MQ138 VOC Gas Sensor

  • • Detection Gas: toluene, acetone, alcohol, hydrogen
  • • Detection Range: 5~500ppm VOC
  • • Application: domestic VOC gas alarm, VOC gas leakage alarm and portable VOC gas detector

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  • Principle Introduction
Principle Introduction:
Winsen Electronics manufacture air quality sensor and VOC sensor MQ138 for IAQ monitor application.
Sensitive material of MQ138 gas sensor is SnO2, which with lower conductivity in clean air. When VOC gas exists, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.
MQ138 gas sensor has high sensitivity to toluene, acetone,alcohol,methanol,also can monitor hydrogen and other organic vapour well. It can detect kinds of organic gases and is a kind of low-cost sensor for kinds of applications.
Applications :
It is widely used in domestic VOC gas alarm, industrial VOC gas leakage alarm and portable VOC gas detector.
Technical parameters :

Tips:For more parameter information, please refer to the latest manual provided by salesman.

Model MQ138
Sensor Type Semiconductor
Standard Encapsulation Bakelite, Metal cap
Target Gas toluene, acetone, alcohol, hydrogen
Detection range 5~500ppm
Standard Circuit Conditions Loop Voltage Vc ≤24V DC
Heater Voltage VH 5.0V±0.1V AC or DC
Load Resistance RL Adjustable
Sensor character under standard test conditions Heater Resistance RH 29Ω±3Ω( room tem.)
Heater consumption PH ≤900mW
Sensitivity S Rs(in air)/Rs(in 50ppm toluene)≥2
Output Voltage △Vs ≥0.5V (in 50ppm toluene)
Concentration Slope α ≤0.6(R200ppm/R50ppm toluene)
Standard test conditions Tem. Humidity 20℃±2℃;55%±5%RH
Standard test circuit Vc:5.0V±0.1V; VH:5.0V±0.1V
Preheat time Over 48 hours
Reference Circuit :

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