MQ-3 Semiconductor Sensor for Alcohol Sensitive material of MQ-3 gas sensor is SnO which with lower conductivity in clean air. When the 2, target alcohol gas exist, The sensors conductivity is more higher along with the gas concentration rising. Please use simple electrocircuit, Convert change of conductivity to correspond output signal of gas concentration. MQ-3 gas sensor has high sensitity to Alcohol, and has good resistance to disturb of gasoline, smoke and vapor. The sensor could be used to detect alcohol with different concentration, it is with low cost and suitable for different application. Character Configuration * Good sensitivity to alcohol gas * Long life and low cost * Simple drive circuit Application * Vehicel alcohol detector * Portable alcohol detector Technical Data Basic test loop Vc V Model No. MQ-3 RL Sensor Type Semiconductor Standard Encapsulation Bakelite (Black Bakelite) Detection Gas Alcohol gas R L Concentration 0.04-4mg/l alcohol V H Loop Voltage V 24V DC c Heater Voltage V 5.0V0.2V AC or DC H Circuit GND Load R Adjustable L Resistance The above is basic test circuit of the sensor. Heater The sensor need to be put 2 voltage, R H 313Room Tem. Resistance heater voltageVH and test voltageVC. Heater VH used to supply certified working P 900mW H consumption temperature to the sensor, while VC used Character Sensing to detect voltage (VRL) on load resistance R 2K-20K (in 0.4mg/l alcohol ) s Resistance RLwhom is in series with sensor. The Rs(in air)/Rs(0.4mg/L sensor has light polarity, Vc need DC Sensitivity S Alcohol) 5 power. VC and VH could use same power Slope 0.6(R /R Alcohol) 300ppm 100ppm circuit with precondition to assure Tem. Humidity 20265%5%RH performance of sensor. In order to make Vc:5.0V0.1V the sensor with better performance, Standard test circuit Condition V : 5.0V0.1V H suitable RL value is needed: Preheat time Over 48 hours Power of Sensitivity body(Ps): 2 2 Ps=Vc Rs/(Rs+RL) Resistance of sensor(Rs): Rs=(Vc/VRL-1)RL Sensitivity Characteristics Influence of Temperature/Humidity Fig.1 shows the typical sensitivity characteristics of Fig.2 shows the typical temperature and humidity the MQ-3, ordinate means resistance ratio of the sensor characteristics. Ordinate means resistance ratio (Rs/Ro), abscissa is concentration of gases. Rs means of the sensor (Rs/Ro), Rs means resistance of sensor resistance in different gases, Ro means resistance of in 0.4mg/l alcohol under different tem. and humidity. sensor in 0. 4mg/l alcohol. All test are under standard Ro means resistance of the sensor in environment of test conditions. 0.4mg/l alcohol, 20/65%RH 3 P.S.: Sensitivity to smoke is ignite 10pcs cigarettes in 8m room, and the output equals to 0.1mg/l alcohol Structure and configuration Structure and configuration of MQ-3 gas sensor is shown as Fig. 3, sensor composed by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-4 have 6 pin, 4 of them are used to fetch signals, and other 2 are used for providing heating current.