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sensors & sensinG sYstems


Why use a fibre optic sensor? The ability of fibre optic sensors to transmit light along a flexible fibre means they can be threaded into narrow locations. They also have little or no detection ‘dead zones’. With no electrical circuitry or mechanical parts, the fibres can safely transport light to a target through dusty, dirty or explosive environments, such as wood processing (Fig 3, right). Because they require little power, fibre optic


systems can reach very high switching speeds. They are highly reliable even under severe environmental conditions, such as extreme temperatures, vibration, shock, moisture, corrosive chemicals or electro-magnetic ‘noise’. The detection principle is independent of object colour, shape or surface, so it can detect virtually any material, and even transparent foils. Some fibres can withstand repeat bending


without degradation of the signal, making them useful in robotic gripper applications, for example.


considerations First, look for an amplifier that minimises inventory. For example, by being able to switch between PNP, NPN or push-pull outputs on the same device, users need only one type of SICK WLL80 fibre optic amplifier for all machine controls. Ensure the amplifier is compatible with


common bus protocols and that sensors can be networked together, without the risk of


Fig 3 - Use case: Reliably detecting the leading edge of wood profiles in a dusty environment


interference. SICK WLL80 sensors can be organised in banks in a master-slave configuration to enable automatic cloning of parameter settings for multiple devices. Look for an amplifier with an OLED


pushbutton display to make setting or adjusting the sensor in situ quick and easy. There should be detailed setting options for detection parameters and switch points, enabling accurate detection and repeatability. Using IO-Link could be an advantage in some


applications for diagnostics and troubleshooting, as well as rapid replacement. By using Smart Tasks for pre-defined parameter configurations, reliable detection of fast-moving, small or transparent objects can be assured within minimal load on the machine control.


automotive applications to benefit from new temperature sensor


New from Sensirion is the STS4xA, a highly reliable digital temperature sensor series for automotive applications. The STS4xA series


currently consists of two versions: STS41A-AD1B and STS41A-AW1B, with the latter offering optional wettable flank packaging to support automated optical inspection (AOI). The sensor has an integrated on-chip heater which enables advanced on-board diagnosis (OBD), making it possible to perform a functionality and plausibility diagnosis instead of simple presence checks. The sensor platform is based on


Sensirion’s CMOSens Technology. The STS4xA features an I²C interface and provides a wide supply voltage range. Thanks to its small size and four-pin dual-flat no-leads (DFN) package, the STS4xA can easily be integrated into a variety of automotive applications. In addition, it meets relevant industry standards, such as 85˚C/85 % RH accelerated life tests. “The expansion of our next-generation temperature sensor series


means more opportunities for our customers to benefit from high precision and reliability in automotive applications. Our STS4xA temperature sensor builds on the established foundation of the STS4x sensor family, delivering a wide supply voltage range and low current consumption while maintaining top performance,” says Matthias Scharfe, product manager for Humidity and Temperature Sensors at Sensirion.


Sensirion www.sensirion.com


september 2022 DESIGN SOLUTIONS 17


feature The SICK WLL80 also offers the advantage


of continuous threshold adaption (CTA) which adapts the signal strength, such as in a dusty environment, or because of contamination build-up on the fibre heads, to maximise periods between maintenance. Vendors offer an extensive range of fibres and


heads with versatile options for light dispersal and orientation, as well as for easy mounting. The SICK LLX range offers 500 different fibre types and a wide range of threaded and smooth-sleeve heads, with both axial and radial head alignment available. A useful innovation is that now any length of LLX fibres up to 20m can be specified. There are some limitations associated with


using fibre optic sensors: it can take a little more effort to install and set the sensor parameters, for example. Also, because they use an energetic detection principle, there is no real background suppression available with fibre optic sensors. However, fibre optic sensors are versatile for a wealth of applications in almost any industry – so it’s always worth considering whether they are the best solution. With so many specification options for fibre


optic sensors, choosing and installing them may seem daunting. However, vendors should now offer easy specification guidance on their website, as well as technical sales support to guide you to a reliable and successful application.


SICK (UK) www.sick.co.uk


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