Technologia zmiennych sieciowych w rozproszonych systemach pomiarowo-kontrolnych

摘要

In the paper possibilities of the new network variable technology used for building application of the National Instruments Lab Windows are presented. The writing distributed application with network data exchange using TCPIP protocol (Fig. 1) is frequently difficult [1]. It is often necessary to write programs using multiprocessing or multithreading techniques, which might be a difficult task because it also involves problems like critical sections and deadlocks [4]. The network variable technology introduced by the National Instruments is a new technology which simplifies building distributed application using Lab Windows or Lab View tools. A network variable can be compared with the classic global program variable but shared between many applications across the network. The application must declare variables divided into processes (Fig. 2) and attach to a given variable (or variables) in order to write and read their values - Fig. 3. A practical exemplary use of this technology as a distributed supervision system to inform about problems with the functioning of devices such as the time and frequency standard generator in the Central Office of Measures in Warsaw is presented [5]. The application consists of many program modules supervising certain devices - Figs. 4 and 5. A number of network variables is used to send alert information by means of SMS to the list of declared users - Fig. 6. The Network Variable technology can be perceived as an interesting alternative to other technologies but can be used only with National Instruments applications.%W artykule zaprezentowane zostan? mo?liwo?ci technologii zmiennych sieciowych firmy National Instruments. Technologia zmiennych sieciowych mo?e znale?? zastosowanie podczas budowy rozproszonych systemów pomiarowo- kontrolnych przy u?yciu pakietu Lab Windows lub Lab View. Jako przyk?ad praktyczny zastosowania technologii przedstawiony b?dzie rozproszony system informowania o nieprawid?owo?ciach pracy urz?dzeń typu wzorce cz?stotliwo?ci i czasu w G?ównym Urz?dzie Miar w Warszawie.