About Multi-Axis Load & Torque Cells
Multi-Axis Load & Torque Cells
Multi-axis load and torque cells are advanced force transducers engineered to measure forces and moments along multiple orthogonal axes simultaneously. Unlike conventional single-axis load cells that only capture force in a single direction, these sensors provide a complete, six-degree-of-freedom (6-DOF) measurement by detecting force components (Fx, Fy, Fz) and torque components (Mx, My, Mz) in three-dimensional space. This makes them essential tools for applications where complex, multi-directional loading occurs and where understanding both translational and rotational effects is critical.
In biomechanics and mechanical test environments, multi-axis sensors play a pivotal role in capturing how systems behave under real-world conditions. Components in engineered systems rarely experience forces in just one direction; instead, they are subjected to combinations of axial loads, lateral shear, bending moments, and torsional forces. Multi-axis load and torque cells enable researchers and engineers to capture the complete load profile acting on a structure or mechanism, offering far more insight than single-axis devices.
These sensors are constructed with precision-machined bodies—typically from high-strength aluminum or stainless steel—and internally bonded strain gauges configured in Wheatstone bridge circuits. The strain gauges are arranged in such a way that each bridge is sensitive to a specific directional component of load or moment. When a force or torque is applied to the sensor, it causes localized strain in the structure, which the strain gauges detect and convert into corresponding electrical signals. High-quality multi-axis cells are engineered to minimize cross-talk between channels, ensuring that each signal accurately reflects the load component it is designed to measure.
Why Are They Important?
In biomechanics, mechanical test systems, and structural validation setups, understanding how components behave under real-world, multi-directional forces is essential. Multi-axis load and torque sensors provide that insight by allowing engineers to measure all the forces and torques acting on a system from a single reference point. This eliminates the need for multiple single-axis sensors arranged at various angles and ensures that all data originates from a common, calibrated frame.
Applications range from machine interface testing and structural joint evaluation to robotic system integration and underwater force measurement. For instance, a six-axis sensor like the AD2.5D can be embedded in a mechanical interface or submerged environment to capture accurate 6-DOF load data in real time. These measurements help validate designs, ensure compliance with force thresholds, and inform decisions in safety-critical or performance-critical applications.
At A-Tech Instruments, our range of multi-axis load and torque sensors is tailored to meet the demanding requirements of biomechanics and mechanical testing fields. From compact underwater-capable sensors to high-capacity, flanged-base transducers for heavy-duty use, our portfolio supports diverse applications with proven accuracy and long-term stability.
Operating Principles
How do the Multi-Axis sensors work?
Multi-axis load and torque sensors operate on the principle of strain measurement, using bonded strain gauges arranged in carefully engineered mechanical structures to detect deformations caused by applied forces and torques. These deformations are extremely small, often in the micrometer range, but are enough to change the electrical resistance of the strain gauges. By organizing these gauges into full Wheatstone bridge circuits, the sensor converts mechanical input into measurable voltage outputs—one for each directional component.
At the core of a multi-axis sensor is a machined flexure element, typically made of high-strength aluminum or stainless steel. This element is designed to deflect in predictable patterns when subjected to external loads. Strain gauges are strategically bonded to the surfaces of this flexure, with each set oriented to sense strain in a specific axis of interest—either translational (Fx, Fy, Fz) or rotational (Mx, My, Mz). When a load is applied, different parts of the flexure experience tension or compression. The resulting change in strain alters the resistance in the gauge circuits, generating voltage signals proportional to the magnitude of the applied force or torque.
To resolve six degrees of freedom, the sensor typically contains six independent measurement channels. Each channel is electrically isolated and calibrated to respond only to its designated component. However, because all components are measured on a single structure, internal coupling effects—referred to as cross-talk—can occur. High-end sensors are engineered with mechanical symmetry, strategic gauge placement, and optimized geometry to minimize this cross-talk. Calibration matrices are often provided to compensate for any residual coupling between axes.
Precision machining and careful design are critical. The geometry of the internal flexure defines how forces and torques are distributed, and even small asymmetries can lead to measurement errors. That’s why sensors like the MC36 or FS6-100 are built to exacting tolerances, using finite element analysis to optimize strain distribution and ensure high linearity and repeatability.
