Filter
Top Products
vi
9.3.2. Changing the O
3
Dryer Particulate Filter...............................................................................................................179
9.3.3. Maintaining the External Sample Pump................................................................................................................180
9.3.3.1. Rebuilding the Pump.....................................................................................................................................180
9.3.3.2. Changing the Inline Exhaust Scrubber..........................................................................................................180
9.3.4. Changing the Pump and IZS Dust Filters .............................................................................................................180
9.3.5. Changing the External Zero Air Scrubber.............................................................................................................182
9.3.6. Changing the NO
2
converter.................................................................................................................................183
9.3.7. Cleaning the Reaction Cell ...................................................................................................................................184
9.3.8. Changing Critical Flow Orifices.............................................................................................................................185
9.3.9. Checking for Light Leaks ......................................................................................................................................186
10. Theory of Operation ...........................................................................................................................................................189
10.1. Measurement Principle...............................................................................................................................................189
10.1.1. Chemiluminescence ...........................................................................................................................................189
10.1.2. NO
X
and NO
2
Determination...............................................................................................................................190
10.2. Chemiluminescence Detection...................................................................................................................................191
10.2.1. The Photo Multiplier Tube...................................................................................................................................191
10.2.2. Optical Filter .......................................................................................................................................................192
10.2.3. Auto Zero............................................................................................................................................................192
10.2.4. Measurement Interferences................................................................................................................................193
10.2.4.1. Direct Interference ......................................................................................................................................193
10.2.4.2. Third Body Quenching ................................................................................................................................193
10.2.4.3. Light Leaks..................................................................................................................................................194
10.3. Pneumatic Operation..................................................................................................................................................195
10.3.1. Pump and Exhaust Manifold...............................................................................................................................195
10.3.2. Sample Gas Flow ...............................................................................................................................................196
10.3.2.1. NO/NO
x
and AutoZero cycles .....................................................................................................................196
10.3.3. Flow Rate Control - Critical Flow Orifices ...........................................................................................................197
10.3.3.1. Critical Flow Orifice.....................................................................................................................................199
10.3.4. Sample Particulate Filter.....................................................................................................................................201
10.3.5. Ozone Gas Air Flow............................................................................................................................................201
10.3.6. O3 Generator......................................................................................................................................................202
10.3.7. Perma Pure
®
Dryer.............................................................................................................................................203
10.3.8. Ozone Supply Air Filter.......................................................................................................................................205
10.3.9. Ozone Scrubber .................................................................................................................................................205
10.3.10. Pneumatic Sensors...........................................................................................................................................206
10.3.10.1. Vacuum Manifold ......................................................................................................................................206
10.3.10.2. Sample Pressure Sensor ..........................................................................................................................206
10.3.10.3. Vacuum Pressure Sensor .........................................................................................................................207
10.3.10.4. O
3
Supply Air Flow Sensor........................................................................................................................207
10.3.11. Dilution Manifold...............................................................................................................................................207
10.4. Electronic Operation...................................................................................................................................................209
10.4.1. CPU....................................................................................................................................................................210
10.4.1.1. Disk On Chip...............................................................................................................................................211
10.4.1.2. Flash Chip...................................................................................................................................................211
10.4.2. Sensor Module, Reaction Cell ............................................................................................................................211
10.4.2.1. Reaction Cell Heating Circuit ......................................................................................................................211
10.4.3. Photo Multiplier Tube (PMT)...............................................................................................................................212
10.4.4. PMT Cooling System..........................................................................................................................................213
10.4.4.1. TEC Control Board......................................................................................................................................213
10.4.5. PMT Preamplifier................................................................................................................................................214
10.4.6. Pneumatic Sensor Board....................................................................................................................................215
10.4.7. Relay Board........................................................................................................................................................215
10.4.7.1. Relay PCA Location and Layout.................................................................................................................215
10.4.7.2. Heater Control.............................................................................................................................................215
10.4.7.3. Thermocouple Inputs and Configuration Jumper (JP5)...............................................................................216
10.4.7.4. Valve Control ..............................................................................................................................................217
10.4.8. Status LEDs & Watch Dog Circuitry....................................................................................................................218
10.4.8.1. Watchdog Indicator (D1).............................................................................................................................218
10.4.9. Motherboard .......................................................................................................................................................219
10.4.9.1. A to D Conversion.......................................................................................................................................219
10.4.9.2. Sensor Inputs..............................................................................................................................................219
10.4.9.3. Thermistor Interface....................................................................................................................................220
10.4.10. Analog Outputs.................................................................................................................................................220
10.4.11. External Digital I/O............................................................................................................................................221
10.4.12. I
2
C Data Bus.....................................................................................................................................................221
04521C (DCN5731)