Quick Start Guide
SERVO
PRO CHROMA/NANOCHROME/ULTRA Gas Analyser
43
04400003A_0
The optional Internal Dilution System (see 3.3.34) is fitted to Sample 2 Inlet.
The internal Dilution System dilutes the span gas with the carrier gas with a
fixed dilution ratio, suitable for the calibration process.
2. Auxiliary Oven
An external auxiliary oven is required to support the determination of N2
impurity in O2 or H2 background gas. The gas connections at the rear of the
oven are shown in Figure 3.
Trap In & Trap Out
The oven
Inlet
gas connector is taken to the analyser chassis
Trap In
gas
connector.
The oven
Outlet
gas connector is taken to the analyser chassis
Trap Out g
as
connector.
VCR tubing should be used in all cases.
3.3.4 Internal dilution system setup (NanoChrome and Ultra only)
The internal dilution system uses carrier gas to dilute a calibration gas to a fixed
ratio, nominally a factor of 20 to generate a suitable span gas concentration. That
means a suitable span gas concentration of 5ppm will be diluted to 250ppb.
Figure 24 : Internal dilution system schematic
The dilution ratio is a function of the carrier gas inlet pressure and span gas inlet
pressure connected to sample inlet 2. The internal restrictors are set during
production but it is important to re-calculate the dilution ratio during installation
or every time the supply pressures are changed.
