GE CGA 351 User manual

GE Infrastructure
Sensing
Model CGA 351
Zirconia Oxygen Analyzer
User’s Manual
910-199C
December 2004
The Model CGA 351 is a GE Panametrics product. GE Panametrics has joined other GE high-technology
sensing businesses under a new name—GE Infrastructure Sensing.
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Warranty Each instrument manufactured by GE Infrastructure Sensing, Inc. is
warranted to be free from defects in material and workmanship.
Liability under this warranty is limited to restoring the instrument to
normal operation or replacing the instrument, at the sole discretion of
GE Infrastructure Sensing, Inc. Fuses and batteries are specifically
excluded from any liability. This warranty is effective from the date of
delivery to the original purchaser. If GE Infrastructure Sensing, Inc.
determines that the equipment was defective, the warranty period is:
•one year for general electronic failures of the instrument
•one year for mechanical failures of the sensor
If GE Infrastructure Sensing, Inc. determines that the equipment was
damaged by misuse, improper installation, the use of unauthorized
replacement parts, or operating conditions outside the guidelines
specified by GE Infrastructure Sensing, Inc., the repairs are not
covered under this warranty.
The warranties set forth herein are exclusive and are in lieu of
all other warranties whether statutory, express or implied
(including warranties of merchantability and fitness for a
particular purpose, and warranties arising from course of
dealing or usage or trade).
Return Policy If a GE Infrastructure Sensing, Inc. instrument malfunctions within the
warranty period, the following procedure must be completed:
1. Notify GE Infrastructure Sensing, Inc., giving full details of the
problem, and provide the model number and serial number of the
instrument. If the nature of the problem indicates the need for
factory service, GE Infrastructure Sensing, Inc. will issue a RETURN
AUTHORIZATION number (RA), and shipping instructions for the
return of the instrument to a service center will be provided.
2. If GE Infrastructure Sensing, Inc. instructs you to send your
instrument to a service center, it must be shipped prepaid to the
authorized repair station indicated in the shipping instructions.
3. Upon receipt, GE Infrastructure Sensing, Inc. will evaluate the
instrument to determine the cause of the malfunction.
Then, one of the following courses of action will then be taken:
•If the damage is covered under the terms of the warranty, the
instrument will be repaired at no cost to the owner and returned.
•If GE Infrastructure Sensing, Inc. determines that the damage is not
covered under the terms of the warranty, or if the warranty has
expired, an estimate for the cost of the repairs at standard rates
will be provided. Upon receipt of the owner’s approval to proceed,
the instrument will be repaired and returned.
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Table of Contents
Chapter 1: General Information
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
The Sensor Enclosure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
The Sample System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
The Zirconia Oxygen Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
The Heater Control Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Chapter 2: Installation
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Choosing an Installation Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Mounting the Model CGA 351 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Connecting the Sample System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Wiring the Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Wiring the Outputs (TB1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Wiring the Inputs (TB2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Wiring the Line Power (TB3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Chapter 3: Operation
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Preventing Common Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Powering Up the System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
User Program Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Configuring the Digital Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Initial Screen Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Switching Display Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Converting mV to Oxygen Concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
Powering Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
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Chapter 4: Setup and Calibration
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Accessing the User Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
The [Cal] Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Setting Up the Alarm Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Setting the Trip Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Setting the Trip Value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Setting the Deadband Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Testing the Alarm Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Selecting the Operating Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Setting the Temperature Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Entering the Setpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Setting the Air Offset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Setting the Proportional Band. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
Setting the Integration Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Setting the Maximum Duty Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Restoring the Default Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
The [Opt-User] Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Setting Fault Alarm Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Setting Up the Analog Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Selecting the Analog Output Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Setting the Zero Setpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
Setting the Span Setpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Testing the Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
Setting the Zero Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
Setting the Span Trim. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
Adjusting the Display Contrast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Setting the Display Backlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-25
Setting Up the Serial Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26
Entering the Node ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26
Entering the Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26
Entering the Number of Data Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27
Entering the Parity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27
Entering the Number of Stop Bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27
Selecting the Type of Serial Port. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27
Setup and Security Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
Setting Up the Option Card Slots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
Setting the Security Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-30
Calibrating the Model CGA 351. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31
Recommended Calibration Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31
Regulating the Calibration Gas Flow Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-32
Adjusting the Calibration Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-33
Checking the Current Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-36
Checking the Sensor Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37
Viewing the Heater Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37
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Chapter 5: Service and Maintenance
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
General Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Checking the Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Checking the Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Checking the Oxygen Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
Checking the Sensor Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
Checking the Sensor Furnace Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Oxygen Measurement Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Oxygen Concentration Reads Constant 20.93% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Oxygen Reading Above 100%. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Oxygen Reading Too Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Oxygen Reading Too High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Calibration Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11
Everything Is Fine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11
Forced Flow Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
Plugging or Dead Space Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11
Parts Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12
The Sensor Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13
The Electronics Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-20
Recommended Spare Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-24
Chapter 6: Specifications
General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Operating Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Appendix A: The Nernst Equation
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Equilibrium Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
The Model CGA 351 Nernst Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2
Appendix B: CE Mark Compliance
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
EMC Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
LVD Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
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Appendix C: Optional Enclosures
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Rack Mount Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Mounting the Rack Mount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Connecting the Sample System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2
Wiring the Rack Mount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2
Rack Mount Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4
Rack Mount Service and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4
Parts Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4
Replacing the Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5
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Chapter 1
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General Information
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
The Sensor Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
The Sample System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
The Zirconia Oxygen Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
The Heater Control Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
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General Information 1-1
December 2004
Introduction The Model CGA 351 monitors the oxygen content of any clean and
dry gas stream. The analyzer can accurately measure oxygen levels
from 0.1 ppm to 100% O2, and can even measure oxygen content in
reducing gases. This is accomplished with a precision, temperature-
controlled, zirconium oxide (zirconia) oxygen sensor.
