Tech Briefs Magazine - October 2021 - ST-19

ment, automatic testing, and robotics
have all contributed. Today, machine
condition monitoring is being added to
the mix. Successful condition monitoring
starts with sensors located on factory
machines constantly reporting data on
their health and operation. By using
real-time analytics, factory operators
can identify problem spots and schedule
the needed repairs and maintenance
without waiting for catastrophic
failures. This will provide productivity
gains to manufacturing. It all starts with
sensors, however.
Eddy Current Displacement Sensors for Industry
ddy current displacement sensors
belong to the inductive displacement
group of sensors and are welladapted
for industrial applications. Unlike
conventional inductive sensors, the
measuring principle for eddy current
sensors enables measurements on nonferromagnetic
materials (e.g., aluminum)
as well as ferromagnetic materials
(e.g., steel). They are designed for
non-contact and wear-free measurements
of displacement, distance, position,
oscillation, vibration, and thickness.
Therefore, they are ideally suited
to monitoring machines and systems -
they can make measurements in harsh
Industrial environments, even where
E
pressure, dirt, or temperature fluctuations
occur.
Typically, eddy current displacement
sensors are used where high measurement
accuracy is required and other sensors
cannot cope with the prevailing ambient
conditions. Optical sensors, for example,
are influenced by dirt or dust in the
measuring gap and by high temperatures.
Conventional inductive displacement sensors
use ferrite cores, which have a comparatively
a high linearity error and a
lower frequency response. Also, their
measurement accuracy decreases with
fluctuating ambient temperature.
Only conductive metallic targets,
whether ferromagnetic or non-ferromagnetic
can be measured using eddy current
displacement sensors. Non-conductive
materials are invisible to the eddy current
measuring system and thus have no
effect on the measurement results. For
this reason, these sensors can measure
through materials such as plastics and oil
onto metallic objects. This enables applications
such as oil gap measurements and
distance measurements against rollers
that guide plastic films.
Limitations of Conventional
Inductive Displacement Sensors
The classic inductive displacement
sensor uses a coil wound around a ferromagnetic
core. Because of that core, the
This article was written by Pete Smith, Sr.
Manager, Sales and Marketing Support, TE
Connectivity Sensor Solutions - TES
(Schaffhausen, Switzerland/Berwyn, PA). For
more information, contact Mr. Smith at
pete.smith2@te.com or visit http://
info.hotims.com/79418-164.
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Sensor Technology, October 2021
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Tech Briefs Magazine - October 2021

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