The gas flow is controlled by a MKS 647 controller and mass flow control valves. The 647 is menu driven from a CRT in the front panel and with a keypad with cursor controls. The 647 features a non-volatile memory so settings are retained even if the unit is unpowered. The initial menu upon startup is the Command Menu. For normal operation use either the User Display menu (Command menu item #1) or the Extended Display menu (Command menu item #2). The User Display menu shows actual flow in each channel and the total flow in all channels. The Extended Display menu shows actual flow, flow set point, units, valve full scale range, gas calibration factor, whether that channel is enabled, and whether each channel is operating in master, slave, or independent mode.
To set flow rates:
The flow rate set points are adjusted from the Extended Display menu. There are two methods to change valve flow rate set point. If you want to enter a specific value you must first turn off the flow in that channel or all of the channels. Using the cursor keys move the cursor to the desired channel. Enter the desired flow rate.
The flow rate set point can be changed with gas flowing using the cursor keys. In the Extended Display mode move the cursor to the desired channel using the left/right cursor keys. The set point can then be adjusted up or down using the cursor up/down keys.
To turn gas flow on or off:
The gas flow can be turned on or off while in any menu. When any of the mass flow valves are open the green LED labeled ``GAS ON" on the 647 is lit. When none of the gas flow valves are open the red ``STAND BY" LED will be flashing. In the Extended Display menu the bottom line displays on or off, by channel, to show which mass flow valves are enabled. The green LED must be lit and an ``ON" must be displayed in the bottom row of the Extended Display menu for gas to be flowing in a particular channel.
Turning the gas on or off is done in two steps which can be done in either order. Each channel must be enabled by pressing ``ON" and then that channel number. The command input must be enabled by pressing ``ON" and then ``ALL" from the keypad. This allows a single channel or all of the enabled channels to be turned on or off at once. Both steps must be performed initially, but thereafter only one of the steps need be performed to cycle the gas flow on or off.
To turn gas off in a single channel press ``OFF" and then the desired channel. If you want to close all the valves simultaneously, press the ``OFF" key and then the ``ALL/0" key. To turn gas back on you must reverse whichever sequence you used to stop the gas flow. For example if you turned the gas off by pressing ``OFF" and then the channel number, it must be turned back on by pressing ``on" and then the channel number. If you turn off all the channels by pressing ``OFF" , ``ALL" you must turn it back on by pressing ``ON" , ``ALL."
To by-pass the alcohol system:
For the HMS: Open valves 12 & 13, then close valves 11 & 14, in that order!
For the SOS: Open valves 8 & 9, then close valves 7 & 10, in that order!
To refill the alcohol bubblers:
The alcohol bubbler system features a refill system that allows filling directly from the bottle, minimizing exposure of the alcohol to air and reducing the possibility of a spill. The reservoirs should be refilled before they become empty to maintain a head of liquid over the float valve which will prevent air from entering the system. In the back of the gas system rack is a holder for gallon sized alcohol bottles and a cap with dip tube. Place a new bottle in the bottle holder and replace the cap with the cap with dip tube.