A-A-50624
j. Interface with airflow display panel. The airflow sensor shall connect to the airflow display panel via a three-conductor cable of a length as specified. One conductor shall carry the airflow signal, one conductor the dc power, and one shall be a common conductor. The cable shall be detachable from the airflow sensor via an accessible screw-lug terminal located inside the airflow sensor assembly. The screw-lugs shall be marked as to function.
k. Reliability. The airflow sensor minimum mean time between failures (MTDF) shall be no less than 25,000 hours.
l. Safety (hazardous environment). The airflow sensor shall be in compliance with the NEC requirements for safe use in Class I, Division 2, Group D hazardous locations.
3. Airflow display panel.
a. Physical Characteristics. The airflow display panel shall not exceed the following outside dimensions: 33 cm in width, 28 cm in height, and 25.4 cm in depth (including any attached mounting pads). The panel shall be bulkhead mountable via the hole pattern as specified. (An adapter plate for matching the panel to the specified hole-pattern may be used.) The panel shall be corrosion resistant. The panel shall incorporate a swing-open panel door with an identification plate affixed on the outside of the panel door and labeled as indicated.
b. Range. The airflow range of the panel shall be manually selectable. Selectable ranges shall include:
0-1 mps
0-2.5 mps
0-5 mps
0-10 mps
0-25 mps
0-50 mps
c. Input signal. The airflow panel shall accept a 4-20 mA signal airflow velocity and a 20 mA output shall correspond to full-scale airflow velocity. Input independence for the signal shall be resistive at 250 ohms ± 1 percent.
d. Airflow display. The panel shall incorporate an illuminated digital readout. The digital readout shall display airflow velocity or trip point setting in meter-per-second (mps) on a selectable basis. Airflow velocity displayed shall be mean airflow velocity for the most recent one-second interval.
e. Trip-point set. The panel shall enable the setting of a low-airflow alarm trip-point for any value in the selected airflow range. The panel shall detect whenever airflow velocity drops the trip-point setting for a period of 30 ± 5 seconds and shall set a low-airflow alarm state accordingly. The panel shall retain memory of the trip-point setting at all times, including power loss times.
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