Pepperl+Fuchs Blog

Defining an Inductive Sensor's Mounting Conditions

Posted by David Rubinski on Fri, Jul 13, 2012

Part One of Two:  Defining the ways sensors can be mounted (embeddable, non-embeddable, quasi-embeddable)

(Read part two of this post: Mounting Conditions for Inductive Proximity Sensors)

Inductive sensors are often specified based on their sensing distance and housing geometry. But you must also be aware of any mounting restrictions that might apply to the specific sensor chosen for the application. Various types of sensors require different considerations when they are mounted to a bracket or machine component. Mounting conditions may restrict the close proximity of any non-target metal in the area around the sensor mounting zone. The effect of the surrounding metal, located within the electromagnetic field generated by the sensor, may result in unintended consequences for the operation of the equipment. Depending upon the sensor, this metal may cause pre-damping of the sensor oscillator resulting in:

  • False triggering
  • Temperature instability
  • Sensor latch-on effects

Several mounting options are available:

Flush mount = embeddable mounting = shielded sensor
These sensors incorporate an electromagnetic shield positioned around the inductive coil that minimizes the effect of surrounding metal. They normally have the widest range of mounting options and the best immunity to mutual interference of nearby sensors.

Non-flush mount = non-embeddable mounting = unshielded sensor
Sensors in this group have no electromagnetic shielding present around the inductive coil system and, therefore, are strongly affected by surrounding metal. These sensors normally have the longest sensing ranges, but require the largest amount of metal-free area around the mounting zone.

Semi-flush mount = quasi-embeddable
These sensors have partial electromagnetic shielding present around the inductive coil. This partial shielding helps to minimize the effect of surrounding metal. Semi-flush mount sensors provide longer range than flush-mount sensors for the same housing size, but have some mounting restrictions that limit the metal allowed in the mounting area.

Inductive sensor mounting conditions
Notes about this image: 

  • The red area shows the metal-free mounting zone required by different sensor types
  • Unshielded sensors have a wider radiated magnetic field
  • Flux lines have a higher field density nearer the coil system
  • Mounting metal closer to the coil will have a more significant effect on pre-damping
Having taken a look at the different inductive sensor types, it's pretty clear that based on the particular sensor type and mounting conditions or environment, each one calls for its own approach when it comes to mounting procedures. In our next blog post on this topic, we'll deal with the preferred methods for mounting each type.

Topics: Terminology, Inductive Sensors, Sensor Accessories

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