Researches On Computer-aided System For Measuring The Pyroelectric Coefficient

The thesis focused on developing a computer-aided system for measuring the pyroelectric coefficient. The magnitude of pyroelectric coefficient directly affects the properties of pyroelectric materials. So empoldering the computer-aided system for measureing pyroelectric coefficient is quite important. It benefits the basic and application research of pyroelectric materials.Up to now, there are various measuring methods of the pyroelectric coefficient, such as the static method, the direct method (includes the pyroelectric current method and the constant heating rate method), the charge integration method and digital integration method and so on. In this system, the measurement of the pyroelectric coefficient is founded on the pyroelectric current method. It has a lot of advantages.This method can not only meet the condition of the zero electric field but also measure the pyroelectric current in the continuous temperature range, and detect the change of the pyroelectric coefficient correctly. The whole system consists of two parts: hardware and software.The function of the hardware is to measure the pyroelectric current and the sample temperature. This part consists of three modules: measuring pyroelectric current, measuring sample temperature and controlling heater temperature. The module design of measuring pyroelectric current is foremost for the whole system. For the properties of the high impedance,low frequency and small signal source, a special amplification circuit of picoampere current is designed. The design of heater is important too. Based on the theory of the pyroelectric current method, the sample temperature variety must be symmetrical. Heater is designed with ampullaceous hearth.The system software mainly consists of communication,data processing and interface. the pyroelectric current and the sample temperature can be collected through RS232 serial port. then pyroelectric coefficient versus temperature can be obtained using the powerful computer's data processing ability. simultaneity more functions can be achieved,such as store,display and print. Besides, in data processing part, the filtering arithmetic program is used to resist the disturbs.At last, by this system ,multiplicate pyroelectric materials, suah as single crystal,thin film,thick film and ceramic, are measured. It shows that the results agree with correlative reports. By longtime runs, the system works well.