Windmill Software Ltd
Windows Engineering Software

March 2004

The Newsletter for PC-Based Data Acquisition and Control
Issue 68          March 2004
--------------------ISSN 1472-0221----------------------

Welcome to the March edition of Monitor.  This month 
we've the results of our survey, notes on dealing with 
alarms in Windmill and a discussion on some of the types 
of chart available in Excel.

We hope you find this issue useful, but should you wish 
to cancel your subscription please do so at

* Windmill News: The Survey Results
* Windmill Notes: Handling Alarms
* Excel Corner: Pie, Doughnut, Bubble and Surface Charts

Windmill News: The Survey Results

Our thanks once again if you returned our January
survey.  Your comments have made interesting reading and
prompted plenty of ideas for the future of Monitor.

After our announcement in the last issue that the
exhibitions section was to be scrapped, we received a
flurry of survey responses in favour of the listings.
We've therefore decided to reinstate them, but on a
quarterly basis.  In the space created we'll run a
series of notes on the Windmill programs.

We've examined your suggestions for topics you'd like to 
See discussed, and will endeavour to cover as many of
these as possible in future editions.

The most popular part of the newsletter was the accounts
of how Windmill was being used in the real-world.  To
include more of these application stories, however, we
need your help.  When people buy Windmill software, or
download it from the web, unless they have a problem we
normally don't hear from them again.  We therefore don't
know how they are using Windmill.  If you have found
Windmill software useful, and would be happy for us to
use your application as an example, please get in touch.
Fill in the form at
Meanwhile, you can find a list of previously covered
applications at

The Excel corner was a close runner-up in popularity.
If you have a question about using Excel with Windmill,
or a tip you'd like to share, let us know.  Previous
Excel notes are archived at

Windmill Notes: Handling Alarms

Windmill lets you set two alarm thresholds on each
measurement channel: a warning alarm and a critical
alarm.  When monitoring temperature for example, you
might specify a warning alarm when the reading rose
above 27 oC and a critical alarm when it exceeded 33 oC.
Alternatively, you could have a warning alarm when a
temperature fell below freezing and a critical alarm
when it rose above boiling.  Use the SetupIML program to
set alarm thresholds.

SetupIML also lets you set the level when the alarm is
to be cancelled.  In our first example above, you might
choose to keep the warning alarm in place until the
temperature returned to below 25 oC. This stops an alarm
continually being switched on and off if the temperature
is wavering around the alarm threshold.

You can choose to output a digital signal when a channel
goes into alarm.  With suitable hardware this lets you
turn on a light, sound a buzzer or activate an
autodialler to ring a telephone number with a pre-
programmed message.

Tip: Every alarm condition you define uses some memory
and requires processing time to continually check
whether the condition is true or false. To optimise
Windmill's performance, therefore, only enable alarms
where needed.


How the Windmill Programs Treat Alarms:
Display, Control, Logging and Telephoning

The Windmill Logger and DDE Panel programs show warning
alarms on a blue background and critical alarms on a red
background.  Windmill Chart shows alarm levels as tick
marks on its axis.  It can also show its traces in
different colours for no alarm, warning alarm and
critical alarm states.

When a channel goes into alarm, you might want a series 
of events to occur.  We've already
mentioned the digital switching, but with the optional
Windmill Test-Seq program you can perform much more
sophisticated control.

Test-Seq interprets a file of commands and controls the
other Windows programs, or data acquisition equipment,
accordingly. With Test-Seq, for example, you could
automatically log at different speeds depending on
whether channels are in alarm. Perhaps taking readings
every 10 seconds when there are no alarms and every
second when there is a channel in alarm. You could also:
- Pass control to another part of the test sequence when
  a specified alarm occurs
- Prioritise alarms
- Latch alarms so the alarm continues to be reported
  until Test-Seq instructs differently
- Wait until an alarm occurs before continuing with your
  test sequence program
- Wait until all alarms are cleared before continuing
  with your test sequence program

For more on Test-Seq see

Logging and Telephoning
Although the standard Windmill Logger program indicates
on screen when channels are in alarm, it doesn't save
any additional information about the alarm.  For this  
you need the Windmill Alarm Logger which records alarms,
and the action taken, in a file.

