Understanding and preventing load cell overloads

Overload detection is critical to maintaining load cell integrity, accuracy and health. Properly detecting and managing overload conditions can prevent permanent damage and ensure sensor longevity.

Overload is not a new concept in measurement technology. You could say that overload protection is in Interface's DNA. Interface founder and inventor Richard F. Caris patented a weighing device with overload protection for off-center loading in 1983. In 2004, Interface engineer and force measurement expert LaVar Clegg patented Interface's overload-protected load cells. Interface's engineering team of LaVar Clegg and Larry Burrow subsequently received a patent in 2012 protecting the intellectual property of load cells for monitoring torsion and overload protection.

Overload protection is not just a theoretical concept, but a practical design feature of a load cellAt Interface, we have made it easy for you to connect load cells with Overload protection This feature is indicated in the model name and specifications, for example 3x overload protection or 10x overload protection. Whether you work in heavy-duty applications or simply want to ensure the longevity and accuracy of your load cells, this feature gives you the peace of mind that your equipment is protected.

TIP: Use the Interface Load Cell Selection Guideto find the standard load cells that provide overload protection tailored to your needs.

What is overload?

Put simply, overloading occurs when the load applied to a load cell exceeds its rated capacity. This can cause permanent deformation of the sensor, disrupting the carefully balanced processing that ensures accurate data. The consequences of overloading are not only detrimental, they can be catastrophic. Overloading can compromise the structural integrity of the load cell itself, causing significant damage and potential system failure. This underscores the importance of understanding and managing overload conditions and the need for reliable overload protection in your load cells.

A calculated Zero point shift of more than 20% clearly indicates an overload. If the calculated zero shift is between 10% and 20%, this indicates a probable overload. It is important to note that such mechanical damage is usually irreversible. Although it is possible to reset the zero point of the load cell electrically, this will not restore the affected performance parameters, which underlines the need for careful and proper handling.

Another, potentially more dangerous, type of overload is shock loading. Shock loading is a sudden force that can cause significant damage to load cells. If the live end of the cell moves more than 150% of its full deflection relative to the dead end, the cell could be overloaded regardless of the duration of the impact. The forces generated by shock loading can be extraordinarily high, leading to potential overload and subsequent damage.

Dealing with external loads

External loads, such as side loads, moments or torques, can also affect the performance of a load cell. These off-center vectors add to the near-axis load vector and can cause an overload condition in one or more calibrated regions of the bend. To determine the allowable overload capacity on the axis when extraneous loads are present, calculate the on-axis component of these loads and subtract it from the rated overload capacity.

SMT Overload Protected S-Cell

The integration of overload protection is a significant innovation in the design of the Interface S-Cell. By removing the large gaps at the top and bottom of the cell and replacing them with small gaps and locking fingers, the entire cell can become "tight" in either mode of operation (tension or compression) before the deflection of the measured area exceeds the allowable overload specification. The double-stepped shape of the gaps in an S-Cell design is necessary to ensure that overload protection works in both modes of operation.

The SMT series is ideal for applications where forces up to eight times the load cell's rated value can occur. The two loading ports are vertically oriented so that the cell can be easily installed in machines that perform a reciprocating or linear motion, either by means of a rotating crank or a pneumatic or hydraulic cylinder.

The covers provide physical protection for the flexure, but the cell is not sealed, so users should be cautioned not to use them in dusty applications where dust accumulation could form in the overload gaps. Should dust accumulation occur, the overload protection would kick in before the load reaches rated capacity, resulting in non-linear performance.

The SMT series is particularly suitable for laboratories or medical facilities where untrained or non-technical personnel could inadvertently apply large loads.

Preventive measures against overload

#1 Check the specification for safe overload

Start with the basics by reviewing the specifications of each load cell to understand the capacity range of the sensor. Interface provides the overload protection value in the product description, features and specifications. The values ​​can be found in the Safe Overload – %CAP mechanical specification.

#No. 2 Use of overload protected load cells with interface

Interface offers Load cells equipped with overload protection This feature limits the travel of the central hub under load and prevents further deflection once a certain limit is reached. This is particularly useful in applications where high shocks or sudden loads are expected.

#3 Regular maintenance and calibration

Regular checks with measuring devices such as ohm meters can help detect overloads early. Insulation resistance tests can also reveal potential problems that could indicate overloading or other electrical problems.

TIP: Calibrate your load cells at least once a year to maintain accuracy and performance. Here you can find a Calibration service arrange.

Detecting and managing overloads is essential to ensuring the reliable performance and longevity of a load cell. By recognizing the signs of overload, managing shock loads, and applying preventative measures, users can maintain the integrity of their measurement systems. Regular maintenance and proper design considerations are critical to avoiding the damaging effects of overloads and ensuring accurate, long-term load cell performance.

By complying with these guidelines, industry can ensure that their load cells continue to perform accurately and reliably, thereby maintaining the overall integrity of their test and measurement systems.