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MQ-138 Dataheets PDF



Part Number MQ-138
Manufacturers HANWEI ELECTRONICS
Logo HANWEI ELECTRONICS
Description GAS SENSOR
Datasheet MQ-138 DatasheetMQ-138 Datasheet (PDF)

HANWEI ELECTRONICS CO.,LTD TECHNICAL DATA MQ-138 http://www.hwsensor.com MQ-138 GAS SENSOR FEATURES Wide detecting scope Fast response and High sensitivity Stable and long life Simple drive circuit APPLICATION They are used in Breath alcohol detector, solvent detectors ,Air quality control equipments for buildings/offices, are suitable for detecting of n-Hexane, Benzene, NH3, alcohol, ,smoke, CO ,etc. SPECIFICATIONS A. Standard work condition Symbol Vc VH Parameter name Circuit vo.

  MQ-138   MQ-138


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HANWEI ELECTRONICS CO.,LTD TECHNICAL DATA MQ-138 http://www.hwsensor.com MQ-138 GAS SENSOR FEATURES Wide detecting scope Fast response and High sensitivity Stable and long life Simple drive circuit APPLICATION They are used in Breath alcohol detector, solvent detectors ,Air quality control equipments for buildings/offices, are suitable for detecting of n-Hexane, Benzene, NH3, alcohol, ,smoke, CO ,etc. SPECIFICATIONS A. Standard work condition Symbol Vc VH Parameter name Circuit voltage Heating voltage Technical condition 5V±0.1 5V±0.1 Remarks AC OR DC ACOR DC RL Load resistance RH Heater resistance can adjust 31Ω±3Ω Room Tem PH Heating consumption less than 850mw B. Environment condition Symbol Parameter name Technical condition Remarks Tao Using Tem -10℃-45℃ Tas Storage Tem -20℃-70℃ RH Related humidity less than 95%Rh O2 Oxygen concentration 21%(standard condition)Oxygen minimum value is concentration can affect over 2% sensitivity C. Sensitivity characteristic Symbol Parameter name Technical parameter Remarks Rs Sensing Resistance 20KΩ-200KΩ (1000ppm Benzene ) Detecting concentration scope: 10ppm-1000ppm α (200/50) Concentration Slope rate ≤0.65 Benzene 10ppm-1000ppm NH3 Standard Detecting Condition Temp: 20℃±2℃ Vc:5V±0.1 Humidity: 65%±5% Vh: 5V±0.1 Alcohol 10ppm-3000ppm NH3 Preheat time Over 24 hours D. Structure and configuration, basic measuring circuit Parts 1 Gas sensing layer 2 Electrode 3 Electrode line 4 Heater coil 5 Tubular ceramic 6 Anti-explosion network 7 Clamp ring 8 Resin base 9 Tube Pin Materials SnO2 Au Pt Ni-Cr alloy Al2O3 Stainless steel gauze (SUS316 100-mesh) Copper plating Ni Bakelite Copper plating Ni Configuration A Fig. 1 Configuration B Fig.2 A A Structure and configuration of MQ-138 gas sensor is shown as Fig. 1 (Configuration A or B), sensor composed by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and TEL: 86-371-67169070 67169080 FAX: 86-371-67169090 E-mail: [email protected] HANWEI ELECTRONICS CO.,LTD MQ-138 http://www.hwsensor.com 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-138 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 Fig.2 sensitivity characteristics of the MQ-138 10 MQ138 Benzene n-Hexane Fig.3 is shows the typical sensitivity characteristics of the MQ-138 for several gases. CH4 in their: Temp: 20℃、 CO Humidity: 65%、 alcohol propane O2 concentration 21% RL=20kΩ Air Ro: sensor resistance at 1000ppm of Benzene in the clean air. Rs :sensor resistance at various 1 concentrations of gases. Rs/Ro Rs/Ro 0.1 100 1000 ppm 10000 1.8 1.6 1.4 Fig.4 is shows the typical dependence of 33%RH the MQ-138 on temperature and humidity. 1.2 85%RH Ro: sensor resistance at 1000ppm of Benzene in 1 air 0.8 at 33%RH and 20 degree. 0.6 Rs: sensor resistance at 1000ppm of Benzene 0.4 at different temperatures and humidity 0.2 degree 0 Fig.4 -20 -10 0 10 20 30 40 50 60 SENSITVITY ADJUSTMENT .Resistance value of MQ-138 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 100ppm Benzene or Alcohol concentration in air and use value of Load resistance that( RL) about 47 KΩ(20KΩ to 100 KΩ). When accurately measuring, the proper alarm point for the gas detector should be determined after considering the temperature and humidity influence. TEL: 86-371-67169070 67169080 FAX: 86-371-67169090 E-mail: [email protected] .


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