The Word Data Point Tag
represents a 16-bit unsigned integer data tag with a range of 0 to 65535.
The Word Data Point Tag supports the configuration properties of the Data Point Tag plus these properties:
Property | Type | Version | Description |
---|---|---|---|
DisplayFormat | WSTRING | 3.73 |
The format used to display the tag's value. This property defines how the value of the tag appears in:
|
NormalColor | STRING | 3.1 | The value of the Color property when the tag is good quality. See Color Values for the different ways you can configure a color. This property supports the color value 'Auto', which selects a contrast color to the current theme background color. |
Units | WSTRING | 3.68 | The unit of measurement of the tag, for example: Meter Pulse Count. |
HistoricEnable | BOOL | 2.5 | Whether the value of the tag is stored in the Data Historian. |
HistoricDataSource | USINT | 3.59 |
The source of historical data. Three options are available:
|
HistoricOriginFilter | USINT | 3.73 |
A filter to choose which data is stored in the historian based on the data origin. Three options are available:
|
HistoricSampleInterval | TIME | 2.5 | The preferred maximum time interval between consecutive values recorded in the history. For information on how this configuration property works, see HistoricSampleInterval Property below. |
HistoricSampleCount | UDINT | 2.5 | The number of samples to retain in the Data Historian. Each historical record requires 14 bytes disk storage. To work out how much disk storage is required for historical data, multiply HistoricSampleCount by 14. |
HistoricSignificantChange | UINT | 2.5 |
The amount the tag value must change before a new value is stored in the historian.
Available only if:
|
HistoricListRecordLimit | UDINT | 3.30 | The number of records to show, when selecting Show Historic Data on the Standard Tag Menu. This value provides the row-count parameter to the FETCH FIRST clause for the SQL command. If HistoricListRecordLimit is set to less than 1, the driver rounds the value up to 1. Using very large values may cause the Show Historic Data command to take a long time to complete. |
TemporaryTrendInterval | TIME | 3.30 | The default time interval of the X Axis in a Temporary Plot of this tag. Values less than 5 minutes are automatically rounded up to 5 minutes by the driver. |
The HistoricDataSource property defines where historical data samples are taken from. There are three options:
Option | Description |
---|---|
Filtered tag value |
The historic samples are taken from the data point tag value after change filtering.
Only significant changes to the data point tag value are stored in the historian.
This is the best option for real measurements. |
Raw tag value |
The historic data samples are taken directly from the data point tag value.
Each update to the tag will create a new historical record.
This option can generate a large amount of historical data.
For example:
|
Write Commands |
The historical samples are taken from write commands to the data point tag.
Each write command will create a new historical record.
This option can generate a large amount of historical data.
For example:
This is the best option for manually entered data. |
A filter to choose which data is stored in the historian based on the data origin. Three options are available:
Option | Description |
---|---|
All data | All data is stored. |
Timestamped data | Only data timestamped at source is stored. |
Sampled data | Only data sampled by Fernhill SCADA is stored. |
The default value of HistoricOriginFilter is All data.
Most data sources provide either Timestamped data or Sampled data data but not both. You should only consider using this configuration property if:
For most applications you should use the default of All data.
The HistoricOriginFilter property is available when:
The HistoricSignificantChange property is used to filter out similar values from the historian.
When a new value is obtained from the data source the new value is compared with the previous value stored in the history:
The effect of filtering out similar data values is shown in this diagram:
The value you choose for HistoricSignificantChange can affect:
For best results, try to set HistoricSignificantChange just above the noise level in the data source.
The HistoricSignificantChange property is available when:
The HistoricSampleInterval property adds extra samples to the history when a data point tag value does not change for a long period of time. The extra samples give confidence in the historical data when the source value is constant.
When a new value is obtained from the data source, a new record is added to the history if:
The effect of adding extra samples is shown in this diagram:
Note: To be effective, HistoricSampleInterval should longer than the interval between new samples from the data source.
The HistoricSampleInterval property is available when:
The Word Data Point Tag supports the data properties of the Data Point Tag plus these properties:
Property | Type | Description |
---|---|---|
Value | UINT | The current value of the tag |
Color | DWORD | Indicates the state of the tag using color |
UpdateReason | USINT | A code to indicate the reason for the last update to the tag. |
IsForced | BOOL | Indicates whether the tag has been forced (true), or not forced (false) |
UnforcedValue | UINT | The current value of the tag when this tag has been forced to a fixed value |
UnforcedQuality | INT | The quality of the current value when this tag has been forced to a fixed value |
UnforcedTimestamp | DATE_AND_TIME | The timestamp of the last update when this tag has been forced to a fixed value |
UnforcedColor | DWORD | The color of the tag when this tag has been forced to a fixed value |
UnforcedUpdateReason | USINT | A code to indicate the reason for the last update to the tag when the tag is forced to a fix value. |
TagErrorCode | USINT | The status of the last update to the tag. A non-zero value indicates an error. |
DataSourceError | UDINT | A data source specific error code. |
The Color property provides an indication of the state of the tag using color:
Tag State | Condition | Color Value |
---|---|---|
The tag is forced | IsForced = True | The ForcedColor defined in the Database Root Tag |
The quality is bad | Quality < 192 | The BadQualityColor defined in the Database Root Tag |
Otherwise | The NormalColor defined above. |
The UpdateReason and UnforcedUpdateReason properties give a reason for the most recent update to the Word Data Point Tag:
Value | Description |
---|---|
0 | None: No update has been stored in the tag. |
1 | Forced Value: The data point tag is set to a fixed value. |
2 | Configuration error: There is an error in the configuration. |
4 | Scanned value: The value originates from an external source. The timestamp is provided by Fernhill SCADA. |
5 | Logged value: The value originates from an external source. The timestamp is provided by the external source. |
6 | Loaded value: The value was loaded from the last saved state of the tag database. |
7 | Initial value: The value was set by the initial value configuration. |
8 | WriteValue tag command: The value was set by the WriteValue Tag Command. |
9 | WriteValueQuality tag command: The value was set by the WriteValueQuality Tag Command. |
11 | Calculated value: The value is the result of a calculation. |
12 | Randomly generated value: The value is randomly generated. |
13 | Device state change: A device state change caused a change of quality. |
14 | Offline tag update: The value is an update to the tag when the data source is offline. |
When the tag is forced to a fixed value: UpdateReason will be Forced value (1) and the actual update reason is stored in UnforcedUpdateReason.
When the Quality of the tag data is 'Bad', the TagErrorCode property indicates the reason for the error:
ErrorCode | Description |
---|---|
0 | No error. |
1 | The tag is not associated with a valid data source. |
2 | The data source reference is valid, but the data source has a configuration error. |
3 | The offset of the tag is outside the boundary of the data source. |
4 | The data type is String, but the source value is not a valid word. |
5 | There was an error converting the data. |
A tag command is an action you can trigger on a tag. The Word Data Point Tag supports these tag commands:
Tag Command | Version | Description |
---|---|---|
ForceValue | 1.2 | Overrides the tag to show a fixed constant value. If the tag value is from a data source, updates from the data source are placed in a set-aside area. Note: The override is applied to the tag in the Fernhill SCADA database, and not to the data source. |
RemoveForce | 1.2 | Removes any override currently active on the tag. The actual value from the data source is restored from the set-aside area. If there is no override currently active, RemoveForce has no effect. |
The Word Data Point Tag builds on the features of these tag types:
The Word Data Point Tag is used as a building block for these tag types:
To learn about properties common to all tags.
Data Point TagTo learn about other types of data tag.
For the meaning of terms used in Fernhill SCADA.