The standard CGA 351 analyzer is supplied in a pair of stainless steel,
Nema 4X/IP66 enclosures mounted side-by-side on a metal plate with
a 40” flexible conduit connecting the two. This compact, wall-
mounted system includes the following components:
•asensor enclosure, which contains the oxygen sensor, sensor
furnace, thermocouple, inlet port with needle valve, outlet port
with flowmeter, and interconnecting cable(s), and
•an electronics enclosure, which contains the temperature control
circuitry, output signal processing circuitry, digital display, user
interface, and wiring terminal strips.
The CGA 351 analyzer is also available in optional enclosures. See
Appendix C for more information.
Figure 1-1: Standard CGA 351 Analyzer
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December 2004
1-2 General Information
The Sensor Enclosure The sensor enclosure, which is shown in Figure 1-2 below, houses the
sample measurement components. The functions of these components
are as follows:
•a zirconium oxide (zirconia) oxygen sensor converts the oxygen
concentration of the sample gas into a mV output signal.
•a sensor furnace heats the oxygen sensor and the sample gas to the
optimum temperature of 700°C.
•a thermocouple precisely regulates the temperature of the oxygen
sensor and the sample gas.
•an inlet needle valve and an outlet flowmeter adjust the sample gas
flow to 1,000 ± 150 cc/min (2.1 ± 0.3 SCFH).
Figure 1-2: Sensor Enclosure
Furnace Bracket
Flowmeter
Thermocouple
Needle Valve
Sensor Furnace
Oxygen Sensor
Manifold
Electrical Conduit
Flowmeter
Furnace Bracket
Flowmeter
Thermocouple
Needle Valve
Sensor Furnace
Oxygen Sensor
Manifold
Electrical Conduit
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General Information 1-3
December 2004
The Sample System In addition to the components supplied with the CGA 351, an external
sample system may be required to ensure that the analyzer is fed a
properly conditioned sample or calibration gas stream. In particular,
the gas must be clean and dry, and it must be delivered to the analyzer
at atmospheric pressure.
Note: A suitable sample system, which will be supplied completely
assembled on its own mounting plate, may be ordered directly
from the factory.
Commonly used sample system components include filters, pressure
regulators, pressure gauges, by-pass loops, and sample pumps. It is
recommended that stainless steel construction be used for all wetted
parts of the sample system. A typical sample system is shown in
Figure 1-3 below.
Figure 1-3: Typical Sample System
SAMPLE
INLET SAMPLE OUTLET
INLET
CAL-GAS
INPUT
OUTPUT
To:CGA351Inlet
From:CGA351Outlet
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December 2004
1-4 General Information
Principles of Operation A gas sample is drawn into the inlet port of the analyzer by gas
diffusion and a gentle convective flow. The sample gas then flows
through a ceramic inlet tube and into the annular space between the
inlet tube and the inside of the zirconia oxygen sensor. The flowmeter
on the outlet port and the needle valve on the inlet port are used to
adjust the sample flow rate to 1,000 ± 150 cc/min (2.1 ± 0.3 SCFH).
In the annular sample space, the gas is heated to the same 700°C at
which the zirconia oxygen sensor is maintained. A mV signal is
generated. This signal is proportional to the logarithm of the ratio of
the oxygen concentration in the sample gas to the oxygen
concentration in a reference gas contacting the outer electrode. Using
the digital panel meter (DPM) the logarithmic signal can be read
directly in unlinearized form, or it can be converted to a 0/4–20 mA,
0–2 V, or Namur linearized signal before display.
