The Research Of Metrological Testing Standard Device For Gas Detector

Chemical gas is usually high-pressure storage, with flammable, explosive, poisonousand harmful features. In order to prevent these factors to dangerous to production andpersonnel, the installation and performance tests of the gas detector are particularlyimportant.The tests including of indication error, response time, repeatability error,drift error for the gas detector is a basic discipline that research contents including ofchemical gas analysis, material science, electronic technology, communicationtechnology, test technology and data processing. The research of standard device canused for the gas detectors that work in industrial field and production workshop.Withthe device,we can test the gas detector to ensure its efficiency and reliabilityaccording to the national verification-regulations.This paper depth discusses themethods and related technologies about the metrological testing tandard device, obtainthe following main achievements:(1) In this paper, with the multi-channel signal collection technology, data processingmethod, high resolution acquisition for small signal,etc. Signal acquisition circuitabord was developed with high resolution. With communication of SPI bus in circuitboards, it can output the five-road analog signal at the same time. In order to improvethe validity and flexibility of communication mode, Wireless fidelity (Wi-Fi) andUSB communication technologyare used between signal acquisition part and PC.The output signal types of gas detectors have a variety of types including voltage,current, frequency and other forms, with current signal majority. Its signal outputrange follows the international standard: the output of current signals is general4~20mA, the output of voltage signal is general 0~5V, the output of frequency signal is general 0~10KHz.These analog signals were output from detector that need atransform circuit to convert to matching digital signals. Finally, circuit board cantransmit the digital signal to the data processing software for processing. Theresolution of this design for acquisition circuit abord: current signal is 0.01 mA;voltage signal is 0.001V; frequencysignal is 1Hz.(2) In this paper, with the electric control-method, mainly including pressure-control,flow- control, on-off for gas channels, vacuum ventilation and the switch of workingstate, etc. completed the electric controlling design and adjustment assembly. Touchscreen and PLC are control core in the electrical parts, with electromagnetic valve,pipeline, vacuum device, relays, power, communication module, ect, to complete theprocess control in the work. To convenient to the operators, provide two ways: manualcontrol and automatic control.(3) In this paper, with the methods that how to collect and process datas. Mainlyinvolves: the soft of touch screen and workstations procedures, driver design, and iwrite data processing and process control-software.The scheduled functions wascompleted including of the automatic control, the automatic-acquisition of datas, theautomatic calculation of datas,ect.The MCGS software was used to complete PC control programs.using Csharp andVS2008 platform, completed workstation programs. The software can upload datasfor acquisition circuit system, and get relevant informations from output signal ofdetectors, and record the informations, finally performance its parameters such as:indication error, response time, repeatability error, drift error, ect.Through analysisingrecords and the results of calculation, we can get the measuring parameters of gasdetectors finally, according to the national verification-regulations, we can completethe evaluation for that detectors.To sum up,combining with theory methods and design requirements above, eventuallycompleted the metrological testing standard device for gas detector.The experimentaltesting results show that, this device can be met on the needs about the metrologicaltesting works.Measurement precision and stability are great. The characteristics andsignificance of this device lies in: with the programs in the device,that can completethe testing works,and it Can collect the signals of five road at the same time,improvethe verification efficiency; Reduce errors with manual operation possiblely, reduce theworkloads,save the human costs;Using Wireless fidelity (Wi-Fi) and USBcommunication technology, instrument operation and installation will become moreflexibility.We also can remotelyaccess database;Automatic certificate system can help operators to reduce the workloads about copying and recording, its convenientfeatures can make our test works become efficiency greatly.