics
Abstract/Summary:PDF Full Text Request
Microelectromechanical systems (MEMS) technology has played an important role in many fields, such as military, agriculture, aviation, navigation, meteorology, industry, biomedicine and consumer electronic products, because of its advantage of miniaturization, microelectronic integration and high precision mass production. In recent years, many national policies and development plannings have been introduced to promote the process of modernization. To improve the ability of traffic weather monitoring, expedite the establishment of wind farms, develop the smart agriculture, the demand of the wind sensors has been increased. It is urgent to improve the measure precision and reduce the drift problems of the wind sensor. By means of commercial CMOS process, with the aim of improving the performance of the sensors, this thesis focuses on the establishment of the wind sensor system, the system-level model of the sensor, ambient humidity effects and ambient temperature effects on the sensor system. The main work and innovations are described as follows:(1) Based on the previous studies of our labotary, the calorimetric wind sensor chips have been produced in the CSMC foundry. The chip has been glued under the ceramic substrate and aluminum ring, which protect the sensor chip from the external damage. The sensor is heated and controlled by an outer circuit with a negative feedback, the output signal is amplified and processed by a signal conditioning circuit. The sensor chip and the outer controlling circuit have been encapsulated in a shell.(2) As the thermal wind sensor involves multi field coupling problems, existing commercial softwares are unable to solve the system-level problem. Based on the thermal-electrical conversion theory, the thermal circuit of the wind sensor has been established. Then, the thermal circuit and the controlling circuit have been simulated in Pspice. The simulation results of the original circuit indicate that the overheat temperature of the sensor increases with the ambient temperature, and decreases with the wind speed. A new circuit is developed to keep the constant temperature difference mode (CTD). The system-level simulation and experimental results have proved the validity of the new circuit.(3) The wind sensor works in the outdoor environment. The ambient humidity changes with the weather conditions. It is obliged to discuss the ambient humidity effect on the thermal wind sensors. Properties of the ambient air are theoretically presented to explore the effects on the performance of the sensor at different relative humidity levels, and the output model of the relative humidity effects is developed. At the same ambient temperature, the output of the wind sensor linearly decreases with the increase of the ambient humidity. The effect of the relative humidity on the wind sensor is less than 0.99% at the ambient temperature 30℃,≤1.71% at 50℃, and ≤3.77% at 100℃. The experimental results prove the output model of the relative humidity effects.(4) The ambient temperature changes with the difference of geography, weather and seasons, which is deadly for the thermal wind sensor. By examing the thermophysical properties of the airflow, substrate and temperature sensitive element, the closed-form semi-empirical model has been developed to understand the physical origins of temperature dirft in the thermal wind sensor. Theoretical calculation, finite element simulation and experimental results prove the validity of the model. Experiments show that the temperature compensated sensor is working well, with the relative error of the wind speed being less than ±3.5% and the error of the wind direction being less than ±3°.This thesis aims at the study of the ambient effects on the thermal wind sensor. The improved controlling circuit has been established, the output model of the ambient humidity effects has been developed, and the semi-empitical model of the temperature compensation has been proposed. Compared with previous studies, the measure precision has been improved and the drift problems have been compensation.
Keywords/Search Tags:wind sensor, system-level model, ambient humidity, temperature drift, compensation
PDF Full Text Request
Related items