Note: A temperature above 650°C is required for proper operation
of the oxygen sensor. Also,ambient air is the usual reference
gas on the outside of the zirconia sensor.
The sensor furnace also generates the convective flow that circulates
the sample gas through the sample path. Pushed from behind by the
hot gases still in the furnace, the hot sample gas in the sensor furnace
rises out of the furnace and cools. The cooled sample gases then pass
through the outlet port, where they are carried away by the main gas
flow.
A platinum coating on the end of the ceramic tube and the zirconia
oxygen sensor ensures that all oxidation/reduction reactions in the
sample gas reach equilibrium. It is therefore possible to measure such
parameters as excess oxygen in air/fuel mixtures and equilibrium
oxygen in reducing atmospheres such as hydrogen.
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General Information 1-5
December 2004
The Zirconia Oxygen
Sensor The inside and outside of the zirconia oxygen sensor are coated with
porous platinum, forming two electrodes. The sample gas flows past
the inside of the sensor, while atmospheric air circulates freely on the
outside of the sensor. This atmospheric air is used as the reference gas
for making oxygen measurements. See Figure 1-4 below.
Figure 1-4: Oxygen Migration in the Zirconia Sensor
At the operating temperature of the oxygen sensor, the atmospheric
reference oxygen is electrochemically reduced at the outer electrode,
and the resulting oxygen ions seek to equalize with the lower oxygen
concentration on the sample side of the cell by migrating through the
porous ceramic toward the inner electrode. At the inner electrode they
give up electrons to become oxygen molecules again, and are swept
away by the sample flow.
The lower the concentration of oxygen in the sample gas, the greater
the rate of ion migration through the ceramic, and the higher the cell
voltage due to electron exchange at the electrodes. The cell voltage
rises logarithmically as the amount of oxygen in the sample gas falls,
allowing the accurate measurement of very low levels of excess
oxygen.
Volts
O22
O
O2
O2
2
OO2
Sample O
Inside Cell
Oxygen ions migrate through the zirconium oxide
along the concentration gradient.
From Outside
Electrode From Inside
Electrode
Zirconium Oxide Ceramic
with Lattice Imperfections
Atmospheric O
Outside Cell
When O concentration in sample gas falls, the cell voltage rises
with increased oxygen migration through the zirconium oxide.
2
2
2
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December 2004
1-6 General Information
The Heater Control
Circuit The oxygen sensor temperature in the CGA 351 is maintained by a
heater, which is part of a complex temperature control loop. This
circuit constantly monitors the oxygen sensor temperature, compares
it to the set point temperature (700°C), and turns the heater ON or
OFF accordingly. The specific type of control circuit, a Proportional
Integral Derivative (PID) loop, is used because of the adjustable
parameters involved:
•Proportional Band: Because the system cannot respond
instantaneously to temperature changes, the actual temperature of
the oxygen sensor oscillates about the set point. In general,
increasing the proportional band reduces the magnitude of these
temperature oscillations.
•Integral Action: A consequence of increasing the proportional
band is the introduction of an offset between the set point and the
control point. The integral portion of the control loop acts to move
the control point back toward the set point within a specified
period of time. Decreasing this integration time reduces the offset
more quickly.
Note: A third parameter, Derivative Action, is not used with the
CGA 351.
The heater control circuit is configured at the factory for optimum
performance. Because of the strong interaction between the
parameters involved, properly setting up the PID loop is a very
complex matter. As a result, randomly changing the P, and/or I
parameters can seriously degrade the performance of the CGA 351.
IMPORTANT: Always contact the factory before attempting to
change the default P and/or I values. The submenu
for performing these changes is password protected
to prevent accidental changes.
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Chapter 2
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Installation
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Choosing an Installation Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Mounting the Model CGA 351 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Wiring the Analyzer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
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Installation 2-1
December 2004
Introduction This chapter provides a general description of the standard CGA 351
and gives directions on how to install and wire the analyzer for proper
operation.
Note: For information regarding component locations and/or wiring
connections in an optional enclosure, see Appendix C.
IMPORTANT: For compliance with the European Union’s Low
Voltage Directive (73/23/EEC), the CGA 351
requires an external power disconnect device such as
a switch or circuit breaker. The disconnect device
must be marked as such, clearly visible, directly
accessible, and located within 1.8 m (6 ft) of the unit.
!WARNING!
