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2.3.6 Display Backlight
The display backlight will be automatically enabled upon connection of an external DC
voltage supply in the range of 12-30V; the backlight is not available when operating on battery
power. If it is required to reduce power consumption while operating on external DC power
the backlight can be overridden by the user.
2.3.7 Unscaled Pulse Output
The Unscaled Pulse Output function is used to retransmit the input signal from the
associated flowmeter; it will maintain the same frequency and duty cycle as the input signal.
The Unscaled Pulse signal is transmitted as an NPN signal from the digital output terminal.
When setting up a system with two separate displays from the same flowmeter the Unscaled
Pulse Output is the best method of transmitting the volume to the secondary instrument. If
this is done, the same calibration data should be entered into both displays.
2.3.8 Scaled Pulse Output
The Scaled Pulse Output is used to transmit the totalised volume at a user selectable
resolution; this is programmed as a number of pulses per unit (e.g. 10 pulses/Litre). This
feature is useful whenever it is required to transmit the total volume to a control system such
as a PLC or SCADA system.
The scaled pulse output is calculated from the accumulated total, so resetting of the total will
not cause any loss of volume on the output signal.
2.3.9 Alarm Output
Flow rate alarms may be programmed for High, Low, or High/Low; the digital output will
trigger when the registered flowrate passes the configured set-point(s). For a Low Alarm the
output will trigger once the flowrate drops below the set-point, a High Alarm will trigger with a
flowrate over the set-point, and a High/Low alarm will trigger if the flowrate is either over the
upper set-point or below the lower-set point.
Each set-point is configured with its own hysteresis (dead-band) percentage which allows the
user to avoid alarm “chattering” (switching quickly on-off-on-off) with a flowrate hovering
around the set-point. The hysteresis setting is entered as a percentage of the set-point value;
for example, a 5% dead-band with a 100L/min High Flow Alarm will trigger ON at 100L/min but
will not turn OFF until the flow drops to below 95L/min.
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