Environmental considerations also play a role in sensor performance. To ensure long-term stability, many models incorporate protective coatings, internal potting, or hermetic sealing. For instance, sensors like the SPC2.5D and SF3-100 are filled with oil or include pressure compensation systems to maintain accuracy during underwater or submerged operation.
In use, each sensor’s output is typically connected to a multi-channel signal conditioner or data acquisition system. The resulting signals—often in millivolts per volt (mV/V)—can then be scaled using the calibration matrix to obtain real-time values for all six components. This structure enables accurate, synchronized force and torque measurement from a single physical point, which is critical in dynamic systems where load interactions evolve over time.
The effectiveness of a multi-axis sensor ultimately lies in the harmony between its mechanical design, strain gauge placement, signal conditioning, and calibration. When these elements are properly integrated, the sensor becomes a powerful tool for capturing complex load profiles with precision and clarity.
Types of Multi-Axis Sensors
Multi-axis sensors can be categorized based on the number of measured components, mechanical configuration, sensing technology, and intended application. While six-axis sensors (measuring Fx, Fy, Fz, Mx, My, Mz) are the most comprehensive, variations exist to support specific test conditions or form factor constraints.
Compact vs. High-Capacity Platforms
Multi-axis sensors range from compact, lightweight transducers for integration into small devices or fixtures to large, high-capacity platforms built for structural or machine testing. For instance, sensors like the AD2.5D and SPI2.5D are designed with a small footprint and waterproof construction, suitable for confined or underwater applications. In contrast, the MC818 or MC5 series offers high-load capacity and rugged bodies that accommodate large forces and moments, making them ideal for evaluating frames, linkages, and machinery.
Flanged and Threaded Mounting Styles
The mechanical interface of a multi-axis sensor significantly influences its application. Flanged-base sensors, such as the MC36 or MC12, are commonly used in fixed test rigs and industrial setups, where a robust connection to t-slot platforms or steel plates is required. Other models offer threaded mounting on both faces, allowing flexible integration into mechanical systems, tooling assemblies, or robotic arms.
Specialty Sensors
Some multi-axis transducers are developed for niche applications where standard geometry is insufficient. For example, the BOLT-3 is purpose-built to simultaneously measure bolt preload, thread friction torque, and applied head torque during fastener testing. Similarly, the MCL6 is designed to monitor cutting tool forces in turning operations, such as in a lathe, combining six-axis output with a mounting fixture suited for rotational tool assemblies.
The MC32xx series, including models such as the MC3232 and MC3246, extends this specialty offering with high-capacity platforms tailored for landing gear simulation. These high-capacity sensors are used during drop testing to capture the Fx, Fy, and Fz forces generated upon tire contact with the ground. The MC3232 is suited for scenarios requiring large, simultaneous multi-axis force measurements that vary in direction and position over time. The MC3246, with its low-mass top plate and high natural frequencies, excels in capturing sharp impact events at high speeds; critical for analyzing touchdown dynamics. Both are manufactured from high-strength aluminum and designed with mounting provisions for stable integration into vertical impact rigs.
These designs demonstrate how multi-axis sensors can be adapted to highly specific mechanical environments without compromising signal resolution.
Environmental Protection and Submersible Designs
For applications involving exposure to liquids, contaminants, or pressure differentials, waterproof and environmentally sealed multi-axis sensors are essential. Models like the SF3-100, SPC2.5D, and UDW3 are engineered with stainless steel construction, internal potting, and pressure-compensation bladders. These features allow accurate six-axis measurement in short-term submersion or in marine and hydrodynamic testing conditions without degradation in signal quality.
Together, these variations allow engineers and researchers to select a sensor configuration that matches both the mechanical and environmental demands of their application, ensuring accurate, multi-dimensional force measurement across diverse test conditions.
Choosing the Right Multi-Axis Sensor
Selecting the appropriate multi-axis load and torque sensor depends on a range of mechanical, electrical, and environmental criteria that must align with your specific test or integration requirements. While all multi-axis sensors are designed to measure forces and moments in multiple directions, differences in range, structure, mounting, and environmental resistance play a critical role in choosing the correct model for your application.
