Design And Realization Of Active Emissivity Measurement System

Emissivity is the main physical parameter that influences the thermal radiation capacity and the spectral distribution of objects. It is significant to develop an accurate apparatus to measure sample and study the standard sample for the measuring emissivity of special materials in industry and set up the standard database of thermal properties.According to the actual requirement of the measuring system, combining all kinds of existing measuring methods, This thesis determines measuring principle based on the reflectivity . Based on the type selection of the infrared emitter and infrared sensor, The thesis designs the structure of detector with good aseismicity and thermal insulation. Combining the non-linear operating characteristics of the infrared sensor, design the signal detection electronic circuit, mainly including driving circuit of the emitter, the circuit of high-pass filter, rectifier filter and sampling control. Based on the analysis of working characteristics of infrared sensor, using the standard template, calibrate model parameters of each set of detector, establish accurate mathematical model of calculating emissivity. Software system mainly includes PLC data acquisition system and PC information processing platform, based on MODBUS communication protocol, using the bus of RS-485, realize the communication between PLC and PC. Data acquisition system mainly completes the collection of temperature and voltage signals and to control the switch of emitter. Information processing platform mainly completes the analysis, preservation, display and graphics of the data and state instructions of the communications.Verification and long online experiments prove the correctness of the mathematical model of calculating emissivity and the model parameters, and the accuracy and conformity of measurement results. The system can adapt to the environment of high temperature and strong vibration, satisfy the demand of long online experiments.