For Flammable And Explosive Liquid Security Detection Sensor Design

Illegal transport and application of liquid hazardous materials has endangeredpublic security seriously, and it has become a new means of terrorist activities. Onceterrorists bring inflammable and explosive liquid to trains or cars and ignite it, it willcause lots of injuries and deaths, and the consequence will be inconceivable. So doingsecurity check for the liquid objects which passengers carry has become urgent.Methods are studied experimentally to quickly identify dangerous liquids in this paper.The state-of-the art of the subject is introduced briefly. The principle of themethods of checking some existing liquids is analyzed, then the performances of eachmethods are summarized. The dielectric constant is a characteristic parameterreflecting the medium dielectric properties. For inflammable and explosive liquid, itsdielectric constant is different obviously from that of water. Based on the differences ofdieletric constant, a capacitance sensor is made and the following signal processingcircuit is studied, then the dielectric properties of water, and several other ordinaryinflammable and explosive liquids are measured. In addition, for the water, itsabsorption ability for980nm infrared light is very strong, but Inflammable andexplosive liquids are weak. Thus dangerous liquids through measuring the differenceof the transmittance of the liquid sample under the irridiation of the characteristicwavelength of980nm can be identified Finally, priliminary experiments on ultrasonicmethod are done, and the further improved is proposed.The ultimate purpose is to usethese methods together to check the liquids which passengers carry.