Two Accuracy Test Methods for Checkweighers
is a key equipment in the automated production line. It has high precision, fast speed, and can save the weight of a single product and the total weight of each batch of products. However, in the process of using the checkweigher, you want to ensure that Each batch of products can be accurately measured, so it is necessary to test the accuracy of the checkweigher. How to carry out the correct and accurate test? The following Xiaobian from Zhongshan Kenwei has collected two test methods for you, hoping to help you. The first test is to pass the same product through the checkweigher 10 or 20 times, making sure that the direction of the product on each pass is the same as your actual production. 1. Record each data, some checkweighers can automatically record and calculate the standard deviation. If the checkweigher cannot calculate automatically, you can use the STDEV formula in the Excel table to calculate. 2. After the standard deviation is obtained, multiply it by 6 to get the unreliable interval (the globally recognized method for calculating the uncertainty of dynamic checkweighing). 3. Search for TNE(-T1) in the table below. For example, if your product weight is 200g, then TNE(-T1) is 5% or 9g. 4. Now calculate a quarter of this 9g, which is 0.25 x 9g u003d 2.25g. This value is your repeatability limit. 5. If the unconfidence interval you calculated at first is greater than 2.25 g, then the checkweigher is not usable at this setting. Products of all different types and weights that are checked on a checkweigher are required to pass this test. To do better, repeat the test every once in a while, and record and analyze the trend of each test to see how the test results change over time. Based on such trends, you can determine how often you need to perform such tests. These records and trend analysis are also valid proofs for checkweigher users to assess property and casualty risks. The second test, also using the product under test, also requires the use of a calibrated static scale. The resolution of the static scale needs to be the same as that of the checkweigher machine, or higher. This check is required before, after, and at the end of a batch. Again, this test can be trended for further risk assessment. 1. Use a calibration weight of similar weight to the product to check whether the static scale can be weighed correctly. 2. Pass the product through the running checkweigher, and then place it on the static scale for weighing. Compare the weight value obtained on the checkweigher with the weight value obtained on the static scale. If the difference is greater than 1/5 TNE, the checkweigher is not suitable. While the batch is in progress, some checkweighers have a built-in weight check function that rejects the product for testing only and displays its weight on the screen as a constant for easy testing. 3. Repeat this test at least once to check the repeatability of the checkweigher. For example, if our product has a rated weight of 200 g, the weight displayed on the checkweigher is 200.4 g, and the same product is taken to the static scale and the weight is displayed as 199.7 g. The difference is 0.7 g. We know that the TNE of a 200 g product is 9 g. One fifth is 1.8 g. 0.7g is less than the limit of 1.8g, the checkweigher can be accurately measured and used normally. For each batch of product inspection accuracy to be up to standard, you need to perform both of the above tests and incorporate them into your standard workflow. Repeat these two tests after a period of time, and once you pass the test, you can use the checkweigher machine with peace of mind. I hope these two methods can help you. If you have anything else you want to know, you are welcome to click here to consult!
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