Gas Sensor Working Principle The Ultimate Guide to 7 Different Sensor Types

Environmental monitoring, safety systems, and industrial operations require gas sensor working principle knowledge. This guide covers the mechanics of seven sensor types, including infrared, electrochemical, NDIR, and MOS gas sensors. From sensing gas molecules absorption to using chemiresistor principles for gas detection, each sensor functions differently. How these sensors detect gases, their electrical output, and their role in CO2 detection will be discussed. In this page Hangweisensors explains the complex world of gas detection technology, from infrared gas sensors to electrochemical and NDIR sensors.

Gas Sensor Working Principle The Ultimate Guide to 7 Different Sensor Types

Understand Gas Sensor Operation

Gas sensors detect and quantify gases in an environment. This skill is essential for industrial safety and environmental monitoring. Interface between target gas molecules and sensor’s active substance is gas sensor working principle. This interaction changes the sensing material’s physical or chemical properties, resulting in an electrical output. This output is proportional to gas concentration, enabling exact detection and measurement.

In this method, gas molecules absorption is key. When gas molecules touch the sensor’s surface, they absorb or adhere, changing its properties. In a chemiresistor gas sensor, gas molecules absorbing onto a conductive polymer modify its resistance, detecting gas presence and concentration.

The sensor’s electrical output—voltage, current, or resistance—is also important in measuring gas concentration. The output is carefully analysed to obtain precise gas concentration readings. Infrared gas sensor, electrochemical gas sensor, and MOS gas sensor all use different techniques to detect this electrical change. Infrared gas sensor uses gas absorption spectra, while electrochemical gas sensor uses redox reactions at electrode surface.

Gas Sensor Types

For various gas detection applications, various sensor types have been designed using different functioning principles. Infrared (IR) gas sensors, electrochemical gas sensor, non-dispersive infrared (NDIR), and metal oxide semiconductor (MOS) gas sensors are examples. Understanding these sensors’ processes is essential for their use in industrial safety and environmental monitoring.

Infrared Gas Sensors use gases that absorb certain wavelengths of infrared light. These sensors measure the intensity of IR light passing through a gas sample to detect gases like carbon dioxide and methane, which have unique IR absorption bands.

Electrochemical Gas Sensors oxidise or reduce target gases when they touch an electrode. This reaction provides an electric current proportional to gas concentration, allowing exact measurements of carbon monoxide and hydrogen sulphide.

NDIR sensors use gas molecules to selectively absorb infrared light. For great selectivity, NDIR sensors use a wavelength of light absorbed by the gas of interest, unlike generic IR sensors. NDIR technology is popular for carbon dioxide detection, and this method works well.

However, MOS Type Gas Sensors modify electrical resistance when gas is present. These metal oxide semiconductor sensors conduct more when exposed to reducing gases. They detect many gases, including ammonia, nitrogen dioxide, and volatile organic chemicals.

Using gas chemical and physical features, each sensor type detects and measures gas concentrations differently. These sensors’ functioning principles—infrared light absorption, chemical reaction on an electrode, or electrical resistance change—allow for the development of complex gas detection solutions adapted to individual needs and challenges.

Infrared Gas Sensors

Due to the fact that distinct gases absorb infrared light at certain wavelengths, infrared gas sensors are unique in gas detection. By sending infrared light through a gas sample and measuring its intensity, an infrared gas sensor works. Infrared-absorbing gases like CO2 and CH4 lower light intensity at wavelengths matching to their absorption spectra.

The sensor has an infrared light source, a light detector, and an optical component to route light through the gas sample. When light hits the detector, the sensor estimates the light intensity reduction, which is proportional to gas concentration. This sensitive and selective approach detects target gases without interference from other chemicals that do not absorb infrared light at the same wavelengths.

Answering: How do infrared gas sensors work? The selective absorption of infrared light by different gases allows it to detect and quantify atmospheric gases. In environmental monitoring, industrial safety, and other applications that require accurate gas detection, infrared gas sensors are vital.

Electrochemical Gas Sensors

Electrochemical gas sensors are known for their accuracy in detecting many gases, including dangerous gases at low concentrations. The redox reactions that occur when a target gas interacts with the electrode surface of an electrochemical gas sensor are the basis of their operation. This contact transfers electrons, creating an electric current that coincides with gas concentration.

A cell with three electrodes—working, counter, and reference—immersed in electrolyte is at the heart of an electrochemical gas sensor. The target gas diffuses into the sensor and oxidises or reduces at the working electrode. Electrons flow to or from the counter electrode in this reaction, creating a current. Quantifying gas is possible since this current is proportional to gas concentration.

How do electrochemical gas sensors work? Redox reactions generate an electric current in response to gas molecules. This current is monitored and converted to gas concentration. Electrochemical sensors are reliable for measuring gas exposure levels in industrial sites, laboratories, and environmental monitoring stations because they use a reference electrode for stability and precision. Their capacity to detect low-concentration gases makes them essential for safety and environmental and occupational health compliance.

NDIR Gas Sensors

In environmental monitoring and indoor air quality evaluation, NDIR (Non-Dispersive Infrared) gas sensors are essential for CO2 detection. Utilising gas molecules’ infrared light absorption, NDIR gas sensors are simple and effective.

NDIR gas sensors emit infrared light from a source within. A gas mixture sampling chamber receives this light. Each gas absorbs infrared light at specific wavelengths due to its molecular structure. For instance, CO2 molecules strongly absorb infrared light at 4.26 µm. The sensor may measure light intensity at the detector on the other side of the sample chamber by passing infrared light via an optical filter that isolates this wavelength.

The NDIR sensor works by comparing gas concentration to light absorption. Light is absorbed more at greater target gas concentrations, reducing detector light. This drop in light intensity is turned into an electrical signal to calculate gas concentration.

Can anyone describe NDIR gas sensors? Yes, NDIR gas sensors use gas molecules to selectively absorb infrared light at specified wavelengths. This selectivity allows NDIR sensors to accurately detect and quantify gases like CO2, making them useful in many gas measurement applications. They are ideal for continuous gas concentration monitoring without calibration or maintenance due to their non-invasive, high sensitivity, and selective detection.

MOS Gas Sensors and Chemiresistors

MOS gas sensors and chemiresistors are a major gas detection technology with applications in industrial safety and environmental monitoring. These sensors use electrical resistance to detect gas concentrations.

MOS Type Gas Sensors function by changing a metal oxide’s surface conductivity in response to gases. Metal oxide surfaces react with gas molecules at high temperatures, usually using a heating device. This interaction changes the metal oxide layer’s charge carrier concentration and electrical resistance. This resistance variation indicates gas concentration. This approach detects carbon monoxide, hydrogen sulphide, and volatile organic molecules.

MOS gas sensors are especially sensitive to a wide range of gases and can work at high temperatures, which enhances their reactivity with gas molecules. To identify gases in complicated surroundings, calibration and temperature control are needed because to this sensitivity.

However, chemiresistors use electrical resistance to sense a specific gas. These sensors use conductive polymers or composite materials that absorb gas molecules, swelling or changing their electrical characteristics. Gas concentration is measured by resistance change. For detecting volatile organic molecules and other gases at room temperature, chemiresistors are energy-efficient and easy to use.

What makes MOS gas sensors work differently? The fundamental difference is their use of metal oxide materials that change electrical conductivity when exposed to gas at high temperatures. This differs from sensors that use optical absorption or chemical reactions at an electrode. MOS type gas sensors can detect a wide spectrum of gases by selecting appropriate metal oxides and working conditions, making them useful tools for air quality and safety in varied contexts.

Gas Sensor Working Principle The Ultimate Guide to 7 Different Sensor Types

Gas Sensor Applications

Industry and daily life depend on gas sensors to detect and monitor gases, protecting health, safety, and the environment. Their uses include industrial process control, indoor air quality management, and environmental protection.

Gas sensors detect hazardous gas leaks in industrial environments to avoid accidents and protect workers. In chemical manufacturing, sensors detect dangerous or explosive gases and alarm when concentrations surpass safe levels. In the oil and gas business, sensors detect methane leaks, which can cause explosions.

