Time and value deadbands for delta storage

To further decrease the resolution of tag values stored in delta mode, use a time deadband or a value deadband.

• A time deadband is the minimum time, in milliseconds, between stored values for a single tag. Any value changes that occur within the time deadband are not stored.

  This illustration shows an example of applying a time deadband:

  

  Data is stored for the time period starting with TS and ending with TE. All points in the graphic represent data values for a given tag over time. The grey areas represent the time deadband, which starts anew with every returned value. Only the green points (P2, P4, P7, P8, P9, P11) are stored. The other points are not stored because they fall within a deadband.

  The time deadband applies to delta storage only. A time deadband of 0 indicates that the system will store the value of the tag each time it changes.

• A value deadband is the percentage of the difference between the minimum and maximum engineering units for the tag. Any data values that change less than the specified deadband are not stored.

  This illustration shows an example of applying a value deadband:

  

  Data is stored for the time period starting with TS and ending with TE. All points in the graphic represent data values for a given tag over time. The grey areas represent the value deadband, which starts anew with every returned value. Only the green points (P2, P5, P6, P7, P10, P11) are stored. The other points are not stored because they fall within a deadband. P9 is not stored because P8 was discarded and it is within the percentage deviation.

  The value deadband applies to delta storage only. A value of 0 indicates that a value deadband will not be applied.