Teledyne 9110T instruction manual Teledyne Analytical Instruments 331

Model 9110T NOx Analyzer Principles of Operation

The actual flow rate of gas through the orifice (volume of gas per unit of time), depends on the size and shape of the aperture in the orifice. The larger the hole, the more gas molecules (moving at the speed of sound) pass through the orifice.

In addition to controlling the gas flow rates into the reaction cell, the two critical flow orifices at the inlets of the reaction cell also maintain an under-pressure inside it, effectively reducing the number of molecules in the chamber and the corresponding incidence of third body quenching (see Section 13.1.5.2) and therefore increasing the chemiluminescence yield.

∙The 9110T reaches its peak sensitivity at about 2 in-Hg-A, below which the sensitivity drops due to there being too few molecules present and a corresponding decrease in chemiluminescence.

13.2.2.2. Locations and Descriptions of Critical Flow Orifices Inside the 9110T

The 9110T uses several of the following critical flow orifices (Figure 13-9) to create and maintain the proper flow rate of gas through its various components. (Please note that not all features displayed in Figure 13-9 are standard components of 9110T analyzers).

SAMPLE/ CAL	NO/NOX
	VALVE
VALVE
ZERO/SPAN
VALVE
	SAMPLE	VACUUM
	PRESSURE	PRESSURE
	SENSOR	SENSOR
		O3 FLOW
		SENSOR
	AUTOZERO
	VALVE
	PMT
	PERMAPURE
	DRYER

Figure 13-9: Location of Flow Control Assemblies & Critical Flow Orifices

Table 13-3: 9110T Gas Flow Rates

Location	Purpose	Orifice	Flow rate
		Diameter	(nominal)
Sample gas inlet of reaction cell	Controls rate of flow of sample gas into the	0.010” (0.25 mm)	500 cm³/min

Teledyne Analytical Instruments 331