Noncontact transducers improve torque measurement

Edited by the Engineeringtalk editorial team May 9, 2005

Series 420 rotating torque transducers are more efficient and cost effective and offer improved longevity over previous models in the marketplace.

Series 420 rotating torque transducers from Datum Electronics operate with no direct contact from the rotor to the stator; they are more efficient, cost effective and have improved longevity than previous models in the marketplace.

They are available either as complete transducers or as separate rotor/stator assemblies for test rig and OEM applications.

They provide a system accuracy of 0.1% of full scale either into a rack-mounted torque indicator, a PC or a control system.

All the transducers have a strain gauged central element and a set of rotating conditioning electronics, the digital signals from this are digitally transmitted to the nonrotating body or stator of the system.

The Series 420 has three different types of transducer, each with its own merits in terms of functionality and use within different environments.

The M420 is the standard rotary torque transducer.

The standard transducer has the rotary shaft and a stator built into its static housing.

The housing is mounted on the shaft with bearings.

Datum has developed four standard sizes to meet the general needs within the torque measuring environment.

The four sizes cover ranges from: 0-5 to 0-100; 0-100 to 0-500; 0-600 to 0-2000; and 0-2500 to 0-10,000Nm.

If requirements do not fit within these four sizes, Datum has engineered units above the standard range of 10,000Nm and has engineered torque measurement transducers up to 250,000Nm.

The M420 is highly accurate, with a combined error of 0.1% as standard on all M420 torque transducer sizes.

They provide a digital data signal (RS232) which can measure torque, speed and power.

They are suitable for use on test rig applications and on permanent installations.

The FF420 is the flange/flange rotary torque transducer.

The transducer element in this case is a flange-flange coupling with the strain gauges and the rotor electronics mounted in the centre section of the coupling.

The signal is transmitted across a digital transmission coupling link to the stator that is mounted around the centre of the coupling.

The rotating element of the transducer is not limited by bearings; therefore it can be used at higher speeds, and places no bearing loads on to the shaft.

The stator needs to be mounted in relation to the shaft within an operating envelope of +/-3 to 5mm.

There are six sizes covering ranges from 5 to 100,000Nm.

The FF420 is highly accurate with a combined error of 0.1%.

It uses a true noncontact transmission signal.

Another advantage of the FF420 is that is tolerable to misalignment, because of the way the transducer is engineered.

The standard ranges are compatible with DIN size flanges.

The RS420 is the rotor/stator transducer with a keyed shaft and a free standing stator.

This type of transducer is very similar to the FF420 but has keyed shafts as opposed to flanges.

The transducer element in this case is a keyway or splined shaft with the strain gauges and the rotor electronics mounted either on the shaft, or inside the shaft depending on shaft size and feasibility.

The signal is transmitted across an inductive link to the stator that is mounted around the centre of the coupling, with a visible air gap.

This type of torque transducer has no bearings, and there is no secondary load on the test shaft which allows for multiple shaft sizes.

Because the torque transducer has no bearings, it can be used at higher speeds, running much faster and longer than traditional transducers containing bearings.

The stator needs to be mounted in relation to the shaft within an operating envelope of +/-3 to 5mm.

Again, there are six sizes ranging from 5 to 100,000Nm.

The RS420 is highly accurate with a combined error of 0.1%.

It uses a true noncontact transmission signal.

Another advantage of the RS420 is that is tolerable to misalignment, because of the way the transducer is engineered.

The standard range of housings cater for torque ranges from 10Nm up to 10kNm, the same modular elements have been applied to bespoke transducers for use down as low as 1Nm and up to 250kNm.

The 420 Series is compatible with Datum's full range of torque indicators (Type 300 torque indicator, Type 310 portable torque and speed indicator, Type 370 torque, speed and power indicator) and a range of data-logging software including TorqueLog.

Among the enhanced features are the additional options for: direct analogue output, direct serial outputs, increased sampling rates and analysis tools.