Definition
Rack balance is a mass measuring instrument designed based on the principle of lever balance, usually composed of two pallets on the left and right, beams, rulers and mobile codes. It is a kind of mechanical balance, which realizes mass measurement through visual comparison and is suitable for conventional weighing scenarios where accuracy is not required.
How it works:
The working principle of the rack pan balance follows the classical law of leverage balance. When the beam is horizontal, the following relationship is satisfied:
F1 × L1 = F2 × L2
where F1and F2The force on the left and right pallets, respectively, L1and L2is the length of the corresponding stress arm. In the gravitational field, the mass of the object is directly proportional to gravity, so in the equiarm condition, when the pointer points to the center of the ruler, the left and right trays are considered to have equal mass.
Measurement method
Before measuring, the balance should be placed on the water platform, and the bubble level should be centered by adjusting the base screw. Place the DUT on the left disk, and gradually add standard weights or moving cursors on the right disk until the pointer is stable in the center of the ruler. At this time, the sum of the weight value on the right disk and the reading of the mobile code is the mass value of the measured object. After the measurement is completed, the code should be zeroed and the weight should be put back in the special box.
Influencing factors
Ambient airflow can cause the tray to shake, affecting hand stability. Temperature changes may cause thermal expansion and contraction of metal parts, changing the proportion of the force arm. The deviation of the horizontality of the platform will produce a fraction of the force, resulting in system error. The wear of the knife edge and the knife bearing will increase the frictional resistance and reduce the sensitivity. The impact caused by weight picking and placing during operation may affect the accuracy of the knife edge structure.
Applications:
In the field of education, it is used to teach basic physics experiments to help students understand the principle of leverage. In the agricultural field, it is used in production links such as seed classification and feed ratio. Used in food processing for the rough name of raw materials. In the chemical field, it is used with weighing paper for rapid weighing of corrosive materials. Used in the textile industry for dye ratios. For preliminary weighing of soil samples in environmental testing.
Key points of selection
The range specification is selected according to the maximum weighing requirements, and the recommended daily use range is 120% of the usual load. Observe whether the index value meets the measurement accuracy requirements, and the index value of conventional models is mostly 0.1 grams or 1 gram. Check the material of the knife edge, the alloy steel knife edge has good wear resistance. Confirm that the level sensitivity is sufficient. Considering the pallet material, stainless steel pallets have strong corrosion resistance. Verify the clarity of the beam marking to ensure accurate code readings.