A torque transducer is a sensor that measures moment or rotational force about an axis. Torque or moment is the product of a force applied at a radius (moment arm). Applications requiring torque measurement include IC engines, electric motors, crankshafts, gearboxes, transmissions, rotors or even seemingly stationary items such as fasteners.

An industrial-grade torque transducer with instrument-like precision consists of strain gages that are bonded to a structural member such as the outer diameter of a shaft, which deforms when a torque is applied. This deformation induces a stress that changes the resistance of the gages within a Wheatstone bridge circuit and converts the resistance change into an accurately calibrated output signal. A wireless telemetry device transmits the data from the rotating world to the stationary receiving electronics for monitoring, recording or controlling the device.

Case Study

Researchers were testing and evaluating a 2004 hybrid automobile using Teledyne LeCroy’s Engine Torque Measurement System. They were mapping the vehicle’s major components and exploring the advanced controls used to achieve high fuel efficiency in its Hybrid Synergy Drive, but found that acquiring clean, accurate data in the hybrid electric vehicles’ high-voltage, electromagnetic interference-filled (EMI) environment posed a significant challenge.

An in-situ torque sensor was installed between the engine and the electric drivetrain, but the off-the-shelf torque-sensing element had temperature limitations (requiring external cooling), was susceptible to damage from torque spikes, and required an additional 3” of powertrain length to accommodate the sensor. A custom spacer between the engine and transmission was also required, as well as modification of the vehicle frame rail. These modifications limited the vehicle to off-road or dynamometer operation.

Teledyne LeCroy provided a newly developed zero-clearance torque sensor, which provided a much more elegant and robust solution. With this new design, no vehicle modifications were required, saving almost $20k in custom brackets and vehicle work, and allowed the vehicle to be driven normally on public roads.

Common Torque Measurement Challenges:
  • Desire to use existing components as the transducer to avoid changes to the powertrain
  • Space limitations
  • High vibration and G-forces
  • Extreme environmental factors such as high temperature, oil, dirt, water and salt
  • EMI/RFI induced noise on low level strain gauge signals

The Teledyne LeCroy Solution

Many disciplines within the automotive community have a need to measure in-vehicle driveline torque during testing. These include engineers testing transmissions, engines, clutches, differentials, ABS and traction control systems, tires, suspension components, and active suspension systems. Efforts to reduce emissions and improve vehicle efficiency also require accurate and non-intrusive techniques of measuring torque and horsepower. Typical powertrain torrque measurement applications include development and verification of engine torque algorithm; measuring engine torque during shift cycles; development of traction control and ABS systems; measuring torsional dynamics/resonance; efficiency testing; and engine and transmission trouble shooting.

While many companies produce off-the-shelf rotating and reaction torque sensors, Teleddyne LeCroy excels at providing custom solutions for unique customer applications that are not often addressed by commercially available alternatives. We have extensive expertise in torque measurement, utilizing and applying strain gauges to rotating equipment and delivering high-frequency data using robust noncontact, wireless telemetry technology.

Automotive Technology Center

The Teledyne LeCroy Automotive Technology Center is the premier Bluetooth device testing and services partner, with an enormous device library comprising 3000+ devices including coverage for every major car model.

Teledyne LeCroy Automotive Technology Center
27007 Hills Tech Court
Farmington Hills, Michigan 48331

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