HP 5890 Series II Plus Reference Manual page 147

Detector Systems
Thermal conductivity detector (TCD)
As Figure 7•9shows, however, the lower the detector zone temperature,
the greater is the temperature difference between the filament versus the
surrounding detector body temperature. Thus, for maximum sensitivity,
the detector zone should be operated at the lowest temperature possible
(limited by highest boiling components condensing inside the detector).
Also, a second advantage is one of increased filament lifetime.
Gas flow rates
After the detector and instrument are allowed time for thermal
stabilization (about 1/2•hourafter the oven and zones achieve desired
setpoint values), two gas flow rates, column and reference gas, must be
set independently.
After setting optimal carrier gas flow rate through the column, Figure
7•10may be used to determine the corresponding optimal reference flow
rate.
Figure 7-10
Relative
Response
TCD Response versus Reference Flow Rate
60
55
50
45
40
35
0
20
Reference Gas Flow Rate
(ml/min)
Column Flow Rate:
30 ml/min
Column Flow Rate:
20 ml/min
Column Flow Rate:
60 ml/min
40 60 80 100
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