Types of Load Cells 

Load cells are the backbone of precision measurement in various industries, offering diverse solutions for measuring force, weight, and pressure. Understanding the different types of load cells is essential for selecting the optimal solution to meet your specific application requirements. In this section, we'll explore strain gauge technology along with three common types of load cells in detail: compression load cells, tension load cells and beam load cells.

Strain Gauge Load Cells:

Strain gauge load cells represent a cornerstone of modern force measurement technology, offering unparalleled accuracy, reliability, and versatility. These load cells operate on the principle of electrical resistance change in strain gauges bonded to a metal element, typically arranged in a Wheatstone bridge configuration. You can understand more on the differences between loads and strain gauges here.

Operating Principle:

Strain gauge load cells rely on the piezoresistive effect, where changes in resistance occur in response to mechanical deformation. When a force is applied to the load cell, the metal element undergoes strain, causing the strain gauges to elongate or contract. This change in length alters the resistance of the strain gauges, resulting in a measurable change in electrical output. By precisely measuring this change in resistance, strain gauge load cells accurately determine the applied force.

Construction and Design:

Strain gauge load cells are typically manufactured from high-quality materials such as stainless steel or aluminium to ensure durability and stability. The strain gauges are carefully bonded to the metal element, with precise alignment to maximise sensitivity and accuracy. Some load cells feature additional protection such as special connectors and cable to safeguard against environmental factors such as moisture, water and explosive atmospheres.

Strain Gauge Load Cell Conclusion:

Strain gauge load cells stand as pillars of precision measurement, offering unmatched accuracy, reliability, and adaptability across a myriad of applications. With their robust construction, high sensitivity, and wide range of capacities, strain gauge load cells continue to drive innovation and excellence in industries ranging from manufacturing and engineering to research and development.

Want to understand more on Strain Gauges click here. 

Compression Load Cells:

A compression load cell is one of the main types of load cell and as their name suggests, measure downward or pushing forces. They are typically placed beneath the object that needs to be measured or weighed, or, in the case of load pins, replace an existing load bearing pin that is directly in the load path.

Their uses are very diverse, ranging from high capacity weighing, such as silos and large offshore structures to crane and winch weighing and overload monitoring.

Let's delve deeper into the key features, advantages, and applications of compression load cells:

Operating Principle:

Compression load cells are transducers that convert force or weight into an electrical signal. They do this via the strain gauges attached around the column of the load cell. When under compressive load, the body of the load cell deforms slightly. This in turn deforms the strain gauges, which produces an electrical signal relative to the amount of compressive force applied.

Construction and Design:

A typical example of a compression load cell is the column load cell. These are cylindrical shaped devices with a flat surface at the top and bottom. Inside there is a central core or column that functions as the load bearing element. Strain gauges are bonded to the surface of this column, orientated in such a way as to detect the deformations that occur under load. The load cell has an outer cover for protection of the strain gauges and to protect it from external environmental conditions. These load cells are robust and provide highly accurate load measurements.

Other common designs for compression load cells include pancake or button load cells, which are compact and low profile, and used when space is an issue. Doughnut or washer load cells feature a central hole so that mechanisms or components can pass through.

Another type of compressive load measuring device is the load pin, which has been designed for many diverse applications as a direct replacement for load bearing pins. They have many advantages over other load sensors in that they do not normally require any change to the structure they are being installed into. Load pins are typically used in rope, chain and brake anchors, sheaves, bearing blocks and pivots. The load pin has a central bore around which the strain gauges are positioned. Unlike the column load cell, this means that they do not need a protective cover, as the strain gauges are fully sealed inside the load pin. However, as they are often subject to dimensional restrictions, they typically offer lower accuracies than other types of compression load cell.

Compression Load Cell Conclusion:

Compression load cells stand as stalwarts of heavy-duty force measurement, offering unparalleled capacity, stability, and reliability in demanding industrial environments. With their robust construction and high accuracy options, compression load cells continue to play a vital role in ensuring safety, efficiency, and quality in a wide range of applications across many different industries.

Tension Load Cells:

Pneumatic load cells are innovative force measurement devices that operate on the principle of air pressure changes to accurately measure force. Renowned for their sensitivity, reliability, and immunity to electromagnetic interference, pneumatic load cells find applications in environments where precise force measurement is critical. Let's delve deeper into the key features of pneumatic load cells:

Operating Principle:

Pneumatic load cells utilise the principle of air pressure changes to measure force. They consist of a diaphragm or bellows that deflects under load, causing a change in air pressure within a closed system. This change in pressure is proportional to the applied force and is measured and converted into an electrical signal, providing an accurate indication of the force applied.

Construction and Design:

Pneumatic load cells are typically constructed with materials such as stainless steel or aluminium to ensure durability and stability. The load cell housing contains a diaphragm or bellows that deforms under load, along with sensors or transducers to measure the resulting pressure changes. The pneumatic system is carefully designed to minimise friction, leakage, and temperature effects to ensure accurate and reliable performance.

Tension Load Cell Conclusion:

Pneumatic load cells offer precision measurement capabilities in controlled environments, providing high sensitivity, reliability, and immunity to electromagnetic interference. With their robust construction, wide operating temperature range, and cleanroom compatibility, pneumatic load cells continue to play a vital role in ensuring accuracy and quality in a variety of applications across industries.

Shear Load Cells:

Hydraulic load cells are robust force measurement devices that utilise hydraulic fluid and piston arrangements to accurately measure force. Renowned for their durability, stability, and high capacity, hydraulic load cells excel in demanding industrial environments where accuracy and reliability are paramount. Let's delve deeper into the key features, advantages, and applications of hydraulic load cells:

Operating Principle:

Hydraulic load cells operate based on Pascal's law, which states that the pressure exerted on a confined fluid is transmitted undiminished in all directions. When a force is applied to the load cell, it compresses the hydraulic fluid within a sealed chamber, causing a proportional displacement of the piston or diaphragm. This displacement is measured and converted into an electrical signal, providing an accurate indication of the applied force.

Construction and Design:

Hydraulic load cells are typically constructed with high-strength materials such as stainless steel or alloy steel to withstand heavy loads and harsh operating conditions. The load cell housing contains a piston or diaphragm that compresses the hydraulic fluid, along with strain gauges or other sensing elements to measure the displacement. The hydraulic fluid is carefully selected for its stability, viscosity, and temperature characteristics to ensure accurate and reliable performance.

Beam Load Cell Conclusion:

Hydraulic load cells stand as stalwarts of heavy-duty force measurement, offering unparalleled capacity, stability, and reliability in demanding industrial environments. With their robust construction, high accuracy, and immunity to electromagnetic interference, hydraulic load cells continue to play a vital role in ensuring safety, efficiency, and quality in a wide range of applications across industries.

Summary

In summary, this section has explored three fundamental types of load cells—compression, tension, and beam—highlighting their distinctive operating principles, construction features. Strain gauge load cells, known for their precision and versatility, represent a cornerstone of modern force measurement, offering unparalleled accuracy and reliability across diverse industrial sectors. Understanding the nuances of these load cell types empowers industries to make informed choices, optimising processes and ensuring top-tier performance, efficiency, and safety standards.