|The OPC DA Client module for the Edge One™ platform implements and OPC Data Access client and provides a reliable, easy to configure interface to connect third party OPC DA Servers.|
The OPC Data Access Specification is the first of a group of specifications known as the OPC Classic Specifications. OPC Data Access is a group of client-server standards that provides specifications for communicating real-time data from data acquisition devices such as PLCs to display and interface devices like Human-Machine Interfaces (HMI), SCADA systems and also ERP/MES systems. The specifications focus on the continuous communication of data.
The OPC Data Access specification is also known as OPC DA. OPC DA deals only with real-time data and not historical data (for historical data you need to use OPC Historical Data Access, or OPC HDA) or events (for Alarms and Events you need to use OPC Alarms and Events, or OPC AE).
There are three attributes associated with OPC DA data. These are
- a value,
- the quality of the value, and
- a timestamp.
The OPC DA specification states that these three attributes have to be returned to an OPC client making a request. Therefore, if the data source is not capable of providing a timestamp, for example, the OPC DA server must create a timestamp.
The Edge One™ OPC DA client implements version 3.0 of the specification. It is important to note that backward compatibility is optional and not mandatory which means that there can be vendors that implement OPC DA servers that conform to one or two of the specifications, but not all. It is important to check with the server vendor, the version(s) that are actually supported.
The guides for the OPC DA Client are under development, and will be available by June 15, 2018. For any questions, please contact firstname.lastname@example.org.