Development Of New Type Thermal Gas Mass Flowmeter

In this paper,the research of the principal and subordinate system of the new type thermal gas mass flowmeter is expatiated in detail.The flowmeter is a device for measuring flux including thermal mass flow sensor and flow transducer, and utilizes heat thansfer theories that is to say exchange for quantity of heat between flowing liquid and heater.Aiming at existing domestic and overseas thermal mass flow sensors having complicated got-up technicis and high cost, applying advanced method of semiconductor and integrate circuit technology, thermal mass flow sensor has two parts: Power sensor with automatic constant temperature and Temperature sensor whose advantage is diminutive volume and easy standardization for production.Thermal mass flow sensor has unique constant temperature principium as mathematical model for measuring medium mass flow without compensation of temperature and pressure.Flow transducer applies intelligent and pocket design, and adopts full integrated mixed signal SoC chip C8051F007 of Cygnal Co. as MCU, which integrates 12-bit 100kps ADC, 12-bit DAC, Programmable Digital I/O port distribution using priority cross bar decoder, Watchdog Timer, abundant On-Board Memory and On-Chip JTAG debug and so on.Measuring precision of ADC has achieved ±0.1%. The device has 4-20mA output with Real-time measurement for inspecting and estimating the actual situationof pipeline.The data is transmitted to computer by isolated RS-485 interface.The disposal software of data acquisition is developed with VB.Computer can finish the parameter setting of data acquisition including diameter of pipeline, full velocity of flow, sensor coefficient, medium coefficient and so on.In addition computer can real-time inspect the device's parameter temperature, Real-time flux and accumulative total flux.Author explains self-defined serial-communication protocol in detail in the paper.In this paper,clueing on the basic procedure of designing a new insertion type thermal gas mass flowmeter,author expatiates the process from pre-research for the domestic and overseas congener products,lay outing of function,building the physical and mathematic model for thermal gas mass flow sensor, software and hardware designing to debugging,developing sample of instrument . In the end , the whole paper is summarized.