Important considerations for overload protection in load cells

Force measurement must be extremely accurate and reliable. However, applying forces beyond a load cell's rated capacity, known as overload, poses a significant threat to the sensor's integrity and the safety of the application.

What are the most important considerations for overload protection, how does it work, and why is it important? Learn how Interface load cells are equipped with innovative features to reduce the risks associated with overloads.

Understanding overload

An overload occurs when the force applied to a load cell exceeds its designed capacity limit. This seemingly simple process can trigger a cascade of adverse effects, ranging from minor inaccuracies in readings to permanent deformation and even catastrophic sensor failure. Overloads can occur for a variety of reasons:

• Unintentional application of excessive force: This is especially common in laboratory or testing facilities where new applications or untrained load cell users may inadvertently apply large loads that can easily exceed a load cell's capacity.
• Off-axis or external loading: Lateral loads, moments, or torques, in conjunction with the primary axial force, can create combined loading conditions that exceed the sensor's safe operating limits. As Interface experts point out, these off-center vectors add to the near-axis loading and can lead to overloads in certain areas of the bend. Always refer to the detailed Specifications your specific sensor model.
• Shock loads: Sudden, high forces or shock loads can cause significant damage to load cells that are not designed to withstand such sudden loads. The rapid deflection caused by shocks can easily lead to overload, regardless of the duration of the shock.
• Dust and dirt buildup: In special load cell designs with overload protection mechanisms that have small gaps, the accumulation of dust or debris can activate the protection prematurely, resulting in a non-linear output even before the rated capacity is reached.

The importance of overload detection and protection

Given the risk of damage and inaccuracies when continuously reaching a load cell's maximum capacity, overload detection and protection mechanisms are critical to ensure the longevity, reliability, and safety of force measurement systems.

Load cells are often integral components of expensive and sensitive equipment. Overload protection protects these valuable assets from permanent damage, ensures their continued functionality, and prevents costly replacements.

Even seemingly minor overloads can cause deformation within the load cell, compromising its ability to provide accurate and consistent readings. By preventing overloads, these systems preserve the integrity of the measurement data.

A failure caused by an overload can have serious safety implications in applications where load cells monitor critical structural loads or control industrial processes. Robust overload detection and protection systems help prevent accidents by ensuring that loads remain within safe operating parameters.

TIP: If you suspect that your load cell is overloaded, request a Repair assessment Also read: How do you know if your load cell needs calibration or repair?

Innovations in overload protection

Overload protection is not a new consideration; Interface is committed to this important feature. Our founder, Richard F. Caris, patented a weighing device with overload protection in 1983, and Interface engineers continued this legacy with patents in 2004 and 2012 specifically addressing load cell overload protection. Our commitment is evident in several innovative approaches:

#1 – Mechanical Stops: Many Interface load cells feature internal mechanical stops – physical barriers that limit the deflection of the sensing element when the load reaches or exceeds the rated capacity. These stops effectively prevent excessive stress on the internal components and protect them from permanent damage. SMT Overload Protected S-Cell is a good example of this, as it features a solid construction with small gaps and locking fingers that prevent excessive deflection during tension and compression. Similarly, the MBP Overload Protected Miniature Beam Load Cell Series EDM-machined hard stops for improved overload protection.

#2 – Customized Solutions: Interface offers customized load cells with customized overload protection features for applications with special overload requirements. The universal LowProfile Load Cell 1000 with fatigue resistance and additional overload protection is an example of this capability.

#No. 3 – Special designs for high-risk applications: Certain Interface load cells are specifically designed for environments where accidental overloads are more likely. With their internal mechanical stops that protect up to 10 times their rated capacity, the SMT mini load cell ideal for low-capacity applications in laboratories or medical facilities. SPI Single Point Impact Cell is also equipped with internal stops and offers pressure overload protection up to four times its rated capacity, making it suitable for applications susceptible to Shock loads .

#4 – Compression Overload Protection on LowProfile Load Cells: Even on designs without explicit EDM capabilities, such as our LowProfile series (e.g., 1000, 1100, 1200), Interface can provide compression overload protection by tightly controlling the tolerances between the base and the bottom of the hub.

Use the Load cell selection guideto find load cells that meet your capacity and overload protection requirements.

Three practical steps to prevent overload

• Check the safe overload specifications: Always familiarize yourself with the capacity and overload specifications of each load cell, as clearly stated in the product documentation.
• Use overload-protected load cells: If there is a possibility of overload, primarily choose load cells with integrated overload protection.
• Perform regular maintenance and calibration: Regular checks and calibrations are critical to maintaining load cell accuracy and performance. Tools such as ohmmeters can help with early detection of potential overload conditions or other electrical problems. Interface recommends annual calibration for optimal results.

Prioritizing overload protection for measurement integrity

Overloads pose a significant threat to the accuracy, longevity, and safety of force measurement systems. By understanding the causes and consequences of overloads and leveraging innovative overload protection features offered by manufacturers like Interface, users can significantly reduce these risks. Whether through mechanical stops, special designs, or engineered solutions, integrating overload protection is a fundamental consideration to ensure the reliability and integrity of your critical measurements.

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