2-Axis Load Cells 101

Two-axis (bi-axial) sensors, such as Interface 2-Axis Load Cells, mark a significant advancement in force and torque measurement. Moving beyond single-axis limits, these advanced transducers are designed to accurately measure forces or torques in two perpendicular directions simultaneously, all from a single, integrated device.

The core technology depends on internal strain gages mounted on a specially designed metallic structure known as a flexure. When mechanical strain is applied, the gages convert this deformation into a proportional electrical signal.

Notably, the 2-axis design includes multiple, isolated strain gage bridges within a single sensor body. While a single-axis sensor uses one bridge to measure force along one axis, such as tension or compression, a 2-axis sensor employs additional bridges to produce separate, independent output signals for the orthogonal axes. This enables the simultaneous measurement of pairs, such as:

• Force in X and Force in Y measure shear or lateral forces.
• Axial Force and Torsional Torque measure compression/tension and twist.

Promises of Multi-Axis Technology

The primary technical advantage of a multi-axis design is the ability to acquire comprehensive, richer data about force interaction from a single measurement point. This consolidation of measurement simplifies the entire testing process while significantly enhancing data quality.

Advantage #1 – Minimizing Crosstalk

A defining technical challenge in multi-axis design is crosstalk, where loading one axis unintentionally influences the output of another. Interface sensors are engineered with low-crosstalk characteristics, ensuring the highest accuracy and fidelity for each independent channel. This results in more reliable data for evaluating structural integrity, load distribution, and performance characteristics.

Advantage #2 – Efficiency and Integration

By replacing multiple single-axis sensors, the 2-axis design offers a compact footprint that saves physical space, simplifies the setup by reducing the required number of sensors, cables, and connections, and maximizes the return on investment for complex testing devices. This makes them ideal for embedding into products in robotics, aerospace, and advanced material testing environments where space is limited.

Advantage #3 – Enhanced Reliability

The increased data density from tracking performance in multiple directions inherently improves the nonrepeatability and overall reliability of test results, providing engineers and researchers with a more complete understanding of complex force dynamics.

Interface 2-Axis Load Cells

Interface’s 2-Axis Load Cells measure any two forces or torques simultaneously, have minimal crosstalk, are standard off-the-shelf, and are high-accuracy sensors.

• TXY 2-Axis Force Load Cell
• AT101 2-Axis Axial Torsion Load Cell
• AT102 2-Axis Axial Torsion Load Cell
• 2816 2-Axis Axial Torsion Load Cell
• 1216 2-Axis Axial Torsion Load Cell
• 1516 2-Axis Axial Torsion Load Cell
• 5600 2-Axis Axial Torsion Load Cell
• AT103 2-Axis Axial Torsion Load Cell

Critical Technical Specifications of 2-Axis Load Cells

 When integrating a 2-axis sensor, key specifications define its operational capability and precision:

• Accuracy metrics are precision definitions, which are quantified by specifications such as nonlinearity (deviation from a straight calibration curve) and hysteresis (output difference when loading versus unloading). Both are critical for maintaining confidence in the force data across the entire full scale (FS) range.
• Temperature performance is specified in the compensated range, which is the ambient temperature window over which the sensor is guaranteed to meet its specified accuracy. Additionally, performance metrics such as effect on zero (zero output shift) and effect on output (sensitivity change) define the sensor’s degradation.
• Safety thresholds are used to prevent structural failure; engineers must adhere to the specified safe overload (maximum load without permanent damage) and maximum overload (ultimate load without structural failure).

TIP: Use Interface’s ForceEDU 2-Axis Load Cell Cheat Sheet for a reference on these types of sensors.

Diverse Applications of 2-Axis Sensors from Wearables to Yokes

While the technical specifications of 2-axis sensors highlight their precision, examining their applications reveals their indispensable versatility across disparate industries. The ability to measure axial force (push/pull) and torsional torque (twist) simultaneously within a single, compact body makes these sensors ideal for both demanding durability tests and critical operational monitoring.

Case 1: Testing the Resilience of Wearable Technology

Engineers developing consumer electronics, such as smartwatches, face the persistent challenge of ensuring durability under repeated, complex stress. Smartwatch bands, for example, undergo stretching, pulling, and twisting during daily wear and removal. To ensure the highest quality standards, the test required a precise method to capture the tensile force needed to detach or deform the band.

Interface’s solution involves integrating the 1216 2-Axis Axial Torsion Load Cell into a specialized force and torque test machine. The sensor was mounted to an actuator to capture the applied forces accurately. The 1216 measures the primary axial pull forces on the band while also monitoring any torsional forces caused by twisting motions. Using this bi-axial data, engineers can successfully identify weak points in the band materials and connectors, enabling them to optimize the design for improved long-term reliability and comfort before mass production. Check out the Smartwatch Band Pull Test app note. 

Case 2: Monitoring Critical Aircraft Controls

At the opposite end of the complexity spectrum, 2-axis sensors are essential for critical operational safety and monitoring in aerospace manufacturing. An aircraft manufacturer aimed to continuously track the forces and torque applied to an aircraft’s yoke (control wheel) to ensure proper function and responsiveness.

Interface recommends the AT103 2-Axis Axial Torsion Load Cell. This sensor can be discreetly installed inside the yoke assembly itself. The AT103 is uniquely capable of measuring the pilot’s inputs, including the torque generated by rotating the yoke and the axial force from pushing or pulling the yoke forward or backward. By pairing the AT103 with a data acquisition system, such as the SI-USB4 4-Channel USB Interface Module, the aerospace equipment manufacturer can accurately measure and monitor these dual inputs. This data is crucial for flight control systems, ensuring that pilot inputs are reliably converted into aircraft movement and validating the proper operational state of the controls. Read more: Aircraft Yoke Torque Measurement.

These two examples highlight the wide range of applications, from ensuring the mechanical integrity of a small consumer device to validating the real-time functionality of a critical aviation control system. In both cases, the efficiency and comprehensive data provided by a single 2-axis load cell used for measuring both linear and rotational forces are essential for high-confidence engineering decisions.

With their inherent precision, low crosstalk, and durable, fatigue-resistant design, Interface 2-axis load cells are ideally suited for critical applications that require detailed analysis from multiple axes. These applications include optimizing prosthetic design, analyzing forces in automotive wind tunnels, and monitoring structural loads in military and aerospace structures.

Learn more about Interface Multi-Axis Sensors: