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How can I properly maintain an oxygen sensor/analyzer?
A zirconia oxygen sensor can be used semi-permanently through regular maintenance if there are no serious problems such as physical damage or serious electrode contamination. In actual use, it is recommended to minimize the possibility of causing any damages to the sensor by following instructions, and to periodically inspect the sensor's condition, since degradation of the sensor can affect precision and lifetime depending on the operating temperature and the type of gas measured. It is recommended to check and calibrate sensors every 3 to 6 months depending on the operating environment. Our company holds the highest level of inspection and calibration system in Korea, and provides onsite inspection services by experts.
When the gas contains moisture, is it required to remove moisture for measurement?
When there is a large amount of moisture in the sample gas, it might condense into water on a sensor and cause damage to the sensor. Hence, measurement should be performed after removing condensed water from the surface of the sensor. Besides, as described in Q6, when moisture is present at above 700°C which is the commonly required temperature range for zirconia oxygen sensors to function properly, it will be decomposed to oxygen and hydrogen to increase oxygen partial pressure. With no hydrogen in the gas, it is not very necessary to remove water vapor for measurement, but if hydrogen exists together in the gas, removal of water vapor will lead to smaller oxygen partial pressure measured than real. Therefore, for accurate measurement, it is recommended to keep moisture from condensing into water rather than to remove it from the gas.
How can I calibrate oxygen sensors?
For oxygen sensors/analyzers to make precise measurement, calibration using standard gases is necessary. Zero point adjustment is performed using the air as reference, and precision calibration is performed by comparing the output voltage and the theoretical value using three or more standard gases. (Standard gases used for calibration: 100% O2, Air, N2 balance 1000ppm O2, N2 balance 1% H2, N2 balance 0.1% H2, etc.) Our company has established the highest level of sensor calibration system in Korea, and conducts precision tests using standard gases to issue test reports. We also provide precision calibration for products in use on customer sites as well as field inspection services.
When the gas contains moisture, is it required to remove moisture for measurement?
When there is a large amount of moisture in the sample gas, it might condense into water on a sensor and cause damage to the sensor. Hence, measurement should be performed after removing condensed water from the surface of the sensor. Besides, as described in Q6, when moisture is present at above 700°C which is the commonly required temperature range for zirconia oxygen sensors to function properly, it will be decomposed to oxygen and hydrogen to increase oxygen partial pressure. With no hydrogen in the gas, it is not very necessary to remove water vapor for measurement, but if hydrogen exists together in the gas, removal of water vapor will lead to smaller oxygen partial pressure measured than real. Therefore, for accurate measurement, it is recommended to keep moisture from condensing into water rather than to remove it from the gas.
How does a oxygen partial pressure change with hydrogen and water vapor?
The oxygen partial pressure of gases including hydrogen and water vapor, is determined by the degree of the chemical reactions among oxygen, hydrogen and water vapor. At low temperatures, hydrogen or water vapor does not affect oxygen partial pressure, but at high temperatures where relating chemical reactions occur fast, water vapor is formed by the reaction between hydrogen and oxygen or decomposed into hydrogen and oxygen, which causes oxygen partial pressure to change. In most cases, operating temperatures of zirconia oxygen sensors are high enough for chemical reactions to occur. The increase or decrease in oxygen partial pressure is thermodynamically determined by the temperature and partial pressure of each gas.
What is the criteria for selecting the oxygen sensor / analyzer for different environments or facilities?
If the sample gas temperature is high enough (above 700 °C) and the ficility has an enough space to install a sensor inside, then OP-B series or OP-P series are recommended. OM-P series or OM-10S are recommended when the sample gas temperature is lower than 700 °C or the facility does not have an enough space inside for installation. If you need one mobile analyzer for unfixed multiple locations, C-100 / CP-100 are recommended.
Does the sensor output vary with temperature?
The output of a zirconia oxygen sensor is a voltage signal. This voltage signal has a feature that it is proportional to temperature, so it increases with a temperature increase in spite of the same oxygen concentration. For this reason, a temperature sensor is configured together inside the oxygen sensor. The oxygen concentration is calculated from the temperature as well as the voltage signal.
What range of oxygen partial pressure can be measured with a zirconia oxygen sensor?
The measurable range of oxygen concentrations by using a zirconia oxygen sensor can be divided into three fields depending on the temperature conditions of the sample gas. Firstly, when the temperature of the sample gas is below 400 °C : 100 % to 1 ppm. Secondly, when the temperature of the sample gas is over 700 °C : 100 to 10-25 atm. Finally, when the sample gas temperature is between 400 °C and 700 °C : The measurable range of oxygen concentration is determined not only by a sample gas temperature but also by other conditions, so contact us before use.
What is the difference between In-situ and Ex-situ measurements?
In In-situ measurement method, an oxygen sensor is inserted into the position exactly where you want to measure oxygen concentrations. Since the sensing tip is in the very position where you want to measure, measurement is made simultaneously, and no other factor than oxygen concentration affects the measurement. However its installation is very limited by the temperature because a zirconia oxygen sensor functions properly only above 700°C. Ex-situ measurement can be recommended when the temperature is below 700°C. In Ex-situ measurement, the gas will be extracted from the location to be measured and injected into an appropriately heated oxygen sensor. Another advantage of Ex-situ measurement is that oxygen concentrations can be measured even when the inside of the facility is too narrow for a sensor to be installed, because we can locate the oxygen sensor outside the facility.
What are the advantages of a zirconia oxygen sensor?
A zirconia oxygen sensor can be widely used in various academic and industrial fields because it works stably under various gas conditions due to its outstanding chemical resistance and corrosion resistance, and it can measure oxygen partial pressures in any practically reliazable range .
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