Step

Enable the Step attribute to treat archived point values as discrete units that would appear stepped on a chart. An archived value is assumed constant until the next archived value, and adjacent archived values are not interpolated. For example:

• at 12:00:00, the value 101.0 is archived

• at 12:01:00, the value 102.0 is archived

• a request for the value at 12:00:30 returns 101.0

Disable Step to treat archived point values as a continuous signal, and linearly interpolate adjacent values. For example:

• at 12:00:00 the value 101.0 is archived

• at 12:01:00 the value 102.0 is archived

• a request for the value at 12:00:30 returns 101.5

  Note: By default, future PI points have their step attribute turned on (set to 1). This is because most future PI Points store discontinuous signals (for example, a series of discrete predictions) for which linear interpolation cannot be assumed. With the step attribute turned on, trends show a staircase pattern. Future PI points, by default, also have compression, excmin, excmax and excdev turned off (set to 0).

The Step attribute also affects compression calculations. When enabled, a linear change of value greater or equal to the compression deviation allows the point to pass compression.

The Step attribute is relevant only to numeric points. In general, data from continuous signals such as thermocouples and flow meters should be archived without stepping. Data from discrete measurements such as lab data and batch charge weight should be stepped.

To access the Step attribute setting:

1. Open PI SMT.

2. Navigate to Points > Point Builder.

3. Search for and select the point for which you would like to check the step attribute.

4. In the Archive tab, you can view/change the step attribute.