The MQ138 gas sensor has a high sensitivity to ethylene glycol, benzene formaldehyde, tetrachloroethylene, toluene, methylene chloride, and other VOC gases. The sensor could recognize different organic steam. The sensor provides various applications at a lower cost.

Features:

Dual signal output (Analog output and TTL Level output)
TTL output effective signal is low. When the output is low, the signal light is on. Can be connected to single-chip Microcomputer IO Mouth）
Analog output increases with concentration. The higher the concentration, the higher the voltage.
It has high sensitivity for formaldehyde – suitable for the detection of aldehydes, alcohols, ketones, and aromatic compounds. Test concentration range of gas sensors:
Benzene 1 to 100 ppm
Toluene 10 to 100 ppm
Methanol 5 to 100 ppm
Alcohol 30 to 300 ppm
Acetone 10 to 300 ppm
Formaldehyde 1 to 10 ppm
It has long-term service life and reliable stability.；
Fast response recovery features
With a mounting hole. Easy to fix and install；
Probe plug-in design. Convenient Test。

Specifications:

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 preheating time 48 hours)