L-VIS User Manual
112
LOYTEC
Version 6.2
LOYTEC electronics GmbH
Scale Labels:
Enables drawing of scale labels. Note that scale labels should
always be enabled for controls which have the
Y-Scaling
option set.
On the right side, the
Time Axis
is configured. Note that some of these options only apply
for data points trended locally by the control while other options apply also for display of
external trend data.
Time Span:
Select a suitable time span for the initial zoom setting, given in time
per page. For example, if you set this to one hour per page, the graph will show
the values of the last hour together on one page. For internal trends, this setting
will also define the interval at which trend data is recorded. For example, if the
control is 200 pixels wide, a time span of 100 minutes will cause the control to
record new data once every 30 seconds since one pixel represents a time span of
30 seconds in this case. For externally recorded data, this setting only defines the
default zoom level of the time axis.
History Buffer:
To keep data which is not visible on the first page because it is
older than the given time span, set the desired amount of history buffer. This
value is given in pages, that is, if you set the time span to one day and configure
one history page, the control will store the values of the last two days. Older data
will be overwritten by new data. For external trend data, this setting has no effect
since no data is recorded locally.
NOTE:
For trend controls which are recording trend data locally, the memory requirements can
become significant if you use a larger number of such controls and set a high number of
history pages. Check the project statistics for more information. In case the control is used
to display the contents of a trend data point (local or remote), it only fetches data from the
trend service and does not record any data by itself. The control will keep a small amount
of data records cached in local memory for faster operation, but the configured size of the
history buffer has no influence in this case.
Shift Interval:
The control normally uses the smallest usable shift interval,
which is the time it takes for the graph to move by one pixel. The graph cannot
be shifted earlier than this, because it needs to move by at least one pixel (can’t
move by half a pixel). If this interval seems unnecessarily small (each shift will
require some processing time), or trend data is recorded locally and you want the
control to average data over a longer time frame without changing the default
time span, you may set a minimum time here. The control will then use the next
higher shift interval which results in an integral shift of the graph (in pixels).
Tick Marks:
Enables drawing of tick marks for the time axis.
Scale Labels:
Enables drawing of scale labels. Note that scale labels should
always be enabled for controls which have the
Absolute Time
option set.
Absolute Time:
Draw absolute date and time on the X axis. Especially if the grid
is enabled, this will require more processing time since the entire grid and the X-
axis scale need to move, but usually absolute time is the preferred setting.
Time Format:
Format string used to display time labels on the time axis. See
section 15.7.2 for a complete explanation of this format. The default is usually a
good choice. Time labels are displayed only when there is more than one label
for one day. Otherwise, time labels will not be used.
Date Format:
Format string used to display date labels on the time axis. Date
labels are shown at midnight of each day which has a label drawn. If the user
zooms out further, date labels will be shown only for every other day, every start
of the week, or every month, as space allows.
