Oxygen analyzers are devices that measure the level of oxygen in a system, therefore, determines if the level needs to be increased or not. Oxygen analyzers, in turn, use a kind of oxygen sensor for their functioning. Oxygen analyzers provide valuable measurements in combustion control, process quality, safety and environmental applications.
The methods of measuring oxygen concentration are classified into paramagnetic methods and electrochemical methods. The magnetic methods employ the force of attraction generated when paramagnetic oxygen molecules are magnetized by a magnetic field. The electrochemical methods use oxidation-reduction reactions of oxygen, or oxygen concentration cells. At present, the zirconia analyzer and magnetic wind method are mainly used in process oxygen analyzers.
Zirconia oxygen analyzer:
This is an electrochemical method, where the electrolyte is a solid zirconium oxide ceramic material which is a sandwiched between two porous Platinum Electrodes.
The solid zirconium oxide ceramic electrolyte covered on two sides by gas-permeable porous platinum electrodes. The zirconia is made conductive by high temperature (600°C or higher) oxygen ions (02 -), If gases with different partial pressures of oxygen are introduced to the two sides of the cell, an oxygen concentration cell is formed. Due to this reaction, an electromotive force is generated between the two electrodes, the magnitude of which is based on the oxygen partial pressure differential created by the reference gas and sample gas.
Advantages:
- It does not require sampler.
- It has relatively much fast response.
- Warm-time is also less than paramagnetic & Zirconia type.
- Operating temperature range is very wide
Magnetic wind oxygen analyzer:
The sample gas flows into the glass ring tube through the gas inlet, then flows through the tube, and out the gas outlet. If oxygen is present in the sample gas, the gas will be pulled from the left to the right within the tube by the magnetic field of the magnet poles. If this gas is heated by a heating coil, the magnetic characteristic of the oxygen will be weakened, and the gas will be pushed out to the right. In this way, a gas flow (magnetic wind) that corresponds to the concentration of oxygen in the sample will be generated in the middle part of the tube.
Thus the left resistor becomes colder than right one & bridge becomes unbalanced. The bridge unbalanced current will be proportional to the % of oxygen in the sample gas.
Advantages:
- Scale is almost linear.
- In comparison to paramagnetic method, it is rugged in design.
- The construction of hot wire is also critical
