Torque sensors used in university teaching equipment

The electrical machines laboratory at the Dublin Institute of Technology (DIT) has improved its effectiveness as a teaching resource since TorqSense non-contact torque sensors from Sensor Technology have been fitted to five machine sets. The new sensors replace a system of machine monitoring that had proved inaccurate.

To provide maximum flexibility, the demonstration equipment in the DIT machines laboratory employs a modular construction. This means, for example, that experiments with both AC and DC machines can be carried out on the same test bed, as whichever machine is needed is simply clamped into place. Whatever the configuration of the equipment, however, the experiments and demonstrations performed in the laboratory require the monitoring and collection of a number of key operating parameters, including torque, speed and power.

Terence Kelly, Technical Officer at Dublin Institute of Technology, comments: "We had tried many methods for measuring these parameters, but had found it impossible to get results we could rely on, particularly in the case of the torque and power measurements. Then we heard about the Sensor Technology's innovative products, and after we had visited the company and seen the sensors in action, we knew that we had found the solution we were looking for."

Beneficial features

The sensors that attracted the attention of DIT depend for their operation on surface acoustic wave (SAW) technology. Other features of these sensors that made them particularly suitable for use in the DIT machines laboratory include a large safe overload margin, high accuracy and resolution, the ability to operate equally well clockwise and anticlockwise, and integral temperature monitoring. As well as measuring torque, the sensors also provide speed and power data.

Kelly states: "The biggest benefit of the TorqSense sensors is, of course, that they use a wireless connection between the transducer itself and the sensor electronics. This solves all of the major problems at a stroke. But they also excel in terms of the amount of information they collect, and because they deliver measurements of all key parameters in real time. In addition, they are robust, which is particularly important in a teaching laboratory and, in the year that we have been using them, they have proved totally reliable."

DIT Machines Laboratory has purchased six RTW321 series TorqSense torque sensors. In addition to two conventional analogue outputs, these also provide data digitally via RS-232 and USB ports. In this application, the USB ports provide a connection to a PC that is also used to configure the operation of the sensor. The sensors have an integral self-diagnostic feature that ensures the data they supply is trustworthy, and also warns users if the maximum speed or torque ratings are exceeded.

Five of the sensors purchased by DIT are currently installed on demonstration equipment, while the sixth is held in reserve in anticipation of use in a future research project. The five sensors currently in operation have a torque range of 0-15Nm, but they are configured for a maximum reading of 10Nm in order to discourage students from pushing them to - and possibly beyond - the limit of their range. The sensors monitor speed from 0-1500rpm, and power from 0-1.4kW.

Kelly concludes: "Since we installed the new sensors, we have had nothing but positive comments from the staff and students who use the machine laboratory. I think it is fair to say that the sensors have greatly improved our facilities for demonstrating machine characteristics and for experimenting with them, and that they are, therefore, a great asset for our teaching programme."

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