Materials for the load cell
What is a load cell?
The load cell is actually a device that converts the quality signal into a measurable electrical signal output. The sensor should be considered in the actual working environment of the sensor, which is essential for the correct selection of the load cell, it relates to the sensor can work properly and its safety and service life, and even the entire instrument reliability and safety Sex. In the load cell main technical indicators of the basic concepts and evaluation methods, the old and new GB quality differences. There are several types of S-type, cantilever type, spoke type, plate ring type, membrane box type, bridge type, cylinder type and so on.
1, Sensitive components
Directly perceive the measured (mass) and output other components that have a certain relationship with the measured relationship. Such as the resistance strain gauge load cell elastomer, is the quality of the measured object into a deformation; capacitive load cell elastomer will be measured to the quality of displacement.
2, Transform components
Also known as sensor components, is the output of sensitive components into a measure to facilitate the measurement. Such as a resistance strain gauge strain gauge strain gauge (or resistance strain gauge), the deformation of the elastomer is converted into a change in the amount of resistance; capacitive load cell capacitor, the elastic body of the displacement into the capacitance changes. Sometimes some components have both the function of both the sensitive and the transform elements. Such as voltage-type load cell piezoelectric material, under the action of external load, in the deformation of the output power at the same time.
3, measuring components
Transform the output of the transform element into an electrical signal to facilitate further transmission, processing, display, recording or control. Such as resistance strain gauge load cell in the bridge circuit, piezoelectric load cell charge preamplifier.
4, auxiliary power supply
Provides energy for the sensor's electrical signal output. General load cell need to be outside the chain power to work. Therefore, as a product must be marked with power requirements, but not as part of the load cell. Some sensors, such as magnetic speed sensor, because of his output of the larger energy, so do not need auxiliary power can work properly. So not all sensors have auxiliary power.
The performance of the load cell depends largely on the choice of manufacturing material. The load cell material includes the following parts: strain gauge material, elastomeric material, patch adhesive material, sealant material, lead sealing material and lead material.
1) Strain gauge and resistance element material:
The strain gauge is the induction part of the load cell. It transforms the external force into the electrical quantity output, which is the most important part of the sensor. The commonly used strain gauge substrate adopts the polymer film material. The strain material is usually high purity. The performance of strain gauges is not only related to the purity of the substrate and the carbon, but also to the manufacturing process. Increasing the level of process technology is also a very important aspect of improving sensor performance.
2) Elastomer material:
The role of the load cell elastomer is to transmit the external force, it must have the same force in the size of the time, resulting in deformation, because the strain gauge is attached to the elastic body above the deformation of the elastic body is the deformation of the strain gauge; With a reset, when the external force disappears, you can automatically reset. Elastomer materials usually choose a variety of metals, mainly aluminum, stainless steel and alloy steel and so on.
3) Patch adhesive material:
Patch adhesive is the strain gauge and elastomer firmly fixed together, so that they produce the deformation is always consistent. It can be seen, patch adhesive is also an important component. At the beginning of the 21st century, the use of multi-component adhesive adhesive is a two-component polymer epoxy series adhesive. At the beginning of the 21st century, its performance and its own purity, mixed mode, storage time, curing mode, curing time and other great relationship, before using it to carefully look at its details.
Early weighing sensor seals are made of sealant, and later due to the development of manufacturing technology, welding technology can improve the stability of the great sensor and service life. Although the early 21st century, many of the use of welding technology, but some important parts need to apply some sealant. Sealants are generally used silica gel, silicone has the advantages of good stability, can be moisture, corrosion resistance, insulation performance is also very good.
5)Lead seals and lead materials
If the sensor output lead is not fixed, it will be damaged or loose, resulting in signal instability or no output. At the beginning of the 21st century, the sensor output adopts the way of the connector, and the material of the connector and the fastening force will also affect the output. It is best to use a connector with a sealant. The internal leads also need to be fixed to prevent them from moving around. Lead quality is also very important, the material properties from high to low order of order silver, copper and aluminum. If the surrounding high-frequency signals, radio interference is serious, then the need to use shielded cable; corrosive environment and flammable and explosive occasions you need to use anti-corrosion and flame retardant cable, plus casing to protect.
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