Detailed Test Parameters:
Model: MQ-3
Detecting gas: alcohol vapor
Detection concentration: 0.04-4mg/L alcohol
Standard circuit condition: Loop voltage VC 24DC
Heating voltage :VH 5.0±0.2V AC/DC
Load resistance: adjustable
Gas sensor characteristics under standard test condition: Heating resistor 31Ω±3Ω
Heating power consumption: 90mW
Sensitive surface resistance: 2KΩ-20KΩ (in 0.4mg/L alcohol)
Sensitivity: (in air) / (0.4mg / L alcohol) 5
Concentration slope: 0.6 (R300ppm/R100ppm alcohol)
Standard test conditions: 20±2; 65%±5% RH
Standard test circuit: 5.0V ± 0.1V
Warm-up time: 48 hours

Electrical Properties:
Input voltage: DC5V
Power consumption (current ): 150mA
DO output: TTL digital 0 and 1 ( 0.1 and 3.3V)
AO output: 0.1-0 .3V, the highest concentration voltage is about 4V
Note: After the sensor is powered, needs to warm up around 20S, measured data was stable , heat sensor is a normal phenomenon , because the internal heating wire , if hot is not normal.

Wiring:
1. VCC: connected to the positive pole of the power supply
2. GND: connected to the negative power supply
3. DO: TTL switching output
4. AO: analog output

Package list:
2 x Alcohol Gas Sensor