Load cells are an important category in mechanical sensors, and they are the most widely used and have many forms. The construction of load cells is generally mainly composed of elastomers, strain gauges, seals and the like. Several of their interactions affect the performance of the sensor, and their respective roles are analyzed below.
The metal material used as the elastomer of the load cell has micro-strain between the small crystal grains due to the internal structure of the complex structure. When the external force disappears, the micro-strain disappears, but can The original state of being completely restored to no force varies depending on the metallic 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 is mainly due to the stability, uniformity of the material itself, the radial structure after heat treatment, and the like. Knowing the cause of hysteresis, we can reduce the hysteresis by selecting the appropriate metal material and using advanced heat treatment 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 through reasonable heat treatment process.
The load cell of the load cell is mainly composed of a sensitive grid, a substrate, a coating layer and a lead wire. It transforms the strain of the elastomer into a change in resistance through the resistance strain effect of the sensitive grid. If the material itself has hysteresis, the strain gauge has hysteresis. At present, the world's most famous strain gauge manufacturers are making strain gauges that fully take into account hysteresis and adopt self-compensation measures to reduce hysteresis to a minimum. This is also a factor that must be considered when selecting a load cell.
After the elastomer and the strain gauge are formed, the sensor needs to be sealed with a sealant, mainly for fixing the circuit and sealing, and preventing the influence of the external environment on the performance of the sensor. On the surface, the sealant is relatively soft after curing, and the strength of the elastomer is almost negligible. This should be considered if applied to small-scale force measurements. When a small force is applied to the elastomer, the deformation of the elastomer is small, and the thickness of the sealant affects the deformation that occurs.
When designing a good load cell, the hysteresis performance of the product must be fully considered. Through the above analysis, combined with the specific situation, the hysteresis can be significantly reduced.
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