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# Grove - Gas Sensor V2(Multichannel)

Tip

We've released the Seeed Gas Sensor Selection Guide, it will help you choose the gas sensor that best suits your needs.

Grove - Multichannel Gas Sensor V2 has 4 measuring units, each of them is sensitive to various kinds of gases, which means you are able to get four sets of data at the same time. And different sorts of gases can also be judged by these four sets of data. The gas sensor used in this module is based on MEMS technology and has the advantage of being in a small size with considerable measurement stability and is more suitable for qualitative than quantitative measurement.

## Features¶

• Four fully independent sensor elements on one package.
• The ability to detect a variety of gases, besides Carbon monoxide (CO), Nitrogen dioxide (NO2), Ethyl alcohol(C2H5CH), Volatile Organic Compounds (VOC) and etc.
• Qualitative detecting, rather than quantitative.
• Compact size for easy deployment.

## Specification¶

Item Value
MCU STM32F030
Interface Grove I2C
Output voltage 3.3V~5V
Sensors GM-102B; GM-302B; GM-502B; GM-702B

GM-102B

Type of product GM-102B
V0(V) 2.5-4.5
V0-VS(V) ≥1.0
Response time（tres，S） ≤30
Recovery Time（trec，S） ≤60
Heating resistance（RH，Ω） 80±20
Operating Voltage（V） VH=2.0±0.1 AC or DC VC=5.0±0.1DC

GM-302B

Type of product GM-302B
Standard package Ceramic package
Concentration 1～500ppm

Standard circuit conditions
Loop voltage VC ≤24V DC
Heating Voltage VH 2.5V±0.1V AC or DC

Gas sensor characteristics under standard test conditions
Heating resistance RH 60~100Ω（Room Temperature）
Heating power consumption PH ≤50mW
Sensitive body resistance RS 1KΩ～30KΩ(in 50ppm Ethanol )
Sensitivity S Rs(in air)/Rs(in 50ppm Ethanol )≥3.0
Concentration slope α ≤0.9(R200ppm/R50ppm Ethanol )

Standard test conditions
Temperature/Humidity 20℃±2℃；55%±5%RH
Standard test circuit VH:2.5V±0.1V； VC:5.0V±0.1V
Preheat time Less than 48hrs

GM-502B

Type of product GM-502B
Standard package Ceramic package
Concentration 1～500ppm
Standard circuit conditions

Loop voltage VC ≤24V DC
Heating Voltage VH 2.5V±0.1V AC or DC

Gas sensor characteristics under standard test conditions
Heating resistance RH 80Ω ± 20Ω（Room temperature）
Heating power consumption PH ≤50mW
Sensitive body resistance RS 1KΩ～30KΩ (in 50ppm Ethanol)
Sensitivity S R0 (in air) / Rs (in 50ppm Ethanol) ≥3.0
Concentration slope α ≤0.9 (R200ppm / R50ppm Ethanol)
Standard test conditions
Temperature / Humidity 20℃ ± 2℃；55% ± 5%RH
Standard test circuit
VH:2.5V ± 0.1V；
VC:5.0V ± 0.1V

GM-702B

Type of product GM-702B
Standard package Ceramic package
Concentration 5～5000ppm(CO)

Standard circuit conditions
Loop voltage VC ≤24V DC

Heating Voltage
VH 2.5V±0.1V AC or DC（High Temperature）
0.5V±0.1V AC or DC（Low Temperature）
Load Resistance RL 60s±1s（H. T)；90s±1s（L. T）

Gas sensor characteristics under standard test conditions
Heating power consumption PH 80Ω±20Ω（Room temperature
Sensitive body resistance RS ≤50mW
Sensitivity S 1KΩ～30KΩ(in 150ppmCO)
Concentration slope α R0(in air)/Rs(in 150ppmCO)≥3

Standard test conditions
Temperature / Humidity 20℃±2℃；55%±5%RH
Standard test circuit VH: 2.5V±0.1V（H. T）
0.5V±0.1V（L. T） VC : 5.0V±0.1V

