Cut Sheet

V8-T4-4 Volume 8—Sensing Solutions CA08100010E—February 2015 www.eaton.com
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4.0
Capacitive Proximity Sensors
Introduction
Capacitive Proximity Sensor Influences
Many of the same factors that influence the sensing range of
inductive proximity sensors, also influence the sensing range of
capacitive proximity sensors.
Typically, capacitive sensors
have a greater sensing range
than inductive sensors.
Sensing distance for
capacitive proximity
sensors is dependent on
plate diameter. With
inductive proximity sensors,
the size of the coil is the
determining factor.
Typical Proximity Sensing Ranges
Sensitivity Adjustment
Most capacitive proximity
sensors are equipped with
sensitivity adjustment
potentiometers. Because the
sensor measures a dielectric
gap, it is important to be able
to compensate for target and
application conditions and
adjust the sensing range.
Target Material and Size
A capacitive sensor should
not be hand-held during set
up. Because your hand has a
dielectric constant greater
than air, the sensor may
detect your hand rather than
the intended target.
Capacitive sensors can detect
both ferrous and non-ferrous
materials equally well. There
is no derating factor to be
applied when sensing
metal targets. But, other
materials do affect the
sensing range.
Because they can be used to
detect liquid through a
nonmetallic material such as
glass or plastic, you need to
ensure that the sensor
detects just the liquid, not the
container. The transparency
of the container has no
effect on the sensing.
Sensor with a
Tubular Diameter of:
Inductive
Unshielded Sensor
Capacitive
Unshielded Sensor
18 mm 8 mm 15 mm
30 mm 15 mm 25 mm
34 mm — 35 mm
Environment
Many of the same factors that affect inductive proximity
sensors, also affect capacitive sensors, only more so.
●
Embeddable mounting—
capacitive sensors are
generally treated as non-
shielded devices, and
therefore, are not
embeddable
●
Flying chips—they are
more sensitive to both
metallic and nonmetallic
chips and residue
●
Adjacent sensors—more
space between devices is
required due to the
greater, non-shielded
sensing range
●
Target background—
because of both the
greater sensing range, and
its ability to sense metallic
and nonmetallic materials,
greater care in applying
these sensors is needed
when background
conditions are present
●
Ambient atmosphere—the
amount of humidity in
the air may cause a
capacitive sensor to
operate even when no
target is present
●
Welding magnetic fields—
capacitive sensors are
generally not applied in a
welding environment
●
Radio Frequency
Interference (RFI)—in the
same way that inductive
proximity sensors are
affected, RFI interferes
with capacitive sensor
circuitry
●
Showering arc (EFT)—
induced electrical noise
affects these sensors in
the same way it does for
an inductive sensor