Setting the Sample Flows

Constant and adequate sample flows are required for reproducible results on the CATS system. Adequate sample flow is required to insure that the sample loop is flushed clean of previous gases and contaminates. Constant flow between all four sample loop positions is needed to reduce any systematic problems with loading the sample loops. Below is a method for setting sample flows:

  1. Shut down the data acquisition software by pressing CTRL-C in the rungc screen and then typing "quit" in the "chroms" screen.

  2. Start-up the "labdoit" program by opening a new shell and typing labdoit. labdoit is a program very similar to the standard data acquisition software but it does not do injections. The operator also has control of the GC via the commands at the bottom of the "chroms" screen.

  3. To check a flow, simply step the stream selection valve (SSV) to the port of interest. You may have to wait for up to a minute for the flow to register on the "chroms" screen.

    Sample Stream
    Port #
    Cal 3 Solenoid
    Cal 1
    2
    Off Always
    Air 1 or Cal 3
    4
    On for Cal 3, Off for Air 1
    Cal 2
    6
    Off Always
    Air 2
    8
    Off Always
  4. To change a cal tank flow rate, adjust the cal tank regulator pressure. To change the air flow rate, adjust the back-pressure regulator on the pump board.

  5. Once all of the flows have been set to approximately the same value quit the labdoit program. Simply type quit in the "chroms" screen.

  6. To start the data acquisition software again. Type "rungc" in an open shell window.
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