## Sample test outcomes¶

Time：2019.06.27
Test conditions：VH=2.5V，VC=3.3V
Type：GM-102B、GM-302B、GM-502B、GM-702B
1# Gas：NO2 Gas：C2H5OH
Type Initial value(V) 5ppm(V) Difference(V) Type Initial value(V) 50ppm(V) Difference(V)
GM-102B 1.41 0.38 -1.03 GM-102B 1.42 2 0.58
GM-302B 0.94 0.48 -0.46 GM-302B 0.95 2.06 1.11
GM-502B 1.42 0.53 -0.89 GM-502B 1.41 2.93 1.52
GM-702B 1.54 0.55 -0.99 GM-702B 1.35 2.86 1.51
2# Gas：NO2 Gas：C2H5OH
Type Initial value(V) 5ppm(V) Difference(V) Type Initial value(V) 50ppm(V) Difference(V)
GM-102B 0.94 0.22 -0.72 GM-102B 0.92 1.41 0.49
GM-302B 0.45 0.24 -0.21 GM-302B 0.35 2.09 1.74
GM-502B 1.45 0.49 -0.96 GM-502B 1.51 2.88 1.37
GM-702B 0.77 0.3 -0.47 GM-702B 0.74 2.73 1.99
3# Gas：NO2 Gas：C2H5OH
Type Initial value(V) 5ppm(V) Difference(V) Type Initial value(V) 50ppm(V) Difference(V)
GM-102B 1.29 0.27 -1.02 GM-102B 1.2 1.62 0.42
GM-302B 1.12 0.61 -0.51 GM-302B 1.12 2.33 1.21
GM-502B 1.82 0.58 -1.24 GM-502B 1.72 2.86 1.14
GM-702B 1.06 0.37 -0.69 GM-702B 1.08 2.8 1.72
1# Gas：CO
Type Initial value(V) 150ppm(V) Difference(V) Types of sensors Gases measured
GM-102B 1.31 1.33 0.02 GM-102B NO2
GM-302B 0.72 0.88 0.16 GM-302B C2H5OH
GM-502B 1.33 1.35 0.02 GM-502B VOC
GM-702B 1.22 2.09 0.87 GM-702B CO
2# Gas：CO

NOTICE: When it comes to judging what the gas is, GM-102B can be taken as an example. As it can be seen from the four charts above and beside, GM-102B has participated three times for each gas detecting. And its number of differences peaked at the most under the atmosphere of NO2 than other gases. Therefore GM-102B is sensible to NO2 and accordingly is able to detect NO2, which is applicable to other sensors and sorts of gases as well. When being put under other kinds of gases, the sensor is able to detect the gas which makes it the most differences.
Type Initial value(V) 150ppm(V) Difference(V)
GM-102B 0.94 0.95 0.01
GM-302B 0.36 0.48 0.12
GM-502B 1.46 1.5 0.04
GM-702B 0.72 1.18 0.46
3# Gas：CO
Type Initial value(V) 150ppm(V) Difference(V)
GM-102B 1.18 1.17 -0.01
GM-302B 1.18 1.25 0.07
GM-502B 1.72 1.71 -0.01
GM-702B 1.01 1.7 0.69

## Characteristic descriptions¶

Rs in the figure represents the resistance value of the sensorin different concentrations of gas; R0 represents the resistance value of the sensor in clean air. All tests in the picture are completed under standard test conditions. Yellow line is Toluene, blue line is Ethanol, red line is Acetone and purple line is Formaldehyde, which is the same as the ones in charts below.

The output voltage in Chart 3 is the voltage across the load resistance (RL) of the sensor in series. The test in the figure is completed under standard test conditions, with a test gas of 50 ppm ethanol. The output voltage in Chart 4 is the voltage across the load resistance (RL) of the sensor in series. All tests in the figure are completed under standard test conditions.

Rs in Chart 5 represents the resistance value of the sensorin different concentrations of gas; R0 represents the resistance value of the sensor in clean air. All tests in the picture are completed under standard test conditions. Yellow line is Toluene, blue line is Ethanol, red line is Acetone and purple line is Formaldehyde, which is the same as the ones in charts below. In Chart 6, Rs represents the resistance value under 50ppm ethanol and various temperatures / humidities; Rs0 represents the resistance value under 50ppm ethanol, 20 ℃ and 55% RH.

The output voltage in Chart 7 is the voltage across the load resistance (RL) of the sensor in series. The test in the figure is completed under standard test conditions, with a test gas of 50 ppm ethanol. The output voltage in Chart 8 is the voltage across the load resistance (RL) of the sensor in series. All tests in the figure are completed under standard test conditions.

In Chart 9, Rs represents the resistance of the sensor in different concentrations of gas Value; R0 represents the resistance value of the sensor in clean air. All tests in the picture are completed under standard test conditions. The black line is for CO, red one is CH4, Purple is for H2 and pink one is Air.In Chart 10 , Rs represents the temperature at 150ppmCO and various temperatures / humidities. Resistance value; Rs0 means resistance value under 150ppmCO, 20 ℃, 55% RH.

The voltage in Chart 11 is the voltage across the load resistance (RL) of the sensor in series. The test in the picture is completed under standard test conditions, test gas 150ppmCO. The output voltage in Chart 12 is the voltage across the load resistance (RL) of the sensor in series. All tests in the picture are completed under standard test conditions.

## Platform Supported¶

Arduino Raspberry Pi

## Getting Started¶

#### Materials Requied¶

Wio Terminal Grove-Multichannel Gas Sensor V2
Get ONE Now Get ONE Now

#### Hardware Overview¶

Notice

The module in the image of Hardware Connection has the same arrangement as the one in the image of Hardware Diagram above. As you can see in the Hardware Diagram, the outlined area in the left is the Grove Interface. And there are four squares with tiny holes refer to the gas sensors. When the board with sensors is connected with Wio Terminal, the information of the gases will display on the screen.

