Welcome back to our series of “What is High Performance HMI?”.
In the previous installments, we covered the current state of HMI’s
and justification of change to High Performance HMI
as well as the Fundamentals of High Performance HMI
and High Performance HMI standards.
In this installment of the series,
we are going to talk about the basic principles of High Performance HMI
and the Development of High Performance HMI.
If you need HMIs for your projects,
you can easily order them online from the RealPars marketplace.
Just head on over to marketplace.realpars.com.
You can find the link to this website in the video description.
When developing a High Performance HMI,
one of the main principles is the use of moving analog indicators
with a moving pointer instead of only a numerical display.
The analog indicators display the span of the instrument being displayed,
and in that range will be an indicator of the normal process limits.
Above and below the indicator
will be white bands indicating abnormally high
and low process values respectively.
Above and below the white bands
are dark gray bands
which indicate High High and Low Low process values.
At a quick glance of a second or two,
the operator will see the pointer position
and will be able to determine the operating status of the process
and be able to move on to the next process.
A High Performance HMI uses another very powerful and useful tool
which is the use of trends.
Making trends available in all HMI applications is important,
but in High Performance HMI,
making access to trend data should be a top priority in your design.
Remember, a High Performance HMI is designed for the operator,
and all available information should be easy to access for every operator.
When developing trends for display,
they should be implemented with certain characteristics and capabilities.
For instance, when a trend graphic is called by an operator,
the Y-axis of the trend should be automatically ranged
to a predetermined scale which is often not the full scale of the value.
Having a tight scale
will make any meaningful change immediately detected by the operator.
The trend screen should give the operator the capability
to alter the timebase and ranges without the requirement of keystrokes,
making use of dragging the cursor to rerange.
The proper use of color in a High Performance HMI
is fundamental to its design.
In many industrial HMIs,
color was improperly used or overused.
In a High Performance HMI,
color is strategically used and applied consistently across the entire project.
Starting with the background color,
a High Performance HMI utilizes a light gray.
The use of light gray will address the problems
with glare, contrast, color interference, and operator fatigue.
Generally speaking,
the ideal background color is “Gray 3” or “Gray 4”.
Foreground colors should be kept to a minimum and used sparingly.
For instance, process lines and tanks should be black,
with more attention on line thickness.
Color should not be used to indicate process material,
such as using white for steam,
green for demineralized water,
and pale blue for ethylene.
Using color to depict processes usually cannot be consistently applied in practice
and proves to be a distraction.
Remember, the use of color in High Performance HMI
is to indicate an abnormal situation,
and is meant to draw the operator’s attention quickly.
If the process is running normally,
then the screen should display little or no color at all.
When creating lines, vessels, and static equipment
it is important to show them correctly.
For instance, process line should be dark gray or black,
with line thickness or weight used to differentiate their significance.
The main process lines should be 3 pixels in width
and secondary lines should be 1 pixel in width.
The use of arrows to depict process flow direction should be kept to a minimum,
and primarily used where lines intersect or tee off from each other.
When you are using different line styles
such as solid, dotted, and dashed,
they should be limited to a maximum of three styles
with the same line thickness.
Process vessels should be depicted in two dimensional and not three.
The vessel exterior should be outlined in a thin black or dark gray line
and the vessel interior should be shaded without gradients
and should be uniform in color.
You can depict an overall vessel shape,
but not get into too much detail.
The vessel size should be relative
and in proportion to the other vessels around it.
Any internal components of a vessel should not be animated
and there should not be any cut-away drawings showing vessel internals.
The process flow is very important
when it is depicted on High Performance HMI.
The process flow should be consistent in layout across all screens
of a High Performance HMI.
General considerations for process flow
are that it should flow from left to right,
vapors should flow up and liquids should flow down.
In some instances,
pumps and compressors can affect the depiction of vapor and liquid flow.
Process lines should enter and exit the screen consistently as well.
Entry and exit points are also navigation targets
and should be shown as a different object
than a non navigation link label.
Static text on displays should be minimized,
but not eliminated.
Some general rules for displayed static text are
that the text should be dark gray
and a simple font that is easily displayed on an LCD screen.
When you are using abbreviations,
the abbreviations must be consistent across the entire project.
Use larger text to identify duplicated equipment
like multiple pumps,
and when you have isolated words, titles, and equipment designations
the text should be in all uppercase form.
Live data should be depicted differently than static text.
The use of a bold dark blue for live data
is a good choice against the gray background
and the dark gray static text.
If live data is shown in a table,
align the numbers on the decimal point
and do not display leading zeros.
When required, the units of measurement are displayed in lower contrast
and adjacent to the live data value.
While there are more details in developing a High Performance HMI,
the information we presented here should give you a very good idea
of how a High Performance HMI should look
and how it gives information to the operators.
By following these guidelines,
you will be more efficient and productive in your design,
and give the operators the best information available to them.
Ok…let’s review what we have learned in this video:
Use analog indicators with a moving pointer instead of a numerical display
Access to trend data should be a top priority in your design
Grayscale is preferred over multiple colors
Screens should display correct process flow, left to right
Text should be consistent across the entire HMI project
Line weight or thickness is more important than color
Thank you for watching,
and be sure to look for Part 4,
Detailed Design Principles of High Performance Displays.
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