nsitive 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.

Features:

1. Wide range of applications
2. Small appearance
3. Long service life
4. Fast response time
5. With mounting holes for easy permanent installation

Specifications:

• Detection Gas: toluene, acetone, alcohol, hydrogen
• Detection Range: 5���500ppm VOC
• Size���32mm X22mm X27mm���� L x W x G
• Main chip���LM393.
• Operating voltage: DC 5V
• Heating voltage: 5 ��0.2V (AC��DC)
• Working current: 180mA.
• Circuit voltage: DC5V (Max DC 24V)
• Load resistance: 10K (adjustable)
• Test concentration range :1-100ppm.
• Clean air voltage: < 1.5V.
• Sensitivity: > 3%
• Response time: < 1S (3-5 minute warm-up, theory pr