• Step 1. Connect Grove - Multichannel Gas Sensor V2 to port I2C of Grove-Base Shield. Plug Grove - Base Shield into Wio Terminal. And connect Wio Terminal to PC via a USB cable.

• Step 2. Download the Grove_Multichannel_Gas_Sensor_v2 Library from Github. And refer How to install library to install library for Arduino.

• Step 3. Copy the code into Wio Terminal and upload. If you do not know how to upload the code, please check how to upload code.

• Step 4. Refer How to TFT LCD Library to install TFT LCD Library. Lastly, upload code from the Software Code below and the data has to be displayed successfully.

#### Software Code¶

#include <TFT_eSPI.h>
#include <Multichannel_Gas_GMXXX.h>
#include <Wire.h>
GAS_GMXXX<TwoWire> gas;

TFT_eSPI tft;
// Stock font and GFXFF reference handle
TFT_eSprite spr = TFT_eSprite(&tft);  // Sprite

void setup() {
// put your setup code here, to run once:
tft.begin();
tft.setRotation(3);
spr.createSprite(tft.width(),tft.height());
gas.begin(Wire, 0x08); // use the hardware I2C
}

void loop() {
// put your main code here, to run repeatedly:
int val;
spr.fillSprite(TFT_BLACK);
spr.setFreeFont(&FreeSansBoldOblique18pt7b);
spr.setTextColor(TFT_BLUE);
spr.drawString("Gas Terminal", 60 - 15, 10 , 1);// Print the test text in the custom font
for(int8_t line_index = 0;line_index < 5 ; line_index++)
{
spr.drawLine(0, 50 + line_index, tft.width(), 50 + line_index, TFT_GREEN);
}

spr.setFreeFont(&FreeSansBoldOblique9pt7b);                 // Select the font
// GM102B NO2 sensor
val = gas.getGM102B();
if (val > 999) val = 999;
spr.setTextColor(TFT_WHITE);
spr.drawString("NO2:", 60 - 24, 100 -24 , 1);// Print the test text in the custom font
spr.drawRoundRect(60 - 24,100,80,40,5,TFT_WHITE);
spr.setTextColor(TFT_WHITE);
spr.drawNumber(val,60 - 20,100+10,1);
spr.setTextColor(TFT_GREEN);
spr.drawString("ppm", 60 + 12, 100+8, 1);
// GM302B C2H5CH sensor
val = gas.getGM302B();
if (val > 999) val = 999;
spr.setTextColor(TFT_WHITE);
spr.drawString("C2H5CH:", 230 -24 , 100 - 24 , 1);// Print the test text in the custom font
spr.drawRoundRect(230 - 24,100,80,40,5,TFT_WHITE);
spr.setTextColor(TFT_WHITE);
spr.drawNumber(val,230 - 20,100+10,1);
spr.setTextColor(TFT_GREEN);
spr.drawString("ppm", 230 + 12, 100+8, 1);
// GM502B VOC sensor
val = gas.getGM502B();
if (val > 999) val = 999;
spr.setTextColor(TFT_WHITE);
spr.drawString("VOC:", 60 - 24, 180 -24 , 1);// Print the test text in the custom font
spr.drawRoundRect(60 - 24,180,80,40,5,TFT_WHITE);
spr.setTextColor(TFT_WHITE);
spr.drawNumber(val,60 - 20,180+10,1);
spr.setTextColor(TFT_GREEN);
spr.drawString("ppm", 60 + 12, 180+8, 1);
// GM702B CO sensor
val = gas.getGM702B();
if (val > 999) val = 999;
spr.setTextColor(TFT_WHITE);
spr.drawString("CO:", 230 -24 , 180 - 24, 1);// Print the test text in the custom font
spr.drawRoundRect(230 - 24 ,180,80,40,5,TFT_WHITE);
spr.setTextColor(TFT_WHITE);
spr.drawNumber(val ,230 - 20 ,180+10,1);
spr.setTextColor(TFT_GREEN);
spr.drawString("ppm", 230 + 12, 180+8, 1);

spr.pushSprite(0, 0);
delay(100);

}


Cautions

• The module should avoid being placed in the volatile silicon compound steam, or it will cause the sensitivity to be reduced and irrecoverable.
• The module should avoid being exposured to high concentrations of corrosive gases (such as H2S, SOX, Cl2, HCl, etc.), otherwise it will be irreversibly damaged.
• The module should not be placed in water or ice.
• After the module is powered on, the sensor will heat up to a certain degree during the process, which is a normal phenomena.
• Users MUST preheat the module before starting measuring gases.

## Tech Support¶

Please submit any technical issue into our forum.