As a seasoned provider of combustible sensors, I've witnessed firsthand the critical role these devices play in ensuring safety across various industries. One of the most common questions we receive is about how our sensors respond to different concentrations of combustible gases. In this blog, I'll delve into the science behind our sensors' operation and explain how they react to varying gas levels.
Understanding Combustible Gas Sensors
Before we explore the sensor response to different gas concentrations, it's essential to understand the two main types of combustible sensors we offer: catalytic combustion and semiconductor sensors.
Catalytic Combustion Gas Sensors: These sensors, such as the Catalytic Combustion Gas Sensor SME - 005, work based on the principle of catalytic oxidation. When a combustible gas comes into contact with the catalytic element of the sensor, it burns in the presence of oxygen at a relatively low temperature. This combustion process releases heat, which causes a change in the electrical resistance of the sensor. The change in resistance is directly proportional to the concentration of the combustible gas in the air.
Semiconductor Combustible Sensors: Our semiconductor sensors, like the Semiconductor Combustible Sensor For Methane SMT - 014 and Semiconductor Flammable Gas Sensor For Propane SMT - 05, operate on the principle of the change in electrical conductivity of a semiconductor material when it adsorbs combustible gas molecules. When the gas molecules are adsorbed onto the surface of the semiconductor, they cause a change in the number of charge carriers (electrons or holes), which in turn changes the conductivity of the material. The change in conductivity is related to the concentration of the combustible gas.
Response to Low Concentrations of Combustible Gases
At low concentrations of combustible gases, the response of our sensors is relatively small but still detectable.
Catalytic Combustion Sensors: In the case of catalytic combustion sensors, the amount of heat generated by the combustion of the small amount of gas is minimal. However, our sensors are designed with high - sensitivity catalytic elements that can detect even these small changes in heat. The change in resistance is small but can be accurately measured by the associated electronics. For example, in an environment where the concentration of methane is around 1% of the Lower Explosive Limit (LEL), the sensor will show a small but distinguishable change in resistance. This allows for early detection of the presence of combustible gases, even at low levels, which is crucial for safety applications.
Semiconductor Sensors: Semiconductor sensors also show a detectable change in conductivity at low gas concentrations. The adsorption of a small number of gas molecules onto the semiconductor surface causes a minor alteration in the charge carrier density. Our semiconductor sensors are engineered to have a high surface - to - volume ratio and a specific doping level to enhance their sensitivity at low concentrations. For instance, when exposed to a low concentration of propane, the conductivity of the Semiconductor Flammable Gas Sensor For Propane SMT - 05 will change slightly, and this change can be used to indicate the presence of the gas.
Response to Medium Concentrations of Combustible Gases
As the concentration of combustible gases increases to medium levels (e.g., 10 - 50% of the LEL), the response of our sensors becomes more significant.
Catalytic Combustion Sensors: At medium concentrations, more gas molecules are available for combustion on the catalytic element. This leads to a greater amount of heat being released, resulting in a more substantial change in the electrical resistance of the sensor. The relationship between the gas concentration and the change in resistance remains approximately linear within this range. Our sensors are calibrated to provide an accurate measurement of the gas concentration based on this linear relationship. For example, when the methane concentration reaches 20% of the LEL, the sensor's resistance change is much larger compared to the low - concentration case, and this can be easily correlated to the actual gas concentration.
Semiconductor Sensors: For semiconductor sensors, a higher concentration of gas means more gas molecules are adsorbed onto the semiconductor surface. This leads to a more significant change in the charge carrier density and, consequently, a larger change in conductivity. The response is proportional to the gas concentration within a certain range. Our semiconductor sensors have a well - defined calibration curve that allows us to accurately convert the measured conductivity change into a gas concentration value. For example, the Semiconductor Combustible Sensor For Methane SMT - 014 will show a more pronounced change in conductivity when exposed to a medium concentration of methane, enabling precise monitoring of the gas level.
Response to High Concentrations of Combustible Gases
At high concentrations of combustible gases (above 50% of the LEL), the behavior of our sensors changes slightly.
Catalytic Combustion Sensors: As the gas concentration approaches or exceeds the upper limit of the sensor's linear range, the combustion process on the catalytic element can become more complex. At very high concentrations, there may be a risk of over - heating the catalytic element, which could potentially damage the sensor. However, our catalytic combustion sensors are equipped with protective mechanisms and self - regulating features. The change in resistance may start to deviate from the linear relationship with the gas concentration at high levels, but our sensors are calibrated to provide a reliable indication of the high gas concentration within their specified operating range. For example, when the methane concentration reaches 80% of the LEL, the sensor will still provide a clear signal that the gas concentration is dangerously high.
Semiconductor Sensors: Semiconductor sensors may also experience a saturation effect at very high gas concentrations. When the semiconductor surface is fully covered with adsorbed gas molecules, further increases in gas concentration may not lead to a proportional increase in conductivity. However, our semiconductor sensors are designed to have a wide dynamic range to minimize this saturation effect. They can still provide a useful indication of the high gas concentration, and the associated electronics can be programmed to handle the non - linear response at high levels. For instance, when the propane concentration is close to the upper end of the sensor's operating range, the Semiconductor Flammable Gas Sensor For Propane SMT - 05 will show a significant change in conductivity, alerting the user to the potentially hazardous situation.
Factors Affecting Sensor Response
Several factors can affect the response of our combustible sensors to different gas concentrations.
Temperature and Humidity: Changes in temperature and humidity can influence the performance of both catalytic combustion and semiconductor sensors. High temperatures can increase the baseline resistance or conductivity of the sensors, while humidity can affect the adsorption and desorption processes of gas molecules. However, our sensors are designed with temperature and humidity compensation circuits to minimize these effects. For example, the associated electronics can adjust the sensor readings based on the ambient temperature and humidity to ensure accurate gas concentration measurements.
Gas Composition: Different types of combustible gases have different combustion characteristics and adsorption properties. Our sensors are calibrated for specific gases, but in a multi - gas environment, the response may be affected. For example, if a catalytic combustion sensor calibrated for methane is exposed to a mixture of methane and propane, the response will be a combination of the combustion of both gases. Our sensors can be configured with algorithms to account for the presence of multiple gases and provide more accurate readings.
Conclusion
Our combustible sensors, whether catalytic combustion or semiconductor types, are designed to respond accurately to different concentrations of combustible gases. From low - level detection for early warning to high - concentration indication for immediate safety response, our sensors play a vital role in ensuring the safety of various industrial and domestic environments.
If you are in need of high - quality combustible sensors for your application, we invite you to contact us for a detailed discussion about your requirements. Our team of experts is ready to assist you in selecting the most suitable sensor and providing you with the best solution for your safety needs.
References
- "Gas Sensor Technology: Principles and Applications" by X. Wang and Y. Li.
- "Catalytic Combustion Gas Sensors: Design and Performance" by R. Smith.
- "Semiconductor Gas Sensors: Fundamentals and Advancements" by M. Johnson.