These units usually sit in a drip pan or similar location where people want to know if there is a leak. If they end up in the thinnest pool of liquid they will alarm. They use a detector looking at an LED and if that light path gets altered at all then it knows there is a liquid there. With that it will detect any liquid as long as it is not exposed to excessive high or low temperatures.
However these units are not rated to operate in a hazardous potential explosive environment.
Detection method
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Infrared Photo-refraction
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Output
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Transistor NO or NC
NPN (50mA MAX) or PNP (18mA MAX)
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Power
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12 – 24VDC
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Response time
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< 1 sec (DI water)
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Current Consumption
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25mA Max
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Indicators
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Normal operation – Green LED on, Red LED off
Detection – Red LED on, Green LED off
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Operating temperature
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- 10 to 60°C
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Material of construction
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PP (Polypropylene)
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Cable
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shielded 2 conductor, PVC (polyvinyl chloride)
2 meter length standard
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Wiring
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+: red
-: shield
Signal: white
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