Oil Leak Detector NAR 300 system
28 Endress+Hauser
6.4 Principle of Alarm operation
The oil leak detection signal detected on the float sensor NAR 300 is converted into 8mA (alarm
OFF), 16mA (alarm ON) at the current output circuit in the transmitter or the Sensor I/F Ex box
and is connected to the current detection circuit through IS safety barrier.
In the current detection circuit, the presence or absence of the oil leak alarm signal is judged
according to the current value size and turns the alarm output relay ON or OFF through the
operation delayed circuit.
The operation delayed circuit has the delay time setting trimmer and possible to set the time of
approx.1 to 30 sec. (furthermore, 6 sec. delay time on detection circuit is added). In the relay
contacts output, the fail-safe performance is available. Please refer to the below table.
Alarm output operating table
NRR 262 N.C to COM NRR 262 N.O to COM
Condition NRR 261 <PP26,27> 11, 13 NRR 261 <26,27> 13, 15
Oil leak alarm Contact Close Contact Open
Power OFF Contact Close Contact Open
Breaking Contact Close Contact Open
Liquid freezing Contact Close Contact Open
Tuning-fork failure Contact Close Contact Open
Non-alarm Contact Open Contact Close
6 Electrical connection
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