Comparison of Analog Input Versus Analog Status Types
This is a legacy tag type. You are advised to use the I/O and Calculations Tag instead.
Use this legacy type only if you are certain that it contains unique features that are absolutely necessary to your work.
Analog Status and Analog Input tags are used for similar purposes. Both are used to monitor analog values and, with only one exception, the same widgets are available to each. Either could be used for the same PLC I/O address and when drawn on the screen, there is nothing to indicate which tag has been used.
A similar relationship exists between Digital Input and Digital Status tags.
A common question then is, "which type should I use?". The following comparison of features should help you choose. Any tag attribute not listed in the following table is the same for both.
| Analog Input | Analog Status |
|---|---|
| No built-in logger | Logger built in, logging on change |
| No deadband option | Deadband option - used to set a minimum change required before logging a new value. |
| No built-in alarm | High and low alarms built-in. |
| Does not support history reads | Supports history reads when used with drivers that have this feature. |
| Not drawn on VTScada Station Pages | Drawn on VTScada Station Pages |
| Does not include the "Draw" widget | Includes the "Draw" widget |
| Can be linked to an "Owner" tag. | Does not have the "Owner" option. |
The feature comparison shows that Analog Status tags have several advantages. There are more built-in features, reducing the need to use extra tags to provide logging and alarms. Analog Status tags also support history reads and are displayed on Station Pages. If you plan to use any of these features, then an Analog Status tag is probably your best choice.
Why then might you ever use an Analog Input tag? First, the dedicated Logging or Alarm tags that you add to an analog input will have more features and therefore more control than the built in logging and alarms of the Analog Status. Secondly, if you do not need the extra features of the Analog Status tag, the smaller Analog Input is a more efficient choice. Finally, for applications that have been coded to make use of tag aggregation, the Owner option of the Analog Input is an essential feature.
When you do add Analog Status tags to your application, there is one extremely important configuration option to remember: You should always set a value for the deadband. The automatic logging feature of these tags will add a new record each time the value changes, regardless of how small that change is. To avoid filling the log file with system noise, you should set the deadband to a small value, thus causing the tag to ignore any change less than this amount. For example, on a input that changes from 0 to 100, you might set the deadband between 0.1 and 1.
Analog Input tag reference. Analog Input Tags
Analog Status tag reference. Analog Status Tags
