Teledyne 2120XL - Trace Nitrogen Analyzer - Manual (Page 26)

Operational Theory Model 2120XL
Teledyne Analytical Instruments 14
After analysis, the gas is returned to the gas flow module. A signal
is produced in the flow transducer that is used by the microprocessor to
control the flow control valve. From the flow control module, the gas
exits the analyzer at atmospheric pressure.
The superior accuracy of the Model 2120XL is achieved through
enhanced coupling of the plasma to the process and an advanced plasma
generator design. Through proper frequency and intensity control a
uniform, precisely located, and highly stable plasma discharge is
produced with minimum heat generation. The resulting emission spectra
is clear and distinct.
The Model 2120XL is fitted with custom optical filtering and an
optics system that is specifically designed to reduce interference. The
desired spectral line used for analysis is sharp and focused on the
detector.
The detector lifetime is enhanced using a “Duty Cycle Controlled
System” by reducing the coating inside the cell. This also results in an
increase in sensitivity.
2.2 Sample System
A suitable external sample system must be provided by the
customer. The external sample system delivers calibration or sample gas
to the analyzer at a suitable pressure.
The sample system may contain a molecular sieve type trap to
reduce moisture levels in the sample gas. Moisture produces a well-
known interference line in the spectrum close to that of nitrogen. It is
necessary to use moisture-free sample gas or install an efficient moisture
trap on the inlet.
Internally the Model 2120XL employs a flow control valve which
provides proper flow through the analyzer when the inlet pressure is
maintained between 4 to 20 psig. The proper flow rate should be
maintained around 100 ccm.