About interpolated variables

An interpolated variable provides the ability to get interpolated stream values in between two good values, when some data samples have become bad or unavailable.

Background

The data streams in AVEVA™ Production Management advance the period of the data stream for as long as there is data available. Occasionally, the stream values become unavailable, or the quality of the stream values differs from good. Therefore, the interpolation variable exists to enable a means to create interpolated data. Interpolation provides a means to construct new samples within two good data samples.

Some guidelines

• Interpolation is done only on numeric values, for example, single, double, decimal.

• Interpolation is done only between two samples of good data quality, for example, Quality=Good.

• Samples with Quality=Bad or Quality=Uncertain are ignored in the calculations.

• The interpolation conditions are used to control the frequency of the interpolation.

• The interpolation variable has two streams: Samples and interpolated samples. The samples stream is the source stream that you want to interpolate, and is defined by the historical expression. The interpolated samples stream is the output stream after interpolation is performed on data samples.

Modes of interpolation

There are two modes of interpolation:

• Average - Provides an average between two values.

• Time weighted average - Instead of providing a constant flatline average between the two known points, the data is time-weighted to provide a gradual ascending line. This is the default mode for interpolation.

  

Related topics

• Data samples before and after interpolation

• Add and configure an interpolated variable

• Interpolated variable properties