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20 Operation
HP289
3.5 The Output Pulse and Flow Alarm
An OUTPUT PULSE is available on terminal 10 for driving remote
counters and produces a pulse each time the Accumulated Total
increments by one digit. For example, if the Accumulated Total has a
resolution of 0.01 gallons, a pulse is produced each 0.01 gallons.
The pulse is a current sinking pulse of approximately 10msec produced
by an open collector transistor and can sink up to 100mA. The
maximum pulse rate is limited to 49 pulses per second and the
resolution on the Accumulated Total must be set so that the
Accumulated Total increments at less than 49 counts per second.
Note that due to the uneven pulse output spacing on this output, the
pulse output cannot be used to drive rate indicators.
The FLOW ALARM uses an identical circuit to the Output Pulse and
is available on terminal 7.
The Flow Alarm will output an alarm condition if the flow times out
during a batch (i.e., there is no flow registered for a time greater that
the Signal Timeout period, provided the Signal Timeout is greater than
0).
The Flow Alarm output will switch “on” (i.e., the signal goes low)
whenever an alarm condition exists. The Alarm will switch “off” (i.e.,
the signal goes high) when the alarm is reset by pressing the DISPLAY
key.