How Does Load Cell Overload Detection Work?

Overload detection is a critical aspect of force measurement systems that ensures the safety and accuracy of load cells. Load cells are integral in various applications and measure forces such as weight, compression, or tension. These sensors can be compromised without proper overload protection, leading to inaccurate readings or permanent damage. Let’s explore how overload detection works, its importance, and how load cells work.

An overload occurs when the force applied to a load cell exceeds its rated capacity. Load cells are designed to operate within specific load limits, and surpassing these limits can lead to permanent deformation, signal distortion, and, in some cases, complete failure.

Load cells are equipped with overload detection and protection mechanisms for prevention; however, they can not prevent someone from using a load cell beyond the designed capacity specifications. For test and measurement programs that need to mitigate the risk of overload, Interface strongly recommends considering designed sensors with overload protection.

TIP: Read Understanding and Preventing Load Cell Overload 

How Overload Detection Works

Overload detection in load cells is typically based on strain gage technology. Strain gages, bonded to the cell’s load-bearing surface, measure the deformation caused by the applied force. When the force exceeds the load cell’s rated capacity, the deformation becomes too great, which can cause the strain gage to output erroneous readings or become damaged.

To mitigate this, overload detection systems are implemented. These systems can involve mechanical, electrical, or software-based methods to detect when the load approaches or exceeds the rated capacity, triggering warnings or shutting down the system to prevent further damage.

As detailed in Interface’s Load Cell Field Guide, load cells can be equipped with various overload protection mechanisms to prevent damage:

1. Mechanical stops are physical barriers within the load cell structure that prevent excessive deformation. Once the load reaches a certain threshold, these stops engage to block further movement, thus protecting the internal components from overload.
2. Overload protection circuits are electrical circuits designed to monitor the strain gage output. If the output signal indicates the load is approaching the danger zone, the circuit can trigger an alert or automatically shut down the system.
3. Strain gage sensitivity adjustments can be fine-tuned to detect overload conditions. By adjusting the strain gage’s configuration, the system can be calibrated to detect slight variations in force that indicate an impending overload.

Importance of Overload Detection

1. Preventing Damage to Equipment: Load cells are used in critical applications such as industrial weighing systems, material testing, and structural testing. Overload detection is essential to protect these costly and sensitive devices from damage and ensure the longevity and reliability of the sensors.
2. Maintaining Accuracy: Even minor overloads can cause deformations that affect a load cell’s accuracy. By detecting and preventing overload conditions, these systems ensure that readings remain consistent and reliable.
3. Ensuring Safety: An overload could lead to catastrophic failures in applications where load cells monitor structural loads or industrial processes. Overload detection systems help prevent accidents by ensuring that loads remain within safe operating limits.

Interface Load Cells with Overload Protection

There are two choices available for overload protection. The first is to utilize the overload protection designed into the standard model, which typically is 4 to 10 times the capacity. The other option is to request an engineered-to-order load cell like our 1000 Fatigue Rated Universal LowProfile Load Cell with overload protection added to the sensor.

One of the most popular Interface Mini Load Cells with built-in protection is our SMT Overload Protected S-Cell, which includes built-in overload protection features. Model SMT is ideal for low-capacity applications where load cells are often inadvertently overloaded. The SMT has internal mechanical stops that prevent overloads for up to 10 times the rated capacity. These cells incorporate locking design elements that engage when the cell reaches its maximum load capacity, preventing further deflection and protecting the strain gage from damage. The design of these cells makes them ideal for environments where large accidental loads might occur, such as in product testing laboratories or medical device research facilities.

Interface’s 2101 Dual Range Standard Compression-Only Load Cell consists of lower and higher capacity model 1200 type load cells stacked with overload protection built into the lower capacity load cell. This permits high resolution to be obtained at low and high capacity levels. The design offers 4x to 5x overload protection on lower-capacity load cells. This LowProfile design has additional 2111, 2121, 2131, and 2141 models.

Another example is the SPI Single Point Impact Cell, which has internal stops to protect the cell from compression overload. This design allows the SPI cell to handle up to four times its rated capacity, making it a popular choice in applications requiring frequent overload protection.

Additional standard load cells and transducers with designed overload protection include:

• 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

Overload detection in load cells is vital for protecting the sensor and the system in which it operates. Mechanical stops, protection circuits, and advanced strain gage technology safeguard load cells against damage from excessive loads. Proper overload detection ensures force measurement systems’ longevity, safety, and accuracy in industrial applications, testing labs, or aerospace systems.

If you’re working with load cells, it’s essential to consider overload protection as a feature if you are concerned about exposure to forces beyond the sensor’s rated capacity.