FAST Technology revolutionises torque measurement

FAST Technology revolutionises torque measurementKeywords: Torque, Force

After several years of development, FAST Technology, a start-up based in Germany, announces the implementation of a totally new technology that will for the first time solve the problem of cost-effective measurement of torque and force in real time in onboard systems. This technology is already integrated in a new generation of non-contact sensors and allows the efficient address of hundreds of industrial applications. This technology meets the need to measure torque directly in systems in real time, and therefore allows an increase in the reliability and performance of millions of devices, in every sector of activity

A problem that has been puzzling engineers for years

For many years, engineers have looked for a method to measure directly the torque and therefore the power) that is transmitted through rotating shafts. Direct measurement of torque is important in that it allows the management of key aspects of a mechanical system, which affects both the performance and reliability of the overall system. Until now, this problem was only partially resolved through the implementation of dynamometers and strain gauges.

Dynamometers have long been used in laboratories or test benches for torque measurement, but they are usually large, expensive and complex systems and cannot be used outside of the laboratory. In most cases strain gauges offer a high degree of accuracy when measuring the torsion that metal is subject to as torque is applied. But they are extremely delicate devices, which require a sensor that is in direct contact with the shaft – while it is rotating– connected to an electronic device that must remain fixed (Plate 6). Their use is therefore restricted to laboratory applications or off-line verifications.

The FAST solution: a revolutionary technology

FAST solves the torque measurement problem by using a sophisticated combination of magnetic induction and electronic processing to measure directly,instantaneously and accurately the torque of a rotating shaft – without contact, in hostile environments and at a very low cost when compared to current solutions. Through special treatment (e.g. magnetisation) of a shaft and the use of proprietary circuitry and signal conditioning, FAST technology measures the modifications of the magnetic field generated by the shaft torsion when torque is applied. The torque can be measured at a considerable distance from the shaft, the usual distance being a few millimetres through dirt and fluids,independent of shaft speed and with negligible hysteresis.

  Plate 6 FAST sensor family

The only limitations on the system are that the shaft must be made of a ferromagnetic material (with a memory of magnetisation), that it does not reach the Curie point during operation, that it is not damaged and that it is not exposed to a strong magnetic field without protection. None of these limitations poses a problem in the vast majority of potential applications.

FAST torque measurement technology consists of three basic modules:

• 1.

  The torque sensing shaft that is subject to torsion, that has been magnetically programmed to become a passive torque sensor.

• 2.

  The magnetic detection head that measures variations the shaft's magnetic characteristics from the torque that is applied to the shaft.

• 3.

  The signal conditioning electronics that connects to the detection head and provides an output electrical signal indicating the magnitude and direction of torque applied to the shaft.

Torque in a rotating shaft can be measured in a range from static (stationary shaft) to more than 100,000rpm. The shaft and sensing electronics can be "sized"to accommodate torque measurement in a very wide range of magnitudes, typically with an accuracy of 0.5 per cent of full scale (see Figure 1).

  Figure 1 Basic diagram of the FAST torque measurement product

Today, FAST Technology is launching the first non-contact torque sensor based on this new technology. Its qualities are:

• excellent accuracy superior to the requirements of the vast majority of industrial applications;

• extremely easy implementation in all types of environments;

• a cost that is from ten to 100 times less than the cost of other torque measurement technologies; and

• reliability and compactness making them appropriate for on-board use even in hostile conditions.

New developments already being studied

Further developments of FAST's sensing capability already allows the measurement of not only the torque but also the shaft angular position,rotational speed and the bending of a mechanical member. These developments will, for example, allow customers to measure directly the true mechanical instantaneous power output of rotating machines with one accurate and economical sensing system. They will also allow direct measurement of the forces in structural members.

FAST is also currently developing torque and force measurement devices that will use non-contact measurement techniques that are different from the current FAST solution: torque measurement on discs, pressure measurement on surfaces,etc.