Hello students! I hope you are doing great. Today, I am going to share a reliable sensor that is widely used to sense the air quality in different types of projects and circuits. The increasing ratio of pollution in the air is alarming, and air quality monitoring systems are the need of the time. The MQ135 can detect and measure a wide range of gases around it and present the output in the form of digital or analogue values.
In this article, we will commence by providing a fundamental introduction to this sensor, outlining the target gases it is designed to detect. Following that, an exploration of the data sheet will be done through its essential elements, incorporating features, specifications, and other basic information. Subsequently, a detailed description of the sensor's working principle and physical dimensions will be presented to facilitate a comprehensive understanding. Finally, the article will conclude by moving towards the various applications where this sensor finds widespread usage. Let's embark on our discussion, beginning with the initial point:
The MQ132 air quality sensor belongs to the MQ gas sensor series, and this does not stick to a single gas but can detect multiple gases at a time, thus contributing to detecting the overall air quality. It operates on 5V and has the feature to set the threshold value, so whenever the air pollutant crosses a certain limit, it sends the signal to its digital pin, which can be used to set the alarm. Moreover, the continuous signal of the air quality values is sent to the analogue pin.
Unlike many other sensors from the MQ series, it is sensitive to multiple gases, and these are mentioned below:
Ammonia (NH3)
Sulfur (S)
Benzene (C6H6)
CO2
NOx
Smoke
The list does not end here; many other harmful gases are detected with this sensor that may cause issues like lung disease, eye infections, and others, but timely detection of these gases can save lives.
A datasheet for any device holds beneficial information and is a prerequisite before choosing any device. I’ve collected some important information from the datasheet that is given below:
It is highly sensitive to a large number of toxic gases that are more likely to be mixed in the air. Some examples are NH3, NOx, CO2, benzene, smoke, etc., which are common air pollutants.
It is a small sensor, and the design is simple, therefore, it is less expensive.
It is a low-power sensor.
Some modules have a power LED that indicates the power mode.
It is an easy-to-use sensor.
The following table will justify the general specifications of this sensor:
Property |
Value |
Model |
MQ135Sensor |
Type |
SemiconductorStandard |
Encapsulation |
Bakelite, Metal cap |
Target Gas |
ammonia gas, sulfide, benzene series steam |
Detection range |
10～1000ppm( ammonia gas, toluene, hydrogen, smoke) |
Standard Circuit Conditions |
Loop VoltageVc5.0V±0.1V DC Heater VoltageVH5.0V±0.1V AC or DC Load resistanceRLAdjustable |
Sensor character under standard test conditions |
Heater ResistanceRH30Ω±3Ω (room temp.) Heater consumptionPH≤950mW SensitivitySRs(in air)/Rs(in 400ppm H2)≥5 Output VoltageVs2.0V～4.0V（in 400ppm H2） Concentration Slopeα≤0.6(R400ppm/R100ppmH2) |
Standard test conditions |
Tem. Humidity20℃±2℃；55%±5%RH |
Standard test circuit |
Vc:5.0V±0.1V； VH: 5.0V±0.1V |
Preheat time |
Over 48 hours |
Oxygen content |
21% (not less than 18%), O2 concentration affects initial value, sensitivity, and repeatability. |
As mentioned in the features, the MQ135 has a simple structure that makes it an ideal choice for different types of projects. Here is the basic circuit diagram that justifies this statement:
Here,
RH= The resistor that provides heat to the circuit.
RL = The load resistor that is connected in series with the circuit. It limits the current flowing through the circuit.
Vc = It is one of the voltage sources, and this label indicates the DC voltage.
VH= it is another source voltage but this can be either AC or DC.
The MQ135 can detect multiple gases, but the sensitivity of these gases is not identical. This depends on the speed of the chemical reaction taking place with the sensing element. Based on multiple experiments, experts have designed the following sensitivity curve graph for users:
The above graph shows the sensitivity of the hydrogen, ammonia, toluene, and fresh air by keeping other parameters constant.
The external parameters of the sensor affect its working and it shows a slightly different behaviour. Here is the diagram that shows the performance graph of the MQ135 air quality sensor at varying humidity and temperature:
The different lines show the performance of the sensor for the same gas at different humidity and temperature levels in the air.
If you want to know more details about the MQ135 sensor datasheet, you must visit the following link:
Based on its structure, I’ve created the table that explains the pinout configuration of MQ135, which is given below:
Pin |
Label |
Description |
1 |
H (VCC, VDD) |
Heater Voltage |
2 |
GND |
Ground |
3 |
A (D0, OUT) |
Analog Output |
4 |
B (D1, S) |
Optional: Digital Output (consult datasheet) |
The pinout may be slightly vary depending on the model of the sensor.
