Teledyne PEM-9004 - Portable emissions analyzer - Manual (Page 22)

Operational Theory PEM-9004
Teledyne Analytical Instruments 10
Figure 2-4: Gas Conditioning System
The gas is passed through a condensation trap to remove moisture
which would otherwise interfere with the measuring process.
CAUTION: THE WATER TRAP SHOULD BE EMPTIED AFTER
EACH USE. IF WATER IS ALLOWED TO COLLECT IN
THE TRAP IT COULD BACK FLOW INTO THE GAS
LINE AND DAMAGE THE PUMP AND SENSORS.
The sample gas is then drawn through a coarse particle filter in
series with a fine filter to remove any solid residue from the combustion
process prior to directing the gas to the sensor block.
The gas is fed to the sensor cells which are arranged in series. The
cell outputs a signal proportional to the concentration of the specific gas
it is sensitive to. Three to five cells are installed depending on the
options installed. A special purge line equipped with a separate pump is
installed to protect the CO sensor from prolonged exposure to high
concentration of oxygen such as atmospheric air. The pump is activated
automatically when the concentration exceeds 4000 ppm. It can also be
operated manually. See Section 4.5.1.13 CO Protect.
After traversing the sensor block, the sample gas is passed back out
through the Gas Out port on the front panel of the instrument.
CAUTION: BOTH TOXIC AND FLAMMABLE GASES ARE
PRESENT IN THE SAMPLE SYSTEM—INCLUDING
THE FILTERS! MAKE SURE THE EXHAUST LINE IS