User guide

164 Advanced User Guide
7 Flow and Pressure Modules
Channel 1: Forward-pressure only
This is identical to the carrier gas channel for the packed
column inlet.
Channel 2: Two-way channel
If gas is supplied at the threaded connection and delivered by
the tubing, this operates the same as channel 1. But the
connections can be reversed—requiring some fittings—so that it
will maintain the gas supplied to it at a fixed pressure. In this
mode it behaves as a controlled leak.
This can be used to maintain the gas in a gas sampling valve at a
fixed pressure, even if the supply varies somewhat. The result is
improved reproducibility in sample amount.
The figure shows the connections with the valve in the Load
position.
Valve
PS
Sample in
Carrier in
To c olumn
Back-pressure regulation
Sample out
Vent
connection
Threaded
connection