基于PLC的气表检定控制系统设计

Design of Gas Meter Calibration Control System Based on PLC

应用音速喷嘴法气体流量标准装置检定气体流量计是一项复杂的过程控制问题,检定仪表时,在水环真空泵的作用下,空气分别流经进气管线、被检流量计、喷嘴进口管线、音速喷嘴和喷嘴出口管线,最后经稳压罐,由真空泵排出。根据检定流量的大小,选择不同的气动阀和不同的喷嘴组合,确定所需的检定流量。为了实现气表精准检定,设计了一套基于PLC的气表检定控制系统。该系统以PLC作为基本控制单元,实时采集系统各项参数,应用顺序控制方式实现气表检定过程自动化,自动计算仪表系数、示值误差和重复性,可减轻操作的劳动强度,保证精准检定。

Using sonic nozzle gas flow standard device to calibrate gas meter is a complex control process. When the instrument is verified under the action of water ring vacuum pump, air will respectively flow through the inlet pipe, detected flow meter, nozzle import pipeline, sonic nozzle, nozzle export pipeline, the buffer tank, and in the end the vacuum pump will discharge it.According to the size of the verification flow,choose different pneu-matic valve and different nozzle combination to determine the required verification flow. In order to realize accuracy verification of the gas meter, a set of gas meter calibration control system based on PLC was designed. Considering PLC as the basic control unit, workers can gather system parameters and apply the way of sequential control to realize gas meter calibra-tion process automation,instrument automatic computation coefficient,repeatability and er-rors of indication,and finally reduce workers’labor intensity and ensure accurate verification.