Rockwell Automation FactoryTalk View Machine Edition Users Guide - Manual (Page 436)

F ACTORY T ALK V IEW M ACHINE E DITION U SER ’ S G UIDE
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How to use bar graphs, gauges, and scales
Bar graphs and gauges show graphical representations of numeric values. The scale is
used with bar graphs to indicate the range of values for the bar graph.
Bar graphs make it easy to compare values
Bar graphs show numeric values in bar graph format. They are useful for allowing
comparisons between multiple values, or for representing the fill levels of tanks for which
a reading on a vertical scale is appropriate.
For example, one bar graph can show the required level of a tank, and a second bar graph
can show the actual level of the tank. The first graph can change to represent the required
level for a particular application, and the second graph changes as the actual level in the
tank rises or drops.
Bar graphs are more useful than numeric displays when it’s important for the operator to
analyze the relationships between numeric values. It’s easier for the operator to see that
one graph is at a lower level than the other, or that one’s fill is blue and the other’s is
yellow, than it is to subtract one numeric value from another.
Thresholds change a bar graph’s fill color
As it fills, a bar graph can change its fill color to help an operator recognize abnormal
conditions. The change in color happens when the tag (or expression) value crosses a
threshold you set up for the graph. For example:
 If the temperature of an oven is lower than required for a recipe, the bar graph can
show the temperature in blue.
 If the temperature is in the correct range for the recipe, the bar graph can show the
temperature in green.
 If the temperature is higher than the recipe allows, the bar graph can show the
temperature in red.
If you want to use a different fill color on a bar graph to show abnormal conditions, make
sure enough of the new fill color is visible when the abnormal condition occurs that the
operator can see the condition.
Use bar graphs with scales to show limits
Unlike gauges, bar graphs do not have integrated scales. You can show values on a bar
graph using a scale graphic object and text.
Scales consist of major ticks, represented by long lines, and minor ticks, represented by
short lines. To indicate the values of major or minor ticks, use text objects.