THEORY OF OPERATION
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6. THEORY OF OPERATION
The UltraRAE monitor uses a newly developed electrodeless
discharge UV lamp as the high-energy photon source for the
PID. As organic vapors pass by the lamp, they are photo-
ionized and the ejected electrons are detected as a current. The
PID sensor will detect a broad range of organic vapors. A lamp
with high photon energy (e.g. 11.7 eV) will measure the most
kinds of compounds, whereas low photon energies (e.g. 9.8 eV)
are selective for easily ionizable compounds such as aromatics.
The gas separation tube filters out unwanted gases and allows
the target gas to be measured.
The RAE-SEP benzene tube uses a combination of adsorption
and oxidation to remove most common organic compounds
other than benzene. Methane, ethane, propane, and some
butane passes through the tube but is not detected by the PID.
Figure 6-1 UltraRAE Block Diagram
Micro-
processor
LCD Display
Keypad
Serial
Port
Battery
PID Sensor
UV lamp
Pump
Light
Sensor
LED
Buzzer
Charger
Gas Separation
(RAE-Sep)
Tube
Gas Inlet
Gas Outlet
