Collecting historical data from a remote PLC

Introduction

In some IGSS installations remote PLCs will collect process data. A typical example could be remote pump stations for a wastewater treatment plant.

These PLCs are not online all the time, but are automatically dialed up with a fixed interval (for example, twice a day). The dial up schedule is set up on the Remote Connection tab. Also the operator can manually dial up the remote PLC.

During the offline period, the remote PLC will store process values with a given interval. Some PLCs will even support storing of events (only changes in process values are stored). This is what we call historical data. The historical data can be collected by IGSS when the remote PLC is online by following the procedure below.

To allow the operator to create graphs and reports for the monitored objects, the historical data must be saved in the IGSS log files and the .bcl files.

Example

To illustrate the functionality, we will make an example based on the IGSS Demo Configuration. We will go through the following steps:

 

    1. In System Configuration add the remote PLC using the General Comli 31 protocol driver.
    2. In System Configuration, define the Historical Data Settings.
    3. In Definition, create the object that collects historical data.
    4. In Definition, create a graph that shows the historical data.
    5. In Supervise, show the graph.