Load Cell Design FAQs and Engineering Tips

A load cell is a high-precision instrument, and like any such tool, its performance is directly tied to its physical integrity. A reliable quality load cell must be designed with appropriate materials, installed correctly, and regularly maintained to ensure accurate output. Whether you are engineering a new test rig or troubleshooting an existing system, understanding the performance characteristics and limitations of your sensors is crucial for high-accuracy measurement data.

Based on the FAQs from our Load Cell Performance Starts by Design Webinar, here are the essential insights from our load cell engineers and experts on design, installation, calibration, and common failure modes.

Evaluating Performance Specifications

Understanding a load cell’s fundamental performance characteristics is a strategic necessity. These specifications, detailed on every Interface product data sheet, are the foundation for accurate and reliable measurement. A thorough review of these values during the design phase of your testing program is the first step toward building a robust, practical measurement system.

When reviewing a load cell to determine capabilities and performance, the Standard Error Band (SEB) is a critical specification to review first, as it provides a comprehensive indicator of overall accuracy.

When a load cell is subjected to forces beyond 100% of its capacity, its output can begin to deviate from its ideal linear curve, compromising measurement accuracy. At or above 150% of rated capacity, there is a significant risk of causing plastic damage and a permanent zero shift, which effectively ruins the sensor’s calibration.

While load cells generally maintain accuracy up to 100% of their calibrated range, a good rule of thumb for low-load testing is to use calibration values at or above 10% capacity. If testing requires data below this threshold, we recommend requesting a specific calibration at that lower point. Conversely, be mindful of upper limits; if a load exceeds 150% of capacity, the sensor may sustain damage to the bridge, resulting in a permanent zero shift.

  ENGINEERING TIP: Operating a load cell within its specified design parameters is crucial for achieving the highest data accuracy and ensuring the sensor’s long-term health. Pushing a sensor beyond its intended limits risks not only inaccurate readings but also the kind of permanent damage discussed earlier. Understanding these boundaries is key to reliable measurement.

Troubleshooting Zero Drift and Temperature

A “wandering zero” during temperature cycles is a frequent concern. If a load cell is sitting isolated (unmounted) and the zero reading drifts significantly during temperature cycles (e.g., up to 170°C), this is not typical behavior for a healthy unit. However, if the sensor is mounted, drifting is often caused by the assembly itself, which can create residual mechanical effects.

Material choice plays a role here. Be cautious with aluminum load cells in high heat. If the temperature exceeds the rated operating range (typically 200°C), the aluminum properties may change (tempering), or the gauges could separate from the flexure, leading to failure.

  ENGINEERING TIP: A drifting zero reading during temperature cycling is not typical for a healthy load cell. Potential causes include residual mechanical effects or operating above the rated temperature range. If you have concerns about performance, it’s time to schedule a calibration check-up.

Installation Strategy Starts with Orientation

How you orient the load cell on an actuator rod directly impacts the accuracy of your data acquisition (DA) system. It is highly recommended that the live end of the load cell be placed closest to the test article. If the “dead end” (containing the base and cable) is closer to the test article, you introduce minor parasitic or inertial mass. This can cause a discrepancy between what the sensor reports and what your data acquisition system sees, particularly in dynamic cycling applications.

  ENGINEERING TIP: Review your sensor model installation manual to identify the live end and dead end. All load cells have a “dead” end and a “live” end. Commonly, the dead end is the mounting end directly connected to the output cable or connector with a solid metal connection. Conversely, the live end is separated from the output cable or connector by the strain gage area of the flexure. Read more in Load Cell Mounting 101.

Managing Crosstalk in Multi-Axis Sensor Applications

For multi-channel sensors, crosstalk can be managed through intelligent flexure design and selection. You should prioritize the model based on your primary measurement axis. For example, if axial load is paramount, choose models that start as LowProfile axial sensors and add torsional bridges, similar to Interface’s 1216 2-Axis Axial Torsion Load Cell. If torque is the priority, select models that begin as reaction torque sensors and add axial bridges, as in our 5600 2-Axis Axial Torsion Load Cell.

Regardless of the model, the best general practice is to characterize crosstalk by applying known loads, observing the signal impact, and adjusting for this in your instrumentation.

ENGINEERING TIP: You have two options to mitigate crosstalk: one is to characterize the load cell and adjust it through instrumentation, and the other is to select a model designed around a primary measurement axis.

Calibration Frequency and Methods

“How often should I calibrate?” is a common question. While most customers recalibrate annually, the answer depends on the severity of use. For harsh or destructive testing, it is highly recommended to calibrate before and after the test to ensure sensor integrity.

You must also decide between system and component calibration. If total performance is the goal, opt for an in-rig system calibration, which calibrates the load cell, cable, and instrument together. However, if you frequently swap sensors, maintaining individual component-level calibrations is more practical.

Interface recommends a system-level calibration when the overall performance of the measurement system is the primary concern. This process calibrates the load cell, cable, and instrumentation together as a single system.

ENGINEERING TIP: Calibrate your transducer before and after a long or harsh test to ensure confidence in the readings. Fatigue testing with high cycle counts needs more frequent calibrations. For newer load cells, we always recommend annual calibrations to maintain your investment. Before you start any critical test, calibration will ensure the load cell is ready for use.

Preventing Failure and Overload

Load cells are very durable instruments. Two common causes of failure are mechanical overload and unexpected forces. We have load cells engineered to withstand extreme environments, from the vacuum of space to 30,000 PSI in downhole applications. The environment is one consideration; however, use also influences performance. Load cells are susceptible to shock loading, off-axis forces, and fatigue. Mechanical overload can be exacerbated by unexpected off-axis or side loads, which create combined loading. Shock loads are another common cause of failure, as load cells are generally not designed to withstand them.

To mitigate these risks, especially in miniature load cells that are prone to overload, look for sensors with built-in overload protection. Beneficial for tests that require a very tight, specific calibration range, but may still subject the assembly to a much larger mechanical load. Proactive protection isn’t optional. It is the first and most critical step in ensuring reliable, repeatable measurements over the long term. Understanding and mitigating the most common risks is fundamental to preserving the sensor’s health and the validity of your data.

ENGINEERING TIP:  Specific LowProfile series can provide compression overload protection of 300–400% by tightly controlling tolerances between the base and hub. Alternatively, you can upsize the load cell capacity to handle higher mechanical loads while requesting specific calibration points to maintain confidence in your lower test range.

Listen to the entire conversation about addressing these top load cell design FAQs:

• What specification is the most important when you evaluate load cell performance?
• How frequently should load cells be calibrated?
• What environments/applications can load cells be used for?
• What % of capacity is a load cell accurate for?
• What are the common causes of load cell failure, and how can they be prevented?
• When do you need to select overload protection?
• How does the number of bridges improve your load cell performance?
• Do you need to do a system-level calibration with your instrumentation?
• What is the FOS of a load cell?
• What makes good material for a load cell?

True precision in force measurement comes from mastering subtle engineering details, in performance by design. Interface has an extensive catalog of transducers. Our team of load cell engineers masters the science of measurement through the careful application of our proprietary sensor technologies. If you are looking for a specific sensor or have questions about a custom application, don’t hesitate to contact our Application Engineers.

If you would like to watch the entire engineering perspective on our YouTube channel, Load Cell Performance Starts by Design Webinar.

Need help selecting the right sensor? Contact our application engineers today to discuss your specific testing requirements.