Teledyne 9110T instruction manual Reaction Cell Temperature Control, List of Interferents

Model 9110T NOx Analyzer			Principles of Operation
		Table 13-1: List of Interferents
	Gas	Interference Type	Rejection Method
		Dilution: Viscosity of CO2 molecules causes them to	If high concentrations of CO2 are suspected,
		collect in aperture of Critical Flow Orifice altering flow
			special calibration methods must be performed to
	CO2	rate of NO.
			account for the affects of the CO2.
		3rd Body Quenching: CO2 molecules collide with
			Contact TAI’s Customer Service Department (see
		NO2* molecules absorbing excess energy kinetically
			Section 12.10) for details.
		and preventing emission of photons.
		Some SOX variants can also initiate a	Wavelengths of light produced by
		chemiluminescence reaction upon exposure to O3	chemiluminescence of SOX are screened out by
		producing excess light.	the Optical Filter.
		Chemically reacts with NH3, O2 and H2O in O3	Most of the ammonium sulfate and ammonium
		generator to create (NH3)2SO4 (ammonium sulfate)
			nitrate produced is removed from the sample gas
		and NH3NO2 (ammonium nitrate) which form opaque
	SOX		by an air purifier located between the O3
		white deposits on optical filter window. Also forms
			Generator and the reaction cell.
		highly corrosive HNO3 (Nitric Acid)
		3rd Body quenching: SOX molecules collide with NO2*	If high concentrations of SOX are suspected,
			special calibration methods must be performed to
		molecules absorbing excess energy kinetically and	account for the affects of the SO2.
		preventing emission of photons.	Contact Teledyne Customer Service Department
			(see Section 12.10) for details.
		3rd Body quenching: H2O molecules collide with NO2*	Analyzer’s operating in high humidity areas must
		molecules absorbing excess energy kinetically and	have some drying applied to the sample gas (see
		preventing emission of light.	Section 3.3.2.6 for more details).
	H2O	Water also reacts with NH3 and SOX in the O3	Water is effectively removed from the O3 gas
		generator to create (NH3)2SO4 (ammonium sulfate)	stream by the Perma Pure® Dryer (Section
		and NH3NO2 (ammonium nitrate) which form opaque	13.2.3.2 for more details). We offer several
		white deposits on the optical filter window. This also	Perma Pure® dryers for the sample stream (see
		forms highly corrosive HNO3 (nitric acid)	Section 3.3.2.6 for more details).
		Direct Interference: NH3 is converted to H2O and NO	If a high concentration of NH3 is suspected, steps
		by the NO2 converter. Excess NO reacts with O3 in	must be taken to remove the NH3 from the sample
		the reaction cell creating a chemiluminescence	gas prior to its entry into the NO2 converter (see
	NH3	artifact.	Section 3.3.2.6 for more details).
		NH3 also reacts with H2O, O2 and SOX in the O3	The Perma Pure® dryer built into the 9110T is
		generator to create (NH3)2SO4 (ammonium sulfate)
		and NH3NO2 (ammonium nitrate) which form opaque	sufficient for removing typical ambient
		white deposits on optical filter window. Also forms	concentration levels of NH3.
		highly corrosive HNO3 (nitric acid).

13.1.5.4. Reaction Cell Temperature Control

The stability of the chemiluminescence reaction between NO and O3 can be affected by changes in the temperature and pressure of the O3 and sample gases in the reaction cell. In order to reduce temperature effects, the reaction cell is maintained at a constant 50° C, just above the high end of the instrument’s operation temperature range.

Two AC heaters, one embedded into the bottom of the reaction cell, the other embedded directly above the chamber’s exhaust fitting, provide the heat source. These heaters operate off of the instrument’s main AC power and are controlled by the CPU through a power relay on the relay board (see Section 13.3.4.4).

A thermistor, also embedded in the bottom of the reaction cell, reports the cell’s temperature to the CPU through the thermistor interface circuitry of the motherboard (see Section 13.3.3.3).

Teledyne Analytical Instruments 325