This part is a kind of semiconductor called MQ-138.

Function of this product has GAS SENSOR.

Manufacturers : HANWEI ELECTRONICS

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Some of the text within the PDF file :

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�� [ ... ]

MQ-138 PDF Datasheet Download