Three factors affecting the performance of weighing sensors

Load cells are an important category of mechanical sensors, and they are also the most widely used. They come in many forms. In general, load cells are mainly composed of elastomers, strain gauges, seals, etc. Their interactions affect the performance of the sensor. Let's analyze their respective roles below.

　　The metal material used as the elastomer of the weighing sensor will produce micro-strain between tiny grains when subjected to external force due to its complex internal organizational structure. After the external force disappears, the micro-strain disappears, but whether it can be completely restored to the original state without force depends on the metal material of the elastomer. If the curve of the loading force and the curve of the unloading force do not coincide, the greater the difference, the greater the hysteresis. The difference mainly comes from the stability and uniformity of the material's own components, the radial organization after heat treatment, and so on. Knowing the cause of hysteresis, we can reduce the hysteresis by selecting suitable metal materials and using advanced heat treatment methods to increase the elastic limit. At present, the elastomer material commonly used in the domestic market is 40CrNiMoA, which can achieve good comprehensive mechanical properties after a reasonable heat treatment process.

　　The strain gauge of a weighing sensor is mainly composed of a sensitive grid, a substrate, a coating and leads. It converts the strain of the elastic body into a change in resistance through the resistance strain effect of the sensitive grid. If the material itself has hysteresis, the strain gauge will also have hysteresis. At present, the world's famous strain gauge manufacturers have fully considered the hysteresis when manufacturing strain gauges and adopted self-compensation measures to reduce the hysteresis to the lowest level. This is also a factor that must be considered when selecting a weighing sensor.

　　After the elastomer and strain gauge are assembled, the sensor needs to be sealed with sealant, mainly to fix the circuit and seal, to prevent the external environment from affecting the performance of the sensor. On the surface, the sealant is relatively soft after curing, and the strength of the elastomer is almost negligible. If it is used in small-range force measurement, this effect must be considered. When a small force is applied to the elastomer, the deformation of the elastomer is very small, and the thickness of the sealant affects the deformation.

　　When designing a good weighing sensor, the hysteresis performance of the product must be fully considered. Through the above analysis and combined with the specific situation, the size of the hysteresis can be significantly reduced.