MQ-2:
Detection concentration: 300-1000ppm(combustible gas).

MQ-3:
Size: 32 *22* 27mm
Main chip: LM393, ZYMQ - 3 gas sensors
Working voltage: DC 5V
Features:
1, With a signal output instructions.
2, two-way signal output (TTL level output and analog output)
3, TTL output signal for low level effectively.(when the low output electric signal lights at ordinary times, 
can be directly by single chip microcomputer)
4, analog 0 - 5V voltage, the higher the concentration, the higher the voltage.
5, to ethanol steam has a high sensitivity and good selectivity.
In June and has long service life and reliable stability.
7, rapid response recovery features.
Application:
Used in motor vehicles and other no drunken drivers homework personnel on-site testing, 
also used in other places of ethanol vapor detection.

MQ-4:
Module Features:
1, using high-quality dual-panel design, with power indicator and TTL signal output instructions;
2, with a DO switch signal (TTL) output and AO analog signal output;
3, TTL output valid signal is low. (When the output low signal light can be directly connected microcontroller or relay module)
4, the analog output voltage, the higher the concentration the higher the voltage.
5, methane, natural gas has better detection sensitivity.
6, there are four screw holes for easy positioning;
7, Product Dimensions: 32 (L) * 20 (W) * 22 (H)
8, with a long service life and reliable stability
9, rapid response and recovery characteristics

Electrical properties:
Input voltage: DC5V power (current): 150mA
DO output: TTL digital 0 and 1 (0.1 and 5V)
AO output :0.1-0 .3 V (relatively clean), the highest concentration of voltage around 4V

MQ-5:
Suitable for home or industrial on LPG, natural gas, coal gas monitoring devices. 
Excellent resistance to alcohol, smoke interference.
Module Features:
1, using high-quality dual-panel design, with power indicator and TTL signal output instructions;
2, with a DO switch signal (TTL) output and AO analog signal output;
3, TTL output valid signal is low. (When the output low signal light can be directly connected microcontroller or relay module)
4, the analog output voltage, the higher the concentration the higher the voltage.
5, for gas, natural gas has better detection sensitivity.
6, there are four screw holes for easy positioning;
7, Product Dimensions: 32* 20 * 22
8, with a long service life and reliable stability
9, rapid response and recovery characteristics

Electrical properties:
Input voltage: DC5V power (current): 150mA
DO output: TTL digital 0 and 1 (0.1 and 5V)
AO output :0.1-0 .3 V (relatively clean), the highest concentration of voltage around 4V

MQ-6:
Module Applications:
Suitable for domestic or industrial on LPG (liquefied petroleum gas), butane, propane, 
LNG (liquefied natural gas) detection devices. Excellent resistance to ethanol vapor, smoke interference.
Module Features:
1, using high-quality dual-panel design, with power indicator and TTL signal output instructions;
2, with a DO switch signal (TTL) output and AO analog signal output;
3, TTL output valid signal is low. (When the output low signal light can be directly connected microcontroller or relay module)
4, 0 ~ 5V analog output voltage, the higher the concentration the higher the voltage.
5, the propane, butane, LPG, LNG has a good detection sensitivity.
6, there are four screw holes for easy positioning;
7, Product Dimensions: 32 (L) * 20 (W) * 22 (H)
8, with a long service life and reliable stability
9, rapid response and recovery characteristics

Electrical properties:
Input voltage: DC5V power (current): 150mA
DO output: TTL digital 0 and 1 (0.1 and 5V)
AO output :0.1-0 .3 V (relatively clean), the highest concentration of voltage around 4V

MQ-7:
Module Applications:
For home, carbon monoxide detection device environment. Suitable for carbon monoxide and gas detection.
Module Features:
Detection of concentration: 10-1000ppmCO
Loop voltage Vc: <=10V DC
Heater voltage Vh: 5.0V ±0.2V ACorDC(high)
Load resistance: adjustable.
Heater resistance RH: 31ohm ± 3 ohm(room temperature)
Heater power consumption PH: <=350mW

Standard test conditions: 
Temperature: 20 degree ± 2 degree
Humidity: 65% ± 5% RH
Standard test circuit: Vc: 5.0V ± 0.1V; Vh(high):5.0V±0.1V
Vh(low):1.5V±0.1V

1, the analog output voltage, the higher the concentration the higher the voltage.
2, the carbon monoxide detection with better sensitivity.
3, there are four screw holes for easy positioning;
4, Product Dimensions: 32 (L) * 20 (W) * 22 (H)
5, with a long service life and reliable stability
6, rapid response and recovery characteristics

Electrical properties:
Input voltage: DC5V power (current): 150mA
DO output: TTL digital 0 and 1 (0.1 and 5V)
AO output :0.1-0 .3 V (relatively clean), the highest concentration of voltage around 4V

MQ-8:
Module Applications:
Suitable for domestic or industrial hydrogen leak on a monitoring device. 
Are not subject to ethanol vapor, soot, carbon monoxide and other gases interference.

MQ-9:
Module Applications:
For home or factory gas leak detection device, suitable for carbon monoxide, combustible gas monitoring device.

can test carbon monoxide: 10 to 1000ppm CO
combustible gas range: 100 to 10000ppm
Module Features:
Loop voltage Vc: <=10V DC
Heater voltage Vh: 5.0V ±0.2V ACorDC
Heater resistance: 31 ohm ± 3 ohm(room temperature).
Heater power consumption PH: <=900mW
Standard test conditions:
Temperature: 20 degree ± 2 degree
Humidity: 65% ± 5% RH
Standard test circuit: Vc: 5.0V ± 0.1V
Vh:5.0V±0.1V
Warm up time: more than 48 hours.

MQ-135:
MQ-135 Sensor Description:
MQ135 gas sensor is sensitive material used in clean air, low conductivity tin dioxide (SnO2). 
When the sensor is kept in their environment
The contaminated gas, the conductivity of the sensor with the air pollution gas concentration increases. 
Using a simple circuit can be changes in the conductivity
Of the concentration of the gas is converted to the corresponding output signal.
MQ135 sensor for ammonia, sulfide, benzene vapor high sensitivity, smoke and other harmful monitor
 is also very satisfactory. This sensor can detect a
Measuring a variety of harmful gases, is a low-cost sensors for a variety of applications.

Module Applications:
For home, environmental harmful gas detection device, suitable for ammonia, aromatic compounds, sulfur, 
benzene vapor, smoke and other gases harmful gas detection, gas sensors tested concentration range: 10 to 1000ppm.

Module Features:
Loop voltage Vc: <=24V DC
Heater voltage Vh: 5.0V ±0.2V ACorDC
Load resistance: adjustable
Heater resistance: 31 ohm ± 3 ohm(room temperature).
Heater power consumption PH: <=900mW
Sensitive body surface resistance Rs:2K ohm - 20K ohm(in 100ppm NH3)
sensitivity S: Rs(in air)/ Rs(100ppmNH3)>=5
Standard test conditions:
Temperature: 20 degree ± 2 degree
Humidity: 65% ± 5% RH
Standard test circuit: Vc: 5.0V ± 0.1V
Vh:5.0V±0.1V
Warm up time: more than 48 hours.