Research Of Colorimetric Infrared Thermometer Based On Cortex-M3

Colorimetric infrared thermometer, which is also called the two-color infrared thermometer or dual-band infrared thermometer, owing to its non-contact and quick response characteristics, it is widely used in all professions and trades. At present, the precision of the domestic infrared thermometers are generally low, though the imported products have high performances, they are too expensive and can’t meet people’s demands. Based on the collection and analysis of the domestic and foreign infrared thermometric technology research results in recent years, researches were carried on the key technologies of the infrared temperature measurement in this paper. The main contents were as follows:1. According to the research of blackbody infrared radiative theories, the response to the band of colorimetric infrared thermometer near infrared was calculated. In comparison with all-radiation thermometry and brightness thermometry, colorimetric thermometry, which can reduce the effects of the test object own emission rate changing with temperature on the results, was adopted in this paper. Because the spectral radiosity of the test object can’t be measured directly, the spectral radiosity ratio was substituted by the voltage signal ratio of Spectrum sensing and the formula of color temperature was deduced.2. The optical system of the traditional colorimetric infrared thermometer was improved. Using concave mirrors to collect infrared radiation signal to replace the traditional colorimetric infrared thermometer, which uses convex mirrors or other reflectors to collect infrared lights simplified the optical system and lowed the cost. In order to solve the DC amplifier zero drift, the infrared radiation was modulated into pulse signal by using stepping motor driving the modulating disk making the amplification precision be improved. Because of the high dielectric constant and low dielectric dissipation of BST film, infrared detector made by BST film can enhance the strength of the outgoing signal; the part of signal processing added phase sensitive demodulation circuit which made the data collection more convenient. The 32 processors based on the cortex-M3 core was used to improve the operation precision.3. In order to do further signal processing on software, module of software of LCD display, PWM and keyboard parts was designed respectively by using RealView MDK concentrated development environment; To improve the accuracy of the temperature display, standard blackbody furnace was used to calibrate the temperature and the BP neural network algorithm was adopted to deal with the calibration results, and least square method was used to revise error. Compared with the experimental data determined by platinum and rhodium thermocouple, the data collected by the infrared thermometer of this paper can meet the e design requirements.