Omron NT - SUPPORT TOOL FOR WINDOWS V4 Operation Manual page 260

Graphs
If the 100% value, 0% value, and –100% value are set using numeral memory
table entries as indicated below, the percentage value of the reference value is
calculated according to the value stored at the specified address.
S The data logging function and background function can be used with the NT21,
NT31, NT31C, NT631, and NT631C.
Data logging function
The data logging function records the values used for display at a PT.
Usually, the data collected in sampling for display in a trend graph are not re-
corded internally. If you use the data logging function, the data are logged and
can be displayed by tracing them back.
The data logging function can be executed for up to 8 kinds of data.
Background function
The background function continues data sampling even when a trend graph is
not displayed.
With a trend graph, data sampling is executed only when a trend graph is dis-
played and stops when the screen is switched from the trend graph screen.
However, if the background function is used, data sampling can be continued
in the background mode (while the trend graph is not displayed). The data
sampled and logged when in background mode can be displayed by tracing
back to the past.
The background function is valid only when it is used with the data logging
function; when the background function is used, the objective data is continu-
ously recorded. Please note that since data sampling is executed continuously
if the background function is used, the processing speed at a PT may be a little
slow.
S How the data recording is changed depending on whether or not the data log-
ging function and the background function are used is shown below. Regard-
less of the use of these functions, the trend graph element always starts draw-
ing a graph from the initial state when the screen is changed to the trend graph
display screen.
<Without logging and background functions>
Switching
the screen
Trend graph screen
Returning
Other screen Trend graph screen
(starts drawing a graph newly)
Data not logged
Section 6-9
Numeral memory
table
0
1
3000
2
0
3
–2000
4
5
247