The load cell is based on the strain resistance conversion element - the principle of the resistance strain gauge to measure strain is to measure a very small change in resistance value, and this resistance value must be stable. When a resistance strain gauge gets damp, it may cause: conduction or corrosion between the wire grids, resulting in changes in resistance value; The size of the substrate, wire grid and the adhesive layer between the substrates of the resistance strain gauge changes, causing the resistance strain gauge to seem to truly sense the strain and resulting in a change in resistance value. This will cause zero drift of the load cell, irregular changes in output, and eventually lead to the failure of the load cell. Sealing protection is a very important link in the manufacturing process of load cells. It is the fundamental guarantee for load cells to operate stably and reliably under the influence of objective and sensing environments. The sealing protection of load cells mainly includes three methods: surface sealing, blind hole potting and welding sealing. This article discusses the technologies and processes of surface sealing and blind hole potting for sealing protection.

It is not difficult to see from the manufacturing process of load cells that whether surface sealing or blind hole potting is carried out. First, apply the protective surface adhesive for the resistance strain gauge. The requirements for the protective surface adhesive are as follows: insulation resistance > 5000MΩ, volume resistance 1014 to 1018Ω.cm. It has a strong adhesion to the metal surface, preventing moist gas from seeping in through the interface. Low hygroscopicity and high cohesive strength; The curing reaction does not release harmful compounds and has no corrosive effect on the resistance strain gauge. After curing and film formation, it is soft and remains elastic within the strain range of the elastic element. The surface sealing method is used for load cells that have neither shell sealing nor blind hole potting, mainly for load cells with aluminum alloy parallel beam structures. The sealing method is to apply another layer of sealing material on the protective surface glue of the resistance strain gauge, the lead and solder wire terminals, and the compensating resistor, so as to isolate the resistance strain gauge and its surface glue from the air and provide good protection, achieving the purpose of sealing protection. Its characteristic is that although the sealing process and coating operation are relatively simple, the cleanliness requirements for the already applied protective surface adhesive and the surface of the elastic element are relatively high. It must be strictly treated and coated under the required environmental conditions. The requirements for surface sealing materials are: excellent bonding performance (good adhesion to the protective surface adhesive layer of the resistance strain gauge and the surface of the elastic element); Good moisture-proof, water-resistant and low-temperature resistant performance; It has high electrical insulation performance and stable physical and chemical properties. The pH value is neutral and it has no corrosive effect on the surface glue of resistance strain gauges, etc. Low coating stress
The curing volume shrinkage is small. It is soft, elastic and does not increase rigidity within the operating temperature range of the load cell. It is easy to operate, has good brushing properties and a simple curing process. Easy to store.