The MQ series is present in different packages for the convenience of the user. Here is a small description that shows the available packages for MQ135 and their features:
Package Type |
Description |
Standard TO-18 |
|
Board-mounted |
|
The MQ series has multiple sensors that can detect the same gases as the QM135 does, but the difference is, that the MQ135 can detect multiple gases at a time. Other members of the series can be used as an alternative to MQ135; if you want to learn about other sensor series that can be used in place of MQ135, here are some options for you:
Sensor |
Target Gases |
Applications |
Features |
MQ2 |
Multiple gases |
General gas detection |
A broad range of gas detection |
MQ3 |
Alcohol, ethanol, smoke |
Breathalyzers, smoke detectors |
Suitable for detecting combustible gases |
MQ7 |
Carbon monoxide, methane |
Indoor air quality monitoring |
Detects common indoor air pollutants |
MQ8 |
Hydrogen, other gases |
Gas leakage detection systems |
Sensitive to hydrogen leaks |
MQ9 |
Carbon monoxide, methane, LPG |
Domestic gas leakage detection |
Detects various flammable gases |
CCS811 |
CO2, TVOC |
Indoor air quality monitoring |
Measures CO2 and total volatile organic compounds |
MiCS-5524 |
CO, methane, LPG, smoke |
Indoor air quality and gas leakage monitoring |
Multi-gas detection for safety applications |
MH-Z19 |
Carbon dioxide (CO2) |
Precise CO2 level measurement |
Accurate detection of CO2 concentration |
Winsen ZE03 |
CO, H2S, CH4 |
Specific gas detection |
Electrochemical sensor for targeted gas detection |
SGP30 |
TVOC, eCO2 |
Measures total volatile organic compounds and CO2 equivalent |
Detects various indoor air pollutants |
It is important to buy sensitive devices like the MQ135 from a reliable source. For this, we have created a list of the platforms to buy the best devices, including the MQ135:
eBay
AliExpress
Amazon
The simple structure of MQ135 is responsible for its ease of use and great performance. The working principle of this sensor can be understood with the help of the following steps:
As soon as the sensor is turned on, it has to be preheated. This is done with the heating circuit of the sensor. It takes 20-30 seconds to reach a temperature of 300°C. Once this temperature is gained, it works on maintaining this temperature as long as it has the power.
The heating mechanism stimulates the sensing element to absorb the oxygen from the air surrounding it. The sensing element is made with tin dioxide that, when it absorbs the oxygen, has a sensing layer on its surface. This happens only for a certain limit because the accumulation of atoms on the surface creates a layer around it. This is the reason why tin oxide has a high electrical resistance in pure air. At this level, the sensing layer has limited availability of free electrons to react with the external pure air.
Whenever the target gas (smoke or ammonia) is present in the air, the gas molecules are absorbed by the atoms of the sensing element, and this reaction results in the absorption of this layer. As a result, the electrical conductance of the sensing element increases, and these values are indicated through the analogue data at the analogue pin.
The greater the target gas concentration in the surrounding area, the greater the analogue values. The whole circuit is designed in such a way that the analogue pins send the data to the output device for the indication of this change.
Some models of the MQ135 have a digital pin that shows the presence of gas only when values reach the pre-set threshold limit. The digital pin then sends the signal to the output device.
The physical dimensions of this sensor may vary from package to package but I’ve created a table for you that generally describes it:
Package Type |
Diameter (mm) |
Height (mm) |
Standard TO-18 |
20-22 |
18-22 |
Board-mounted |
Varies (typically larger) |
Varies (typically taller due to additional components) |
Because of its multiple gas detection capabilities, this sensor can be utilized in multiple types of projects. The general list of some important and commonly used terms is given below:
Domestic gas leak detection
Indoor air quality monitoring
Industrial air quality monitoring
Smart home appliances (air purifiers, ventilation systems)
Portable air quality detectors
Automotive applications (emissions, in-cabin air quality)
I hope I have covered all the points that you were searching for. I started with the basic introduction and then moved forward with the datasheet elements of this sensor. We also saw the features, specifications, and working principle in detail and in the end, we say the physical dimension and its applications in different fields of life. I hope it was helpful for you and if you ant to ask more, you can contact us in the comment section.
