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Automation Technologies 2/2014

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Automation Technologies 2/2014

Sensors and Measurement

Sensors and Measurement back to current issue Mid range ultrasonic sensors reduce the number of variants Markus Bregulla Anyone wishing to sense objects in the mid distance range up to 300 cm previously had to keep a large number of variants in stock, as each one could only cover a limited measuring range. Turck provides a solution to the problem: Three sensor lines that cover all requirements - and offer additional handy features. Author: Markus Bregulla, product manager for optical and ultrasonic sensors at Turck GmbH & Co. KG in Mülheim an der Ruhr, Germany Ultrasonic measuring requires special attention in some respects: Sound is a mechanical wave that is propagated in solid material, gases or liquids. The speed of this propagation depends on the composition of the parameters for pressure, temperature and the ambient medium. Ultrasonic sensors measure the time of flight of their signal, the accuracy of the result depends on the speed at which the sound is propagated. This means that factors that can be ignored with other technologies have an effect here. Another special requirement is presented by the measuring principle: All ultrasonic sensors have a large blind zone directly in front of the sonic transducer. The size of this depends on the frequency at which each sensor switches between emitter and receiver. Sensors with large sensing ranges work at low frequencies and have accordingly large blind AUTOMATION TECHNOLOGIES 2/2014

Sensors and Measurement zones. The aim of the manufacturer is to keep the blind zone as small as possible in order to cover a large operating range with one sensor. Turck has made a major step towards this aim with its RU-U ultrasonic sensor series. The sensors operate with longer measuring ranges and shorter blind zones than the previous models. The new ultrasonic sensor series also offers features such as the easy-teach function and IO-Link capability. Blind zone shortened The short blind zones enable objects to be detected that are close to the sensor. For example, the M18 version with a 40 cm range has a blind zone of only 2.5 cm. This increases flexibility in many mounting positions. The mounting depths — such as for level sensing applications — are less, as space does not have to be reserved for a large blind zone. Thanks to the shorter blind zones it was also possible for Turck to reduce the number of variants in the series. The sonic transducers offer particularly large measuring ranges over the entire sensor series: In the M18 model up to 130 cm, in the M30 version up to 300 cm. In addition, every sensor of the series being phased out can be replaced directly with a model from the RU-U series. It is also possible to use the previous accessories. Operating safety increased Ultrasonic sensors are used in particularly harsh environments and therefore must be able to withstand a wide range of different environmental conditions such as dust, water, temperature changes or vibration. Their improved process safety is firstly Company: Hans Turck GmbH & Co. KG Headquarters: Mülheim an der Ruhr, Germany Turnover: ~ 450m € (2013) Employees: more than 3,350 Products: sensors, fieldbuses, interfaces, RFID due to their robust metal housing design: threaded sleeve and plug thread are designed as one piece. The male thread on all new models runs over the entire length of the sensor so that customers can adjust the mounting position within the mounting bracket. The smooth front flush sonic transducer membrane also contributes to greater process safety as it cannot accumulate dirt that may cause incorrect signals. The mechanical movement of the membrane even shakes off deposits and thus cleans itself. Particle deposits that can arise when the air humidity is high can be simply wiped off. Setup simplified A teach-in setting is possible for all sensors via pin 5. Depending on the model, users can teach the sensors via pushbuttons directly on the sensor, with a teach adapter, or via a teach cable. The teach function enables the setting of individual switching or measuring range limits. With the M18 series, the start of switch and measuring ranges can be set without any additional software. Alternative concepts use potentiometers, but the turn setting of these devices is often unreliable and imprecise. next page About 01 The sensors provide very short blind zones AUTOMATION TECHNOLOGIES 2/2014

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