The performance of a load cell depends largely on the choice of manufacturing materials. These materials include components such as the strain gauge substrate, the elastic body, the bonding adhesive, the sealant, the lead wire seal, and the lead wire itself.
Resistive Element Materials
The strain gauge is the sensing component of the load cell; it converts the magnitude of an external force into an electrical output and is the most critical part of the sensor. Commonly used strain gauge substrates are made of polymer film materials, while the strain-sensitive material is typically high-purity Constantan. Strain gauge performance depends not only on the substrate and the purity of the Constantan but also on the manufacturing process; advancing manufacturing technology is a crucial aspect of improving sensor performance.
Elastic Body Materials
The function of the load cell's elastic body is to transmit external forces. It must exhibit consistent deformation under identical force loads-since the strain gauge is bonded directly to the elastic body, the deformation of the elastic body translates directly into the deformation of the strain gauge. Additionally, it must possess restorative properties, allowing it to automatically return to its original state once the external force is removed. Materials chosen for the elastic body typically include various metals, primarily aluminum alloys, stainless steel, and alloy steels.
Adhesive Materials
The bonding adhesive firmly secures the strain gauge to the elastic body, ensuring that their deformation remains perfectly synchronized. Thus, the adhesive is a vital component. Two-component polymer epoxy adhesives are commonly used. Their performance is heavily influenced by factors such as purity, mixing method, storage duration, curing method, and curing time; therefore, one should carefully review the detailed specifications before use.
Sealant Materials
Early load cells relied on sealants for protection. While advancements in manufacturing technology-specifically welding-have significantly improved sensor stability and service life, sealants are still required for certain critical areas. Silicone-based sealants are generally used due to their excellent stability, moisture and corrosion resistance, and superior insulation properties.
Lead Wire Sealing
If the sensor's output lead wires are not properly secured, they may become damaged or loose, resulting in signal instability or a complete loss of output. In the early 21st century, sensor outputs relied on connectors, where the connector material and tightening force could affect the output signal; ideally, connectors should be used in conjunction with sealant. Internal lead wires must also be secured to prevent movement. Lead wire quality is critical; the materials, ranked from highest to lowest performance, are silver-plated wire, copper wire, and aluminum wire. Shielded cables are required in environments with significant high-frequency signal or radio wave interference, while corrosive, flammable, or explosive environments necessitate the use of corrosion-resistant, flame-retardant, and explosion-proof cables, supplemented by protective conduit.