Research On Intrinsically Safe Ultrasonic Distance Measurement System In Flammable And Explosive Environment

Ultrasonic wave is a kind of elastic wave with strong directivity and low energy consumption.It spreads far away in the medium,so the ultrasonic ranging is used widely,such as reversing radar,obstacle avoidance,position detection,water level measurement etc..But in the environment of coal dust and coal gas explosion,the existing ultrasonic ranging system is limited by the fact that the large capacity energy storage element in the drive circuit which contains the secondary transformer is not in conformity with the essential safety requirements.For this reason,the research on the ultrasonic ranging system in the flammable and explosive environment has been carried out gradually,and the design method of the intrinsically safe ultrasonic ranging system is usually adopted in the design of the transformer without transformer.There are two key points in the traditional method of central drive.The first point is boost.Boost is to ensure that the driving voltage of the transducer is higher,which makes the system more stable to measure thelonger distance.The second is impedance matching.The secondary drive can realize the impedance matching between the transformer secondary coil and the transducer,so that the energy conversion efficiency of the energy conversion system is improved.The study of intrinsically safe ultrasonic distance measurement system in flammable and explosive environment is mainly divided into the study of ultrasonic distance measurement and the impedance matching of ultrasonic drive transducer.Firstly,the design theory of intrinsically safe circuit is described.The design requirements of intrinsically safe circuit,the discharge spark energy in flammable and explosive environment,and the protection method of intrinsically safe circuit are introduced.Then the theory of ultrasonic ranging is studied.The principle and method of ultrasonic distance measurement and the structure of ultrasonic ranging system are expounded.Due to the existence of aftershocks after the ultrasonic transducer drive,resulting in the blind area.And the aftershocks of the transducer are related to their own properties,so the classification of the ultrasonic transducer is introduced.The factors affecting the blind area are analyzed.In order to study the intrinsic safety of the ultrasonic ranging driver circuit,different driving methods are designed and analyzed.Finally,the high speed optocoupler drive system is adopted.For the improvement of the energy transfer efficiency,the impedance matching of ultrasonictransducer is studied,and the impedance matching theory of ultrasonic ranging system is expounded under intrinsically safe driven.Finally,the impedance matching network of the ultrasonic ranging system is analyzed,and the impedance matching design of the transducer is completed.The power supply circuit of the ultrasonic ranging system is multilevel voltage supply,so the power supply circuit is designed.After the driven of ultrasonic transducer,it is necessary to carry out the echo processing,so the echo processing circuit in the back of the system is explained.Ultrasonic ranging system is based on MSP430 microprocessor.The use of microprocessor is for early warning and12864 LCD display.Finally,the drive waveforms of different distance measurement system are tested.The driving ability of different distance measurement system is analyzed and compared.The minimum driving voltage of the converter is analyzed,and the performance of the ranging system is tested.For example,the measurement of the concave convex surface is analyzed.The development of the intrinsically safe early warning system in the flammable and explosive environment broadens the application environment of the ranging system,so it has strong practical value.