Danfoss MCO 305 Design Manual page 128

MCO 305 Design Guide
Interpolation
Data are recorded for a curve as a series of discrete sample points. This setting specifies how the
Oscilloscope will interpolate values between the actual sample points. The settings are illustrated below:
Typically, the choice of interpolation depends on the type of value being recorded. For example, any sort of
"state" value will normally be displayed using Values since states are usually discrete in nature (i.e. they are
one value or another and never have "in between" values). Values that are continuous in nature, such as
position, velocity, etc., will normally be displayed using Lines.
Spline interpolation should only be used in very exceptional cases where a curve contains only a very
limited number of sample points and is specifically intended to represent a spline (e.g. CAM Editor curves).
In general, Spline should not be used when doing normal time-based sampling of data values.
NB!:
This setting may override the Display setting for some columns in the "Curve Selection List". If
Values is selected, then the values in the "Curve Selection List" will be displayed according to the
Display setting. However, if Lines or Spline is selected, then the values for the mouse position
column and all the cursor columns will be interpolated values and will be displayed as Decimal regardless of
the Display setting.
Enable scaling
For convenience, values recorded from the controller can be scaled in the Oscilloscope. For example, the
user might want a value that is recorded in millimeters to be displayed in centimeters. This affects both the
curve in the Chart Window and the displayed values in the "Curve Selection List". Two choices of scaling
algorithms are available:
"(y-offset)*scale" and "(y*scale)-offset". Usually, one or the other will be more natural in any particular
application. In the millimeter-to-centimeter example, Offset would be set to 0 and Scale would be set to
0.1.
Enable range validation
Often, it is useful to know if a curve value has gone "out of bounds". This can be done by enabling range
validation and setting the low and high bounds of the valid range of values. Any value that is not within the
valid range will then be displayed in the "Curve Selection List" with a red background.
Note that if only one bound is appropriate, then the
other bound can be left blank. An example is shown
below where the maximum value for the second
curve has been set to 4900.
Smoothing width
In some cases, measured values can contain a certain amount of "jitter" (i.e. oscillations that are fast,
somewhat random, and usually small). This can be distracting in the chart. An example is shown below.
Setting Smoothing width will reduce the appearance of this jitter by averaging the values of adjacent
sample points.
Note that this is visual in the Oscilloscope only; it does NOT affect any of the actual values in the controller.
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