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Detector Systems
Thermal conductivity detector (TCD)
146
Optimizing performance
The following sections aid in choosing operating parameters to obtain
optimal TCD performance.
Temperature
TCD sensitivity increases as the temperature difference between the
detector filament (automatically set) and the surrounding detector body
(chosen detector zone temperature) increases.
To minimize changes in detector sensitivity with different operating
temperatures, filament temperature is maintained at a relatively
constant difference above detector operating temperature. Filament
resistance (proportional to temperature) is monitored, and power is
adjusted as needed to maintain the filament at constant temperature.
500
400
300
200
100
0
100 200 30
0
400
Detector Temperature (Body
Temp)
C
Block Temperature
50 C
T
135
C
0
Filament Temperature
Filament
Temp
(
C)
Filament Temperature versus Detector Block Temperature
Figure 7-9