I. Influencing factors of gas permeability test There are many factors affecting the gas permeability test, such as sensor accuracy, effective range, system leakage, sample processing, material properties, test environment, hardware design, software processing, and so on. Many of the influencing factors are determined by the innate nature of the design. From the application point of view, the user is not concerned with how the manufacturer improves these conditions, but what requirements are met, and what conditions are met before the objective and accurate can be obtained. Test data, this article describes two main measures - "blank test" and test results repeatability.
Second, the "blank test" data 1. "blank test"
The “blank test†is a reflection of the comprehensive error of the equipment. The test error is due to the fact that there are indeed factors in the gas permeability test that cannot be effectively improved, such as system leaks and other unpredictable factors. Although there has been no clear "blank test" in the air permeability test standard, the test work on the "blank test" has been widely recognized by the society.
2. VAC-V1 “Blank Test†Data In order to obtain the comprehensive impact value of all factors, VAC-V1 uses a sample that is considered to be completely airtight to be tested according to normal operating procedures, and then to observe system leakage and other factors for the entire device. The combined impact. The "blank test" value obtained by this method determines the pros and cons of the device to be more credible.
Labthink VAC-V1's "blank test" uses 55μm copper foil (also can use thicker aluminum foil sample) as a sample to test, strictly sealed, the system is vacuumed for 48h (before entering the test state, the vacuum of the upper and lower chambers should be Below 10 Pa), the test was carried out using the conventional volume of the VAC-V1 (the device has an optional extended volume function). In order to analyze the influence of environmental temperature and humidity changes on the test, there is no self-temperature control function of the starting device. The pressure time curve is obtained as shown in Fig. 1. (In addition, there are temperature time and humidity time curves, which will not be described here)
The test lasted for 12 days (including vacuuming time), the temperature was between 18 and 23 °C, and the ambient humidity was 50±8% RH (if the self-temperature control function of the equipment was used, the test effect was better). After entering the test state, the lower chamber pressure increased by 6.0 Pa, and the test result was 0.023 ml / m 2 · 24 h · 0.1 MPa (if the extended volume or fuzzy test mode is selected, the comprehensive effects of the above various factors can be effectively reduced, and the obtained The test results will be more accurate). It is not difficult to find out that the influence of temperature and humidity changes on the test is small when the whole test curve is analyzed with the data list.
During the first 60 hours, the pressure change was relatively large, rising from 0 Pa to 3.84 Pa. In the subsequent 180 h, the pressure increase was decreased, and the equivalent gas permeability was 0.012 ml/m 2 · 24 h · 0.1 MPa. The reason for this phenomenon is related to the degassing state. The test proves that prolonging the vacuuming time can effectively improve the impact on the test results.
Third, data repeatability 1. The factor of data repeatability is due to the large gap between the components selected by each manufacturer when implementing a test method. Therefore, the data repeatability of the equipment is also an important indicator for evaluating equipment. By analyzing the data repeatability of the device, it is possible to better understand the error and fluctuation of the detection data of the device and improve the detection efficiency. Data repeatability includes: S (standard deviation standard deviation), CV (percent coefficient of variation data fluctuation percentage) and LSD (least significant difference between two individual test results based on a 95% confidence level confidence level 95% of two independent test results Minimum effective difference).
Second, the "blank test" data 1. "blank test"
The “blank test†is a reflection of the comprehensive error of the equipment. The test error is due to the fact that there are indeed factors in the gas permeability test that cannot be effectively improved, such as system leaks and other unpredictable factors. Although there has been no clear "blank test" in the air permeability test standard, the test work on the "blank test" has been widely recognized by the society.
2. VAC-V1 “Blank Test†Data In order to obtain the comprehensive impact value of all factors, VAC-V1 uses a sample that is considered to be completely airtight to be tested according to normal operating procedures, and then to observe system leakage and other factors for the entire device. The combined impact. The "blank test" value obtained by this method determines the pros and cons of the device to be more credible.
Labthink VAC-V1's "blank test" uses 55μm copper foil (also can use thicker aluminum foil sample) as a sample to test, strictly sealed, the system is vacuumed for 48h (before entering the test state, the vacuum of the upper and lower chambers should be Below 10 Pa), the test was carried out using the conventional volume of the VAC-V1 (the device has an optional extended volume function). In order to analyze the influence of environmental temperature and humidity changes on the test, there is no self-temperature control function of the starting device. The pressure time curve is obtained as shown in Fig. 1. (In addition, there are temperature time and humidity time curves, which will not be described here)
The test lasted for 12 days (including vacuuming time), the temperature was between 18 and 23 °C, and the ambient humidity was 50±8% RH (if the self-temperature control function of the equipment was used, the test effect was better). After entering the test state, the lower chamber pressure increased by 6.0 Pa, and the test result was 0.023 ml / m 2 · 24 h · 0.1 MPa (if the extended volume or fuzzy test mode is selected, the comprehensive effects of the above various factors can be effectively reduced, and the obtained The test results will be more accurate). It is not difficult to find out that the influence of temperature and humidity changes on the test is small when the whole test curve is analyzed with the data list.
During the first 60 hours, the pressure change was relatively large, rising from 0 Pa to 3.84 Pa. In the subsequent 180 h, the pressure increase was decreased, and the equivalent gas permeability was 0.012 ml/m 2 · 24 h · 0.1 MPa. The reason for this phenomenon is related to the degassing state. The test proves that prolonging the vacuuming time can effectively improve the impact on the test results.
Third, data repeatability 1. The factor of data repeatability is due to the large gap between the components selected by each manufacturer when implementing a test method. Therefore, the data repeatability of the equipment is also an important indicator for evaluating equipment. By analyzing the data repeatability of the device, it is possible to better understand the error and fluctuation of the detection data of the device and improve the detection efficiency. Data repeatability includes: S (standard deviation standard deviation), CV (percent coefficient of variation data fluctuation percentage) and LSD (least significant difference between two individual test results based on a 95% confidence level confidence level 95% of two independent test results Minimum effective difference).