PLC Programming

Sampling Trace
Display of the Sampling Trace
Sampling Trace of Differ ent Variables
If a trace buffer is loaded, then the values of all variables to be displayed will be read out and
displayed. If no scan frequency has been set, then the X axis will be inscribed with the continuous
number of the traced value. The status indicator of the trace window (first line) indicates whether the
trace buffer is full and when the trace is completed.
If a value for the scan frequency was specified, then the x axis will specify the time of the traced value.
The time is assigned to the "oldest" traced value. In the example, e.g., the values for the last 25
seconds are indicated.
The Y axis is inscribed with values in the appropriate data type. The scaling is laid out in a way that
allows the lowest and the highest value to fit in the viewing area. In the example, Var 0 has taken on
the lowest value of 6, and the highest value of 100: hence the setting of the scale at the left edge.
If the trigger requirement is met, then a vertical dotted line is displayed at the interface between the
values before and after the appearance of the trigger requirement.
A memory that has been read will be preserved until you change the project or leave the system.
'Extras' 'Cursor Mode'
The easiest way to set a cursor in the monitoring area is to click there with the left mouse button. A
cursor appears and can be moved by the mouse. At the top of the monitoring window the current x-
position of the cursor is displayed. In the fields next to 'Var 0', 'Var 1', ..., 'Var n' the value of the
respective variable is shown.
Another way is the command 'Extras' 'Cursor mode'. With this command two vertical lines will appear
in the Sampling Trace. First they are laying one on the other. One of the lines can be moved to the
right or to the left by the arrow keys. By pressing + or + the speed of the
movement can be increased by factor 10.
If additionally the key is pressed, the second line can be moved, showing the difference to the
first one.
'Extras' 'Multi Channel'
With this command you can alternate between single-channel and multi-channel display of the
Sampling Trace. In the event of a multi-channel display, there is a check (ü) in front of the menu item.
The multi-channel display has been preset. Here the display window is divided into as many as eight
display curves. For each curve the maximum and the minimum value are displayed at the edge.
In a single-channel display, all curves are displayed with the same scaling factor and are
superimposed. This can be useful when displaying curve abnormalities.
6-46 CoDeSys V2.3