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Intrinsically Safe Interface Solutions:

Introduction
Interface selection
Zener barriers
Isolation interfaces
Zener barriers: Intrinsic safety solutions.
 

These are typical system diagrams using Isolation interfaces for E2S Intrinsically safe sounders and beacons.
The following .circuits are for are for illustration only, installation and details may be omitted for clarity.
Please refer to the relevant certification prior to use.  As all E2S sounder and beacons have the same entity parameters in most circuits different E2S intrinsically safe field apparatus may be used providing it has the relevant input feature.   Where examples show the IS-mini range a direct replacement can be made using the IS-A105N and IS-L101L or combination.

Please contact E2S for further information.

The basic installation is straightforward on/off control using a zener barrier with entity parameters 28v 93mA (often referred to as 28v 300Ω) which is an industry standard barrier (Power driver).
This is suitable for all E2S Intrinsically safe sounders and beacons..

B1 Simple Driver IS-mB1
IS-L101
IS-mA1
IS-A105N

To simplify drawings the rest of the illustration do not show the representative voltage clamping diode.
The 2nd tone on a sounder is switched down to zero volts. This can be achieved in the safe area by using a Diode return barrier..

B2 Simple Driver IS-mA1

IS-A105N

Similarly another diode return can be added for the 3 rd stage audible alarm
This can be acheived with a single 3 channel barrier

B3 Simple Driver IS-mA1

IS-A105N

The sounder and beacon IS-mC1 or the combination of IS-105N and IS-L101 can be powered from a single zener barrier.  Similarly an IS-mA1 plus IS-mb1 could be run from a single zener barrier

B4 Simple Driver IS-mA1

IS-A105N

For independent control use a double channel Zener barrier.

B5 Simple Driver IS-mA1

IS-A105N

Again with the option of 2nd tone switch.  This can be extended further using 2 power and diode returns zener barriers to switch the 3rd alarm tone (not shown).

B6 Simple Driver IS-mA1

IS-A105N

The combined IS-A105N / IS-L101L has a mute option, adding a switch will mute the alarm
Depending on the DIP switch settings on the IS-L101 reset occurs:
On alarm condition being removed i.e. power down of IS-L101L or
after a dip switch selectable interval – from 5 seconds to 2 hours.
Note the reset switch does not need to be certified as it is considered to be simple apparatus..

B7 Simple Driver
IS-A105N

However many DCS cards use pull down signals such as open collector, common emitter outputs. Then a common power feed would be used with all switching being done via a diode return barrier
Here is a simple on off control

B8 Simple Driver IS-mB1
IS-L101
IS-mA1
IS-A105N

Adding another diode return gives a second stage alarm.

B9 Simple Driver IS-mA1

IS-A105N

Zener Barriers

Any interface with parameters
Uo  ≤ 28v I o  ≤ 93mA P o  ≤ 660mW
or for the Diode return channel
Uo  ≤ 28v I o  ≤ 0mA  

 

 

Single Power

Double Power

Power Plus Diode Return

Double Diode Return

Power + 2x Diode Return

Triple Diode Return

 

Zener Barrier

Double Zener Barrier

Diode Return Barrier

Double diode return barrier

Triple diode

Pepperl & Fuchs

Z728

Z779

Z787 or Z787F

 

Z789

Z786

MTL

7728+ or 7706+

 

7787+ or 7707+

 

7789+

 

Stahl

9001/01-280-085-101

9002/11-280-186-001

9002/13-280-093-001

9002/33-280-000-001

 

 

Should you manufacture a suitable Intrinsically safe interface or wish to comment on these applications please email sales@e2s.com

Further Reading:

EN1127-1  Explosive atmospheres: Explosion prevention and protection
  Part 1: Basic concepts and methodology

 

EN 60079 ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES
  Part 0 General requirements
  Part 14 Installation (and selection) of equipment in hazardous areas
  Part 25 Intrinsically safe systems

Suggested reference book on intrinsic safety and hazardous areas
Electrical Apparatus and Hazardous Areas by Robin Garside. 5th Edition 2007
ISBN 978-0-9516848-4-9

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Introduction
Interface selection
Zener barriers
Isolation interfaces

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