New range of TORQSENSE Rotary Torque Transducers.
Sensor Technology Ltd announces that, after more than
10 years of development, a range of Rayleigh Wave
TORQSENSE (RWT) transducers is now available.
Their experience of working with this relatively simple patented technology
also means that it can now be embedded into OEM products.
A family of TORQSENSE transducers is now available in 7 sizes
measuring torque from 100mNm up to 10,000 Nm at Full Scale Deflection
with smaller ranges having speeds up to 30,000 rpm. The advantages for
using SAW devices in torque transducers are:
Cost sensitive
Minimum length of shaft
Low inertia
Non contact between housing and shaft
Simplicity
High Bandwidth
Signal immunity
Non speed dependent
Rotary torque has historically been difficult and expensive to measure.
The patented method uses SAW devices as 'frequency dependent'
strain gauges to measure the change in resonant frequency caused
by the applied shaft strain. By using a frequency-based device, the
signal bandwidth is increased, and the problem of electronic interference
common with other analogue based technologies is eliminated.
TORQSENSE transducers have a minimum length and relatively high
stiffness of shaft, low inertia, no physical contact between shaft and
housing, wide bandwidth, high resolution and accuracy, and excellent
noise immunity. TORQSENSE technology is suitable for utilization in
OEM applications where knowledge of torque is critical.
In a TORQSENSE transducer, surface waves are produced by passing
a high frequency voltage across the terminal of two interleaved
comb-shaped arrays that are layered onto one end of piezoelectric
substrate. A similar 'receiving' terminal, at the other end of the transducer,
converts the wave back in to an electric signal.
The frequency of the wave generated is dependant on the spacing of the
'teeth' in the comb array and as the direction of the wave propagation is
at right angles to the teeth, any change in its length alters the spacing of
the teeth and hence the operating frequency.
To measure torque in a shaft, two SAW transducers are bonded at 45
degrees to the shaft's axis and connected in a 'half bridge' configuration,
so that when the shaft is strained, the difference in frequency output
between the two SAWS relates to the applied torque.
TORQSENSE transducers require no physical connection to the
shaft's housing. Instead, the signals are transmitted via a coupling
device.
OEM applications for TORQSENSE include automotive, manufacturing
machines, condition monitoring, tightening procedures and monitoring
and control of viscosity during mixing processes.
__________________________________________________
For more information, please contact :-
Sensor Technology Ltd.
Tel: +44(0)1295 730746 Fax: +44(0)1295 738966
Email: info@sensors.co.uk
Website: www.sensors.co.uk
June 2002
