Research Of Measurement And Control System Of Universal Gas Mass Flowmeter Based On Labview And PLC

High precision gas flow calibrator,based on volume and time,has the advantages of high degree of accuracy and high measuring repeatability and stability,which has been applied in all kinds of small gas flow meter calibration in recent years more widely.Instead of bell gas flow standard device,high precision gas flow calibrator can greatly reduce the measurement uncertainty of calibration and improve efficiency of calibration of gas mass flowmeter,gas mass flow controller,float flowmeter,soap membrane flowmeter,etc.However,as a new model of flow standard device,the high precision gas flow calibrator has not been matched a set of automation control system.The article formed a new set of fully automatic universal small gas flowmeter measuring system based on the existed manual high precision gas flow calibrator device by adding upper computer,lower computer and flow control system into the system.Choosing PC notebook computer as the upper computer of the system.Choosing SIEMENS S7-200 PLC programmable logic controller as lower computer of the system.Connecting upper and lower computer with USB/PPI cable.Using three gas mass flow controllers of different range replacing the manual flow control valve.The upper computer uses the USB/RS232 cable to direct control standard device.The lower computer uses the signal cable to communicate with the device flow control part and the measured part.In the software aspect,LabVIEW is used to program the upper computer,Step 7 MICRO/WIN is used to program the lower computer,and use OPC communication protocol to realize the data transmission of the upper machine and the lower machine.Finally,the target and the automatic control and the acquisition of the analog output signal of the measured gas mass flowmeter are realized,and the measurement accuracy and efficiency are improved.