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Planning and
Installation Guidelines
Technical Description
2
2.1 Sensor head properties
2.2 Functional principle of the sensor heads
2.3 Switching distance of the sensor heads
14
Planning and Installation Guidelines
Wireless proximity switches
Wireless proximity switches consist of a communication module and a sensor head which can
be selected from a range of different designs and properties depending on the application.
The sensor heads operate as inductive proximity switches and therefore have standardized
properties and operating conditions. This allows an easy application without any problems.
• They exclusively detect metal objects.
• They have an exactly defined detection range.
• They work reliable and without any impairment by light, noises, non-conducting dust
and fluids such as oil.
• They detect precisely without any adjustment.
• They substantially work according to standardized detection characteristic curves.
The fundamental component of the sensor heads is a resonating circuit with an open coil. When
a metal object comes close, the oscillation is attenuated until it is completely interrupted
according to the further decrease of the distance. This effect is evaluated by a subsequent trigger
stage and converted into a binary output signal.
The most important and distinguishing characteristic of the sensor heads is their switching
distance. The switching distance depends on the dimensions and the electronic circuitry of the
sensor head as well as on the size and chemical consistency of the actuator (target).
The actuator can be moved in axial as well as in radial direction towards the sensitive part of the
sensor head.
Nominal switching distance s
Like conventional inductive proximity switches, the sensor heads are categorized according to
their nominal switching distance (rated switching distance according to EN 60947-2-5). This
value does neither consider any manufacturing tolerances nor any kind of environmental
influences such as the ambient temperature.
Standard measuring plate
Switching distances are determined using a 1 mm thick square smooth standard measuring
plate made of ST37 steel. The edge length of the plate is the higher value of the active sensor
face's inner circle diameter and the triple nominal switching distance. The standard measuring
plate determined this way is the optimum actuator for the sensor head.
Example WSIF020-M12N: inner circle diameter = 12 mm; 3 x nom. switching distance = 6 mm.
The resulting edge length of the standard measuring plate is 12 mm.
Example WSIN080-M18N: inner circle diameter = 18 mm; 3 x nom. switching distance = 24 mm.
The resulting edge length of the standard measuring plate is 24 mm.
Real switching distance s
The real switching distance of a single sensor head considers the manufacturing tolerances and
is determined at ambient temperatures of (23 ± 5) °C. It can be up to 10 % above or below the
nominal switching distance.
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Wireless Proximity Switches / Issue: 09.2004
V 6
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