A Circuit Design Of Protable Spectrophotometer For Color Measurement

In some occasions where the consistency of the color needs to be maintained, the scientific and quantitative description of the color becomes urgently important in order to avoid losses due to the subtle differences in color. The domestic instruments is mainly consists of chroma and desktop spectral color measuring instrument. The chroma can't detect the tristimulus values and chromaticity coordinates of color sources accurately, which makes it keep away from the delicate measurements such as the evaluation of subtle chromatism. Desktop measuring instrument is not portable due to the huge size and goes against the on-site measurements. In order to realize the high-precision, fast and low-cost color test, this paper introduces a working circuit design for the portable spectral color measuring instrument.This paper researched the development and features of the color measurement both at home and abroad, then starting from the colorimetric theories, working principle and design key points for color testing instrument, working process of various modules and performance of the photoelectric sensor were all analysed and studied, and then devices were chosen according to the requirements , finally a working circuit system which is based on LPC2478 microcontroller was designed.The system firstly charged the capacitance by controlling the MAX8622 microcontroller, after that the tested object was illuminated by controlling the exposure of pulse xenon lamp, then using the self scanned photodiode array S4114-46Q and the multiplexer ADG738, the 40 time-sharing spectral signals produced by the optical system were collected, afterwards, these weak current signals were converted to voltage signal corresponding with spectral signals after I/V conversion and amplification, finally the color information of the tested object was attained by using the A/D converter and data processing method, then was outputted by the LCD displayer.The results indicate that the power of the system is less than 5W, more than 1000 measurements of every four new batteries, single measurement time is 1.5s, and the intervals between two tests is 3s. The realization of working circuit sets up the foundation for the integration with the optical system. With the merits of the short measuring time, small size, low power consumption and so on, this system can be applied to printing, dyeing and textile which need on-site measurements.