Key Considerations for Overload Protection in Load Cells

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

What are the key considerations surrounding overload protection, how does it function, and why is it important? Discover how Interface load cells incorporate innovative features to reduce the risks associated with overloading.

Understanding Overload

An overload occurs when the force exerted on a load cell surpasses its designated capacity limit. This seemingly simple act can trigger a cascade of detrimental effects, ranging from subtle inaccuracies in readings to permanent deformation and even catastrophic failure of the sensor. Overload can arise from various sources:

• Accidental Application of Excessive Force: This is particularly prevalent in laboratory or testing facility environments, where new applications or untrained load cell users may unintentionally apply large loads that can easily exceed a load cell’s capacity.
• Off-Axis or Extraneous Loading: Side loads, moments, or torques, combined with the primary axial force, can create combined loading conditions that exceed the sensor’s safe operating limits. As Interface experts emphasize, these off-axis vectors add to the on-axis load, potentially causing overload in specific areas of the flexure. Always reference the detailed specifications of your specific sensor model.
• Impact Loads: Sudden, high-magnitude forces, or shock loads, can significantly damage load cells, which are not inherently designed to withstand such abrupt stresses. The rapid deflection caused by impact can easily lead to overload, regardless of the duration of the impact.
• Dust and Debris Buildup: In specialized load cell designs with overload protection mechanisms that involve small gaps, the accumulation of dust or debris can prematurely engage the protection, resulting in non-linear output even before the rated capacity is reached.

The Importance of Overload Detection and Protection

Given the potential for damage and inaccuracies when consistently reaching the peak of a load cell capacity, overload detection and protection mechanisms are crucial for ensuring the longevity, reliability, and safety of force measurement systems.

Load cells are often integral components in expensive and sensitive equipment. Overload protection safeguards these valuable assets from permanent damage, ensuring their continued functionality and preventing costly replacements.

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

An overload-induced failure can have severe 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 loads remain within safe operating parameters.

TIP: If you suspect your load cell has overloaded, request a repair evaluation. Also, review How Do You Know if Your Load Cell Needs Calibration Service or Repair?

Interface Innovations in Overload Protection

Overload protection isn’t a recent consideration; Interface is committed to this critical feature. Our founder, Richard F. Caris, patented a weighing apparatus 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 incorporate internal mechanical stops – physical barriers that limit the deflection of the sensing element when the load approaches or exceeds the rated capacity. These stops effectively prevent excessive strain on the internal components, safeguarding them from permanent damage. The SMT Overload Protected S-Cell exemplifies this with its “go solid” design, utilizing small clearance gaps and locking fingers to prevent over-deflection in tension and compression. Similarly, the MBP Overload Protected Miniature Beam Load Cell series features EDM-machined hard stops for enhanced overload protection.

#2 – Engineered-to-Order Solutions: Interface offers engineered-to-order load cells with customized overload protection features for applications with unique overload challenges. The 1000 Fatigue Rated Universal LowProfile Load Cell with added overload protection demonstrates this capability.

#3 – Specialized Designs for High-Risk Applications: Certain Interface load cells are specifically designed for environments where accidental overloads are more likely to occur. With its internal mechanical stops protecting up to 10 times its rated capacity, the SMT Mini Load Cell is ideal for low-capacity applications in laboratories or medical facilities. The SPI Single Point Impact Cell also features internal stops, offering up to four times its rated capacity in compression overload protection, making it suitable for applications prone to impact loads.

#4 – Compression Overload Protection in LowProfile Load Cells: Even in designs without explicit EDM features, like our LowProfile series (e.g., 1000, 1100, 1200), Interface can offer compression overload protection by precisely controlling the tolerances between the base and the bottom of the hub.

Use the Load Cell Selection Guide to find load cells that fit your capacity and overload protection requirements.

Three Practical Steps for Overload Prevention

While built-in overload protection is a vital safeguard, proactive measures can further minimize the risk of overload events:

1. Review Safe Overload Specifications: Always thoroughly understand each load cell’s capacity and overload specifications, as clearly stated in the product documentation.
2. Utilize Interface Overload Protected Load Cells: When the potential for overload exists, prioritize selecting load cells with integrated overload protection features.
3. Implement Regular Maintenance and Calibration: Periodic checks and calibrations are crucial for maintaining the continued accuracy and performance of load cells. Tools like ohm meters can aid in the early detection of potential overload conditions or other electrical issues. Interface recommends annual calibration for optimal results.

Prioritizing Overload Protection for Measurement Integrity

Overload significantly threatens the accuracy, longevity, and safety of force measurement systems. By understanding the causes and consequences of overload and leveraging the innovative overload protection features offered by manufacturers like Interface, users can significantly mitigate these risks. Whether through mechanical stops, specialized designs, or engineered solutions, incorporating overload protection is a fundamental consideration for ensuring the reliability and integrity of your critical measurements.

Popular Overload Protected Load Cells

• SMT Overload Protected S-Cell
• MBI Overload Protected Miniature Beam Load Cell
• MBP Overload Protected Miniature Beam Load Cell
• SMTM Micro S-Type Load Cell
• LBMP Overload Protected Compression Load Button Load Cell
• WMCFP Overload Protected Sealed Stainless Steel Miniature Load Cell with Female Threads
• WMCP Overload Protected Stainless Steel Miniature Load Cell with Male Threads
• MRTP Miniature Overload Protected Flange Style Reaction Torque Transducer
• MRT2P Miniature Overload Protected Flange Style Reaction Torque Transducer
• 2101 Dual Range Standard Compression-Only Load Cell
• SPI Single Point Impact Cell

Interface has long recognized the critical need for overload protection, embedding this principle in our design philosophy. For further technical consideration information, consider Interface’s Load Cell Selection Guide. Contact us today if you need an overload-protected load cell tailored to your application needs.

Additional Resources

How Does Load Cell Overload Detection Work?

Understanding and Preventing Load Cell Overload

The Crushing Reality of Impact Loads

Demystifying Specifications Webinar

Load Cell Performance Starts by Design Webinar Recap