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087-0020 REV
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Intrinsic Safety
The Freedom™ 5000 has been designed to be intrinsically when used with an approved
safety barrier. Refer to Figure for “Generic Intrinsically Safe Barrier Wiring Diagram”.
An intrinsically safe circuit is simply defined as: "an electrical circuit which does not
contain, or store, enough energy to cause ignition of a given explosive atmosphere”. As
a power supply is inherently not intrinsically safe, it has to be protected by a safety
barrier. In most cases this is a resistor/diode network that will automatically limit the
supply current and voltage to below a given figure, under fault conditions.
Because intrinsically safe systems do not pose an explosion risk, physical protection of
the circuit from the explosive atmosphere (such as an explosion proof enclosure) is not
required.
The Freedom™ 5000 can be used with two different types of safety barrier: a diode
shunt type or a current mirror type. The advantage of the current mirror type is that is
does not create a load on the 4-20 mA loop; whereas a diode shunt type will account,
typically, for about 250 ohms. This is important in applications where a number of other
loads are already present on the loop, or long cable lengths are required.
Freedom 5000 Universal Analog Toxic Gas Detector
Instruction Manual
