The Design And Implementation Of Gass Mass Flow Controller

With modern advanced manufacturing industry and the needs of the development of scientific research,in order to be more convenient,quick,accurate and effective to the operation of the production and manufacturing process for precision and control,usually involves a variety of media,including various types of gases and liquids.In actual application of the medium,there will be some phyical parameters such as temperature,pressure,flow,etc.,among them,the flow in the process of production and manufacturing is one of the important parameters to measure and control.There are two kinds of flow measurement and control method,is a kind of measuring volume flow medium,one is a medium of mass flow rate measurement.Due to the volume of the medium is influenced by outside conditions such as temperature and pressure changes,leading to the precision of measurement and control is bad,can not meet the needs of advanced manufacturing industry and high-tech research fields such as high precision requirements,therefore,generally USES mass flow measurement and control methods.Is currently the most widely used thermal type gas mass flow controller,however,the equipment is low accuracy,latie temperature drift,defects such as slow response speed.In order to overcome the disadvantage of thermal gas mass flow controller,based on the principle of differential pressure type,studied the gas mass flow controller,the design and implementation,this topic main research contents include the following:(1)hardware system design and implementationHardware system by adopting the idea of modular design,mainly divides into four parts:one is signal acquisition module,the other is computing module,the third is the communication module,the fourth is the control module.Signal acquisition module includes three main sensor unit,namely the differential pressure sensor,temperature sensor and pressure sensor.This module will receive the three sensor unit convert the signal through the operation of traffic signals,then convert traffic signals into electrical signals,finally through the signal adjust output signal.Arithmetic module output signal of the signal acquisition module analysis and calculation,get the instantaneous gas mass flow rate,and through the signal output line transmission to the secondary display instrument or PC.Communication module’s main function is to communicate with PC.Control module USES electromagnetic valve door of fluid flow for precise control.Gas mass flow controller is implemented by computing module for gas flow measurement and control of mass flow controller,select AD7799 chips and Cygnal company in the United States during production of C8051F020 microprocessor as the core component.(2)software system designSoftware system design according to each function module in the program design,covering the A/D conversion,flow calculation,control functions,buttons and display function,flow output function,communication function,system mainly aims at the design of single-chip computer parts to software,its main function is to realize the data acquisition,data processing,data operation and input and output,and other functions.On the specific implementation,the Software system based on Windows platform,using Keil Software companies in the United States(ARM)is one of product compatibility 51 series microcontroller,Keil C51,programming language is the C language.(3)test and realization of the gas mass flow controllorIn this paper,the research object,linear precision accuracy and repeat precision of the three parameters adopted American DHI company produces the MOLBLOC and MOLBOX shown in the experimental platform to test parameters,to study the response time of use within 300 MHZ bandwidth digital oscilloscope in the response time of the test paper,the research object of the influence of environment temperature test platform adopts the temperature test chamber for testing.Through the above three experimental platform,according to the test data in this paper,the developed gas mass flow controller performance index has reached the expected results,meet the design requirement.