Oxygen Analyzers

Oxygen analyzers provide valuable measurements in combustion control, process quality, safety and environmental applications. These are used in a variety of measurement scenarios including, but not limited to, boiler trimming in power plants, furnace optimization in refinery and petrochemical applications, process safety in vent headers, and product quality in ethylene production.

Yokogawa offers a full range of product solutions including an industry leading zirconia oxygen probe series, as well as a line of cutting edge tunable diode laser spectrometers. 


  Tunable Diode Laser
Zirconia type(Concentration cell system)
Zirconia type(Limiting Current type)
Magnetic type
Combustion /
Process management
Semiconductors /
electronic components / manufacturing process
Measurements containing flammable gas    
No sampling required  

>> Please refer to the Measurement Systems of the Oxygen Analyzer

  • In-Situ Gas Analyzer TDLS8000

    Yokogawa’s new TDLS™8000 houses all of the industry’s leading features in one robust device. The platform design is for in situ measurements which negate the need for sample extraction and conditioning.

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  • Zirconia Oxygen/Humidity Analyzer ZR22G, ZR802G

    This Oxygen concentration and humidity at high temperatures consists of a ZR22G detector equipped with a long-life and highly reliable zirconia sensor, and a converter ZR802G equipped with digital communication and data log functions.
    ZR22G and ZR802G can be measured directly and continuously without a sampling device. It is easy to maintain and reduce operating costs by self-diagnosis of sensor deterioration (without using calibration gas )and replacing the heater assembly on site.

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  • Explosion proof Zirconia Oxygen Analyzer, Converter ZR802S, ZR22S

    Oxygen Analyzer ZR802S, and ZR22S are most suitable for monitoring combustion and controlling the low-oxygen combustion of various industrial furnaces in explosive atmosphere at petroleum refinery, petrochemical plant, and natural gas plant.
    Contributes to OPEX reduction in safe operation and maintenance work.

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  • Multi Channel Oxygen Analyzer System ZR22/AV550G

    The AV550G multi channel oxygen analyzer system allows for measurements on up to 8 ZR22 probes simultaneously.The ZR probe's in-situ measurement method does not require any process conditioning or extractive sampling. This reduces maintenance costs and allows faster measurement response to changes in the process.

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  • Integral Oxygen Analyzer ZR202

    The EXAxt ZR202 transmitter / detector combines benefits of the ZR402 remote analyzer and the ZR22 detector into an intelligent, rebuildable, low-cost measurement device for in-situ humidity measurement.

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  • Paramagnetic Oxygen Analyzer (Flameproof Type) MG8E

    The MG8E paramagnetic oxygen analyzer measures the concentration of oxygen, employing a technique that is based on the fact that a magnet attracts gaseous oxygen. Whereas zirconia oxygen analyzers cannot measure oxygen in flammable gas mixtures, the MG8E can measure not only the oxygen concentration in flammable gas mixtures but also in low concentrations, with high precision.

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  • Paramagnetic Oxygen Analyzer (General Purpose Type) MG8G

    The MG8G paramagnetic oxygen analyzer measures the concentration of oxygen based on the fact that a magnet attracts gaseous oxygen. Whereas zirconia oxygen analyzers cannot measure oxygen in flammable gas mixtures, the MG8G can measure oxygen concentration in flammable gas mixtures.

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  • Product Finder

    This web tool makes it easier to find products according to the application, measurement conditions and required specifications.

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Oxygen Analyzer Measurement Systems and Their Advantages and Drawbacks

The measurement system of the oxygen analyzer we currently sell is as follows.

Zirconia type measurement system:

  • Concentration cell system: ZR22G/ZR802, ZR202G, ZR202S and OX400
  • Limiting Current type: OX100 and OX102

Magnetic type measurement system:

  • Paramagnetic system: MG8G and MG8E

Tunable Diode Laser measurement system:

  • Tunable Diode Laser measurement system: TDLS8000, TDLS8100, TDLS8200

Since each measurement system has its own advantages and drawbacks, it is important to select an oxygen analyzer that is appropriate for your application and intended use. Below is an overview of each measurement system and its advantages and drawbacks.

Zirconia type measurement system

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.

Concentration cell system


  • Can be directly installed in a combustion process such as a boiler’s flue and requires no sampling system. And response is faster (ZR22G, ZR202G).
  • Capable o f measuring trace oxygen concentration (OX400).


