Datum Electronics Ltd. - PRODUCT NEWS


Datum Electronics - Experts in Torque

Datum Electronics are an established supplier of Torque Transducers and other torque measurement systems based in the UK. Our torque transducers and torque sensors use strain gauges bonded to a shaft for reliable and accurate torque measurement solutions.

What is a Torque Transducer?
Torque Transducers, or Torque Sensors measure torque in a variety of methods. The basic principle is in essence is a very simple mechanical process, it is a measure of the ‘force’ being used in turning (or attempting to turn) an element. When a force or ‘torque’ is applied to a shaft; the shaft twists (by a very small amount). This twisting produces a ‘stretch’ in the material of the shaft, in a direction at 45 degrees to the axis of the shaft, between points on the shaft that are moved apart by the twisting motion. The material of the shaft also sees a ‘compression’ in the opposite 45 degree direction.

Datum Electronics torque transducers utilise this shaft bending and measure the change in order to calculate the torque. This measurement is achieved by the use strain gauges bonded to the shaft, measuring the strain induced in the shaft by the applied torque or ‘force’. There are various methods of measuring this twist through a shaft; strain gauges are recognised as one of the most reliable methods, if you have the expertise to achieve this.

Strain Gauges are incredibly accurate, if you have the expertise and experience of using and understanding how they work. They have been traditionally associated with in-accurate and un-reliable measurements. If used correctly with the right understanding, they are very reliable, stable, robust and a cost effective method of torque measurement.

Definition of a Strain Gauge
A strain gauge is a small electrical ‘element’ printed on a non-conductive substrate. The pattern of the element is arranged so that if the gauge is stretched (or compressed) in one direction (along operating axis of the gauge), the resistance of the element increases (or decreases) in relation to that stretch. A stretch perpendicular to the axis of the strain gauge has little effect on the resistance of the element.

If a gauge is bonded to the shaft, with its axis aligned with the direction in which the shaft material stretches when a torque is applied, the strain gauge will also stretch and therefore the element will increase in resistance. If a gauge is bonded to the shaft, with its axis aligned with the direction in which the shaft material compresses when a torque is applied, the strain gauge will also compress and therefore the element will decrease in resistance. In the Torque transducer, strain gauges making up four resistive elements are bonded to the shaft. Two elements are aligned with the direction of Tension (stretch). The remaining two are aligned with the direction of Compression.

The four resistive elements are electrically connected in a ‘Wheatstone Bridge’ configuration. The Wheatstone Bridge configuration is appropriate for measurement of the small resistance changes produced in the strain gauges, as the combination increases and decreases in resistance it produces a change in output voltage which is only proportional to excitation voltage and change of resistance between opposing elements, not to any overall change in resistance such as might be produced by a change in temperature.

Torque Transducers – Measurement Defined
The Datum Series 420 Rotary Torque Transducers transmit digital data providing the end user with clean and definitive data. The on-shaft signal provided by the Wheatstone Bridge is amplified and converted into a digital value. This signal is transmitted off the shaft and then processed digitally and amplified; this signal is taken off the shaft and then processed to provide a measurement of torque. Digital Data can be provided with up to 24 bit resolution or up to 96,000 samples per second providing valuable and accurate data for the end user.

Series 420 In-built speed sensor
Our rotary torque transducers provide not only torque measurement but also speed indication (rpm). Combining both torque and speed data allows you also to measure power as a calculated figure.

The series 420 torque transducers measure speed by counting 1 pulse per revolution and then converts this figure to (rpm). Using an in-built hall-effect sensor, our torque range is capable of measuring speed at up to 20,000rpm.

Torque Transducer Specifications
Torque Measurement 0 - 10,000Nm as standard.
System Accuracy 0.1% FSD
True non contact torque measurement.
M420 Torque Transducer
FF420 Torque Transducer
RS420 Torque Transducer
Accurate and Reliable measurement
Output of digital RS232 with USB option
Analogue Output also available
Flexible shaft fittings (spline/keyway shaft)
Modular System Assembly
Non-contact Signal Transmission
Proven Technology
Low Maintenance
Simple Linear Calibration
Engineered to fit most drive components
Rotary and Static Torque Measurement
Optional Analogue Data Output
Optional Speed / Power Output

About Datum Electronics
Datum Electronics is a world-leading manufacturer and supplier of torque & shaft power measurement devices, namely torque sensors, torque transducers, marine shaft power meters, bolt-on strain sensors, and wind turbine monitoring systems.

For more information, please contact:

Datum Electronics Ltd.
Castle Street , East Cowes PO32 6EZ United Kingdom
Tel: +44(0) 1983 282834

February 2008

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