A-A-50624
f. Audible alarm. The panel shall incorporate an audible alarm which generates an audio output of from 75 to 95 dB at two feet. The audible alarm shall sound whenever a low-airflow alarm state is first set and shall remain activated until: 1) airflow rate rises above the trip-point setting for at least 10 seconds, or 2) an audible alarm silence switch that shall be incorporated in the panel is manually operated. The audible alarm silence switch shall be labeled as to function.
g. Visual alarm. The panel shall incorporate a visual alarm which flashes on and off when an alarm state is set. Alarm flashing shall not cease until the alarm state is reset to indicate normal airflow. The visual alarm shall be labeled as to function.
h. Test mode. The panel shall incorporate a manually-initiated test mode which demonstrates/verifies functionality of the visual and audible alarms.
i. Airflow velocity output signal. The panel shall output a 0 Vdc to 10 Vdc analog scalar signal linearly proportional to airflow velocity over the specified range. The output circuitry shall supply a 10 mA maximum current and shall be “short” protected. The airflow velocity output signal shall be instantaneous airflow velocity damped by a one-second time constant. The airflow velocity signal shall be available on an accessible screw-lug terminal located inside the airflow panel. The screw-lugs shall be marked as to function.
j. Airflow-loss alarm output signals. The panel shall provide isolated switch-closure discrete outputs. Closed-contacts shall indicate a low-airflow alarm state or that power has been lost for more than 30 ± 5 seconds. Open-contacts output shall indicate that airflow and power are normal. The switch contacts shall be rated at not less than 1.5 Amps, 115 Vac. The switch-closure output signals shall be made available on an accessible screw-lug terminal located inside the airflow panel. The screw-lugs shall be marked as to function.
k. Accuracy. The airflow panel circuitry shall add no more than ± 1.75 percent error to the data received from the airflow sensor. The ± 1.75 percent maximum allowable error applies to both the digital display of airflow velocity and to the Vdc analog scaler output signal which carries airflow velocity information. Panel trip-point detection accuracy shall be within ± 3.0 percent of the nominal trip-point setting.
l. Response time. When operating in a standard one atmosphere environment and an airflow velocity of 25 percent full-scale; the airflow display panel shall achieve a full-accuracy output signal within 1.1 seconds for an airflow velocity signal step increase to 75 percent full-scale. For the same conditions, the airflow velocity display shall achieve a full-accuracy readout of airflow velocity within 2 seconds.
m. Repeatability. Repeatability shall be to within ± 1.0 percent of full-scale.
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