Servomex NanoTrace DF-760E, Instruction Manual

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Sample Gas Preparation and Delivery DF-760E 119
8 Sample Gas Preparation and
Delivery
8.1
Introduction
The DF-760 consists of two separate analyzers, joined together by a common gas delivery
system. It is important to note key differences in the method of operation of each analyzer
to ensure a properly functioning system. Parameters such as flow, pressure, and
background gas will have major effects on total system performance.
8.2
Sample Flow Rate and Pressure
8.2.1 Moisture
Proper moisture analyzer operation is dependant upon the pressure of the sample gas. For
each sample gas, there is a unique pressure range that the analyzer must operate under. See
Table 10 for the proper settings. Proper analyzer operation is contingent upon maintaining
the sample pressure for a given background gas within this range. The pressure can be
adjusted by balancing the inlet regulator setting with the throttling valve in the aspirator or,
if equipped, with the needle valve in the vacuum pump assembly. When adjusting sample
pressure, be aware of the effects on the oxygen sensor that is sharing the feed.
Background Gas Pressure
N2 200 +/- 50 Torr
Ar 330 +/- 50 Torr
He 780 +/- 50 Torr
H2 350 +/- 50 Torr
O2 350 +/- 50 Torr
Table 10: Sample Outlet Pressure
8.2.2 Oxygen
The oxygen sensor is factory calibrated at a flow rate of 1.0 slpm, in N2, and should be
operated at that level for optimal accuracy. However, the oxygen sensor is relatively
unaffected by gas sample flow rate, within limits. Sample flow rate should be maintained
within the recommended range of 0.5 to 1.5 slpm as indicated on the front panel display.
The oxygen sensor can be operated at flow rates outside that range, but it should be
recalibrated at that different flow rate to maintain optimal accuracy.