Design Of Ultrasonic Methane Concentration Transmitter

Methane is mainly extracted from natural gas, biogas, coal pit gas, etc.Methane is a high-quality energy which can replace coal, while it is the essentialraw material in manufacture of synthetic gas and producing a variety of chemicalproducts in the industry. As China’s coal reserves are very rich, the associatedlayer with rich methane gas resources, methane is flammable gas, so there aresafety problems in the process of mining, so how to achieve cleanly, safely, andeffectively developing methane gas resources in the layer is a strategic task tosolve the energy problem. With this background, therefore the subject ofdetecting methane concentration raised has the great significance.Based on the principles of ultrasonic wave propagation velocity different inthe different components and different concentration, this paper presents thedesign of ultrasonic methane concentration transmitter, proposes a measurementmethod of gas concentration using phase difference based on time-differencemethod, expounds the phase detected measurement principle of gas concentration,and establishes the mathematical model of the phase, temperature and gasconcentration, completes the design of ultrasonic methane concentrationtransmitter.Measure the transmission phase difference between methane and pure airwhich is on two equal paths of ultrasonic pulse, gets an DC voltage signal fromthis phrase difference by the analysis of analog amplifying circuit and analog-digital hybrid circuit, and sends the DC voltage signal exchanged from timedifference to SCM, then methane concentration is gotten after processing in SCM.The hardware design of the transmitter are mainly: the SCM system design andits peripheral circuits design, the power supply design, the ultrasonic drivingcircuit design, signal receiving processing circuit design and standard signal output circuit design. The software designs are mainly: the main program design,calibration program design, infrared remote controlling program design,temperature measurement program design and signal output program design.In this paper, analyzed the principle of ultrasonic measuring methaneconcentrations, identified the effects of the sinusoidal signal frequency drivingthe ultrasonic transducer and ambient temperature on the measurement results.By selecting the appropriate drive frequency and measuring the ambienttemperature to complete the temperature compensation, make sure that thetransmitter enables real-timely, accurately measure the methane concentration.