Oxygen gas analyzer

3. Concentration cell system
A solid electrolyte like zirconia exhibits conductivity of oxygen ions at
high temperature. As shown in the figure below, when porous platinum
electrodes are attached to both sides of the zirconia element to be heated
up and gases of different partial oxygen concentrations are brought into
contact with the respective surfaces of the zirconia, the device acts as an
oxygen concentration cell. This phenomenon causes an electromotive
force to be generated between both electrodes according to Nernst’s
equation

4. The principle of the zirconia oxygen analyzer is as follows:
Zirconia is one of the few compounds that actually become conductive at high
temperatures & more conductive as its temperature increases
Zirconia starts out with a very high resistance at room temperature greater then one
trillion ohms / cm , Having less then 1000 ohms / cm resistance at 1000 degrees
Celsius & become a very good conductor
Heating the element allows different partial oxygen concentrations of the gasses to
come into contact with the opposite side of the zirconia’s creating an oxygen
concentration cell.
These ions travel through the zirconia’s element to the other electrode. At that
point, the Nernst expression applied to calculate the force by measuring the
electromotive force generated between the two electrodes.

5.  Reference gas on one side and sample
gas on the other side
 Oxygen ions move from the side with
the highest concentration of oxygen to
that with the lowest concentration.
 The movement of ions generates an
EMF (Electro Motive Force) which can
be measured to determine the oxygen
content.

6. the EMF varies depending
on
 the temperature of the
zirconia sensor and
 the oxygen concentration
of the reference gas (PR),
in the actual device.
• the zirconia sensor is
placed in a constant
temperature oven
• air is generally used as
the reference gas
Limitations
 Flammable gases cannot be used
 Sensor degradation occurs if corrosive gas (fluorine-based gases, chlorine-
based gases, sulfate-based gases)is measured

11. System Configuration
This system is for monitoring and controlling oxygen concentration in the
combustion gases of a large-size boiler or heating furnace. Clean (dry) air (21%
O2) is used as the reference gas and the span gas for calibration. Zero gas is fed
in from a cylinder during calibration.

12. System Configuration
This example, represents typical applications in large boilers and heating
furnaces, where there is a need to monitor and control oxygen concentration. The
reference gas and calibration-time span gas are (clean, dry) instrument air. Zero gas
is supplied from a gas cylinder
System uses auto calibration unit, with auto-switching of the calibration gas.

16. Calibration
The converter is calibrated in such a way that the actual zero and span gases are
measured and those measured values are used to agree with the oxygen
concentrations in the respective gases.
There are three types of calibration procedures available:
(1) Manual calibration conducting zero and span calibrations, or either of these
calibrations in turn.
(2) Semi-automatic calibration which uses the touchpanel or a contact input
signal and conducts calibration operations based on a preset calibration time
and stable time.
(3) Automatic calibration conducted at preset intervals.

17. Calibration Setting Procedures
Select “Points” (calibration procedure) in the Calibration setup display to display
the “Span – Zero,” “Span, Zero” selection display. In this display, select “Span –
Zero.”

18. Calibration Gas Concentration Setting
(1) Zero-gas concentration
If zero-gas concentration is selected, the Numeric-data Entry display then
appears.
Use this display to enter an oxygen concentration value for the zero-gas
calibration; if the oxygen concentration is 0.98 vol%O2, enter 00098.
(2) Span-gas concentration
With “Span gas conc” selected in the Calibration setup display, display the
Numeric-data Entry display and enter an oxygen concentration value for the
span-gas calibration; If instrument air is used, enter 02100 for a 21 vol% O2 value.

19. Manual Calibration
Preliminary
Before performing manual calibration, Setting Unit zero-gas flow valve is fully closed.
Open the zero-gas cylinder pressure regulator so that the secondary pressure equals
measured gas plus approx. 50 kPa (or measured gas pressure plus approx. 150 kPa when a
chack valve is used, maximum pressure rating is 300 kPa)..

22. Thermox Ametek WDG-IV
The same main principle for YokoJawa oxygen Analyzer using Zirconium
Oxide material

23. Thermox Ametek WDG-IV

24. Sensor operation:
A sample is drawn from the process stream by means of an air-operated
aspirator and is immediately returned to the process. A portion of this gas
rises past the oxygen measuring cell.

25. Assemble sensor’s parts

27. 400-AT-001

28. Thermox Series 2000 WDG-IV

29. Manual Calibrate/Manual Verify
To perform a manual calibration or verification, follow these steps:
1. Enter the calibration gas values to match the span and zero calibration gases you
intend to use to calibrate or verify your system
2. Select Initiate Cal or Initiate Verify from the Calibrate key menu, depending on
whether you want to perform a calibration or verification.
3. Select Manual Calibrate or Manual Verify. You are then prompted to apply the 02
span gas to the calibration gas inlet port on the sensor (tubing must be free of oil and
dirt):
4. Press the Enter key once you have applied this calibration gas. The span display
then appears (display line 2 will only appear if you have the combustibles option;
display line 3 will only appear if you have the combined combustibles and
methane option):

30. 5. Press the Enter key once the 02 reading on the far left of the first display line
stabilizes. The reading on the far right of the first display line shows the
setpoint value you entered using the Cal Gas Values menu option. This
setpoint value should match the cal gas cylinder for the 02 span gas.
If your 0, reading on the far left of the display has stabilized, yet is not near the
setpoint value on the right of the display, you should check the cal gas value
you entered and ensure that this value matches the cal gas cylinder for the gas
you applied to the cal gas inlet port of the sensor.
You are then prompted to apply the 02 zero gas to the calibration inlet port of
the sensor:

31. 6. Press the Enter key once you have applied this cal gas. The zero gas display
then appears (display line 2 will only appear if you have the combustibles
option; display line 3 will only appear if you have the combined combustibles
and methane option):
7. Press the Enter key once the zero gas reading(s) on the left of the display have
stabilized. If you don't have the combustibles option, you only need to wait until
the 02 zero gas value stabilizes. The reading on the far right of the first display line
shows the setpoint value you entered for the 02 zero gas using the Cal Gas Values
menu option. This 02 zero gas setpoint value should match the cal gas cylinder for
the 02 zero gas.