CO2 gas detection is another important gas sensor application, notably for indoor air quality and HVAC systems. To maintain a healthy indoor environment, offices, schools, and public facilities must monitor CO2 levels because high levels can lower productivity and cognition. In agriculture, CO2 sensors optimise greenhouse plant development by maintaining appropriate CO2 concentrations.

Beyond CO2, petrol sensors help us understand air quality and develop pollution control strategies by monitoring NOx, SO2, and ozone levels.

Petrol sensors also manage emissions and monitor cabin air quality to alter ventilation in the vehicle industry. Gas sensor breath analysis can identify biomarkers in exhaled breath to diagnose asthma, diabetes, and gastrointestinal diseases non-invasively.

Modern gas sensors are used in various applications because of their adaptability and sensitivity, improving safety, health, and the environment. Gas sensors will become ever more important in our daily lives and industrial operations as sensor technology improves in specificity, reliability, and miniaturisation.

Gas Sensor Choice

The gas or gases you need to detect, the sensor’s operating environment, and the application’s sensitivity, accuracy, and reaction time must be considered while choosing a gas sensor. Tips and considerations when choosing a gas sensor:

Gas Identification: Sensors are optimised for distinct gases. Electrochemical sensors are sensitive enough to detect harmful gases like carbon monoxide and hydrogen sulphide, however NDIR sensors are superior for CO2 due to their specificity and long-term stability.

Consider the Application Environment: Dust, humidity, and severe temperatures might impair sensor performance. Industrial applications utilise MOS gas sensors due of their durability in demanding environments. In contrast, infrared and NDIR sensors may work best in regulated conditions.

Determine Required Sensitivity and Accuracy: Sensor selection depends on the minimal concentration levels to detect and measurement precision. Electrochemical sensors detect low hazardous gas concentrations with excellent sensitivity and specificity. In contrast, semiconductor sensors may be better for gas concentration detection.

Evaluate Response Time and Recovery Time: Sensor types vary in how quickly they detect and recover from gas. Emergency safety applications like chemical plant leak detection necessitate fast response times.

Duration and Maintenance: Consider the sensor’s lifespan and maintenance needs. Some sensors, such electrochemical gas sensors, have a short lifespan due to reactive material consumption, however NDIR sensors have a longer lifespan and require less maintenance.

Gas sensors vary in price depending on technology, sensitivity, and endurance. Consider the purchase price, maintenance, and sensor replacement costs.

By carefully evaluating these factors, you can choose a gas sensor that satisfies your gas detection needs and is reliable and efficient in your application. The correct gas sensor can give precise data for air quality monitoring, industrial safety, and scientific research, improving human and environmental safety.

Common Questions Answered

How can gas sensors identify various gases?

Specific gas qualities are used by gas sensors to detect them. A gas reacts with the sensor’s active substance to provide a measurable reaction. This response varies by sensor type and gas detected. Infrared gas sensor technology uses the fact that certain gases absorb specific infrared light wavelengths. Based on the drop in light intensity at certain wavelengths, the sensor recognises and quantifies the gas in the gas sample.

Electrochemical gas sensors react chemically with the target gas to provide an electrical signal proportional to gas concentration. In contrast, MOS gas sensors change their electrical resistance when exposed to gases, revealing their kind and concentration.

Each gas sensor works differently to detect individual gases or groups of gases with great sensitivity and accuracy. The sensor type relies on the gas to be detected, the desired sensitivity and selectivity, and the operating environment.

Additional practical thoughts on gas sensor use:

Understand gas sensors’ capabilities and limits to use them efficiently. Sensor calibration is essential for reliable results. Choose a sensor that’s suitable for the application because temperature, humidity, and other gases might affect sensor performance.

Durability and maintenance are also vital. Electrochemical sensors feature consumable parts that need regular replacement, but NDIR sensors last longer and require less care.

Sensor integration is essential for system reliability. Physical and software integration are needed to accurately interpret sensor outputs and act on gas concentrations.

Understanding these factors helps improve gas detection tactics, improving safety, environmental monitoring, and process control in many applications.

Related Posts:

A Comprehensive Guide to Gas Sensors Types

Electrochemical Gas Sensor: Advancements In Gas Sensing Technology


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