Step attribute in PI points

The Step attribute applies only to numeric PI points. It controls how PI handles the data between archived events.

• When Step OFF (0), values are treated as a continuous signal. Data Archive fills in values by assuming a steady rate of change between events, a process known as interpolation.

• When Step ON (1), values are treated as discrete. No interpolation occurs; the value remains constant until the next archived event.

  Note: For non-numeric point types (Digital, String, Timestamp), Step is always On (1).

How Step attributes affect data between events

Suppose the following values are archived:

• At 12:00:00, the value 101.0 is archived.

• At 12:01:00, the value 102.0 is archived.

If you request for 12:00:30, here's what Data Archive returns:

• Step OFF (0): The value is estimated between using interpolation and returns 101.5.

• Step ON (1): The last values is held until the next event and returns 101.0.

When to use Step ON or Off

• Step OFF (0): Use for continuous signals, which are values that changes smoothly over time. For example, thermocouples, and flow meters.

• Step ON (1): Use for discrete data, which are values that change at specific times. For example, lab samples, and batch charge weight.

  Note:The default behavior is step OFF (0).

Impact on compression

• Step = 1: Compression testing is not applied. Instead, the system archives new values only if the absolute difference from the last archived value exceeds CompDev.

• Step = 0: Standard compression applies, interpolating values between valid numeric events.

  Note: Compression maximum and minimum limits work the same as for points with the step flag not set.

For more information, see Compressing.

How to enable or disable the Step attribute

To change the Step attribute for a PI point:

1. Open PI System Management Tools (PI SMT).

2. Navigate to Points > Point Builder.

3. Select the specific PI point you want to modify.

4. In the Classic or Extended tab, locate the Step attribute.

5. Set Step to 0 (OFF) or 1 (ON).

6. Select Save.

Alternatively, use PowerShell or PI Config:

• PowerShell:

  Set-PIPointAttribute -Server <PIServerName> -PointName <PointName> -AttributeName "step" -Value 1

• PI Config:

  @table pipt

  edit <PointName>

  step=1