The Design And Realization For Gas Analysis Instruments Based On PLC

Modern gas analysis instruments include two design proposals. One is the handling scheme of analog signal based on discrete parts and small-scale integrated circuit, another is the handling scheme of digital circuit based on the monolithic processor. However, it is still quite difficult that the gas analyzer based on the monolithic processor meets requirements of gas measurement in multicomponent, multiplexer channel and adverse circumstances and applied requirements for pre-treating the sampled gas.By analyzing advantages and disadvantages and applications of modern gas analysis instruments, in view of concrete demands, a new design proposal has been put forward in this paper, It makes the detailed introduction on the overall proposal of PLC-based gas analyzer, various functions, each components and the implementation of software and hardware, including the choice of PLC systems, and the designation of gas sensor and its processing circuit of the signal, gas collecting system, and the program of touchable LCD and PLC.It takes the large screen touch liquid crystal display as the man-machine interface, applies multiple extended inputting ports to collect signals of concentration, humidity, temperature and pressure on various gases and also employs the data model to carry out data calculation and handling. The instrument possesses the strong environmental adaptation and is able to keep high precision and stability in the environment of unsteady temperature, humidity and pressure. It also has multiple outputting ports to control the multiple sampling inlets, can detecte gas at several sampling points by means of scanning and extend the sampling routes according to applied demands.