Rosemount 3491, Справочное руководство, Страница: 79 / 152

Reference Manual
00809-0100-4841, Rev. AA
May 2007
4-47
Rosemount 3490 Series
Figure 4-33. Filling tank
application - Stage 2 of 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 4-34. Filling tank
application - Stage 3 of example
In a filling application, the Common Off point is always the Off point of the
Standby, Common Off mode relay with the highest On point, which in this
example is P412 of Relay RL1.
When the measured level rises above 8 metres (P412, Common Off), the
relay RL2 will de-energise to close Valve 2.
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.)