Electricity + Control May 2018

In addition to these measuring distance sensors, miniaturised sensors, such as photoelectric sensors and light diffuse sensors, are preferred for use in shuttles. This is due to the limited available space.

SENSORS, SWITCHES + TRANSDUCERS

Adding to this scenario is the ready availability of these products from international online sources, where a buyer chasing short term savings can buy just about anything. In these instances, an individu- al would select a sensor from the photograph and brief description which appears on their screen and not have any method of verifying that the sensor in question is suited for the application at hand. Both of these scenarios have created problems not only in indus- try, but also for original equipment manufacturers of sensing equip- ment and their distributors worldwide. Information shared between players in this market show an increase in situations where incorrect devices have been retrofitted with major and even catastrophic dam- age being caused during operation or where technical support for devices is not readily available. Reputable suppliers This would suggest that it is preferable for end users to deal with reputable suppliers that are able to provide optimum levels of techni- cal support at any stage. It also points to need to further educate the market as to why it so important to use appropriate sensing technol- ogy for a given application. Given the strained state of the economy, particularly in South Africa, the risk level associated with purchasing sensing devices on price alone is simply too great. It is critical that the right sensor is selected for the right job. As an example, if you want to detect either position or speed of bottles on a conveyor belt, a non-polarised photo cell would not be the correct sensor choice. This is because the reflective properties of glass make detection difficult and therefore render this data provided by this type of sensor inaccurate. It is essential that a polarised photo electric sensor is used for this particular application. Further challenges can be in experienced in bottling and packaging applications depending on the materials used for labelling on the bot- tles as well as the packaging or shrink wrap used on the pallet. It is essential to take these factors into account when specifying a sensor for a bottling plant. There are sensors that have been specifically de- veloped to accurately detect printing on different coloured surfaces, and using these would ensure accurate detection. A shaft encoder, also known as a rotary encoder, is an electro-me- chanical device that converts the angular position or motion of an axle of shaft to an analogue or digital signal. Two main types of shaft encoders exist – absolute encoders and incremental (relative) encod- ers and it is essential that the correct encoder is used to achieve the required end result. Incremental encoders operate by generating a series of pulses during movement, and must always come back to a reference point. Absolute encoders are more sophisticated and provide a unique code for each shaft position. These encoders are available as either single channel or multiple channel devices depending on the application. A single-turn encoder can verify position with a single channel of the encoder shaft which makes these devices ideal for short travel scenarios. In contrast, the multiple channel encoders are suitable for more complex and longer positioning applications. Shaft encoders are used extensively on cut-to-length lines where it is essential to accurately control the required desired length. In

The Leuze RK46C-VarOS retro-reflective photoelectric sensor is ideal for packaging systems and intralogistics where it will detect objects with various sizes and shapes.

Leuze offers a wide range of laser Class 1 sensors and the advantage of these devices is that the laser radiation emitted by these sensors does not pose a hazard to the human eye.

The Leuze DDLS 500 photoelectric sensor enables the transparent, contact- and wear free transmission of data over distances of up to 120 metres in 100 Mbit/s real-time.

Electricity + Control

MAY 2018

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