How does the load cell work?

To answer "How does the load cell work?", we first need to know "How does the strain gauge work?" The strain gauge is a device that measures the resistance change when a force is applied. A typical strain gage consists of very thin wire or foil mesh, set in a grid pattern, which produces a linear resistance change when strain is applied along an axis. There are many types of strain gauges to choose from:

Linear strain gauge: the wire connected to the back of the strain gauge is parallel to the edge of the strain gauge. These are used to measure axial and bending strains.

Shear strain gauge: the wire connected to the back of the strain gauge is arranged on both sides of the pressure frame in the 45o direction. These are used to measure shear strain.

Strain gages are often used with more strain gages to improve accuracy. One active strain gauge is called a quarter bridge, two active strain gauges are half bridges, and four active strain gauges are called full bridges.

The change of strain gauge resistance in tension weighing cells is different from that in compression weighing cells. The tension makes the strain gauge thinner and longer, increasing the resistance. The compression force makes the strain gauge thicker and shorter, and the resistance decreases. The strain gauge is attached to a thin back (bracket), which is directly connected to the weighing cell, enabling the strain gauge to experience the strain of the load cell.