Target: C2H5OH
Model: MQ303B
Detection range: 20-500ppm
Detection principle: Semiconductor
Characteristics: High sensitivity to C2H5OH and quick response and resume
Size: φ9.4×6
Working conditions: Loop Voltage:≤6V
Heater Voltage:0.9±0.1V
Heater consumption:≤140mW

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Sensitive material of MQ303B gas sensor is semiconductor material which is with lower conductivity in clean air. When the target alcohol 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.


It has high sensitivity to alcohol and quick response and resume, widely used in portable alcohol gas detector.


High sensitivity, quick response and resume, long lifespan, low power consumption, low cost, small sizes. 


Model MQ303B
Sensor Type Semiconductor
Standard Encapsulation Metal
Target Gas Alcohol gas
Detection range 20~ 500ppm alcohol
Standard Circuit Conditions Loop Voltage V H 0.9V±0.1V AC or DC
Heater Voltage V c ≤6V DC
Load resistance R L Adjustable
Heater Resistance RH 4.0Ω±0.5Ω(room temp.)
Heater consumption PH ≤140mW
Sensor character under standard test conditions Zero point V0 0.01~0.45V
Sensitivity VS 1.0~2.5V (in 125ppm C2H5OH)
Concentration Slope α ≤0.6(R300ppm/R50ppm C2H5OH)
Standard test conditions Tem.  Humidity 20℃±2℃ 55%±5%RH
Standard test circuit Vc:3.0V±0.1V DC  VH:0.9V±0.1V DC
Preheat time Not less than 48 hours

* The description and specifications might be changed without notice. Please contact us for the latest information before placing orders.

Technical Support:

Customized technical design and function, LOGO and package are available without extra charge (including molding fee) for mass volume.

The sensors don't have sleeping mode. It can be set in program if needed.

All Winsen products go through strict inspections and tests to make sure they are 100% qualified before shipping out.

The sensor has been fully tested (not calibrated) before leaving the factory. However, after transportation and storage, the environment conditions change, and the surface of the sensor absorbs moisture, mixed gas, pollution matters, etc. It is recommended that customers perform aging and calibration after sensors become stable according to the program and use occasions of the whole device.

15﹪-90﹪RH without condensation,greater or less than this range or long-term high temperature and high humidity will affect the life of the sensor.

Our sensors are certified with CE, 3C, ROHS, anti-explosion, fire prevention, and coal mining safety according to different applications. And we provide assistance for new certification.

Many factors can cause the sensor to fail such as broken wires in transportation, poisoning, falling off of the sensitive material, damage to the heating wire (device), etc. Please find specific cause in each category with Winsen’s aftersales.

Winsen provides professional consultation and service before and after sales. We will recommend the best fitting sensor for your demand. If you have any problem, don’t hesitate to email us to

Due to high volume of daily incoming emails and time zone difference, we may not be able to reply your emails immediately. But we will reply to your inquiry in 24 business hours.