Mq-7

Henan Hanwei Electronics Co., Ltd

www.hwsensor.com

MQ-7 Semiconductor Sensor for Carbon Monoxide
Sensitive material of MQ-7 gas sensor is SnO2, which with lower conductivity in clean air. It make
detection by method of cycle high and low temperature, and detect CO when low temperature (heated
by 1.5V). The sensor’s conductivity is more higher along with the gas concentration rising. Whenhigh
temperature (heated by 5.0V), it cleans the other gases adsorbed under low temperature. Please use
simple electrocircuit, Convert change of conductivity to correspond output signal of gas concentration.
MQ-7 gas sensor has high sensitity to Carbon Monoxide. The sensor could be used to detect
different gases contains CO, it is with low cost and suitable for different application.Character

Configuration

*Good sensitivity to Combustible gas in wide range
* High sensitivity to Natural gas
* Long life and low cost
* Simple drive circuit
Application
* Domestic gas leakage detector
* Industrial CO detector
* Portable gas detector

Technical Data

Basic test loop

Model No.

MQ-7

Sensor Type

Semiconductor

Standard Encapsulation

Plastic

Detection GasCarbon Monoxide

Concentration

10-10000ppm CO

VRL

Loop Voltage
Heater Voltage
Circuit

Vc
VH

Heater Time

TL

60±1S（High）90±1S（Low）

RL

Adjustable

Load
Resistance
Heater
Resistance
Heater
Character

consumption
Sensing

5.0V±0.2V ACorDC（High）
1.5V±0.1V ACorDC（Low）

RH

31Ω±3Ω（Room Tem.）

PH

≤350mW

The sensor need to be put 2 voltage,
VHused to supply certified working
to detect voltage (VRL) on load resistance
（RL）whom is in series with sensor. The

S

Rs(in air)/Rs(100ppm CO)≥5

Slope

α

≤0.6(R300ppm/R100ppm CO)

sensor has light polarity, Vc need DC
power. VC and VH could use same power

Tem. Humidity

20℃±2℃；65%±5%RH
Vc:5.0V±0.1V；

Standard test circuit VH（High）: 5.0V±0.1V；
VH（Low）: 1.5V±0.1V

Tel:86-371-67169070/80

The above is basic test circuit of the sensor.

temperature to the sensor, while VC used

2KΩ-20KΩ(in 100ppm CO )

Preheat time

GND

heater voltage VH） and test voltage VC）
（
（
.

Sensitivity

Condition

RL
VH

≤10V DC

Rs

Resistance

Vc

circuit with precondition to assure
performance of sensor. In order to make
the sensor with betterperformance,
suitable RL value is needed:
Power of Sensitivity body(Ps):
Ps=Vc2×Rs/(Rs+RL)2

Over 48 hours
Fax: 86-371-67169090

Email: sales@hwsensor.com

Henan Hanwei Electronics Co., Ltd

www.hwsensor.com

Resistance of sensor(Rs): Rs=(Vc/VRL-1)×RL

Sensitivity Characteristics

Influence of Temperature/Humidity
1.9

Fig2

1.7

60%RH
30%RH
85%RH

Rs/R0

1.5
1.3
1.1
0.90.7
0.5
-20

-10

0

10

20

30

40

50 ℃

Fig.1 shows the typical sensitivity characteristics of

Fig.2 shows the typical temperature and humidity

the MQ-7, ordinate means resistance ratio of the sensor

characteristics. Ordinate means resistance ratio

(Rs/Ro), abscissa is concentration of gases. Rs means

of the sensor (Rs/Ro), Rs means resistance of sensorresistance in different gases, Ro means resistance of

in 100ppm CO under different tem. and humidity.

sensor in 1000ppm Hydrogen. All test are under standard

Ro means resistance of the sensor in environment of

test conditions.

100ppm CO, 20℃/65%RH

Structure and configuration

Structure and configuration of MQ-7 gas sensor is shown as Fig. 3, sensor composed by micro AL2O3 ceramictube, Tin
Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel
net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-7 have 6 pin, 4
of them are used to fetch signals, and other 2 are used for providing heating current.

Tel: 86-371-67169070/80

Fax: 86-371-67169090

Email:...