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5.6 Process Monitoring
The Loop and Overview screens provide the current process values of the MCT. In order to view the process
inputs over time, the MCT provides real-time charts. Eight user configurable trends are provided with up to
eight plot points per trend. In addition, MCT provides status monitors for all of the digital inputs and outputs of
the system. This allows an operator to keep track of all inputs and outputs of the control module.
5.6.1 Charts
The Chart screen is accessed from the home
“View” menu. The real-time charts can be configured to display
the process variable (PV), set point (SP) and percentage of output (%) of each control loop and the process
variable of monitor points over a selectable period of time. The vertical axis determines the range of displayed
data while the horizontal axis determines the history period. The maximum time period that can be shown in a
chart is 24 hours.
The rate at which the chart plots a new point is based on the time period to be shown. Each buffer can hold a
total of 720 readings for each of the selected channels to plot. The update rate can be calculated by the formula:
time period (in minutes) * 60 / 720. Note that for time periods less than 72 minutes, the update rate will be held
to a minimum of 6 seconds. Thus, the update rate will vary from a minimum of 6 seconds (for time periods of
72 minutes or less) up to a maximum of 120 seconds for 1440 minutes (24 hours).
The
Labels button allows the user to cycle through each of the configured plot channels to determine what
each colored plot represents as well as view the current value without having to return to the Control Monitor
or Overview screens. When both left and right vertical axis are shown on the trend, the label will append a left
axis indicator “<” or right axis indicator “>” to point to the axis the plot point is assigned to.
The charts also
allow you to “zoom in” on a particular area to have a more detailed look at current data. By
using your finger to select an area on the screen, the chart will zoom in on that area. To select a portion of the
plot, touch and hold the screen with your finger. Drag your finger across the graph and a box will be drawn
around the selected area. Removing your finger from the screen will cause the chart to redraw with only the
selected plot
area. To return to the normal view, touch the ‘X’ or ‘Y’ axis and select zoom out to return to the
previous zoom setting or zoom normal to return to the full display.
NOTE: When a chart is zoomed in, it will not update with new information. The chart must be in normal view
mode in order to update at each time interval. The chart will return to normal automatically when
selecting a different screen to view.
5.6.1.1 Chart Setup
To configure a chart, press
the “Set” button in the upper right corner of the display. The setup screen will be
shown. To assign channels to the chart, simply touch the on/off button for the desired items in the list to select