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ISC #2: Flammable Gas Detection – Infrared or Catalytic Bead

One of the latest and fastest growing trends in gas detection today is the use of infrared sensors to detect %LEL levels of flammable gases. I was involved in a long debate with clients about whether infrared technology was really suitable for the work I was doing. The question is, is it true for your application?

Many have followed the trend of leaning towards infrared-type gas detectors for flammable gases based on the belief that the technology will provide greater stability when measuring, longer-life sensors, less need for correction, or even no need to correct at all. To some extent this is also true, but I will come back and discuss them later. There are other points to consider in advance between the infrared sensor and the catalyst sensor.

Infrared sensors offer two clear advantages for the detection of flammable gases. They do not lose sensitivity due to chemical poisoning (the form of an excessive amount of gas that acts on the sensor at the same time) and do not require proper oxygen (the catalyst feels oxygen is required to measure flammable gases) to act as traditional touch sensors.

Infrared TYPE LEL Explosive Gas Sensor
Infrared TYPE LEL Explosive Gas Sensor
Catalyst TYPE LEL explosive gas sensor
Catalyst TYPE LEL explosive gas sensor

But this is the point where the obvious advantages are no longer available: The signal output of the infrared sensor can be greatly affected by high humidity, temperature changes and environmental pressures. The effects of these factors on the touch sensor are often considered insible.

Signal output from non-linear infrared sensors and different reaction curve characteristics for each specific gas. This means that the sensors must be characterized and adjusted for each specific gas to be able to give a linear result. The linear reactions of the reaction sensor very easily predict its reaction to different gases and provide a correlation based on virtually any gas used for correction.

But most importantly, infrared sensors are not capable of detecting hydrogen gas. If you are using a gas detector with infrared sensors in a secure application where there may be an explosion risk hydrogen gas exists, STOP! Right away! You made a serious mistake!

Return to the initial beliefs about infrared sensors. Generally, infrared sensors have higher long-term stability and provide longer service life because of the use of infrared light sources. However, these sensors are still exposed to hazardous environments on a daily life, so they are still susceptible to air jams/jams into the sensor by dirt and debris. If the gas cannot enter the sensor, it cannot be detected. The characteristics of light sources and infrared detectors can also be altered due to physical shock. For these reasons, frequent bump testing and calibration are important in measuring explosive gases

Infrared sensors for detecting flammable gases will likely be the latest wave.And they can be the perfect and necessary choice in the detection applications of known gases in a low oxygen environment. But before you use the mounted infrared sensors for your gas detectors, make sure they will actually work for your application.

SPORTS – TES Industry

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