How it Works!!!

by Don Eberhart

This online system is composed of a dual Pentium-Pro 300Mhz machine acting as the server, and five client machines ranging in speeds from a MAC IIx to a Pentium Pro 200Mhz with each controlling a different Physical system. The server machine is running Windows NT 4.0 Internet information server, NT windows file server and Mac file server.

Each of the client computers communicate with the server via NT file server and client software written with LabVIEW. The clients scan for command files to appear on the server which are produced by the LabVIEW WEB server each time an experiment is run by the user. The client software reads the command files off the server and decodes them into variables used by the DAQ cards to control the physical systems.

Once an experiment has run, the client software writes a results file back onto the server. The WEB server creates unique web pages with custom links to the pages and pictures produced for each experiment that is run by the user based on the time the experiment was requested. In addition to creating custom web pages, the WEB server graphs the results and produces JPEG images of the graphs linked by the web pages. It is also necessary for the WEB server to stack the commands from the users since the systems run in real time with time delays for each experiment. If more than one user requests an experiment for the same system, the requests are stacked in a temporary file and executed in the order in which they are received.

To add to the complexity of the LabVIEW WEB server, additions have been added to make it a "SMART SYSTEM". Since the client computers are accessible by students which may close the client software to run experiments locally, the server performs tests every few minuets to check each client's status. If any clients are not running properly, the WEB server edits the web pages to prevent users from accessing systems that will not operate.

The hardware of the physical systems are controlled and monitored using National Instruments data acquisition cards in the client computers. The DAQ cards allow the software to communicate using low level analog and digital signals to the outside world. The outside world may be variable motor speed controllers, temperature sensors, pressure sensors, or almost anything.

Hot Links

Pictures of the system components

Papers written by Dr. Jim Henry about the laboratory and its installation on the Internet.

Internet Laboratory Server in Engineering Systems Laboratory, Conference at M.I.T., June, 1997

Controls Laboratory Teaching via the World Wide Web , ASEE Paper, Washington, DC, June 1996.

"LabVIEW Applications in Teaching Controls Systems Laboratories", ASEE Annual Meeting, Anaheim, CA, June, 1995.

"Engineering Controls Systems with LabVIEW", Scientific and Engineering Applications for Macintosh, Woburn, MA, August, 1993.

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