First, the first choice of well-known brands and suitable for their own use of the quantity and model specifications of the product. 2. Appearance inspection: Pay attention to check whether the product's instruction manual, warranty card and certificate are complete. Good product shell surface should be smooth and smooth, uniform color, no cracks, scratches, display board without depression, text marks clear. The weighing body should be sealed with lead and intact. Adjust the bottom corner bolt of the scale properly, and the horizontal bubble in the horizontal indicator should have obvious movement phenomenon, indicating that the function of the horizontal indicator is normal. The product nameplate should be marked with the product name, model specifications, production, out number, maximum weight, minimum weight, index value, accuracy grade symbol, manufacturing measuring instruments license number and symbol CMC. Third, function check: turn on the power supply, the digital display should be clear, no flicker phenomenon, and have zero, peeling, overload symbol display. When adding and subtracting items on the pan, the weight and amount display should have a stable digital display value within 5 seconds. Check the correctness and reliability of each digital key, function key and its combined application according to the operation requirements of the product manual. Fourth, weighing accuracy: the same item is placed on the pan many times, and the weight display value is observed to determine the accuracy.