Power up the CGA 351 as quickly as possible after
introduction of the sample gas. If the analyzer is left
installed without power, the unit’s components become
susceptible to acid condensation that will cause corrosion.
Be sure to observe all installation limits and precautions described in
this chapter. Pay particular attention to the ambient temperature range
of –25 to +50°C (–13 to +122°F) specified for the instrument.
!WARNING!
To ensure safe operation of the CGA 351, the unit must be
installed and operated as described in this manual. Also,
be sure to follow all applicable local safety codes and
regulations for installing electrical equipment.
In addition, all procedures should be performed
by trained service personnel.
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December 2004
2-2 Installation
Choosing an Installation
Site All environmental and installation factors should have been discussed
with a GE Infrastructure Sensing applications engineer or field sales
person at the time the CGA 351 was ordered. Thus, the equipment
should be suited to the application and the planned installation site.
Before installing the unit, however, read the following guidelines to
verify that the best installation site has been chosen for optimum
instrument accuracy and reliability. Make sure that:
•the CGA 351 enclosures are suitable for the environmental
conditions at the installation site.
•the analyzer system will be installed in a location with little or no
vibration.
•the ambient temperature at the installation site is between –25° and
50°C (–13° and 122°F).
•there are no restrictions in the discharge line (i.e. flow control
valves downstream of the meter).
•the CGA 351 system is installed in a location that provides ready
access for programming, testing, and servicing the unit.
•the cables will be protected from excessive physical strain
(bending, pulling, twisting, etc.). Do not subject the cables to
temperatures above 65°C (149°F) or below –50°C (–58°F).
•the line voltage used at the planned installation site corresponds to
the factory preset line voltage rating for the meter.
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Installation 2-3
December 2004
Mounting the Model CGA
351 This section explains how to mount the analyzer components at the
installation site and how to connect the sample system to the analyzer.
Note: If more than one analyzer system is being installed, be aware
that each system is a matched set (i.e., each sensor enclosure
must be matched to a specific electronics enclosure). Refer to
the identification tags on the enclosures to match the systems
correctly.
IMPORTANT: For compliance with the European Union’s Low
Voltage Directive (73/23/EEC), the CGA 351
requires an external power disconnect device such as
a switch or circuit breaker. The disconnect device
must be marked as such, clearly visible, directly
accessible, and located within 1.8 m (6 ft) of the unit.
IMPORTANT: This symbol indicates Caution - risk of electric
shock:
Refer to Figure 2-1 on page 2-9, and complete the following steps to
mount the CGA 351:
1. Select a flat surface on a vertical wall or instrument panel with
sufficient space to hold the mounting plate with both of the CGA
351 enclosures.
Note: Mount the system in an upright position, so that the sample
inlet and outlet fittings are on the bottom of the sensor
enclosure.
2. Using the mounting dimensions shown in Figure 2-1 on page 2-9,
locate and prepare four (4) mounting holes or two (2) horizontal
mounting rails on the vertical surface.
3. Secure the system to the mounting surface with four (4) sets of
mounting hardware. Be sure that the enclosures are in a vertical
position, with the inlet/outlet connectors on the bottom.
4. The flowmeter, which is fastened to the right side of the sensor
enclosure, is connected to the discharge port on the bottom of the
unit with a length of 6mm stainless steel tubing. Make sure that
the factory-installed Swagelok fittings are secure.
5. A flow control valve is attached to the inlet port on the bottom of
the sensor enclosure with 6mm stainless steel tubing and
Swagelok fittings. Point the valve in the proper direction to
receive the inlet piping from the sample system, and securely
tighten the fittings.
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December 2004
2-4 Installation
Connecting the Sample
System The sample system should be located so that it is able to deliver a
sample at a flow rate of 1,000 ±150 cc/min. For best results, mount
the sample system as close as possible to the CGA 351. An ideal
location would be on the same panel, just below the analyzer. If there
are questions, consult with an applications engineer at GE
Infrastructure Sensing.
See Figure 2-1 on page 2-9, and complete the following steps to
connect the sample system to the analyzer:
1. Using 6mm stainless steel tubing (or ¼” stainless steel tubing with
adaptors), connect the gas source from the sample system to the
Swagelok fitting on the flow control valve at the inlet port on the
analyzer.
2. Using 6mm stainless steel tubing (or ¼” stainless steel tubing with
adaptors), connect the Swagelok outlet fitting at the top of the
flowmeter on the analyzer to the gas discharge connection on the
sample system.
Note: If desired, a suitable sample system may be ordered directly
from the factory. The sample system would be supplied fully
assembled on a flat plate with four (4) mounting holes.
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