Cut Sheet

Volume 8—Sensing Solutions CA08100010E—November 2012 www.eaton.com V8-T12-13
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12.1
Sensor Learning Course
Learning Module 23: Limit Switches, Proximity Sensors and Photoelectric Sensors
Hazardous Location Switch
The hazardous location
switch is ideal for use in
harsh or dangerous
environments. This switch is
tough enough to contain an
explosion within itself.
The one-piece switch body/
receptacle is much heavier
and thicker in construction
than standard oil-tight
switches. Like standard oil-
tight switches, hazardous
location switches have
removable actuating heads
attached to the switch body
with four screws.
Hazardous Location Switch This switch type generally
meets NEMA 1
requirements, and the
hazardous location
requirements of NEMA 7,
Class I, Groups B, C and D;
and NEMA 9, Class II, Groups
E, F and G. Some
manufacturers offer models
rated NEMA 4X and 13 as
well (see “Enclosure
Ratings” on Page V8-T12-39
for more information).
Precision Limit Switch
The precision limit switch is
widely used in both
commercial and industrial
applications, ranging from
appliances to farm
equipment. It is often
chosen for its precise
operating characteristics,
small size and low cost.
Precision Limit Switches Precision switches are
typically available in two
types: basic precision and
enclosed precision. The basic
precision switch is of one-
piece construction. The
enclosed precision switch is
simply a basic switch inside a
die cast housing. Basic
precision switches are
generally not given a NEMA
enclosure rating, while some
enclosed precision switches
can be rated NEMA 4 or 13.
Special Purpose Limit Switch
Some applications require
a limit switch to perform a
special detection function.
Let’s take a look at some
of the special purpose
limit switches.
Special Purpose—
Safety Guard
This type of switch is used to
ensure safety for the operator
of a dangerous machine. A
standard limit switch could be
false tripped or false
actuated, posing a danger to
the person operating the
machine.
Actuation of this switch
occurs only when a keyed
interlock is inserted into
the key slot. The key is
usually mounted on a safety
door or machine guard so that
when it is closed, the key
slides into the slot, actuating
the switch.