Mitigating Position Sensor Failure in Safety Applications

Position sensors are one of the most basic elements of modern technology. These are used in various machines and equipment across different industries. Such sensors can be found in the simplest to the most complex machines. In this case, the nature of the application determines how rigid the safety requirement is. In a majority of applications, position sensor failure may not have any safety implications, but in other applications, there can be monumental effects.  

This is the reason why engineers need to follow certain design techniques and guidelines to ensure that each sensor developed guarantees operational safety.

Qualifying failure in position sensors

To determine the methods of execution that will result in safe devices, it is also important to understand how failure is qualified in terms of position sensors. There are several kinds of position sensors such as linear encoders, linear transducers, and potentiometers. In these devices, failure can mean any of the following:

  • No output – the sensor has stopped reporting the signal output either permanently or intermittently.
  • Error flag showing incorrect output – the sensor was able to flag incorrect output.
  • Incorrect output not indicated by an error flag – there is an error in output, but the sensor was not able to flag it.

There are other terms used to define safety in position sensors such as safety-critical or safety-relevant. The term safety critical is used to define failure that has significant implications while safety-relevant only pertains to failure that may have some significance.

Designing sensors for safety-related applications

For applications where safety is important, engineers need to design according to a spectrum. The range should be from zero relevance to critical safety relevance. When the need for safety relevance increases, one of the first things an engineer should do is to design a sensor that has built-in diagnostic capabilities.

Another way to increase safety relevance is to design sensors with internal and external reference. Furthermore, engineers can also use duplex arrangements that can help prevent common failure modes in position sensors.

Inductive sensor technology

These days, the preference of most industries is for sensors created with inductive or contactless technology. This ensures that the sensor is not susceptible to damage, making them highly reliable and robust, even when applied in hazardous conditions. Non-contact sensors can be applied in extreme conditions, even submerged underwater for long periods of time.

Contactless sensors also eliminate the negative effects of moisture, wear and tear, friction, and dirt. Most manufacturers today produce sensors using contactless technology. Some may even have patented designs unique to their brand. In some instances, you can find manufacturers that custom-build sensors depending on the specifications of the applications.

The possibilities for developing safe and robust position sensors are limitless. Engineers today are constantly looking for ways to mitigate problems and produce the most reliable devices for use in industrial and practical applications. In fact, sensors today are being used in a wide range of applications including smart appliances, consumer electronics, satellite technology, advanced automobiles, robotics, and medical equipment.

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