What are load cells and torque sensors?
A load cell is a transducer that converts force into an electrical signal, and a torque sensor does the same for twisting moment on a shaft or flange. Nearly all precision force and torque sensors use bonded foil strain gauges on a machined metal element, which gives excellent accuracy, stiffness and long-term stability.
Test engineers use them to measure what a structure or machine actually experiences: actuator loads on a fatigue rig, driveline torque on a dynamometer, clamp force on a press, or capping torque on a packaging line. When the measurement does not fit a catalog part because of a rotating shaft, tight packaging or multiple load directions, a custom-engineered sensor is often the practical answer.
How strain-gauge force and torque sensing works
A strain gauge is a fine foil grid whose resistance changes as it stretches or compresses. Sensor designers place gauges where the element strains most predictably under the load to be measured and least under loads to be ignored.
- Wheatstone bridge: Four active gauges form a bridge. Load unbalances it, producing a millivolt output proportional to force or torque, while matched gauges cancel temperature effects.
- Excitation and output: A conditioner supplies a stable excitation voltage. Sensitivity is stated in mV/V, so a 2 mV/V cell excited at 10 V gives 20 mV at full scale.
- Torque elements: Gauges on a shaft or flange are oriented at 45° to the axis, where torsional shear produces the largest principal strains.
- Getting the signal off a rotating shaft: slip rings, rotary transformers or on-shaft wireless telemetry.
| Sensor type | Measures | Typical use |
|---|---|---|
| Fatigue-rated pancake cell | Cyclic tension and compression | Servo-hydraulic durability rigs |
| Universal or S-beam cell | Tension and compression | Presses, material testing, force control |
| Reaction torque sensor | Static or dynamic torque, non-rotating | Motors, brakes, fastening tests |
| Slip ring torque sensor | Rotating torque | Intermittent drivetrain testing |
| Rotary transformer torque sensor | Rotating torque, no brushes | High-speed, long-duration dynamometers |
| Wireless torque sensor | Rotating torque, no housing | Vehicle wheels, confined shafts |
| Multi-axis sensor | Two or more forces and moments | Drilling, capping, component fatigue |
Common applications
- Automotive test and production: wheel torque, driveline and transmission dynamometers, pedal and seat belt force, and assembly-line fastening across the Southeast automotive corridor.
- Aerospace and defense: structural testing, actuator load monitoring and component R&D for Huntsville’s aerospace and Army programs.
- Packaging and pharmaceutical: torque and thrust measurement on bottle-capping heads.
- Heavy equipment and industrial automation: press force, conveyor diagnostics and off-highway equipment loads.
- Universities and research labs: material testing and biomechanics.
Choosing the right load cell or torque sensor
Accuracy on a data sheet assumes the sensor sees only the load it was designed for. In practice, bending, side load and misalignment cause most measurement errors, so start with the mechanical load path and mounting design. For cyclic loads, fatigue rating matters more than a few hundredths of a percent of nonlinearity.
For rotating torque, think about speed, test duration and what moves. A slip ring may be fine for short tests, while a rotary transformer or wireless design avoids brush wear and cabling on long or mobile tests. Finally, plan how the sensor will be calibrated and verified throughout its service life.
Manufacturers we represent for force and torque
SensorData Technologies in Shelby Township, Michigan, has engineered strain-gauge force and torque transducers since 1992, many of them custom. Its range includes fatigue-rated load cells from about 250 lb to 1,000,000 lb, reaction torque sensors, slip ring, rotary transformer and true wireless rotating torque sensors, and multi-axis sensors.
RDP Electrosense supplies tension, compression and universal load cells along with S7 and DR7 strain-gauge amplifiers, E-series indicators and the Modular 600 multi-channel system for test stands.
Get local application support
Vaughn Associates’ engineers can review your load path, mounting and data acquisition setup and bring the factory in for custom designs. Visit engineering support, request a quote, or find your area manager on the territories page.
