Optocouplers for Hazardous Enviroments0 pages

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:: Optocouplers for Hazardous Enviroments ::

Optocouplers Handle Hazardous
Environments And Meet ATEX Intrinsically Safe Requirements - By John
Beigel, Standex-Meder Electronics
Many manufacturing plants are considered
hazardous environments particularly in petro-chemical and grain processing plants. Any
electrical arc could ignite a fire or major explosion. Since these factories use vast arrays of
electric and electronic circuitry care must be
taken when selecting components.

nent, where the key output component is a
photo-detector. Passing a current of approximately 10 ma through the two input terminals
and through the light emitting diode, with the
correct polarity, converts the electrical current
into photons. The photons are then directed

Standex-Meder Electronics optocouplers
offer insulation resistances as high as 1013
ohms, operate in less than 10 µsec, and
creepage distances from input to output are
greater than 14.5 mm.

Standex-Meder Electronics is now offering
a line of optocouplers that can safely handle
input/output isolation as high as 20,000 VDC
that have met and been certified for the stringent requirements of ATEX (Directive 94/9/
EC and 1999/92/EC). This directive applies
to equipment and protective systems that are
used in factories where potentially explosive
atmospheres exist. The ATEX offers the requirements needed for approval of safety
devices, controlling devices and regulating
devices.
The ATEX directive is also a requirement in
mining operations, flammable gas processing plants, some medical processing plants
where ESD could be a real problem, and in
any factory that requires high isolation and
non-arcing environments.
How they work
The optocoupler is composed of two circuits:
an input circuit and an output circuit. A light
emitting diode (LED) is the key input compo-

© Standex-Meder Electronics. All Rights Reserved.

sulation resistance and high voltage isolation.
In contrast, electro-mechanical relays, produce arcs when their contacts close. These
arcs could represent ignition points under the
right circumstances. Switching signals with
semiconductor switching devices generally
do not have high isolation from input to output. If a breakdown occurs in the circuitry arcing may occur initiating an ignition point.

ATEX: 11ATEX 0086, gem. EN 60079
down a light tube or tunnel. At the end of the
tunnel, the photons are incident on the photo detector that converts the photons back to
an electric current. In this manner, the input
information is transferred and amplified in
the output detection circuit without any direct
electrical conducting path. The longer the
light tube the greater the distance between
the metalized input terminals to the metalized
output terminals. This insures a greater in-

These optocouplers essentially operate in
all kinds of extremely hazardous, explosive,
moist, dirty environments and operate from
-40°C to 85°C. They also transfer their digital or analog signal information from input to
output drawing no potentially hazardous arc.
They have no moving parts and operate safely for billions of operations, are not affected
by magnetic fields and can operate or transfer
information at a 50 kHz rate. Several products are available that most closely aligns
with your design requirements.
Along with the optocouplers, Standex-Meder Electronics also supplies Reed Relays
and Reed Sensors that are ATEX certified as
well. For more details please see our web
site: www.standexmeder.com to review these
products. Also, contact information is available, where engineers can help with your application and select the best product for your
requirement.