WFI N2 Flushing
System

The WFI N2 Flushing System

There is a solenoid valve mounted on the telescope base at the low pressure side of the N2 gas supply. This valve is driven by the TCS VME computer under the supervision of a program task plus a set of commands that can be issued from the vxte2p2 console (or from any console using an rlogin) for; opening the valve, closing the valve, reading the status, and switching the system to automatic and manual modes.

The commands are the following five:

N2_status

Informs if the system is either in automatic or manual modes and if the valve is open or close.

N2_mode_manual

Switch the system to manual mode. In this mode the valve remains open or close, as manually set, regardless of the humidity conditions. When this mode is selected a message with a beep comes every five seconds to the vxte2p2 console saying: "WARNING N2 mode is set to manual".

N2_mode_automatic

Switch the system to automatic mode. In this mode a low priority task running in the TCS computer is doing the following:

Checks if the system is in manual or automatic mode.
If in manual mode; send the above mentioned warning message to the console every 5 seconds.
If in automatic mode; read the humidity every 2 seconds, average 150 values and open the valve if the humidity average is >= 60% and close the valve if the humidity average is <= 50%.

N2_open

If the system is in automatic mode the command returns "Please set N2 mode to manual". If the system is in manual mode the command opens the valve.

N2_close

If the system is in automatic mode the command returns "Please set N2 mode to manual" If the system is in manual mode the command closes the valve.

Note1: Always at boot time the conditions by default are the following:

System mode in automatic.
<=50% closing and >=60% opening.

Note2: After boot it is possible, if desired, to change the opening and closing points just by changing the globals, "double N2cls = X.X" and "double N2opn = X.X" to any value between 0.0 to 100.0.