DsTrendCurve

Fig Trend configured with DsTrendCurve

The DsTrendCurve object store trends with external buffer objects, where the size of the
Buffer objects limits the number of samples that can be stored. A CricBuff100k object, as
in the example below, can contain 25000 samples. The storing can be done with scantimes
down to 20 ms. There are also a snapshot function where the current trend is frozen and
displayed in a curve window where it can be analyzed in detail. The snapshot curve can be
stored to files and opened at a later occasion.

The trend is configured with a DsTrendCure object. Up to 10 different attributes that is
to be stored, can specified in the Attribute array. For each attribute, a buffer object of
type CircBuffer is created and stated in the Buffer attribute. The size of the buffer object
should be adapted to the number of samples in the trend. Also a time buffer can be stated,
but this is only necessary if the snapshot function is to be used. The time resolution
determines the size fo the time buffer. For a resolution of 1 s, 4 bytes per sample is
used, and for a resolution of 1 ns 8 bytes is needed.

Fig Configuration of DsTrendCurve with buffer objects

Fig Configuration of DsTrendCurve

Snapshot means that you take a copy of the data, and display it in a separate window. You
can configure the trend to show only a limited part of the stored data and that data is
stored for a longer period of time, and also with higher resolution. In the snapshot window
it is then possible to go further back in time or to zoom in and increase the resolution of
the curve.

The attributes DisplayTime and DisplayResolution in the DsTrendCurve object is used to
specify the part of the data that is displayed in the trend window. In the example above
the total storage time is 500 s, while only the last 20 s (DisplayTime) is shown in the
trend window. DisplayResolution is set to 4, which states that every forth sample is
displayed. As the scan time is 20 ms a value i shown every 80 ms, and to totally
20 s/0.08 s = 250 samples is viewed. The total data contains 500 s/0.02 s = 25000 samples
that thus are available in the snapshot window.

See also DsTrendCurve in Object Reference Manual.