Figure 3-26: Rear Panel Layout With Internal Span Source (Izs) Opt 50G - Teledyne T200 Operation Manual

Teledyne API – T200 NO/NO
Figure 3-26:
06858E DCN7057
/NO Analyzer Operation Manual
2 X
Rear Panel Layout with Internal Span Source (IZS) OPT 50G
I S G
NTERNAL PAN AS
The primary component of the internal span option is a permeation tube containing
liquid NO As zero air is passed over a permeable membrane on the end of the tube,
2.
molecules of NO slowly pass through the membrane mixing with the zero air.
2
The resulting concentration of the NO

size of the membrane (the larger the area of the membrane, the more permeation
occurs)

temperature of the NO
increases the pressure inside the tube, thereby increasing the rate of permeation)

flow rate of the zero air (if the previous two variables are constant, the permeation
rate of the NO into the zero air stream will be constant; therefore, a lower flow rate
2
of zero air produces higher concentrations of NO
In the Model T200 the permeation tube enclosure is heated to a constant 50° C (10°
above the maximum operating temperature of the instrument) in order to keep the
permeation rate constant. A thermistor measures the actual temperature and reports it to
the CPU for control feedback.
The flow rate of zero air across the permeation tube is maintained at 50 ± 10 cm³/min
by a critical flow orifice located in the analyzer‟s exhaust manifold.
G
ENERATION
span gas is determined by three factors:
2
(increasing the temperature of the permeation tube
2
Getting Started
)
2
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