The decision for the sensor state is based on the current sensing on the high side with thresholds set at 0.4 mA, 1 mA, 2.2 mA,
and 5.85 mA. Faults as well as normal sensor low and high current states are detected as follows:
• If the current is seen to be less than 0.4 mA then an open circuit is declared with an alarm.
• Between 0.4 and 1 mA, the sensor is in a low current state
• Between 1 and 2.2 mA, the sensor is declared as faulty
• Between 2.2 and 5.85 mA, the sensor is in a high current state
• Above 5.85 mA, the sensor is faulty with a short or IO+ is miss-wired to ground.
NAMUR sensors come in both normally open and normally closed styles. The default polarity is for the channel's contact
state value to be set if current is between 0.4 and 1 mA.
YUAA Universal I/O Modules GEH-6855_Vol_II System Guide 195
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