Two common problems in the use of colorimeter

With the widespread application of colorimeter, the principle of colorimeter involves the comprehensive knowledge of colorimetry, optics, mathematics, materials science, biology, psychology, etc., which is not involved in many of our current learning and education. There are many problems and controversies about how to use colorimeter. Here, we will give a simple and practical solution to some basic conceptual problems according to the situation reported by most users.
Color is a subjective feeling produced by human brain on the appearance and color characteristics of objects, which is difficult to describe with mathematical methods. Color measurement and data management is the measurement and management of visual perception (including physiological and psychological effects such as mood and age). Because the digital information provided by modern colorimeter has been connected with people’s visual sense as far as possible, it has been widely used in scientific research and production activities.

The following are two basic problems that we often encounter when using a colorimeter.
I: Why not use the Lab value of the color standard plate as the standard to control the color quality and use the color difference data △ E?
The quality management that people are used to usually uses some data indicators plus the allowable upper and lower limit deviation, but the color is not good, and the standard should be determined with the real color plate. This is because:
1. The existing shortcomings of color theory, together with the complexity of spectral measurement and mathematical processing, the color difference meter developed by companies in various countries according to international standards can always measure the same color plate with the same color from red to blue.
2. The color difference instrument of the same model of the same company will have a platform difference. When measuring the same standard color plate, the readings of the two instruments will be different. As the time goes by, especially when the users of each instrument keep and use their own calibration whiteboard, the difference will expand.
3. Although the color tristimulus values measured by different instruments have deviations, they are used to compare the color difference between the same reference standard and another sample plate. The color difference values measured by different instruments: △ E, △ a, △ b are very close. This is just the basic requirement for color management. Therefore, with the reference standards, color difference values measured by different instruments have practical application value. This is also the reason why the colorimeter is widely used. The parties will define the allowable color difference through agreement, and the acceptable tolerance will be managed by avoiding the specific value of tristimulus value Lab.

II: Why should the current colorimeter be calibrated every day? Why is it necessary to return to the factory for calibration? Why does the original color plate data change after returning to the factory for calibration?
1. The traditional colorimeter widely used in the market uses xenon lamp or halogen tungsten filament lamp for lighting, and the brightness of the lamp will have deviation when it is turned on for each measurement. In addition, the bulb has a slow aging process (it needs to be replaced regularly). In order to overcome the above problems, the instrument needs to be calibrated with its own white standard plate every time it is turned on or after several hours of use, so as to revise the error of bulb and instrument system changes. As the use time of the white board increases and the barium sulfate coating inside the integrating sphere of the instrument is polluted and yellowed, the instrument will slowly deviate from the original factory benchmark. At this time, although the user color standard data stored by the instrument has not changed, the retest results have already had a slow deviation.
2. In view of the above reasons, the colorimeter shall be returned to the factory for calibration once a year according to the factory requirements, so that the deviation will not be too far. However, due to the cost, users often return to the factory for maintenance only when the instrument fails. At this time, a common problem is that the original color plate will be measured after the calibrated instrument comes back, and the value will change a little. The reason is that there is a slow change before the chromatic aberration meter is calibrated, and people cannot detect it. The factory corrected and calibrated the deviation error according to the benchmark, which is a sudden change. If the sample plate is re measured, the change will be detected. The change depends on the change degree of the instrument white standard plate, the aging degree of the lamp, the change of the grating and other factors.
The solution is that for the standard plate data measured when there is a large error in the colorimeter before calibration, the standard data has a large deviation, but because the general time interval is not long, as long as the standard color plate is taken out properly and measured again, new and correct standard data can be obtained. If the standard data is measured when the instrument is qualified, the original standard data should be correct, but the product sample data before calibration is biased due to the instrument deviation.

LISUN lauched Portable Colorimeter/Chroma Meter is an innovation color measuring tool with powerful configuration to make color measurement easier and more professional; It support Bluetooth to connect with Android and ISO devices, Portable Colorimeter/Chroma Meter will take you into a new world of color management; It can be widely used to measure color value, color difference value and find similar color from color cards for printing industry, paint industry, textile industry, etc.

CD-320PRO_Portable Colorimeter/Chroma Meter

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