Page 9 of catalogue Position sensors and object detection systems of ifm Electronic GmbH

Inductive sensors

Inductive Sensors

System description

Introduction In all automated processes sensors are absolutely necessary to provide the PLC with information. They supply the necessary signals on positions, limits or serve as pulse pick-ups for counting tasks or for monitoring rotational speed. Inductive and capacitive Proximity sensors are nowadays indispensable for industrial usage. As compared to mechanical switches they offer almost ideal conditions: non-contact operation free from any wear and tear, high switching frequencies and accuracy. In addition, they are insensitive to vibration, dust and moisture. Inductive sensors detect all metals without contact, Capacitive sensors almost all solid and liquid media such as metal, Glass, wood, plastic, water, oil, etc. Operating principle of inductive proximity sensors Inductive proximity sensors take advantage of the physical effect of the change in the quality factor in a resonant circuit caused by eddy current losses in conductive materials. This is how it works: A LC tuned circuit generates a high frequency electromagnetic field. This field is radiated from the active face of the sensor. If a conductive material enters this field, eddy currents will be formed in accordance with the law of inductance which draw energy from the oscillator. This reduces the oscillation amplitude. The change is converted into a switching signal. The operating principle permits detection of all metals irrespective of whether they are moving or not. Important: The high frequency field causes no measurable heat in the object nor is there any magnetic interference. The operation of the sensors is without interaction. The distance to the active face at which an electrically conductive material causes a change of signal in the sensor is called sensing range. The sensing range of an inductive proximity sensor is defined by means of a target of mild steel (Fe 360). If the switch is damped by other metals, e.g. aluminium or copper, this is reduced. Using correction factors for every kind of metal the user can calculate the attainable sensing ranges. Modular sensors A special series of inductive proximity sensors are the application sensors which are called “efectorm”. “m” stands for modular technology on the basis of a new mechanical concept, new mounting technologies and an innovative sealing system. It is based on an O-ring (made of Viton / EPDM) which is in the front cap and in the plug area. In addition, these areas are sealed using a special cast resin. The reinforced housing provides additional mechanical stability. Manufacturing has achieved a high degree of automation. This new production technology supplies high quality sensors. During production all components and the individual production steps are subjected to a continuous function check. This severe quality test guarantees a permanent reliable operation even under extreme conditions. The feature shared by these proximity sensors is an increased sensing range. It permits use where standard units meet their limits. All units have a permanent laser-etched type label. This allows clear identification of the units even after many years. No sensor leaves production without a functional test. Furthermore each unit is tested for full sealing. This philosophy is specially rewarding for applications in wet areas. A universal connection technology has been developed so that the user can react to his customers and markets flexibly. The switches can be used as 3wire or 2-wire units. Thus one unit incorporates two connection variants. Pure 2-wire versions are also available. Particularity: The low leakage current of less than 0.5 mA allows connection to every PLC types 1, 1+ and 2 without problem.

Typical application: Positioning sensing in automation technology; proximity sensors operate reliably and without wear.

High frequency electromagnetic field: The inductive proximity sensor detects all metals.

efectorm series with increased sensing range.

increased sensing range [mm]

10 8 6 4 2 0 M12 M18 non-flush proximity switches

common setting standard sensors common setting sensors with increased s n optimised setting ifm sensors with setting LED

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