Recently updated on August 21st, 2024 at 07:40 am

Load cells are crucial components in many industrial applications, providing the precise measurements needed for weighing, force measurement, and monitoring systems. These devices are renowned for their accuracy and reliability, but achieving and maintaining this performance requires proper installation and regular maintenance.

This guide offers practical tips and essential advice, focusing on the critical aspects of installation, environmental considerations, maintenance, and troubleshooting. By following these best practices, you can ensure that your load cells deliver accurate and reliable results, even in demanding environments.

1. Preparing the Mounting Frame

One of the most critical factors in the successful operation of a strain gauge load cell is the preparation and design of the mounting frame. The mounting frame supports the load cell and the structure or object being measured, and its design directly impacts the accuracy and reliability of the measurements.

a) Importance of a Rigid, Non-Deflecting Frame

The mounting frame must be rigid and non-deflecting to ensure accurate measurements. Any deflection or movement in the frame can introduce errors, as it effectively acts as an unintended spring element that absorbs some of the load that should be measured by the load cell.

• Structural Integrity: The frame should be designed to support the maximum expected load without bending, flexing, or twisting. This requires careful consideration of the materials used and the design of the frame. For heavy-duty applications, materials like stainless steel or reinforced steel are often preferred due to their strength and rigidity.
• No Deflection: The frame must be strong enough to resist any deflection under load. Even small amounts of deflection can lead to significant errors in the measured values. The goal is to ensure that the entire load is transmitted directly to the load cell without any loss through the frame.

For instance, in large-scale industrial applications that use shear beams, the frame must be designed to handle the maximum load without any deformation. Similarly, when using canister load cells, which are typically employed for high-capacity measurements, ensuring a stable and non-deflecting frame is crucial to maintain accuracy under heavy loads.

b) Ensure the Mounting Area is Flat and Free of Imperfections

The flatness and condition of the mounting area are critical for accurate load cell performance. Uneven surfaces can cause uneven loading, leading to inaccurate measurements and potential damage to the load cell.

• Surface Preparation: Before installing the load cell, the mounting area should be machined or prepared to a high level of flatness. This involves ensuring that the surface is free of any ridges, bumps, or machining marks that could interfere with the load cell’s operation.
• Cleanliness: The mounting surface should be thoroughly cleaned before installation. Any debris, dirt, or grease can prevent the load cell from seating properly, leading to uneven loading and inaccurate readings. Use appropriate cleaning agents to ensure the surface is free of contaminants.
• Tolerance Checks: Regularly check the flatness and condition of the mounting area using precision tools. If necessary, re-machine the surface to maintain the required flatness and ensure consistent load application.

c) Why Frame Preparation Impacts Load Cell Accuracy

Proper frame preparation is essential because the frame acts as the foundation for the load cell. If the frame is not correctly prepared, it can introduce several types of errors:

• Load Misalignment: An improperly prepared frame can cause the load to be misaligned with the load cell’s axis, resulting in bending moments that affect the accuracy of the measurements.
• Stress Concentrations: Imperfections in the mounting surface can create stress concentrations, which may lead to localized deformations in the load cell. This can cause non-linear behavior and reduce the accuracy of the load cell.
• Long-Term Stability: A well-prepared frame ensures the long-term stability of the load cell installation. This reduces the need for frequent recalibration and maintenance, ensuring consistent performance over time.

2. Installation Best Practices

Correct installation is vital for ensuring that load cells perform accurately and reliably. The following best practices focus on aligning loads correctly, mitigating external factors, and ensuring proper electrical connections.

a) Aligning Loads Correctly

The accuracy of strain gauge load cells is highly dependent on the correct alignment of the load. Misalignment can lead to bending moments and torsional forces, which introduce errors in the measurement.

The load must be applied along the correct axis, as indicated by the markings on the load cell. This is known as axial loading, and it ensures that the full force is transmitted directly through the load cell. Misalignment can cause part of the load to bypass the load cell, resulting in inaccurate measurements.

In applications using single-point (platform) load cells, such as in retail scales or small platform scales, it’s critical to ensure that the load is evenly distributed across the load cell. Uneven loading can cause one side of the platform to bear more weight than the other, leading to skewed measurements.

For shear beams, maintaining axial loading is equally important. These load cells are often used in floor scales and other heavy-duty weighing systems. The load must be centered and applied evenly to prevent bending moments that could compromise the measurement accuracy.

