Pyroelectric Coefficient Testing System With Improved Serial Port Of Computer Feedback Control

The pyroelectic coefficient is the most important indicator to evaluate the pyroelectric effect of pyroelectric materials. In case that there is no uniform standard for measurement of the pyroelectric coefficient, how to accurately measure the pyroelectric coefficient is critically important in the study of pyroelectric materials. The purpose of this thesis is to improve the lack of the original test system, and develop a new pyroelectric coefficient testing system with single serial port of computer feedback control for accurate evaluation of pyroelectric coefficient.The new testing system is still using the direct method, and a lot of improvements on the hardware and software have been done on the original system.Improvements of hardware are as follows: (1) designing a serial port decoding circuit to achieve the function of four-way conversion from a single serial control, (2) recalibrating the pre-conversion amplifier circuit to obtain the same positive and negative current zoom range, (3) adopting computer feedback temperature control method in replacement of the original heating control means of using the time relay, (4) redesigning the anti-jamming system to reduce interference on the measurement results.Improvements of software are as follows: (1) modifying the structure of testing softwareto achieve user-friendly computer interface, beautifying software interface, improving the software features, and achieving automatic measurement, (2) designing a targeted computer weak feedback temperature control algorithm to provide a stable uniform heating rate environment for the testing sample, (3) proposing the theory of using the change rate of the standard lithium niobate sample temperature to fit the other pyroelectric samples and make up the objection that can not measure the rate of temperature change of pyroelectric sample directly, (4) improving the current filtering algorithm and adding the error handling mechanism using the pyroelectric current. I have completed the overall commissioning of the new test system and verified the functionality of the system with the samples of lithium niobate and lithium tantalate single crystals. The testing results are consistent with internationally recognized standards. Many other types of pyroelectric materials have been measured by this new system and the results are in good agreement with the reported values from the domestic and foreign research literatures.