User guide

Valves 11
Advanced User Guide 339
The Valve Box
The GC holds up to four valves in a heated valve box on top of
the oven.
The valve box is the preferred location for valves because it is a
stable temperature zone, isolated from the column oven.
Valves may also be mounted inside the column oven.
Heating the valves
The valve box contains two heated blocks, each with two valve
mounting locations (shaded in Figure 3).a The middle hole on
each block is used to pass tubing into the column oven.
If two valves are used, mount them on the same block. This
allows them to be heated using only one control channel (Aux
Temp 1 or Aux Temp 2, depending on how the heaters are wired).
With more than two valves, both channels must be used for
heating the two blocks. Set them at the same temperature.
Valve temperature programming
Most valve applications are isothermal; however, you can define
three temperature ramps if desired. Press [Aux Temp #], then [1]
or [2]. Program this ramp the same as an oven ramp. Refer to
“Setting the oven parameters for ramped temperature” on
page 282 for more information.
Figure 3 Diagram of valve locations on GC
Valve heater
blocks
Valve box,
cover removed
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