The mechanical weight scale is similar to a balance. The force on the load-bearing plate is transmitted to the internal torque conversion mechanism through the mechanical linkage mechanism, and the force is converted into torque. The torque generated by the incoming force is balanced, and at the same time drives the pointer of the instrument panel to rotate, indicating the weight value.

There are three principles of mechanical scales:

1\When the weight (two forces) is balanced, the gravity is equal to the support force of the table;

2\Support force and pressure are a pair of action force and reaction force, which are equal in magnitude;

3\The scale shows the pressure on the table;

Mechanical scales are energy-saving and environmentally friendly and do not require batteries. It has a simple structure and is cheap. The disadvantage is that it needs to be zeroed every time it is used, and the measurement results are prone to deviation. The period of use is relatively short, generally about three years. Compared with mechanical scales, electronic weight scales have high measurement accuracy, long service life, lockable display, and convenient reading. However, the price is high, and batteries are required, making the initial adjustment more complicated.