LEL sensor

ISC #6: Why do LEL sensors drift so much?

  • Many customers wonder why the catalyst-type LEL explosive gas sensor is drifting with a lot of sensitivity, especially in hot and humid weather, wanting to understand this, first we need to understand the principle of operation of the touch sensor.
  • The LEL catalyst sensor (or catalyst particle sensor) is made up of: 2 refined wires, one in the gas detection component and the other in the reference component. When the gas detection component encounters flammable gases, the temperature of the particles in which the resistance increases (the current is the directional displacement of electron particles, the temperature rises causing the electrons to move chaotically, this movement will reduce the conduction , that’s why the call is up). The difference of this against the edic out of the reference component is the measured gas concentration.
  • Theoretically, if the air detector is left in clean air, then the electrical composition does not change, the signal remains zero, but is practically not theoretical. In fact, this resistance is also altered by ambient temperature. I thought I was smarter than the manufacturer, don’t you think? but not, read on: In theory, if the resistance of the two components is equal, any change in the temperature of the environment without flammable gases, then the two components should have changed equally and, of course, the deviation signal between the two components is still zero. But that is still only theoretical, the accuracy of these two electronic components is not absolute, when there is a change in the thermal conduction of the environment but the steam, humidity, resistance of the two components will vary resulting in a signal from the sensor and creating drift. The drifting up high or vice versa depends entirely on the issue of the surrounding environment.
  • Gas meter manufacturers and sensor manufacturers, both of which have certain options for dealing with drifting sensors. Some gas sensor manufacturers will block any drift signal in a reduced direction, others block the drift of sensitivity in both directions by introducing a “dead-band” dead zone into the read value of the sensor where the dead zone is located as zero. Gas meter manufacturers use algorithms in more complex software, many gas detection machine manufacturers will simply ignore drift points if it is only at a few %LEL. In this regard, the best way is for the gas detector to work stably in an environment with the same temperature and humidity so that the sensor can drift as it wishes, then zero the machine in this environment.
  • It’s great, today is still buying spring, although it is a little humid but the temperature is cool, the drift of the sensor is very little, but next summer, remember zero and re-calibration the machine.
  • And finally, everyone also candles to accept nothing is absolute.
Explosive gas sensor for Ventis MX4 gas detector
Explosive gas sensor for Ventis MX4 Industrial Scientific gas detector


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