PA-DIM
| Document | OPC 30081 |
|---|---|
| Version | 1.02.0 |
| Published | 2025-11-10 |
| Namespace | http://opcfoundation.org/UA/PADIM/ |
| Sector | Process automation |
PA-DIM is the Process Automation Device Information Model, the process-industry counterpart to DI. It standardises a vendor-neutral core set of device identification, signals and diagnostics for process instruments, and its distinguishing feature is semantic identifiers: nodes are tied to IRDI dictionary entries so meaning is machine-resolvable.
Where it sits in the stack
PA-DIM sits on DI and is aimed at process instrumentation rather than discrete machinery: flow meters, pressure and temperature transmitters, valve positioners. Where the machinery stack expresses meaning through type hierarchies, PA-DIM adds Part 19 dictionary references pointing at IRDI and eCl@ss identifiers, and ships its own IRDI dictionary namespace, http://opcfoundation.org/UA/Dictionary/IRDI, at the same 1.02.0 version. It coexists with FDI and IO-Link rather than replacing them.
The types that matter
| Type | What it carries |
|---|---|
PADIMType | The root object type applied to a process device, gathering the standardised identification, signal and diagnostic content that a PA-DIM client can rely on across vendors. |
SignalSetType | The container for the device's measurement signals, so a client finds them structurally instead of by vendor tag name. |
AnalogSignalType | One analog measurement with its engineering unit and range, which is the primary payload of a process instrument. |
DictionaryEntryType | The Part 19 base type for a dictionary entry. This is the mechanism that lets a node point at an external semantic definition rather than relying on its BrowseName. |
IrdiDictionaryEntryType | A dictionary entry identified by an IRDI, the identifier scheme used by IEC CDD and eCl@ss. This is what makes a PA-DIM pressure value resolvable to a standard concept. |
HasDictionaryEntry | The Part 19 reference type that links a node to its dictionary entry. Follow it to discover what a node means without asking the vendor. |
DeviceType | The DI base type PA-DIM devices are built on, which is why a PA-DIM server also loads Opc.Ua.Di.NodeSet2.xml. |
IVendorNameplateType | The DI identification interface PA-DIM reuses, providing manufacturer, model, serial number and revisions. |
Using it on a real machine
- Confirm the namespacesRead NamespaceArray for http://opcfoundation.org/UA/PADIM/, the DI URI, and the IRDI dictionary URI. A PA-DIM device without the dictionary namespace loses the semantic layer that is the point of the model.
- Read identification, then the signal setTake the nameplate first and store it with your data, then browse the signal set rather than hunting for value nodes across the device tree.
- Follow HasDictionaryEntry to establish meaningFor each signal, follow the dictionary reference and record the IRDI alongside the value. That identifier, not the BrowseName, is what makes two vendors' devices comparable in your historian.
- Keep units with valuesRead the engineering unit and range for each signal and persist the UNECE unit code with the samples. Process instruments are configured in the field and units get changed.
- Subscribe with deadbands and keep the statusUse a deadband appropriate to the process rather than the sensor's resolution, and store the StatusCode. Instrument values that arrive as Uncertain or Bad are common and must not be averaged into a KPI.
What it gives you for OEE
PA-DIM is a device model for process instruments and gives you no OEE terms: no machine state, no part counts, no downtime reasons. In a process plant OEE is usually replaced or supplemented by throughput, yield and utilisation, and PA-DIM's contribution there is trustworthy, semantically identified measurement: flows and masses you can integrate for yield, and instrument diagnostics that explain a measurement you should not trust. If you need discrete-style availability and counts, they come from the control system or from a machinery-side model, not from here. The genuine long-term value is the IRDI identifiers, because they let you build one analytics mapping that survives an instrument being replaced by a different manufacturer's device.
Gotchas
- Two nodesets, one version. PA-DIM 1.02.0 ships alongside its IRDI dictionary at 1.02.0; loading only the device model leaves the dictionary references dangling.
- The semantic layer is optional in practice. A device can be PA-DIM-shaped and carry no usable dictionary references, which quietly removes the reason you chose the model.
- PA-DIM standardises a core set, not everything a device does. Vendor-specific parameters remain vendor-specific, and expecting full device configuration through PA-DIM leads to a redesign toward FDI.
- Version 1.02.0 dates from November 2025. Installed instruments will be on earlier versions with different optional content.
Once the machine speaks a companion spec, the OEE mapping is portable across vendors, which is the point at which analytics stops being a per-machine project.
See Jemba →Last verified 7 September 2026 against OPC UA 1.05.07. Version and publication date read from the released nodeset. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.