Micromod Micro-PWC: 53PW6000 MicroPWC Operators Manual - Manual (Page 73)

Micro-PWC OPERATOR’S MANUAL
Trend Displays 59
6.1 Trend Display Format
A Trend Display consists of numerous parts, each of which is described in detail in the following para-
graphs. Briefly, the central area of the display is a Trend Graph containing colored traces which represent
up to eight trendable variables.
Above the Trend Graph are eight sets of three buttons each, one set per trace. These buttons are used to
manipulate individual traces or to replace the default range of the Trend Graph with the range for an indi-
vidual trace. Below the Trend Graph are additional buttons; these buttons, which include the
Compression, Zoom, Reset, Pause, and Segment buttons, affect all traces on the trend graph equally.
6.1.1 Trend Graph
The Trend Graph portion of theTrend Display occupies the lower two thirds of the Operator Window. Up to
eight process variables can be displayed graphically as traces plotted on the Trend Graph. The vertical
axis represents the percentage of display range, while the horizontal axis depicts the time base in minutes.
Each process variable is plotted on the graph in a different color.
Using the Trend Readout arrow (displayed at the top of the Trend Graph), the operator can point to any
display value of a process variable on the graph. See
Section 6.1.3, Trend Readout Arrow , for detailed
information on this item.
6.1.2 Time Base and Size of Display Window
The displayed time base of a trend display is separated into five sections, and is based on segment size.
Segment size is a user-configurable parameter, and is determined by the values entered to define the
number of SECONDS and the number of POINTS in a segment. The POINTS referred to here should not
be confused with the Historical Database point(s) for which values are being collected; rather, POINTS are
the values collected for the Historical Database point, which then become POINTS plotted as a trend trace.
(See the Micro-PWC Configuration Guide for details on trend configuration.) By default, the number of
POINTS and the number of SECONDS are both set to 60, and display as five 1 minute intervals (seg-
ments) on the Trend Graph.
The Micro-PWC locates the points which lie within each time interval. If one point is found, the value of the
point is used to plot it on the trend display. If more than one point exists within the interval, the assigned
Display Option (MINimum, MAXimum, AVeraGe, or INSTantaneous) is used to calculate one value from all
points which exist in the interval. This value is then plotted on the trend display. (If the INSTantaneous Dis-
play Option is used, the last value found will be used to plot the point on the Trend Graph.) The resulting
value is used to plot the point on the trend display. If no points are found in an interval, no point is plotted
for that interval.
This method of plotting trends permits greater flexibility in trend configuration. For example, points with dif-
ferent collection rates can be plotted on the same trend graph, and non- periodic data can also be trended.
6.1.3 Trend Readout Arrow
The Trend readout arrow enables the operator to determine the collection time and value at any point
where the arrow intersects with the horizontal axis of the graph. TheTrend Readout arrow is controlled by
the
L EFT A RROW and R IGHT A RROW buttons, which bracket the Time At Arrow button, located above the upper
✎ NOTE
The Zoom item on the Trend Display menu bar operates
independently of the Zoom button on the Trend Display itself, which
is described in
Section 6.1.13, Zoom/Unzoom Button . Operation of
the menu bar Zoom is identical to that of the Zoom item found on
graphic displays, as described in
Section 7.6, The Zoom Menu
Item .