How Do Load Cells Work?

Here's a step-by-step guide to how a load cell works:

1. Securing the Load Cell: One end is usually secured to a frame or base, while the other end is free to attach the weight or weight-bearing element.
2. Applying Force: When force is applied to the body of the load cell, it flexes slightly under the strain. This is similar to what happens to a fishing rod when a fisherman hooks a fish.
3. Proportionate Flexing: Just as a fisherman experiences more rod bending with a bigger, stronger fish, a load cell flexes more significantly under greater applied force.
4. Detecting Deformation: Although the deformation is very subtle and not visible to the naked eye, it is detected by the strain gauges.
5. Measurement of Deformation: To measure the deformation, strain gauges are tightly bonded to the body of the load cell at pre-determined points, causing them to deform in unison with the body.
6. Load Measurement: The resulting movement alters the electrical resistance of the strain gauges in proportion to the amount of deformation caused by the applied load. This altered resistance provides a precise measurement of the load or force applied.

Technology of a Load Cell Sensor

A load cell, sometimes referred to as a load sensor or load cell transducer, typically consists of two main parts: the main body and an attached electrical circuit. The main body of the load cell, a crucial component in load cells for weighing, bears the weight or force and accounts for most of the load cell’s size. Typically, it is made from high-grade steel or aluminium, which ensures mechanical reliability, and predictable and uniform strain distribution.

The load cell circuit is housed within the sensor, tightly bonded to the main body. The system includes strain gauges which are specialised parts of the circuit designed to sense the deformations of the main body.

These strain gauges consist of thin, electrically conductive wire or foil arranged in a tight zig-zag pattern. This pattern makes them sensitive to stretch and compression along their length, but insensitive across their width. As such, they can be precisely positioned to sense forces that run along particular axes. For example, shear beam load cells have their strain gauges positioned at a 45-degree angle to the loading axis, so as to maximise the detection of the shear strain running through the load cell.