2pcs MQ-3 Alcohol Gas Sensor Module Ethanol Detector Breath Gas Detection Board Features: 1. Using double-sided circuit board design, with power indicator and TTL signal output indicator. 2. With DO switching signal (TTL) output and analog output AO. 3. TTL output valid signal is low level. (When the output is low level, the signal light is on, it can be directly connected to the MCU or relay module) 5. High sensitivity for the detection of alcohol gas. 6. Rapid response and recovery characteristics. 7. There are four screw holes for easy positioning   Detailed Test Parameters: Model: MQ-3 Detecting gas: alcohol vapor Detection concentration: 0.04-4mg/L alcohol Load resistance: RL 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: Rs (in air) / Rs (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: Power consumption (current ): 150mA DO output: TTL digital 0 and 1 ( 0.1 and 3.3V) 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 signal output 4. AO: analog signal output Package list: 2 x Alcohol Gas Sensor