26 February 08

Experts in Torque Measurement

UK Suppliers of Torque Transducers

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.


M420 Torque Transducer Range

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 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

To get in touch with our team, use our contact form or contact us on:

Telephone: +44 (0) 1983 28 28 34
Fax: +44 (0) 1983 28 28 35

Commerical Enquiries: Email:

We also have a network of partners, distributors and re-sellers
around the globe able to assist you locally in certain areas,

View our Where to Buy page

We look forward to hearing from you!