SAW Technology

FAQ's

Questions and answers on our patented Transense Torque and Temperature sensors

What is the size of the torque sensor?

The actual SAW torque sensor package is approximately 8 x 6mm by 2mm thickness.

What is the operating temperature range of the torque and temperature sensors?

Our standard operating temperature range for the torque and temperature sensor is from -40⁰C to 125⁰C. In some applications extending the upper limit to 150⁰C may be possible.

How small are the electronics?

Excluding passive components, and voltage regulators, there are 2 key components on the SAW reader electronics printed circuit board (PCB). These are the Radio Frequency Application Specific Integrated Circuit (RF ASIC) and the Digital Signal Processor (DSP). These components are 7mm x 7mm and 14mm x 14mm respectively. The electronics may be supplied as a standalone PCB or integrated into the customers electronics. The small size of the electronics also enables them to be integrated into different form factors.

What is the torque sensor accuracy?

An overall torque accuracy with an error of better than 1% full scale can be achieved.

Is the torque and power measurement sensor affected by mechanical shocks or vibration?

Unlike magnetic technology torque sensors the Transense SAW torque and power measurement sensor is not affected by mechanical shock or vibration.

How rugged is the torque sensor? Is the torque sensor affected by dust?

Unlike some optical torque sensors SAW torque sensors are not affected by dust and may also be used in a liquid environment such as transmission oil. The torque sensors are also very rugged and have exceeded expectations when qualified for use within military aircraft applications.

Can the torque sensor measure static as well as dynamic torque?

Yes, the Transense torque sensor has been designed to measure dynamic and static torque without the need for batteries on the shaft, energy harvesting or inductive coupling.

How does a torque sensor work?

Torque Sensors (or Torque Transducers), measure torque in a variety of methods. The basic principle is, in essence, a very simple mechanical process, it is a measure of the “force” being used (or attempting) to turn an element. When a force of “torque” is applied to a shaft, the shaft twists (by a very small amount). The Transense torque sensor is a non-compliant sensor that measures minute changes in surface strain using Surface Acoustic Wave (SAW) technology. Please see a video explaining the principle of operation at Surface Acoustic Waves - An Introduction by Dr. Victor Kalinin of Transense Technologies plc and also a short brief at SAW Technology and Torque Sensor Measurement

Is the torque sensor suitable for Electric Power Assisted Steering systems?

The Transense Torque sensors are suited well for Electric Power Assisted Steering (EPAS) systems because of their torsional stiffness, small size, batteryless and wireless benefits. With the exception of 2 small flat spots on the shaft to accommodate the sensing elements, no other mechanical structures are required. SAW torque sensors are very sensitive to strain, non-compliant and do not require expensive torsion bars. This enables the use of a far less complex and lower cost mechanical design, a significant advantage over Hall effect and optical sensors. Vehicles with EPAS systems installed reportedly see a better fuel economy due to decreased loss of engine power. CAN outputs can be provided to send signals to an ECU.

Is the SAW sensor affected by stray magnetic fields?

Unlike some torque measurement sensors, SAW sensor technology is not affected by magnetic fields.