Reference Manual
00809-0100-4841, Rev. AA
May 2007
Rosemount 3490 Series
4-50
Figure 4-39. Stage 2 of Standby
split-off filling tank example
However, if the measured level falls below 2 metres (P421, On point), the
relay RL2 will be energised to open Valve 2. Relay RL1 is de-energised to
close Valve 1.
Figure 4-40. Stage 3 of Standby
split-off filling tank example
When the measured level rises above 6.5 metres (P422, Off point), the relay
RL2 will de-energise to close Valve 2. Relay RL1 is then energised to open
Valve 1.
When the measured level rises to 8 metres (P412, Off point), the relay RL1
de-energises to close Valve 1.
However, if the measured level did not fall below 2 metres, the relay RL1
would remain energised to keep Valve 1 open until the level rises to 8 metres.
(Safeguards to prevent overuse of the relay (valve) are in Section “Relay
Safeguard Options“ on page 4-43.)
NOTE:
For optional auto-sequences, see “Auto-Sequence (Models 3491 and 3492
only)“ on page 4-53.
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