OPC Item
An item in an OPC UA Server
The OPC Item item type has the following properties:
| Name | Description | ID | Flags |
|---|---|---|---|
| DeadbandType | The monitoring deadband. Default = None. | 10550 | Persisted, Enumerated |
| DeadbandValue | The value of the monitoring deadband. Ignored when 'Deadband' is 'None'. | 10560 | Persisted |
| DiscardOldest | A boolean parameter that specifies the discard policy when the queue is full and a new notification is to be queued. It has the following values: True - the oldest (first) notification in the queue is discarded. The new notification is added to the end of the queue; False - the last notification added to the queue gets replaced by the new notification. Default = true. | 10530 | Persisted |
| ExcludeFromCatchup | If true, this item is excluded from catchup, ie. no historical data is read from the server, for this item, during the catchup process. | 10600 | Persisted |
| MonitoringMode | The monitoring mode parameter is used to enable and disable the sampling of a MonitoredItem, and also to provide for independently enabling and disabling the reporting of notifications. This capability allows a MonitoredItem to be configured to sample, sample and report, or neither. Default = Reporting. | 10500 | Persisted, Enumerated |
| MonitorState | The actual state of the monitored item. | 11030 | ReadOnly |
| Quality | Item quality - this tells you whether an item currently has a good or bad quality. It might be bad, for example, because it isn't connected or is set to the wrong type. | 3 | ReadOnly |
| QueueSize | The requested size of the "MonitoredItem" queue. Default = 1. | 10520 | Persisted |
| RevisedQueueSize | The actual queue size that the Server will use. | 11020 | ReadOnly |
| RevisedSamplingInterval | The actual sampling interval that the Server will use. This value is based on a number of factors, including capabilities of the underlying system. The Server shall always return a revisedSamplingInterval that is equal or higher than the requested samplingInterval. If the requested samplingInterval is higher than the maximum sampling interval supported by the Server, the maximum sampling interval is returned. | 11010 | ReadOnly |
| Rights | Item access rights - this property may be "read", or "read write". This means that the property may only be read from, or also can be written to. For OPC items, this written value will be passed on to the external items this item comes from. | 5 | ReadOnly |
| SamplingInterval | The interval that defines the fastest rate at which the MonitoredItem(s) should be accessed and evaluated. This interval is defined in milliseconds. The value 0 indicates that the Server should use the fastest practical rate. The value -1 indicates that the default sampling interval defined by the publishing interval of the subscription is requested. A different sampling interval is used if the publishing interval is not a supported sampling interval. Any negative number is interpreted as -1. Default = -1. | 10510 | Persisted |
| SrcUaNodeId | UA Node ID in source. | 5031 | Persisted |
| SrcUaNodeId-HA | UA Node ID in source, used for reading history, if the UA server has different nodeids for reading real-time data versus historical data. If empty, history reads defaults to using the 'SrcUaNodeId'.
| 10505 | Persistd |
| Time | The date and time when this item was last updated. | 4 | ReadOnly |
| Trigger | This property specifies the conditions under which a data change notification should be reported: Status: Report a notification ONLY if the StatusCode associated with the value changes; StatusOrValue: Report a notification if either the StatusCode or the value change. The Deadband filter can be used in addition for filtering value changes; StatusOrValueOrTimestamp: Report a notification if either StatusCode, value, or the SourceTimestamp changes. If a Deadband filter is specified, this trigger has the same behaviour as StatusOrValue. Default = StatusOrValueOrTimestamp. | 10540 | Persisted, Enumerated |
| Type | The item canonical data type - the specific type of this item. Whether it's an integer, string, date, etc. | 1 | ReadOnly |
| Value | The current value of the item. | 2 | NormalPage |
| Write as server datatype | If false, using current value datatype when writing this item to the server. If true, convert to datatype initially reported by server for this item, when writing to the server. | 10610 | Persisted, Expert |