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The probe assembly consists of the following components:
• A 9" long 3/8" OD piece of inconel tubing and an inconel-sheathed type K
thermocouple located inside the inconel tube for protection. Both probe and
thermocouple are mounted on an aluminum head that includes a support handle.
• A 10 ft. long 1/4/” OD Viton sampling hose and thermocouple extension cable
equipped with quick disconnects on both sides for easy storage. Viton tubing is
used to prevent adsorption of NO
2
and SO
2
gases from the sample.
• A condensation trap and particulate filter assembly to remove the excess water
and clean the sample. The condensation trap is mounted for convenience to the
side of the hand-held analyzer. Figure 1 shows the probe assembly. The
optional thermoelectric cooler assembly replaces the condensation trap.
C. THERMOELECTRICALLY COOLED CONDENSATION TRAP
The thermoelectrically cooled condensation trap, better known as “Peltier Drier” is
an optional accessory device for the model 500 emissions analyzer.
Its purpose is to replace the standard condensation trap of the Model 500 for those
critical applications, that demand higher accuracy for the measurement of nitrogen
dioxide (NO
2
) and sulfur dioxide (SO
2
).
NO
2
and SO
2
are gases that are highly soluble in water. The exhaust sample
contains typically between 5% and 20% of water vapor, most of which will
condense in the probe and sample line.
To prevent significant loss of NO
2
and SO
2
during transport of the sample from the
probe to the analyzer, the following conditions must be satisfied:
1. Rapid sample transport. This is accomplished by maintaining a high flow
rate using a relatively small diameter sampling line.
2. Use of a sample line made from a highly hydrophobic material. A Teflon
sample line limited to 15 ft. long is used.
3. Minimum contact of the gas sample with the water collection mechanism
and also no additional condensation occurring following the Peltier drier.
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