  • If the sample gas contains a flammable gas, a measurement error occurs (combustion exhaust gas causes almost no problem because it is completely burned).

Limiting Current type

As shown in the figure below, if the flow of oxygen into the cathode of a zirconia element heated to high temperature is limited, there appears a region where the current becomes constant even when the applied voltage is increased. This limited current is proportional to the oxygen concentration.

Limiting Current type


  • Capable of measuring trace oxygen concentration.
  • Calibration is required only on the span side (air).


  • If the sample gas contains a flammable gas, a measurement error occurs.
  • The presence of dust causes clogging of the gas diffusion holes on the cathode side; a filter must be installed in a preceding stage.

Magnetic type measurement system

Paramagnetic system

This is one of the methods utilizing the paramagnetic property of oxygen. When a sample gas contains oxygen, the oxygen is drawn into the magnetic field, thereby decreasing the flow rate of auxiliary gas in stream B. The difference in flow rates of the two streams, A and B, which is caused by the effect of flow restriction in stream B, is proportional to the oxygen concentration of the sample gas. The flow rates are determined by the thermistors and converted into electrical signals, the difference of which is computed as an oxygen signal.

Paramagnetic system


  • Capable of measuring flammable gas mixtures that cannot be measured by a zirconia oxygen analyzer.
  • Because there is no sensor in the detecting section in contact with the sample gas, the paramagnetic system can also measure corrosive gases.
  • Among the magnetic types, the paramagnetic system offers a faster response time than other systems.
  • Among the magnetic types, the paramagnetic system is more resistant to vibration or shock than other systems.


  • Requires a sampling unit corresponding to the sample gas properties or applications.

Tunable Diode Laser measurement system

Tunable Diode Laser measurement system

Tunable Diode Laser (or TDL) measurements are based on absorption spectroscopy. The TruePeak 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.
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 = Io e-EGL
where I is the radiation intensity after absorption
Io 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

Yokogawa Electric’s model : TDLS8000

Tunable Diode Laser measurement system


  • Capable of measuring a number of nearinfrared absorbing gases in difficult process applications.
  • Capability of measuring at very high temperature, high pressures and under difficult conditions (corrosive, aggressive, high particulate service).
  • Most applications are measured in-situ, reducing installation and maintenance costs.
  • Most measurements are rapid (5 seconds) and interference free.


  • Initial installation for the mounting flange is required.


  • Yokogawa's CENTUM CS 3000 DCS Monitors and Controls Operations at Poultry Litter-to-energy Plant
  • The boiler and turbine startup procedures reduces operator workload and helps to ensure a smooth and safe startup

If a sensor is not operating, the manufacturer cannot detect moisture in the chlorine and must stop the process. Unfortunately, sensors can deteriorate and deliver inaccurate measurements due to contact with the process.


A furnace for heating slabs needs to be operated under low oxygen conditions at high temperatures of 1000°C and above to prevent oxidation of the steel. The measurement of oxygen concentrations in the furnace is essential in this process. (AN 10M01F01-03E)


O2 measurement in hydrocarbon vapor is used for safety monitoring in vacuum distillation columns in petroleum refining. With conventional paramagnetic oxygen analyzers, O2 concentrations are obtained through an extractive sampling system, which conditions the sample prior to being analyzed.


The ammonia (NH3) gas is injected to remove the NOx and thus reduce the NOx concentration in the stack flue gas. With conventional NH3 analyzers that perform measurements indirectly, NH3 concentrations are obtained through a sampling system. Therefore, there are problems with the maintenance and running costs of the sampling system, and time delays in measurement. The TDLS8000 Laser Analyzer is the solution to all these problems.


In a hot blast stove, the by-product gas produced in a coke oven is burned to preheat the air blast for the blast furnace. To improve the combustion efficiency and conserve energy in a hot blast stove, it is essential to be able to control combustion by measuring and adjusting the oxygen concentration in the exhaust gases.


A package boiler operates more efficiently if the oxygen concentration in the flue gas is reduced. Optimizing air intake for boiler operation requires continuous measurement of the oxygen concentration in the flue gas.


Combustion furnaces such as heating furnaces and boilers in plants include various sizes and types, and serve as energy sources, that is, they are cores in all production activities. Because a large amount of fuel such as gas or fuel oil is consumed in plants, their combustion efficiency directly affects the performance and running cost of the plants. 


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