Choosing the Best Position Sensor for your Application

Selecting the appropriate measurement technology for your industrial automation application is key to preventing production interruptions and unexpected downtime as a result of unreliable electronic measuring.

When choosing a suitable position sensor, it is important to understand the requirements of sensor size, resolution, repeatability, accuracy, mounting constraints and environmental ruggedness before making a final commitment. This is particularly important in the industrial automation industry in which fast and accurate positioning is required for the efficient running of manufacturing processes.

In this article, we discuss the sensor technologies available and how to select the best position sensor for your needs.

String Potentiometers

String potentiometers, also known as a string pot, draw wire senor, string encoder or a yo yo pot, have been used for electronic measurement for over 40 years. These devices use braided steel wires (“strings”) wrapped around spools and require the release of the coiled string.

Using string pots in heavy industry, crude oil processing, waste water treatments and other industrial applications can lead to potential issues due to its high rate of wear and tear, ultimately leading to:

  • The springs in the reel failing over time
  • The wire eventually jamming from rust, mechanical failure or other environmental factors
  • The high contact nature of the devices causing friction among the components, resulting in excessive wear and failure after a few thousand rotations

These issues can result in expensive downtime, costly repairs and loss of productivity, all of which are detrimental when used in the high speed and demanding environments of industrial automation applications.

Highly Accurate Position Measurement

Certain industries including assembly, energy and plastics manufacturing require advanced, versatile and resilient position measurement technology to meet the demands of its challenging applications. Where string pots fail to provide the kind of reliable position measurement required in operations such as these, magnetostrictive linear transducers, like the Balluff BTL series, allow for precise, absolute measurement without a reference run.

It replaces the trouble-prone mechanism of the string pots with a moveable free-floating or captive magnet that rides the length of a sensing rod as it follows the target object. It works by emitting a short duration pulse along the sensing element, known as the waveguide. The resulting magnetic field interacts with the magnetic field of the position magnet and generates a mechanical force on the sensing element. The time interval between the initial current pulse and return pulse is measured and converted into an absolute position value, resulting in a constant, precise, accurate and smooth position measurement.

Ultimately, using a magnetostrictive linear transducer for position measurement:

  • Eliminates impact damage due to its non-contact design
  • Offers short- and long-range measuring distance of up to 3 metres
  • Is composed of fewer components compared to string pots, meaning fewer parts to replace and maintain
  • Adaptable to nearly any industrial control system, available in common analogue, as well as digital interfaces

This post was adapted from Balluff’s Insights’ blog.

Contact Us

Pacific Automation supplies a range of magnetostrictive linear position sensors from first-class sensor specialists Balluff.

As distribution partner for Balluff in Australia, Pacific Automation can provide application and technical support for mining, industrial, manufacturing and food production.

For more information about the Balluff range of sensors, contact the team at Pacific Automation.

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