Define Your Measurement Axes and Capacity
Begin by determining whether your application requires measurement of just forces (Fx, Fy, Fz), torques (Mx, My, Mz), or a full six-axis solution. Some applications only demand 3-axis force measurement, while others require all six degrees of freedom to understand system behavior. Once axes are defined, select a sensor with appropriate load and torque ranges. For example, if your setup involves high-magnitude vertical forces but limited lateral torque, choose a model with high Fz capacity but moderate moment capacity—such as the MC5 series.
Consider Mechanical Interface and Geometry
Mounting configuration and physical dimensions are equally important. Choose between flanged bases for rigid mounting (e.g., MC12) or threaded interfaces for inline integration. Evaluate the available space in your setup to ensure the sensor's footprint, height, and weight are compatible with your fixture or machine. Compact sensors like the FS6-100 offer high precision in space-constrained environments, whereas large-format designs like the MC818 provide enhanced stiffness and load capacity.
Evaluate Cross-Talk Sensitivity and Accuracy
Sensor precision is defined by more than just accuracy; cross-talk performance and repeatability are equally critical. Look for sensors with low non-linearity (e.g., ±0.2% FS or better) and proven calibration matrices that decouple force and torque signals. Products engineered for high-fidelity measurement, such as the BOLT-3, incorporate internal compensation to minimize cross-axis interference during simultaneous loading.
Match Environmental Protection to Application
If your application involves exposure to liquids, high humidity, or submersion, select a sensor rated for waterproof or sealed operation. Sensors like the SPI2.5D, UDW3, or SF3-100 offer stainless steel housings, pressure-compensation systems, and internal potting to protect sensitive components. These are ideal for tow tanks, ocean engineering, and any environment requiring sustained exposure to water or contaminants.
Electrical Integration and Data Acquisition
Check compatibility with your data acquisition system or controller. Most multi-axis sensors output analog signals (mV/V) per axis and require multi-channel instrumentation for signal conditioning. Some models may offer pre-calibrated outputs or digital interfaces. Ensure your DAQ hardware can accommodate the number of channels, bandwidth, and voltage range required by the sensor.
At A-Tech Instruments, we offer more than just a wide selection of multi-axis sensors; we provide hands-on support to help you make the right choice. Our team of application specialists and technicians is available to review your application requirements, discuss your test environment, and guide you toward the model that best fits your needs.
Applications
Multi-axis load and torque sensors are indispensable in research and development environments where the interaction between force and torque must be captured with high spatial accuracy. In biomechanics, they are frequently embedded in custom rigs, simulators, and instrumented equipment to evaluate the mechanical behavior of joints, implants, or assistive devices under realistic, multi-directional loading. For example, during joint simulator tests, components often experience a mix of axial loading, shear, and torque—conditions that cannot be replicated or measured accurately using single-axis load cells. Multi-axis sensors allow engineers and researchers to resolve these combined forces into precise, orthogonal components, making it possible to study not only the peak loads but also how these loads are distributed and interact.
Beyond biomechanics, these sensors are crucial for systems where force and moment vectors are variable and coupled. In fatigue testing of mechanical structures, the accurate capture of bending and torsional moments is essential to predict failure modes. In robotic systems, multi-axis feedback enables compliant interaction with unknown or dynamic environments, which is especially important in rehabilitation robotics and exoskeleton design, where safety and responsiveness are priorities. Similarly, underwater research applications—such as hydrodynamic drag studies on biomimetic devices—require sensors that can withstand immersion while capturing full 6-DOF load profiles.
In aerospace engineering, multi-axis force sensors play a vital role in landing gear testing and structural impact simulations. Sensors like the MC3232 and MC3246 are widely used in drop test platforms that simulate the vertical impact of landing. These tests are designed to replicate the forces experienced during touchdown and ground roll, with the sensors capturing critical data along the Fx, Fy, and Fz axes. This data informs the design of shock absorption systems, evaluates structural resilience, and ensures regulatory compliance. Their high-frequency response and ability to withstand large, transient loads make them indispensable tools in validating aircraft performance and safety.
Across all these applications, the use of a multi-axis sensor is not just about adding measurement capability; it is often the only way to obtain meaningful, reliable data when load paths are multidirectional, evolving, or highly sensitive to positioning. Whether in academic research, clinical validation, or engineering development, these sensors serve as the backbone of systems that require complete mechanical insight.