Small-range weighing sensors have a small range and need to have high sensitivity and rigidity. If the elastic element structure is selected according to conventional design principles, its rigidity will inevitably be small, which will lead to the deterioration of the nonlinearity, repeatability, hysteresis and creep performance indicators of the weighing sensor, and fail to meet the requirements of higher accuracy levels. Therefore, correctly solving the contradiction between sensitivity and rigidity is an important prerequisite for small-range weighing sensors to have excellent comprehensive performance indicators. In order to effectively solve the contradiction between the sensitivity and rigidity of small-range weighing sensors, general designers are accustomed to using parallel beam structures. When selecting elastic element materials, they often use hard aluminum alloys or beryllium bronze with small specific gravity, high yield strength ratio, high specific strength and low elastic modulus. However, for those who require elastic elements to have small size, low height, light weight, good cold and hot processing performance, and high stability, hard aluminum alloys, beryllium bronze and other materials are powerless. In order to adapt to the new development of small-range electronic scale structure, this paper introduces several low-profile small-range beam-type weighing sensors with alloy steel as elastic element material.
Small-range double-end clamped beam and cantilever beam weighing sensor

Small-range integrated circular plate double-end clamped beam and cantilever beam elastic element, as the name suggests, is a double-end clamped beam or cantilever beam type weighing sensor with an integrated overall structure, which is processed with a thin strain beam, annular support and load introduction auxiliary beam or pressure head on a circular flat plate. When an external load is applied to the load introduction pressure head or auxiliary beam of the double-end clamped beam or cantilever beam, the strain beam is bent and deformed, resulting in the maximum tensile stress and maximum compressive stress on the upper and lower surfaces of the strain zone of the double-end clamped beam or cantilever beam, and this stress can be used to complete the weighing measurement task.

The small-scale integrated circular plate cantilever beam weighing sensor integrates the cantilever beam, support and loading point or loading beam on a circular plate to form an integral structure. There are two structural forms. One is a weighing sensor consisting of a circular support, a central cantilever strain beam, and a U-shaped auxiliary loading beam punched out on a circular alloy steel or spring steel thin plate. The other is a weighing sensor consisting of a semi-circular support, a cantilever strain beam, and an auxiliary loading beam punched out on a circular alloy steel or spring steel thin plate . The semi-circular support cantilever beam weighing sensor is taken as an example for force analysis and theoretical calculation. Its structure and size parameters are shown in Figure 3. The function of the horizontal auxiliary beam is to achieve support and central loading of the cantilever strain beam, and at the same time change the strain direction of the end of the cantilever strain beam. The strains on both sides of the center line of the cantilever strain beam are equal in magnitude and opposite in direction, which is very suitable for pasting full-bridge resistance strain gauges. It not only optimizes the manufacturing process and improves work efficiency, but also ensures the uniformity of the measurement performance of the weighing sensor.

Although the small-scale circular plate type double-end fixed beam and cantilever beam type weighing sensor has the characteristics of simple and compact structure, low profile; the strain beam is integrated with the annular support and loading point, without the influence of end effect; the sensitivity and stiffness are well combined. However, the elastic modulus effect, temperature effect and pressure effect caused by the narrow and thin elastic strain beam are the primary problems that must be solved. Secondly, the flat elastic element structure itself also determines that the resistance strain gauge is not pasted in a centralized position, which brings certain difficulties to the bridge wiring, circuit compensation and adjustment, especially the protection and sealing technology and process requirements are very high. Only when the protection and sealing problems are solved can the small-scale weighing sensor work stably and reliably.