The uncertainty of the coating's measurement of the ratio

The ratio is an important index in the performance of the coating, which refers to the ratio of the reflectivity of the same paint film applied to the specified reflectivity black and white substrates. It reflects the white and light paint to eliminate the color of the substrate, the higher the ratio of the coating, the better the product's cover performance, on the other hand, the worse it does not cover the substrate. In this paper, according to the JJF 1059-1999 "Measurement Uncertainty Assessment and Representing" provisions, the paint to the ratio of the measurement results of uncertainty analysis and assessment
China
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1, measurement method
according to GB / T9755- 2001 "synthetic resin emulsion exterior paint", GB / T9756 - 2009 "synthetic resin emulsion inner wall" Coatings, GB/T9757-2001 Solvent Exterior Paints and GB/T23981-2009 White and Light Paint To Ratio Determination In the room temperature (23±2) degrees C, relative humidity (50±5) % of the environment, in the black and white card paper with a specification of 100 wire rod coater uniform coating of the coating, after 24 hours of maintenance, with a reflectivity meter directly determine the black and white coating film at least 4 positions of the reflectivity, and calculate the average reflectivity RB (black paper) and RW (white paper), respectively, to find the ratio.
2, mathematical model
X-RB/RW (1) in
: X: The ratio of the coating film; RB: the reflectivity of the coating film on the black paper card; and the reflectivity of the coating on the white paper card.
3, the source of uncertainty
there are many factors affecting the measurement of paint uncertainty, such as ambient temperature, humidity on the maintenance of lacquer film has a certain impact, because the whole experiment in the constant temperature and humidity room, the impact on measurement uncertainty is negligible. The operating level of the personnel, the uniformity of the coating and the performance of the film, the appearance and flatness of the coating film, the thickness of the coating film, etc. all have a certain impact on the results, so in the course of the experiment should pay attention to increase the number of tests, with a view to reflecting in the repetition of the measurement results. The influence factors of coating on ratio uncertainty mainly come from the following two aspects: the uncertainty part introduced by measuring repeatability, and the uncertainty part introduced by reflectivity meter calibration.
4, uncertainty part calculation
(1) measurement repeatability introduced in the standard uncertainty part experiment using the mean of two parallel measurements, this test measured a total of 8 sets of samples, the resulting data is as follows:
measurement standard deviation In the daily analysis,
the standard deviation of the average is:
The standard deviation of the measurement repeatability is the synthesis of all random effects of this measurement, so there is no need to consider random influence in the subsequent evaluation of the components.
(2) the uncertainty part introduced by the reflector calibration
The reflectivity meter calibration certificate indicates that the instrument's extended uncertainty U-1.8%, including factor k-2, so its standard uncertainty should be:
6, extended uncertainty calculation
take the inclusion factor k The confidence level is about 95%, the extended uncertainty is:
U (x) s kuc s 0.02
7, measurement uncertainty report
paint contrast rate: x s 0.87±0.02, k s2.