Whiteness and colorimeter standards and value transfer methods

    As more and more units use the whiteness colorimeter YQ-Z-48A, the standard of the instrument becomes very important, because the standard is the basis for reference of each unit. However, many users still have many doubts about the use of the standard, such as what is the basis of the standard, how to keep the standard, how to transfer the value of the standard, etc.

　　Before explaining standards and value transfer, let's first briefly introduce the concept of standard instruments. The standard of an instrument should be calibrated with a suitable standard instrument, which can be divided into two types: transfer standard instruments and working standard instruments.

　　Transfer standard instruments are standard instruments used to transfer values ​​to working standard instruments. Currently, the commonly used materials in China are: barium sulfate powder or magnesium oxide powder; white ceramic plate; non-fluorescent plastic plate or fluorescent plastic plate; fluorescent whitening paper sample or non-fluorescent paper sample, etc. Transfer standard materials are required to have a uniform, flat, and evenly colored diffuse reflective working surface.

　　At present, the highest value transfer standard in China is in Beijing, among which the standard traceability unit for barium sulfate and white ceramic plate is: China Institute of Metrology; the standard traceability unit for fluorescent whitening paper sample and non-fluorescent paper sample is: National Paper Quality Supervision and Inspection Center. According to the author's experience, the closer the properties of the transfer standard are to the tested sample, the smaller the test error will be.

　　The standard reference of whiteness colorimeter YQ-Z-48A is the barium sulfate standard of China National Institute of Metrology and the standard paper sample of National Paper Quality Supervision and Inspection Center. Many users here want to ask, why the calibration value of China National Institute of Metrology is different from that of National Paper Quality Supervision and Inspection Center? In fact, the two are consistent. The calibration value of China National Institute of Metrology is the three stimulus values ​​X10, Y10, Z10, while the calibration value of National Paper Quality Supervision and Inspection Center is the value of three diffuse reflection factors Rx, Ry, Rz and R457. The two can be converted by the following formula:

　　Rx=1.301355X10-0.217961Z10

　　Ry=Y10

　　Rz=0.931263Z10

　　The value transfer method of whiteness colorimeter YQ-Z-48A is as follows:

　　The instrument is equipped with 3 working standard white plates (NO1/NO2/NO3) and 1 black tube.

　　First, use a black tube to perform zero adjustment, and then do R457/Rx/Ry/Rz in turn. Then put the standard instrument (barium sulfate or 3# paper sample) on the sample holder, and input the standard values ​​of R457/Rx/Ry/Rz into the instrument in turn. Next, remove the standard instrument, put the working standard white plate (NO1/NO2) on, and measure R457/Rx/Ry/Rz in turn. Then modify the values ​​on the working standard white plate.

　　If the instrument needs to test the fluorescent whitening F, the instrument will be used to test the R457 value of the 4# standard paper sample, and the adjusting screw will be adjusted with a flat screwdriver to make the R457 value displayed by the instrument consistent with the value of the 4# standard paper sample (the difference should not exceed 0.3). By adjusting the instrument fluorescence factor u, the F value displayed by the instrument will be consistent with the F of the 4# standard paper sample. In this way, we say that the value on the standard instrument has been transferred to the working standard instrument, and the daily detection in the future will still be based on the working standard plate.