What is a Strain Gauge Load Cell

A load cell is a conversion device used to convert a weight/mass signal or a force signal into an electrical signal. The strain gauge load cell is based on the strain effect. Under the action of external force, the resistance strain gauge pasted to the surface of the elastomer is deformed together with the elastomer. After the strain gauge is deformed, the resistance value changes, and the measuring circuit will convert the changes into an electrical signal and output, which indirectly measures the external force. According to the working principle, strain gauge load cell is mainly composed of three parts, namely an elastomer, a resistance strain gauge and a measuring circuit.
Strain gauge load cell construction

1. Elastic element
   Elastic element is a structural component with a special shape. It has two functions. First, it bears the external force of the load cell, and produces a reaction force for the external force to achieve a relative static balance. Second, it produces a high-quality strain zone, so that the resistance strain gauges pasted in this area can be relatively ideal for finishing strain and electrical signal conversion tasks. The metal material used as the elastic element of the load cell has micro-strain between the tiny crystal grains due to the internal structure of the complex structure. When the external force disappears, the micro-strain disappears. Whether elastic element can completely restore to no load original state, depends on the metallic material of the elastomer.
2. Strain gauge
   Mechanically distribute a resistance wire on a substrate made of organic material that is a strain gauge. It can convert strain changes on mechanical components into resistance changes. The strain gauge has two structure types, one is wire type and the other is foil type. The working principle is the same, only the manufacturing method is different. The foil type is formed by photographic etching method, and has various shapes, small difference in resistance value, large through-current, good creep resistance and anti-drift performance.
   The strain gauge is made of a two-layer insulating sheets (substrate) with a Φ=0.02-0.05 mm constantan wire or a nickel chrome wire wind into a grid shape (or etched into a grid shape by a thin metal foil) between them. A silver plated copper wire is connected to the strain gauge wire/foil as a strain gauge wire lead.
3. Measuring circuit
   The function of the measuring circuit is to convert the resistance change of the strain gauge into a voltage output signal. Because the Wheatstone bridge has many advantages, such as suppressing the influence of temperature changes and suppressing lateral force interference, and it can conveniently solve the compensation problem of the load cell. So the Wheatstone bridge is widely used in load cell.
   Because the full-bridge type equal arm bridge has the highest sensitivity and the parameters of each arm are the same, the influence of various disturbances is easily offset. All the strain gauge load cells use the full-bridge type equal arm bridge.
   

According to its structure, strain gauge load cells can be divided into: s type load cell, shear beam load cell, bending beam load cell, pancake load cell, cantilever beam load cell, column type load cell, ring load cell, etc. According to the force mode, the load cell can also be divided into compression load cell, tension load cell, and tension compression load cell.
As the technology develops, the electronic scales made of load cells have been widely used in various industries to achieve fast and accurate weighing of materials. Especially with the advent of micro-processing technology, load cells are used in all the field of industrial process control that requires weighing. Due to its simple manufacturing process and low processing cost, the strain gauge load cells have been mass-produced and widely used in the fields of industrial process detection and control, automatic metering and other fields. Such as weight measurement of truck scale, hopper scale and other scales, weighing control of hook scales, the mixing and distribution of a variety of raw material batching system, crane and other lifting equipments force measurement and control, wire rope tension measurement and control, and even material testing machine force measurement and control.