Study On Complex Permittivity Measurement System Of P(VDF-Tr Fe) Under Microgravity Environment

The space microgravity environment provides a new research method for the new characteristics of materials, the research about this has developed as a new subject. Polyvinylidene fluoride trifluoroethylene(P(VDF-Tr FE)) is a kind of important polymer. It's very important to research the melt and crystallization behavior of P(VDF-Tr FE) in a microgravity environment and analyze the influence of gravity on the melt and crystallization behavior of polymer. It has important scientific significance in developing and researching of new properties of electronic materials under weightless space. The crystallinity of ? phase of P(VDF-Tr FE),which can be reflected by complex permittivity, is studied. Thus a system with high reliability is designed for measuring complex permittivity, matching the apparatus of polymer crystal experimental.In this paper,a 1KHz sinusoid wave which is generated by DDS signal generator AD9833, acts as excitation sigmal. An I/V conversion circuit which can suppress high –frequency noise is applied in this system, also the system uses the RF / IF gain phase detector AD8302 components for phase and gain measurement, by this we can achieve higher accuracy. Thus the admittance of parallel equivalent circuit of P(VDF-Tr FE) will be calculated, and the complex permittivity also can be obtained. The temperature acquisition part of the system uses a platinum thermal resistance Pt100 as temperature sensor, with the help of AD7793,realizes temperature measurement. Reliability design is considered in this system. In the hardware, many radiation hardness methods are applied, like derating design,tolerance design and redundancy desig. In the software, measures avoid wrong are used to ensure software reliability. In addition, a SEL resistance protection circuit is given in the design of power supply. All the reliability design of software and hardware make the system can work stably in the space microgravity environment.The measurement results of the system show that this system is reliable and stable in the weightless environment, the precision of complex permittivity is 5% and precision of temperature measure is 1%, this system can measure the dielectric constant and temperature of the P(VDF-Tr FE) and it's temperature range is 0?~200?.The bulk of the system is 15cm×13.5cm×5cm,and the power consumption is 1.82 W,so the system meets the requirements of high precision, small bulk and low power consumption of the microgravity environment, the complex permittivity of P(VDF-Tr FE) under microgravity space can be measured accurately using this system.