TECHNICAL DATA MQ-2 GAS SENSOR FEATURES Wide detecting scope Fast response and High sensitivity Stable and long life Simple drive circuit APPLICATION They are used in gas leakage detecting equipments in family and industry, are suitable for detecting of LPG, i-butane, propane, methane ,alcohol, Hydrogen, smoke. SPECIFICATIONS A. Standard work condition Symbol Vc VH RL RH PH Parameter name Circuit voltage Heating voltage Load resistance Heater resistance Heating consumption B. Environment Symbol Tao Tas RH O2 Technical condition 5V±0.1 5V±0.1 can adjust 33 5% less than 800mw Remarks AC OR DC ACOR DC Technical condition -20 -50 -20 -70 less than 95%Rh 21%(standard condition)Oxygen concentration can affect sensitivity Remarks Room Tem condition Parameter name Using Tem Storage Tem Related humidity Oxygen concentration minimum value is over 2% C. Sensitivity characteristic Symbol Rs Parameter name Sensing Resistance (3000/1000) isobutane Standard Detecting Condition Preheat time Technical parameter 3K -30K (1000ppm isobutane ) Concentration Slope rate 0.6 Temp: 20 2 Humidity: 65%±5% Vc:5V±0.1 Vh: 5V±0.1 Over 24 hour Ramark 2 Detecting concentration scope 200ppm-5000ppm LPG and propane 300ppm-5000ppm butane 5000ppm-20000ppm methane 300ppm-5000ppm H2 100ppm-2000ppm Alcohol D. Strucyure and configuration, basic measuring circuit 1 2 3 4 5 6 7 8 9 Parts Gas sensing layer Electrode Electrode line Heater coil Tubular ceramic Anti-explosion network Clamp ring Resin base Tube Pin Materials SnO2 Au Pt Ni-Cr alloy Al2 O3 Stainless steel gauze (SUS316 100-mesh) Copper plating Ni Bakelite Copper plating Ni Fig.2 Fig. 1 Configuration A Configuration B Ａ向 Ａ向 Structure and configuration of MQ-2 gas sensor is show n as Fig. 1 (Configuration A or B), sensor composed by micro AL 2O3 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-2 have 6 pin ,4 of them are used to fetch signals, and other 2 are used for providing heating current. Electric parameter measurement circuit is shown as Fig.2 E. Sensitivity characteristic curve ＭＱ－２ Ｒｓ／Ｒｏ １０ １ Fig.3 is shows the typical sensitivity characteristics of the MQ-2 for several gases. in their: Temp: 20 Humidity: 65% O2 concentration 21% RL=5k Ro: sensor resistance at 1000ppm of H2 in the clean air. Rs:sensor resistance at various concentrations of gases. Ｈ２ ＬＰＧ ＣＨ４ ＣＯ ａｌｃｏｈｏｌ ｓｍｏｋｅ ｐｒｏｐａｎｅ ａｉｒ ｐｐｍ ０．１ １００ １０００ １００００ Fig.2 sensitivity characteristics of the MQ-2 １．８ １．６ ３３％ＲＨ ８５％ＲＨ Ｒｓ／Ｒｏ １．４ １．２ １ ０．８ ０．６ ０．４ ０．２ Fig.4 ｄｅｇｒｅｅ Fig.4 is shows the typical dependence of the MQ-2 on temperature and humidity. Ro: sensor resistance at 1000ppm of H2 in air at 33%RH and 20 degree. Rs: sensor resistance at 1000ppm of H2 at different temperatures and humidities. ０ －２０ －１０ ０ １０ ２０ ３０ ４０ ５０ ６０ SENSITVITY ADJUSTMENT Resistance value of MQ-2 is difference to various kinds and various concentration gases. So,When using this components, sensitivity adjustment is very necessary. we recommend that you calibrate the detector for 1000ppm liquified petroleum gas<LPG>,or 1000ppm isobutane<i-C4H10>concentration in air and use value of Load resistancethat( RL ) about 20 K (5K to 47 K ). When accurately measuring, the proper alarm point for the gas detector should be determined after considering the temperature and humidity influence.