SENSORS
Power Supplies / Isolating Switching Amplifiers (Ex Barriers)
What is an Isolating Switch Amplifier?
An isolating switch amplifier is an interface device used to safely transmit switching signals from sensors or contacts to a PLC or control system while providing electrical isolation between the field and control circuits. Ex-certified isolating switch amplifiers can also provide intrinsic safety by limiting the electrical energy supplied to sensors located in potentially explosive atmospheres. They are commonly used with NAMUR sensors and switches in chemical, petrochemical, pharmaceutical, mining and other hazardous-area applications.
How does an isolating switch amplifier work?
A typical installation looks like:
Hazardous-area sensor → Ex isolating switch amplifier → PLC / control system
The amplifier receives a low-power signal from a field device such as a NAMUR proximity sensor, switch or contact.
It then:
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Detects the sensor's ON/OFF state.
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Converts or amplifies the signal into a usable output for the PLC.
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Provides galvanic isolation between the hazardous-area circuit and the control system.
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On intrinsically safe versions, limits voltage and current supplied to the hazardous area.
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Often provides wire-break and short-circuit monitoring.
The PLC therefore receives a clean, reliable switching signal while the field circuit remains appropriately protected.
Why are they called "switch amplifiers"?
The term can be slightly misleading. They aren't primarily used to make a signal "bigger" in the conventional amplifier sense.
They act as signal conditioners and interface modules, taking the relatively small signal from a sensor—particularly a NAMUR sensor—and converting it into a clearly defined switching output such as a relay contact or transistor output.
What is an Ex barrier?
"Ex" refers to equipment designed and certified for use in or in connection with potentially explosive atmospheres.
An intrinsically safe (Ex i) barrier restricts the amount of electrical energy that can reach equipment installed in the hazardous area. Even under specified fault conditions, the available electrical energy is kept below levels capable of causing ignition.
These systems are commonly found in industries such as:
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Chemical and petrochemical plants
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Oil and gas
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Fuel storage and handling
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Pharmaceutical manufacturing
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Mining
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Paint and solvent processing
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Distilleries and alcohol production
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Grain, flour and other combustible-dust applications