Teledyne 9110T - Nitrogen Oxides Analyzer - Manual (Page 329)

Model 9110T NOx Analyzer Principles of Operation
Teledyne Analytical Instruments 329
Figure 13-7. Vacuum Manifold, Standard Configuration
Configurations will vary depending on the optional equipment that is installed. For example:
 An 9110T with the optional internal span gas generator installed will add another FT8 connector and
orifice assembly to the manifold where the FT28 fitting is shown in the above drawing.
 An optional sample gas dryer will add a Tee-fitting so that two ¼” tubes can be connected to the
same port.
13.2.1.2. Sample Gas Flow Valves and Routing
As discussed in Section 13.1, the measurement of NO
x
, NO and NO
2
requires that the sample gas flow
cycles through different routes that include and exclude various scrubbers and converters. There are
several valves that perform this function:
 The NO/NO
X
valve directs the sample gas either directly to the reaction cell or through the unit’s
NO
2
converter, alternating every ~8 sec.
 The Auto Zero valve directs the sample gas stream to completely bypass the reaction cell for dark
noise measurement once every minute, which is then subtracted as a measurement offset from the
raw concentration signal.
Table 13-2: 9110T Valve Cycle Phases
Phase
NO/ NO
X
Valve
Status
Auto Zero
Valve
Status
Time
Index
Activity Figure
NO
Measure
Open to
Auto Zero
valve
Open to
reaction cell
0 - 2 s
Wait period (NO dwell time). Ensures reaction cell has
been flushed of previous gas.
Figure
13-3
2 - 4 s Analyzer measures chemiluminescence in reaction cell.
NO
X
Measure
Open to
NO
2
converter
Open to
reaction cell
4 – 6 s
Wait period (NO
X
dwell time). Ensures reaction cell has
been flushed of previous gas. Figure
13-3
6 – 8 s
Analyzer measures NO + O
3
chemiluminescence in
reaction cell.
Cycle repeats every ~8 seconds