Please note: Bending moments occur when the load is not applied perpendicular to the load cell’s surface. This can cause the load cell to bend, leading to inaccurate measurements. To avoid this, ensure that the load path is aligned with the load cell’s axis and that the mounting plates are level and parallel.

b) Mitigating External Factors

Several external factors can affect the accuracy of strain gauge load cells, including vibration, thermal expansion, and rotation in suspended loads.

• Vibration: Vibration can introduce noise into the load cell’s signal, leading to erratic or inaccurate readings. Vibrations can be particularly problematic in environments where shear beam or single-point load cells are used. These load cells are often installed in environments with high levels of mechanical activity, such as factories or warehouses. To mitigate this, install the load cell on a stable, vibration-free surface. If vibrations are unavoidable, use vibration dampers or filters to reduce their impact. Additionally, securing the frame to a hard, flat surface can help minimize the transmission of vibrations from nearby machinery or vehicles.
• Thermal Expansion: Thermal expansion can cause components of the mounting frame to expand or contract, leading to shifts in the load cell’s readings. To address this, design the mounting frame to allow for movement due to thermal expansion. This may involve using materials with low thermal expansion coefficients or incorporating expansion joints into the design. Shielding the load cell from direct heat sources can also help maintain temperature stability.
• Preventing Rotation in Suspended Loads: In suspended load applications, such as those involving cranes or hoists, rotation can cause the hardware to loosen over time, leading to misalignment and measurement errors. To prevent rotation, use anti-rotation features such as locknuts or rotation stops. These features help maintain the correct alignment of the load cell, ensuring consistent measurements.

c) Electrical Considerations

Proper electrical connections are essential for ensuring that the strain gauge load cell operates correctly and that its output signal is accurate and stable.

Proper Grounding

Grounding the load cell and the surrounding structure is crucial for preventing electrical noise from interfering with the signal. Proper grounding helps to dissipate any stray electrical currents that could affect the load cell’s performance. Ensure that all connections are secure and that the grounding is in accordance with the manufacturer’s specifications.

Cable Routing

The cables connecting the load cell to the data acquisition system should be routed away from sources of electrical interference, such as motors, power lines, and transformers. Shielded cables are recommended to protect the signal from external noise. Additionally, ensure that the cables are properly supported and that there is no tension or strain on the connectors.

Connector Inspection

Regularly inspect the connectors for signs of wear, corrosion, or damage. Damaged connectors can lead to signal loss or introduce noise into the system, resulting in inaccurate readings. Replace any damaged connectors immediately and ensure that all connections are tight and secure.

3. Environmental Considerations

Environmental factors play a significant role in the performance of load cells. Understanding and managing these factors is key to maintaining accurate measurements.

a) Temperature Effects

Temperature fluctuations can affect the material properties of the load cell and its components, leading to inaccurate readings.

• Temperature Compensation: Many strain gauge load cells are equipped with temperature compensation features, which help to mitigate the effects of temperature fluctuations. When selecting a load cell, ensure that it has appropriate temperature compensation for the expected operating environment. This information is typically provided in the load cell’s datasheet.
• Shielding and Insulation: For single-point load cells used in retail environments, maintaining a stable temperature is key to ensuring accuracy. In these settings, insulating the load cell and shielding it from direct sunlight or heat sources can prevent temperature-related measurement drift.
• Ambient Temperature Control: Whenever possible, install the load cell in an environment where the ambient temperature is controlled and consistent. If this is not possible, consider using temperature-controlled enclosures or heating/cooling systems to maintain a stable environment around the load cell.

b) Moisture and Corrosion

Moisture and corrosive environments can damage the load cell and its components, leading to measurement errors or complete failure of the device.

• Material Selection: For environments where moisture or corrosive substances are present, choose load cells made from materials that resist corrosion, such as stainless steel. Stainless steel load cells are designed to withstand harsh environments and maintain their accuracy over time.
• Protective Coatings: Some load cells are available with protective coatings that provide additional resistance to moisture and corrosion. These coatings can help extend the lifespan of the load cell and ensure reliable performance in challenging environments.
• Keeping the Load Cell Dry: It is important to keep the load cell and the surrounding area dry to prevent moisture-related issues. In environments where moisture is unavoidable, consider using protective covers or enclosures to shield the load cell from direct exposure. Regularly inspect the load cell for signs of corrosion or moisture ingress and take corrective action if needed.

c) Electrical and Magnetic Interference

Electrical and magnetic interference can disrupt the operation of strain gauge load cells by affecting the electrical signal generated by the strain gauge.

