Teledyne GC-Pro/TCD - Gas Chromatograph - Manual (Page 25)

GC-Pro TCD Operational Theory
Teledyne Analytical Instruments 11
detector for the analysis of the compound of interest in the
stream. If configured to do so, the analyzer may read the detector
for a programmed 5 second period at some point within this
mode cycle to obtain a baseline reading for further calculation.
This mode is usually programmed to continue until the
compound of interest is fully eluted from the column. It is
possible to set it up to 25 minutes.
During the Analysis Mode, a ‘Peak Detect’ period is programmed at
which time the analyzer reads the detector output. The analyzer
integrates the peak area during this time in conjunction with the baseline
settings to calculate the concentration of the compound of interest. The
calculation is performed at the end of the ‘Peak Detector’ period and the
result is displayed at the end of Analysis Mode.
2.3 Analyzer Subsystems
The Model Analyzer is composed of four subsystems:
1. Sample System
2. GC Column
3. Detector Cell
4. Electronic Signal Processing, Display and Control
2.3.1 Sample System
All components used to control the sample and supporting gases are
located on the front panel or inside the analyzer chassis. For the internal
components, they are accessible after removing the top cover of the
analyzer. Adjustments are made to the carrier gas pressure and sample
flow using the controls on the front panel. See Figure 1-1. Other
adjustments are made using the touch screen and are described in
Section 4.
The analyzer contains three separate isothermal chambers
‘SAMPLE’, ‘Sensor’, and ‘COLUMN’ that are controlled individually.
Temperature and control information are available onscreen. See Section
4.5.7. The chambers and the switching valve are identified in Figure 2-
1.