32. Error Messages
Cell is Over Temp
This error message indicates that the senSor temperature is 30 'C or more
over its correct operating temperature. The software shuts off the furnace
until the temperature returns to a normal operating range.
If this message soon goes away, it indicates that the temperature has
returned
to an acceptable range. If there is a problem with the sensor temperature
control system, you will see another error message after this message
appears.
Excessive Cal Error
If a primary calibration cannot correct the sensor temperature within the
software's allowable limits, this message is displayed to indicate the primary
calibration has failed. This message could indicate one of the following
problems:
• Calibration gas setup problem
• Process pressure incorrectly entered
• Failed cell
• Leak or plug in plumbing

33. Span Gas Range Error
This error message occurs if the calibration span gas does not read within the
software's allowable limits. Once this error occurs, calibration of the system is
aborted.
This message could indicate one of the following problems:
• Calibration gas setup problem
• Process pressure incorrectly entered
•Aspirator air not turned off during calibration (WDG-IV only)
•Failed cell
•Cell wiring reversed (Cell + and Cell - wires)
•Leak in plumbing
•Plugged plumbing
Zero Gas Range Error
This error message occurs if the calibration zero gas does not read within
the software's allowable limits. Once this error occurs, calibration of the
system is aborted. This error indicates one of the following problems:
•Calibration gas setup problem
•Process pressure incorrectly entered.
•Cell wiring reversed (Cell + and Cell- wires)
•Aspirator air not turned off during calibration (WDG-IV only)
•Failed cell (primary calibration should be run at this time)
•Leak or plug in plumbing

34. Temp Rise Failure
This error message indicates that the sensor has failed to increase in temperature
a minimum of 10 °C in a 60-second time frame during start-up. Once the system
reaches the operating set point, this message will only occur if the sensor falls
below the set point by 15°C and fails to recover within 60 seconds. The problems
that can cause this error are as follows:
•AC line power problem at the sensor
•Open furnace
•Over-temperature protection circuit trip on the sensor board
•Sensor board failure
•Loss of furnace drive signal
•Interconnecting wiring problem
Thermocouple Failure
This error message occurs when the indicated sensor temperature falls below -
70°C. This error message can be the result of one of the following:
• Open thermocouple
• Faulty interconnecting wiring
•Control unit display module failure

35. T/C (Thermocouple) Circuit Failure
This message appears when the control unit recognizes a sudden drop in
temperature (greater than 100°C). The thermocouple circuit failure message
can be the result of one of the following problems:
•Shorted thermocouple
•Faulty interconnecting wiring
•Control unit display module failure
•Sensor board failure

37. Paramagnetic Analyzer
High magnetic susceptibility of oxygen as compared to other gases allows it to be
attracted to a magnetic field
Magnetic susceptibility is a measure of the intensity of the magnetization of a
substance when it is placed in a magnetic field
In Simple word Oxygen is attracted to a magnetic field several hundred times
stronger than any other gas
Let’s see the
video

38. Paramagnetic Analyzer
In the cell, two glass spheres filled with nitrogen gas are suspended with strong
metal.
At first, the spheres are kept in balance in an magnetic field. When oxygen
molecules having a large magnetic susceptibility flow there, the molecules are
pulled toward the stronger magnetic field zone and the spheres are moved away
from the zone.
The resulting deviation of the spheres is detected with the light source, reflecting
mirror and light receiving element, and a current is flowed through the feedback
loop to control so that the spheres can return to the initial balanced state.
The current flowing through the feedback loop is proportional to oxygen
concentration.
Thus, oxygen concentration is converted into an electric signal.

40. Tunable Diodel Laser measurement system
Tunable Diode Laser (or TDL) measurements are based on absorption spectroscopy.
Analyzer is a TDL system and operates by measuring the amount of laser light that is
absorbed (lost) as it travels through the gas being measured.
In the simplest form a TDL analyzer consists of a laser that produces infrared light, optical
lenses to focus the laser light through the gas to be measured and then on to a detector,
the detector, and electronics that control the laser and translate the detector signal into a
signal representing the gas concentration.

41. Gas molecules absorb light at specific colors, called absorption lines. This
absorption follows Beers law.
TDL Analyzers are effectively infrared analyzers which obey the Beer-Lambert
Law.
I = I0•e-E.G.L
where I is the radiation intensity after absorption
I0 is the initial radiation intensity
E is the extinction coefficient
G is the gas concentration and L is the path length of the measurement area
Advantages:
• Capability of measuring at very high temperature, high pressures and under
difficult conditions (corrosive, aggressive, high particulate service).
• Most measurements are rapid (5 seconds) and interference free .
Disadvantages:
• Initial installation for the mounting flange is required.