Saelig Company, Inc. has introduced the Sensor Technology TorqSense SGR510/520 Torque Sensors which use a four-element strain gauge bridge design with non-contact surface acoustic wave (SAW) detection. These sensors offer a 250% over-range reading capacity, allowing sudden spikes in torque to be measured and recorded accurately without clipping. The new design compensates for extraneous, inadvertent forces such as bending moments, improves sensitivity over previous models and offers a wider operating temperature tolerance.

The measurement range of the SGR series is 1Nm to 500Nm (up to 13000Nm available soon), accurate to +/-0.1% and with a resolution to +/-0.01% of the transducer’s full scale. With a sample rate of 4000 samples per second, the digital transmission between rotor and stator eliminates all cyclic fluctuation of the signal due to shaft rotation. This avoids the noise pickup and signal corruption associated with conventional slip rings and other analog methods of transferring torque data from rotor to stator.

The sensing bridge consists of four strain gauge elements permanently attached to a rotating shaft in a square formation, set at 45deg to the axis of rotation of the monitoring shaft. As torque is applied to the shaft two of the gauges are stretched into tension and two are compressed. A rotor-mounted ultra-miniature microcontroller, powered by an inductive coil, measures the differential values in each strain gauge and digitally transmits them back to the stator via the same coil. The SGR510/520 series of transducers then use advanced strain gauge signal conditioning techniques to provide high bandwidth, low-cost torque measuring solutions with high over-range and overload capabilities. Other features of the series include an optional adjustable moving-average filter, an input power supply range from 12VDC to 32VDC, user-configurable analog output voltages, a choice of communications (RS232, USB, CAN, Ethernet), and LabView Virtual Instrument capability.

External noise pickup by the wiring is virtually eliminated due to the short distance between the strain gauge elements and the rotor’s measuring circuits. Multipoint calibration reduces any linearity errors within the sensor. The large functional over-range capability allows the peaks of a torque signal to be captured faithfully without any clipping when operating the sensor close to its full-scale rating. This, combined with a mechanical overload capability of over 400%, means that the SGR510/520 series torque sensor provides a very robust torque measuring solution.

The new SGR510/520 series suits torque measuring applications for testing, feedback control of drive mechanisms, and a wide range of process control applications: motorsport and automotive design, wind and other renewable energy, aerospace, machine diagnostics, pharmaceutical, and food manufacturing, etc. These sensors are made by Sensor Technology Ltd., Europe’s premier torque transducer supplier, and are available from their USA distributor Saelig Company, Inc. Fairport, NY.