Internet-based data acquisition system via a PSTN

This paper presents the design and implementation of a web-based data acquisition system from remote station sites. It allows regular updates of telemetry data to be made at pre-defined intervals, for a multiuser environment. The proposed system is constructed around a host PC connected to the PSTN via an internal modem at one end, and a number of remote terminal units (RTU), each located at one of the sites. The host PC is part of a LAN, and is connected to a server. Data acquired from the sites by the host PC, are finally transferred to the server, which is configured as an Internet Information Server (IIS). A web site is hosted on that server to allow user-access to the data. The system can be operated in both on-line and off-line modes.