Surface Acoustic Wave (SAW) sensors

Surface Acoustic Wave (SAW) technology offers wireless, batteryless, non-contacting strain measurement suitable for the measurement of torque, pressure, temperature and other parameters.

The SAW propagation mode is characterized by velocities typically 5 orders of magnitude below electro-magnetic waves with amplitudes in the order of nanometers and wavelengths in micrometers. Most energy is confined to within one wavelength of the surface. These characteristics have made SAW devices ideal for the design of delay lines and filters widely used in radar, TV and the mobile telecommunications industry. SAW devices are typically designed to operate within the frequency range 30MHz to 3GHz.

However, unlike filters for telecoms, some SAW torque sensor technology exploits the influence of strain, mechanical and thermal, on the resonant frequency of a single port SAW resonator – the first order effect being a reduction in resonant frequency with increase in surface strain and hence in the distance that the wave has to travel. SAW torque sensor technology exploits the principal tensile and compressive strains on the surface of a shaft in torsion for the measurement of torque.

SAW devices operating at 433MHz are bonded to metallic packages in order to protect them from surface contamination. However, again unlike filters in mobile phones, it is a requirement to couple the devices into the external strain field rather than to isolate them. As a result the bond-lines must be highly elastic with no micro-plasticity over the operational temperature range in order for the sensors not to exhibit unwanted creep or hysteresis. The development of this know-how has been an essential element in the development of successful sensors.

	Surface Acoustic Wave (SAW) Torque Sensor Technology White Paper
	Surface Acoustic Wave (SAW) Sensors in Automotive Applications (PPT 4 MB)

For more information, please contact us at info.sc@honeywell.com .