Hi peeps! Welcome to another tutorial where we are discussing the MQ sensor elements. Today, our focus is on the MQ131 ozone gas sensor. Ozone is a major component of air pollution and it leads to multiple health problems related to the respiratory system and other issues. It also has an adverse effect on the plants and agricultural lands. It is a pungent gas with a pale blue color and usually, it is present in very low concentrations in the normal air. The MQ131 ozone gas sensor is used in outdoor monitoring stations, industries that use ozone for experimentation, laboratories, and sensitive areas that have a high concentration of ozone gas in the environment.
In this article, we’ll study the MQ131 ozone gas sensor in detail. We’ll kick off the discussion with the introduction of this sensor. After that, we'll unveil the datasheet of this sensor where you will see the features and specifications of this product. After that, you will see the working principle and other details followed by an exploration of this product's dimensions and applications.
The MQ131 is specially designed to detect the presence of ozone gas concentration. We know that Ozone is an allotrope of oxygen gas made with three atoms and is indicated as O3. The core component of this sensor is the tin dioxide that can react with the ozone gas therefore, with the specialized structure, it can detect the presence of this gas in the environment.
This sensor has a lower conductivity in fresh air whereas, a high conductivity when the ozone gas is present in the surrounding air. Let’s find out the basic components of this sensor:
There is a small cylindrical shaped tube made of alumina (AL2O3) that forms the sensor base. It has excellent thermal stability and great electrical resistance. The role of this tube in the sensor is to perform two functions:
Unlike many other members of the MQ series that have tin oxide as the sensing element, the MQ131 ozone gas sensor has Tungsten Oxide (WO3). It is present in the form of a thin layer around the ceramic tube. This structure acts as the heart of the whole sensor because Tungsten Oxide (WO3) is a metal oxide therefore, its conductivity lies between the conductors and insulators. The MQ131 works on the chemiresistor principle that is defined as:
"The chemiresistor principle refers to the sensing mechanism of an element in which the electrical resistance of the element changes when it absorbs a particular gas or any other material."
This will be more clear when we’ll learn the working principle of this sensor.
There are measuring electrodes made of metals like gold (Au) that connect the sensing element with the ceramic tube. It creates a contact between these two and allows the current to pass through the sensing element. These are also responsible for allowing the circuit to measure the electrical resistance instantly.
A heater circuit is required to allow the tungsten oxide to absorb the gases. This circuit consists of a coil made of nichrome wire. This coil is embedded near the sensing layer and maintains the sensor temperature at 300°C. This temperature is crucial for the reaction between gases and the sensing element.
The whole structure mentioned before is placed and protected on a strong housing. It is enclosed in plastic or bakelite material that performs the following operations:
It provides a strong base to the circuit so that it may act as a complete device.
It allows the gases to pass over it and renders the other particles or substances so that the internal structure is not disturbed.
It provides the connection and completes the device so it may be used in different circuits.
Other MQ series members such as MQ-3, MQ-2, etc have a metallic mesh-like structure for the same purpose but in MQ131, most of the models have the plastic housing and only some of them have the metallic structure.
In addition to these, other elements are present in the basic structure such as the pins of the MQ131 ozone gas sensor and we’ll discuss these in detail in the datasheet.
A datasheet is considered an important repository for the devices such as the MQ131 ozone gas sensor and it is always advisable to learn the datasheet before utilising any device in the circuits. Here are the important pieces of information from the MQ131 sensor.
The MQ131 is a highly sensitive device and provides the best sensitivity to the ozone gas O3 over a large range. As a result, it detects even a low concentration of the target gas.
It operates on very low power and, therefore, is a suitable device to be used in the Internet of Things (IoT) and other projects.
It is a cost-effective option for multiple types of projects.
It shows the analogue and digital output pins where the analogue pin shows the continuous change in the gas concentration and the digital pin shows a binary signal based on pre-set threshold values.
It has a compact size design that makes it suitable for almost all types of circuits.
