Understand Synthetic or Logical valve types

The valve record represents a combination of status or multistate records, each of which is represented by a valve record. Synthetic types (Synthetic PLC-based and Synthetic AVEVA Enterprise SCADA Host-based) have an associated status or multistate to which commands can be issued, while the Logical type does not.

The position of a Programmable Logic Controller (PLC)-based synthetic valve is read from the underlying status or multistate point. The position of the Synthetic AVEVA Enterprise SCADA Host-based valve is calculated by the AVEVA Enterprise SCADA system from the position of the child valves that are associated with this synthetic valve. Both synthetic AVEVA Enterprise SCADA Host-based valves and PLC-based valves can be used as a parent valve for other valve types, including other Synthetic AVEVA Enterprise SCADA Host-based or PLC-based valves.

When a command is issued to either a Synthetic Host-based valve or a Synthetic PLC-based valve, the command is sent using the configured underlying status or multistate point, similar to Physical valves. For example, when a valve configured with an underlying status point has an OPEN command sent to it, then a single OPEN command will be sent to the underlying status point only. The OPEN command is not propagated to any valves that are configured as child valves. Regardless if the synthetic valve is configured as either a Host-based valve or a PLC-based valve, it is the PLCs responsibility to propagate the command to the appropriate child valves.

To configure the synthetic or logical type, it is necessary to define the connection type as Series or Parallel, depending on the relationship between the valve records. For more information, see Understand connection types. The valve will have one or more valve records (child records) referring to it as a parent record (field Parent Valve). If a child record is a synthetic or logical type, it will have further child valves.

Note: Any combination of series and parallel valves can be configured using these parent-child relationships.

If the valve is configured as a synthetic type, a reference to a status or multistate record must be set in the Path field of the valve record. Valve commands are forwarded to this record. If the valve is configured as Logical, the Path field is left blank.