Picking the New > Database Source or Edit a Database source in the SCADA signals dialog opens the Database Source editor.

The first step is to establish a database connection which initiated by pick the Edit button, in the Connection field (see “Database Connection Dialog”-623)..

Once the Connection to the file has been established, the user can further refine the connection. For example in an Excel file or an Access database, the user can specify which table is to be used for the connection. If multiple tables are used, each one must have its own connection.

The user must pick from one of two data source formats: One value per row or Multiple values per row.

In the "One value per row" format, each row/record must contain the signal name field (e.g. Pressure Main St.), the value field (e.g. 60) and a time stamp filed (e.g. 2/4/2015 14:30). Optionally, the user may also specify if there is a field indicating the quality of the data, Questionable Field (e.g. Missing). There may be other fields on each record but these are ignored. The order of the fields doesn't matter. The Time Stamp Field must include a recognized Windows data/time value. A typical row might include:

3:40 am 3/5/2016 Flow Pump 3 34 Good

In Multiple values per row, there must be a field/column header with the signal name and there may be multiple fields in a single row. A typical first row and subsequent row may include:

Date/time Pressure Main St Flow Main St. Temperature Tank Level South

2 Oct 14 13:08.15 48.34 834.2 35 12

Within a Database source, there are two ways that time is used. The user selects these under Options. In "Historical", the values can be read for any time for which data are available. For "real time", only the most recent value is read and then, only if it is within the time tolerance specified by the user. This is used for importing initial conditions for starting a run or viewing the latest value that has been placed in the datasource file. The time is based on the clock in the computer running the model.

The "Time Tolerance" field is used because the time stamp on a SCADA signal may not correspond exactly to the time for which data are called for from the model. For example, the model may require a value at 5/16/2015 3:15:00 am but the closest value in the SCADA system may be 5/16/2015 3:13:25 am. If the difference is greater than the tolerance, no value is obtained. It is best to set a wide tolerance initially which can be reduced as higher quality information is required. If multiple values are available within the tolerance, the value closest to the required time is used.

To select which signals from the SCADA system are to be mapped to the SCADA signal element, the user picks "Select SCADA Signals" (see “OPC Select Signals Dialog”-628).

The units for an imported value are assumed to be the display units in the model. If there is a chance that the units may be different in the SCADA file than in the model, the user can override the units by selecting the units tab and entering the "Storage units".