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Terminology for inductive sensors |
OPTIMUM
Sensors
Automation |
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Operating
Principal
An inductive proximity switch works
with a high frequency oscillating
circuit that creates an alternating
electromagnetic field on the active
sensor surface by meaning of a coil.
When a metallic object nears this
field a damping occurs in the
oscillating circuit. If this damping
exceeds a threshold value, a
switching signal is generated.
Operating
distance
The operating distance is the
distance between an object and the
active sensor surface at which a
switching signal is generated. The
operating distance depends on the
diameter of the coil. Therefore
larger sensors are required for
longer operating distances. On some
of the Optimum sensors the operating
distance is adjustable ( capacitive
).
If a metal object dampens only a
part of the alternating field, the
operating distance decreases: a
larger object increases it. The
following approximate values are
derived from a standard rectangular
measurement plate made of steel ST
37 with an edge length that
corresponds to the diameter of the
sensor coil or three times the rated
operating distance, whichever is
greater |
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The operating distance
is influenced by the
material of the object:
Constant dimensions for
different materials
against Steel ST 37
yield a changed
operating distance.
The following table list
approximate values for
the material dependent
reduction factors. In
practical applications
variations could occur
due to different
alloying, for example. |
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Rated operating
distance Sn
The rated operating
distance is a device
parameter that does not
make into account sample
variances and external
influences such as
temperature and supply
voltages
Effective operating
distance Sr
The effective operating
distance is the
operating distance at
normal voltage and a
nominal temperature of
23 degrees Celsius. it
is between 90% and 110%
of the rated operating
distance.
Usable operating
distance Su
The usable operating
distance lies in the
entire allowable
temperature and voltage
range between 90% and
110% of the effective
operating distance.
Assured operating
distance Sa
The assured operating
distance takes into
account all the external
influences and sample
variances and lies in
the range from 0% to 80%
of the usable operating
distance.
within this range a
guaranteed switching is
ensured. |
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