The Research Of Platinum Resistor System Based On Heat Transfer Equation

The platinum resistance is the most convenient temperature measurement and control instrument in industrial applications. Because of the accuracy, it is defined as the international practical temperature scale, and widely used in Automatic Weather Station. However, comparing with the traditional passive devices, the self-heating effect exists in measurement. It is certainly that the high-precision temperature measurement is necessary in the research of the test technique of comprehensive climate observation measurement. The dissertation focuses on the self-heating effect of the platinum resistance in order to put forward a new approach in analyzing the measurement error.By concentrating on the self-heating effect, the second section is going to research the nature-flow heat transfer in limited and large-spaced condition in three aspects, which are heat convection, heat conduction and heart radiation.The third section focuses on the application of modeling analysis, test and argument. By combing thermodynamics theories with practice, the dissertation researches the relationship of energy dissipation in heat transfer on the basic of the designed testing environment of platinum resistance-air tank. It is followed by the established mathematic model for calculation of self-heating and simulation calculation with Matlab. The research, which is set on controlled pressure (15hpa-1000hpa) and fixed temperature (0.01℃), collects data by high-precision test bridge and testifies the self-heating effect of the platinum resistance in fixed working current from0.5mA to1mA.Besides that, the dissertation designs and analyses the four-wire platinum resistance, which consists of main program module, A/D module, display module, and the module for data communication. By using the four-wire platinum resistance as senor, signal is amplified and debugged, transformed into digital signals by AD7714, and sent into STC89C52Single Chip Microcomputer. The resistance value is displayed in LCD1602and sent to principal computer through the serial. The four-wire platinum resistance meets the demand the combining research with practice, in order to argue whether it is in accordance with the self-heating effect in practical application.It is proved that in certain conditions, the greater the current is, the greater the temperature variation caused by the self-heating effect of platinum resistance is; in certain condition of flexed working current and temperature and low tension, the less the pressure is, the greater the self-heating effect is. In this circumstances, the error is between0.0to0.05℃.