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MQ136 Semiconductor Sensor for Sulfur Dioxide
Sensitive material of MQ136 gas sensor is SnO2, which with lower conductivity in clean air. When the target SO2 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.
MQ136 gas sensor has high sensitity to SO2, also could be used to detect other vapor which contains Sulfur. It has low sensitivity to normal combustible gases, which is with low cost and suitable for different application.
Character
* Good sensitivity to SO2 * Long life and low cost * Simple drive circuit
Configuration
Application
* Domestic SO2 concentration detector * Industrial SO2 leakage detector * Portable SO2 detector
Technical Data Basic test loop
Model No.
MQ136
Sensor Type
Semiconductor
Standard Encapsulation
Bakelite (Black Bakelite)
Detection Gas
SO2
Concentration
1-200ppm (SO2)
Circuit
Loop Voltage Heater Voltage
Load Resistance
Vc VH
RL
≤24V DC 5.0V±0.2V ACorDC
Adjustable
Heater Resistance
RH
31Ω±3Ω(Room Tem.)
Character
Heater consumption
Sensing Resistance
PH Rs
≤900mW 2KΩ-20KΩ(in 50ppm SO2)
Sensitivity S Rs(in air)/Rs(50ppm SO2)≥3
Slope
α
≤0.6(R100ppm/R50ppm SO2)
Tem. Humidity
20℃±2℃;65%±5%RH
Condition Standard test circuit
Vc: 5.0V±0.1V; VH: 5.0V±0.1V
Preheat time
Over 48 hours
Power of Sensitivity body(Ps): Ps=Vc2×Rs/(Rs+RL)2
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:
Resistance of sensor(Rs): Rs=(Vc/VRL-1)×RL
Sensitivity Characteristics
Influence of Temperature/Humidity
Fig.1 shows the typical sensitivity characteristics of the MQ136, 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 50ppm SO2. All test are under standard test conditions.
Fig.2 shows the typical temperature and humidity characteristics. Ordinate means resistance ratio
of the sensor (Rs/Ro), Rs means resistance of sensor in 50ppm SO2 under different tem. and humidity. Ro means resistance of the sensor in environment of 50ppm SO2, 20℃/65%RH
Structure and configuration
Structure and configuration of MQ136 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.