What Are Load Cells?

From weighing instruments to medical equipment to drilling tools, load cells are used in a wide variety of applications. But what exactly are they?

[Fun fact: The circuit used for load cells was invented almost a century before load cells were created.]

Let’s find out more about load cells, how they work, where they are used, and what makes them so interesting!

Load Cells: What They Are

Simply put, load cells are transducers that convert mechanical forces into readable electrical signals. Load cell sensors typically work with strain gauges, although hydraulic and pneumatic load cells also exist. However, strain gauge load cells are used most commonly.

Load Cells: How They Came to Be

Before strain gauge load sensors came along, mechanical lever scales were used for weighing applications. However, the foundation of load cells was laid when Sir Charles Wheatstone, an English physicist, invented the Wheatstone bridge in 1843.

This circuit could measure unknown electrical resistance, and it wasn't until the 1940s that the first sensor to measure resistance using strain gauges was developed. Once modern electronics became sophisticated enough, strain gauge load cells became economically and technically feasible. Today, strain gauge load cells are in most of the weighing technologies we use.

Load Cells: How They Work

Load cells typically house a strain gauge assembly, and when the load cell comes under a force, either tensile or compressive, the voltage fluctuations in the strain gauge, as it undergoes deformation, are measured.

The strain gauges themselves are bonded to a structural beam that undergoes deformation when weight is applied. Modern load cells typically contain for strain gauges—two of these in tension and the other two in compression—to increase the measurement accuracy.

When the strain gauge elements come under load, they signal voltage irregularities, and this voltage change is then converted to a digital reading, which we see as the weight.

Load Cells: Most Commonly Used

Although there are many types of load cells, the two most commonly used are compression load cells and tension load cells.

Compression Load Cells

As the name suggests, compression load cells measure the downward or push forces, similar to a typical weighing scale. These load cells are perfect for weighing applications with limited spaces.

 

Tension Load Cells

Tension load cells measure the pull forces that typically act from below; think of a hanging digital scale. In industrial applications, these are used for power tongs, hopper weight indicators, and Flushby rigs.

 

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