The following table outlines the key specifications of this high-performance ozone sensor:
Parameter |
Description |
Type |
Gas Sensor |
Model |
MQ131 |
Detection Gas |
Ozone (O3) |
Operating Voltage |
5 V DC |
Heater Voltage |
5 V ± 0.1 V |
Load Resistance |
Adjustable |
Heater Resistance |
31 Ω ± 3 Ω |
Heating Power |
<900 mW |
Sensitivity |
≥3.6 (Rₒ/R₀) in clean air |
Response Time |
≤10 seconds |
Recovery Time |
≤30 seconds |
Heating Resistance |
33 Ω ± 3 Ω |
Heating Current |
<180 mA |
Ambient Temperature |
-10°C to 50°C |
Humidity |
<95% RH |
Dimensions |
32 mm x 20 mm x 22 mm |
To measure the performance of MQ131, a comparison between its sensitivity curve in fresh air and the one in the presence of ozone gas is useful. Here is the graph that shows both these curves:
Here,
Ro= Resistance of MQ131 sensor in the clean air
Rs= Resistance of MQ131 sensor in the air with ozone gas
Ro/Rs= Ratio of the MQ131 sensor performance in polluted air to the clean air
Just like other devices, the MQ131 does not perform ideally in all severe conditions. Factors like humidity and temperature affect the performance and the graph given below will explain the difference:
If you want to know more details about the datasheet then here is the link to visit:
The MQ131 has four pins in most of its models and in some models, it has additional pins such as a heater and is not connected (NC). Here is the table that shows the description of each basic pin:
Pin Number |
Pin Name |
Description |
1 |
AO |
Analog Output |
2 |
DO |
Digital Output (optional) |
3 |
GND |
Ground |
4 |
VCC |
Power Supply (5V to 12V) |
For the convenience of the user, the MQ131 sensor is present in the form of different packages. A small description of each package is given next:
Package Type |
Description |
Through-Hole |
It is the traditional pin configuration with individual wires for connecting to a circuit board. |
Surface Mount (SMT) |
It is a compact package with smaller pins soldered directly onto a PCB. it is easy to fix in the circuit. |
Pre-Assembled Module |
This package has the sensor integrated with additional components like resistors, capacitors, and voltage regulators on a small PCB. |
Sensor Array |
It is a specialized package that has multiple MQ-131 sensors combined on a single PCB, sometimes with additional components for individual sensor control and signal processing. |
Just like the MQ131, there are some other sensors that are created to detect the ozone gas concentration in the air. Some of these are:
Figaro TGS series gas sensors (e.g., TGS2600, TGS2602)
Winsen ZE08-O3 Ozone Gas Sensor Module
SPEC Sensors O3 Ozone Gas Sensor
Figaro TGS series gas sensors (e.g., TGS4161, TGS4161-E00)
Always choose a trusted source to buy sensitive devices like MQ131. Here are the reliable options for you from where you can get different types of products and devices without any difficulty:
eBay
Amazon
AliExpress
The structure of this sensor is designed for uncomplicated working and effective results. Here are the steps that are involved in the working principle:
The heater circuit heats the sensing element at the temperature of 300C and maintains it.
The continuous heating stimulates the sensing element to absorb the gases at a high rate.
When the ozone gas is present around the sensor, the surface of the sensing element absorbs the ozone molecules.
The adsorption affects the electrical conductance of the sensing element. This change is sensed through the sensor.
The higher concentration of the ozone layer means a great change in the analogue values of the sensor that are indicated through the signals at the analogue pin.
If the threshold value is set for the sensor, then on a certain limit, the digital signal at the digital pin is shown.
These signals are sent to the output devices for further processing.
The MQ series features a straightforward design, and here is a diagram illustrating its internal structure:
The MQ131 is available in multiple packages and models but usually, the general dimensions are considered so I’ve created a table with the standard size and dimensions of the MQ131 ozone gas sensor:
Dimension |
Value |
Units |
Diameter |
18 |
mm |
Height (excluding pins) |
17 |
mm |
Pin height |
6 |
mm |
Total height (including pins) |
23 |
mm |
Approximate pin spacing |
2.5 |
mm |
Weight |
5 |
grams |
Ozone is not extensively present gas or is not used as a fuel therefore, it is not present in the common areas just like methane, butane, and other such gases. But, it has different kinds of applications that are used in the specialized departments. Here are some domains where the MQ131 ozone gas sensor is widely used:
It monitors ozone levels produced by air purifiers.
It tracks racks of ozone levels in various industrial processes here.
It is used by personnel working in environments with potential ozone risks.
It detects ozone levels in ambient air.
It monitors ozone levels in specific locations.
It is used in educational settings to learn about gas sensing principles.
It is used in various DIY projects requiring basic ozone detection.
It integrates with smart home systems for automated ozone monitoring and control.
Hence in this way, we have understood the basic and fundamental concepts of the MQ131 ozone gas sensor. We commenced with the introduction of this gas sensor and then we saw some points of the datasheet such as the features, specifications, and some graphs. After that, we saw the working principle of this sensor and moved forward with the physical dimensions and application of this sensor. I hope all the things are clear to you but if you want to know more about this sensor then you can ask in the comment section.