• Avoiding Interference from Nearby Equipment: Install the load cell and its associated wiring away from large electrical equipment, motors, transformers, and other sources of electromagnetic fields. These sources can introduce noise into the signal, leading to inaccurate readings.
• Shielding and Grounding: Use shielded cables and grounded enclosures to protect the load cell’s signal from external electrical and magnetic interference. Proper grounding practices are essential to prevent the buildup of static electricity and to ensure a clean, stable signal.
• Regular Inspections: Regularly inspect the load cell installation for potential sources of interference. This includes checking for loose or damaged cables, ensuring that grounding is secure, and verifying that shielding is intact. If interference is detected, take immediate steps to mitigate it, such as rerouting cables or adding additional shielding.

4. Common Installation Mistakes

Even experienced professionals can make mistakes during the installation of load cells. Understanding and avoiding these common pitfalls can help ensure accurate measurements and prolong the life of the load cell.

a) Choosing the Wrong Capacity

Selecting a load cell with the incorrect capacity is one of the most common installation errors.

If the load cell has a higher capacity than necessary, it may not be sensitive enough to detect small changes in the load. This can lead to poor resolution and inaccurate measurements. This is particularly problematic in applications requiring precise measurements, such as pharmaceutical manufacturing or high-precision industrial processes.

Conversely, choosing a load cell with too low a capacity can result in overloading, which can cause permanent damage to the load cell. Overloading a load cell can lead to inaccurate measurements, reduced lifespan, and potential failure. Always select a load cell with a capacity that exceeds the maximum expected load but is not excessively high.

b) Ignoring Safety Considerations

Safety is a critical aspect of load cell installation, particularly in hazardous environments where explosive or flammable materials are present.

In hazardous environments, such as chemical processing plants using canister load cells, intrinsic safety features are essential to prevent ignition in explosive atmospheres. Intrinsically safe load cells are designed to operate safely in environments with flammable gases, dust, or other hazardous materials. These load cells are typically certified to meet specific safety standards and should be used in any environment where there is a risk of explosion.

Even if safety features introduce force shunts or other measurement errors, they must not be ignored. Safety features such as backup cables, stops, and shields are essential for preventing accidents and ensuring the safety of personnel and equipment. Whenever possible, use flexible safety structures that minimize their impact on measurements while maintaining a high level of safety.

5. Regular Maintenance Tips

Regular maintenance is key to ensuring the long-term accuracy and reliability of strain gauge load cells. By following these maintenance tips, you can prevent issues before they lead to significant problems.

a) Inspection and Cleaning

Routine inspections and cleaning are crucial for maintaining the performance of load cells.

• Visual Inspection: Regularly inspect the load cell and the mounting frame for signs of wear, corrosion, or damage. Pay particular attention to the strain gauge area, as any damage here can significantly impact performance. Also, inspect the cables and connectors for signs of wear, fraying, or corrosion, and replace them if necessary.
• Cleaning Procedures: Clean the load cell using gentle, non-corrosive cleaning agents. Avoid using high-pressure washers or abrasive materials that could damage the load cell’s sensitive components. Ensure that the load cell and surrounding area are kept free of debris, dust, and other contaminants that could interfere with the operation of the load cell.

b) Recalibration

Recalibration is necessary to maintain the accuracy of load cells over time.

• Recalibration Frequency: Load cells such as shear beams or canisters that are used in high-precision applications may require more frequent recalibration, especially if they are exposed to harsh conditions or continuous use.
• Recalibration Process: Follow the manufacturer’s guidelines for recalibration, applying known loads to the load cell and adjusting the output as needed to ensure accurate measurements.

Read this post to learn more about load cell recalibration.

Conclusion

Proper installation and maintenance of load cells are essential for ensuring accurate and reliable measurements in a wide range of applications. By following the best practices outlined in this guide, including careful preparation of the mounting frame, correct load alignment, and regular maintenance, you can avoid common installation mistakes and troubleshoot issues effectively. Regular inspections, recalibrations, and attention to environmental factors will help extend the lifespan of your load cells and ensure consistent, accurate performance over time.

As this guide illustrates, the accuracy and reliability of your load cell system are heavily influenced by proper installation and ongoing maintenance. Every application has its unique challenges and specific requirements. The experts at Microtess are here to assist you with any installation or application questions regarding our strain gauge load cells and weighing solutions. Contact Microtess today to ensure your system is optimized for peak performance and precision.