Valve Control
Valve configurations
194
Figure 31 External valve drivers
Valve configurations
There are five possible valve types:
• Gas sampling—a two-position (load and inject) valve. In load position, an
external gas stream flows through an attached sampling loop and out to
waste. In inject position, the filled sampling loop is inserted into the carrier
gas stream. When the valve switches from Load to Inject, it starts a run if
one is not already in progress. See the example on page 198.
• Switching—a two-position valve with four, six, or more ports. These are
general-purpose valves used for such tasks as column selection, column
isolation, and many others. For an example of valve control, see page 197.
• Multiposition—also called a stream selection valve. It is usually used to
select one from a number of gas streams and feed it to a sampling valve for
analysis. It has a special actuator that advances the valve one position each
time it is activated, or it may be motor driven. An example that combines a
stream selection valve with a gas sampling valve is on page 199.
• Other—could be anything.
• Not installed—self-explanatory.
Keyboard
or
Run time
program
or
Clock time
program
External valve drivers
(5 through 8)
External event connector
on back panel
Valve 5 (pin 1) and
ground
(pin 3 or 4)
Valve 6 (pin 2) and
ground (pin 3 or 4)
Valve 7
(pin 5 and pin 6)
Valve 8
(pin 7 and pin 8)
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