3.4 2-Relay Operations
The 2-Relay option allows you to configure
individual setpoints, LO or HI operation, and
hysteresis values for two independent on/off
relays.
• Relay Setpoints: Setpoints represent the flow
rate at which each relay is energized.
• Relay Hysteresis: Hysteresis values directly
effect the LO and HI relay modes, specifying how
far the flow will rise above (LO Relay Mode) or fall
below (HI Relay Mode) each relay's setpoint prior
to de-energizing the relay. The main purpose for
hysteresis is to eliminate relay "chatter", caused by
a flow hovering around a relay's setpoint.
Hys-teresis values are programmed in direct flow
units and must be less than the corresponding relay
setpoint. Hysteresis only applies when exiting an
alarm condition.
• LO Relay Operation: In LO operation, the relay
is energized when the flow drops below the
set-point, and is de-energized when the flow rises
above the setpoint plus hysteresis. See Figure 8.
• HI Relay Operation: In HI operation, the relay
is energized when the flow rises above the
setpoint and is de-energized when the flow falls
be-low the setpoint plus hysteresis. See Figure 9.
• Pulse Relay Setting: Setting relay 1 or 2 to the
Pulse operation mode means the relay will be
cycled (energized) for a 150 ms period each time
a user specified quantity is measured.
Figure 9
HI
relay operation mode
= HI setpoint
= Hysteresis
= Relay energized
= Relay de-energized
Flow
Figure 8
LO
relay operation mode
= LO setpoint
= Hysteresis
= Relay energized
= Relay de-energized
Flow
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