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ETC |
MQ-2 Semiconductor Sensor for Combustible Gas
Sensitive material of MQ-2 gas sensor is SnO2, which with lower conductivity in clean air. When the
target combustible gas exist, The sensor’s conductivity is more higher along with the gas concentration
rising. Please use simple electrocircuit, Convert change of conductivity to correspond output signal of
gas concentration.
MQ-2 gas sensor has high sensitity to LPG, Propane and Hydrogen, also could be used to Methane
and other combustible steam, it is with low cost and suitable for different application.
Character
*Good sensitivity to Combustible gas in wide range
* High sensitivity to LPG, Propane and Hydrogen
* Long life and low cost
* Simple drive circuit
Configuration
Application
* Domestic gas leakage detector
* Industrial Combustible gas detector
* Portable gas detector
Technical Data
Basic test loop
T
Model No.
Sensor Type
Standard Encapsulation
Detection Gas
Concentration
Loop Voltage
Circuit
Heater Voltage
Load
Resistance
Heater
Resistance
Heater
consumption
Character Sensing
Resistance
Vc
VH
RL
RH
PH
Rs
Sensitivity S
Slope
α
Tem. Humidity
Condition Standard test circuit
Preheat time
MQ-2
Semiconductor
Bakelite (Black Bakelite)
Combustible gas and smoke
300-10000ppm
( Combustible gas)
≤24V DC
5.0V±0.2V ACorDC
Adjustable
31Ω±3Ω(Room Tem.)
≤900mW
2KΩ-20KΩ(in 2000ppm C3H8 )
Rs(in air)/Rs(1000ppm
isobutane)≥5
≤0.6(R5000ppm/R3000ppm CH4)
20℃±2℃;65%±5%RH
Vc:5.0V±0.1V;
VH: 5.0V±0.1V
Over 48 hours
Vc VRL
RL
VH
GND
The above is basic test circuit of the sensor.
The sensor need to be put 2 voltage,
heater voltage(VH)and test voltage(VC).
VH used to supply certified working
temperature to the sensor, while VC used
to detect voltage (VRL) on load resistance
(RL)whom is in series with sensor. The
sensor has light polarity, Vc need DC
power. VC and VH could use same power
circuit with precondition to assure
performance of sensor. In order to make
the sensor with better performance,
suitable RL value is needed:
Power of Sensitivity body(Ps):
Ps=Vc2×Rs/(Rs+RL)2
Resistance of sensor(Rs): Rs=(Vc/VRL-1)×RL
Sensitivity Characteristics
Fig1
Fig.1 shows the typical sensitivity characteristics of
the MQ-2, ordinate means resistance ratio of the sensor
(Rs/Ro), abscissa is concentration of gases. Rs means
resistance in different gases, Ro means resistance of
sensor in 1000ppm Hyrogen. All test are under standard
test conditions.
Structure and configuration
Influence of Temperature/Humidity
1.9
1.7
Fig2
60%RH
1.5 30%RH
85%RH
1.3
1.1
0.9
0.7
0.5
-20
-10
0
10 20 30 40 50 ℃
Fig.2 shows the typical temperature and humidity
characteristics. Ordinate means resistance ratio
of the sensor (Rs/Ro), Rs means resistance of sensor
in 1000ppm Butane under different tem. and humidity.
Ro means resistance of the sensor in environment of
1000ppm Methane, 20℃/65%RH
Structure and configuration of MQ-2 gas sensor is shown as Fig. 3, sensor composed by micro AL2O3 ceramic tube, 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-2 have 6 pin, 4
of them are used to fetch signals, and other 2 are used for providing heating current.
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