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Accurate control of the conveyor comes from the ability to monitor accurately the power being used to drive the conveyor. This information can then be fed into computerised control systems to ensure the belt conveyor is always moving at optimum speed. Real time data from the belt conveyor is collected by having sensors monitoring the critical variables – in this case the torque on the drive shaft, the speed of the motor, and the drive power – and fed back to the control system. However, torque data can be hard to collect, with traditional technologies introducing as many problems as they solve. Because the shaft is rotating wires attached to it would wind up and snap, so a special way of monitoring it is required. The traditional solution is to use slip rings, but these are expensive, diffi cult to set up and far too delicate in use for most belt conveyor applications. However, with over 20 years of research and development into digital non-contact torque monitoring, Sensor Technology Ltd is at the forefront of an important enabling technology. Mark Ingham one of the company’s managers says: “Our TorqSense transducer is based on the patented technology of measuring the resonant frequency change of surface acoustic wave (SAW) devices. It’s a proven technology that has solved torque measuring challenges in a host of industries.” TorqSense torque sensors use two tiny

SAW devices or SAWs made of ceramic piezoelectric material containing frequency resonating combs. These are glued onto the drive shaft at 90 degrees to one another. As the torque increases the combs expand or contract proportionally to the torque being applied. In effect the combs act similarly to strain gauges but measure changes in resonant frequency. The adjacent RF pickup emits radio waves towards the SAWs, which are then refl ected back. The change in frequency of the refl ected waves identifi es the current torque. This arrangement means there is no need to supply power to the SAWs, so the sensor is non-contact and wireless. “TorqSense measurement together with the digital outputs it offers is often the only practical way to measure torque and integrate it into an industrial environment. And once you are Solids and Bulk Handling September 2014 15

collecting torque data this way, you are well on the way to sophisticated real-time control of complex process.” Born out of the need to solve a particular challenge in the automotive industry, TorqSense is now widely used throughout the spectrum of industries, including many liquid handling applications, in mixers, in the nuclear industry, for testing aerospace components, and running drug trials. It is applicable to all sizes of torque measurement tasks, from dispensing active pharmaceutical ingredients, through stirring industrial quantities of cook-chilled curries, to modelling

storm and fl ood water fl ows. Now this innovative method of measuring

torque is bringing distinct advantages to belt conveying of dry bulk products. A process that was once regarded as very diffi cult to monitor can now reap the same benefi ts as many other industrial processes, enabling dry bulk handling operations to be optimised for the highest levels of productivity with the lowest cost. n

For more information please contact Sensor Technology on tel: 01295 730746 or visit:

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