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Compact photoelectric sensors designed for wet areas

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Compact photoelectric sensors designed for wet areasDesigned with wet areas in view, the new O6 WetLine photocells from ifm electronic may be small, but contain of lot of technology. The O6 WetLine is a stainless steel sensor rated IP69K, addressing many needs of users with wet production areas.

The O6 series claims to possess best-in-class optical performance. One of the available variants, the O6H, a diffuse reflection sensor with background suppression – designed to detect the direct reflection from an object without sensing what is behind it – has a sensing distance up to 200mm, regardless of the colour of the target object. Even a black object (with 6 per cent remission) poses no problem. In a wet environment sensors sometimes suffer with fine water droplets in the air (either just a misting or steam) causing unwanted reflection. Not so the O6H. Compensation of the detection in the case of steam and mist is built in, and a patent for this novel approach has been applied for. Accurate sensing by the O6H is further aided by maintaining a tight beam (light spot diameter of 8mm even at the 200mm range.

Other problems encountered in a food environment stem from the reflections off stainless steel surfaces. ifm has countered this with optics capable of ignoring shiny surfaces not simply behind a target, but also below the light beam path. When a stainless steel target surface is not precisely perpendicular, this can cause unwanted signals; again, this has been eliminated with the O6H optical performance.

ifm electronic paid particular attention to the housing, of which several aspects must be right for food production areas, notably the seal, the housing materials and the ability to keep the sensor clean. Testing in an autoclave and repeated dunking in boiling water then ice water have proven the resistance of the O6 to steam and temperature shock. All significant IP tests have been passed: IP65, for cold water jets from one direction; IP67, for 0.1 bar immersion for 30 minutes; IP68, for cold water immersion at 0.1 bar for seven days; and IP69K, for hot water jets (80degC) at 80 to 100bar from four directions over 2 minutes. It is also worth noting that the O6 range will happily operate up to 80degC (from -25degC).

Compatibility, of the housing itself and the materials used, with cleaning chemicals has also been independently verified by Ecolab and Johnson Diversey. Equally important in a food environment is the ‘cleanability’ of the housing, which was another focus point for the ifm design team. Even the potentiometer concept presents a cleanable surface.

PNP and NPN switching variants

Ease of use is important, and the ifm designers did not overlook this aspect. Important details were considered, so for example, the LED indicators are rendered highly visible by being embedded in a dark background material for the highest contrast. The full O6 WetLine range also includes standard (energetic) diffuse reflection types, with a range up to 500mm; retro-reflective (reflex) versions with 5m range; and through-beam (transmitter/receiver) with 10m range. All are available with either a 2m fixed cable, or a short cable fitted with an M12 connector. All O6 types can switch light-on or dark-on (equating to normally open or normally closed), and both PNP and NPN switching variants are on offer.

ifm always recognises that a sensor is not a stand-alone device: in needs to be installed and connected; to that end the O6 series is complemented by accessories equally optimised for wet areas. These include stainless-steel mounting brackets, the EVT range of mating M12 connectors, and also new chemically-resistant reflectors.

To find out more about the O6 WetLine photocells from ifm electronic, please go to www.ifm-electronic.co.uk.

 
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