Whenever Alarm Logger finds a channel that is in alarm,
it pops into the foreground of the computer screen and
beeps. It can also alert you by playing an audio file
through a sound card, switching a digital switch
(buzzer, light, etc) or by telephoning an engineer.  
Alarm Logger software also lets you insert delays 
between an alarm being registered and an output
being switched - useful in reducing the instances of
false alarms.  If, say, the temperature of a freezer was
to momentarily rise when the freezer lid was opened; the
alarm would not activate unless the temperature remained
over the limit for a certain time.

You can tell Alarm Logger that you're aware of the alarm
and not to report it again until a set time has passed,
so acknowledging the alarm.  Operators are asked what
action they have taken on the alarm and their comments
are recorded.

It is easy to run Alarm Logger over an Ethernet 
network, as it actually consists of three
programs: a Setup, a Monitor and a Viewer. The Alarm
Setup configures the system, letting you set such things
as the time between alarm checks or an advisory message
to be displayed when a specific alarm occurs. The Alarm
Monitor watches the hardware for alarms. When the
Monitor flags an alarm, the Alarm Viewer tells engineers
about it.  The Setup, Monitor and Viewer programs can be
run on different computers around a network.

For more on Alarm Logger see

Excel Corner: Pie, Doughnut, Bubble and Surface Charts

Excel offers many different ways to chart data.  In
Issue 34 of Monitor we discussed Stock, Column, Bar,
Line and xy Scatter charts, and their suitability for
data acquisition applications. Today we cover some more
chart types with tips on their strengths and weaknesses.
For illustrations of these and other Excel chart types
see the Microsoft site:

Pie Charts
  A pie chart shows data from one row or column of data.
  They are good for comparing quantities, letting you see
  at a glance the relation of each item to the whole.
  They are also valuable when you want to emphasize the
  importance of one measurement compared to the rest.

  If you were monitoring electricity meters at four
  locations, a pie chart showing the percentage
  contribution of each to the total consumption might be a
  good choice.  However, the more values you include the
  more difficult it becomes to compare data, and the more
  unsuitable a pie chart becomes.  It is much easier to
  examine values that are numerically close with a bar or
  column chart.

Doughnut Chart
  A doughnut chart is like a pie chart but can contain
  more than one data series.  It has the same drawbacks as
  a pie chart, but the extra data series make it even more
  difficult to interpret easily.  I've yet to see a set of
  data collected by Windmill that couldn't be better 
  represented by another choice of chart.

Bubble Charts
  Bubble charts are similar to xy scatter charts.  In
  scatter charts you plot two variables against one
  another.  For example, you might plot latitude on the x
  axis against longitude on the y axis.  With a bubble
  chart, three variables are represented.  Each data point
  has two values, as in the scatter chart, but is shown as
  a bubble rather than a point.  The size of the bubble
  indicates the value of a third variable.
  Suppose, for example, you were a train operator trying
  to find out on which parts of the track the train wheels
  were slipping.  A device in the train logs latitude,
  longitude and the duration of the train's wheel
  slippage.  In Excel you plot latitude against longitude
  and show wheel slippage duration as the bubbles.  The
  largest bubbles show where the problem is the greatest.

Surface Charts
  A surface chart is a 3-dimensional graph which is good
  for showing the relationship between three variables.
  It looks like a topographic map with colours showing
  areas that have similar values.  For example, the
  strength of a material decreases with time and increases
  with temperature.  A surface chart would let you quickly
  see the combinations of temperatures and time that
  produce the same strain results.

  However, Excel's surface charts are not true 3D scatter
  charts. Excel treats the x and y values as categories
  and thus expects a grid of data. If you were comparing
  rainfall in different areas during different months, for
  example, you would have a grid like this (you need to
  set your e-mail viewer to courier font to get it to
  display correctly)
        Area1  Area2  Area3
  Jan   106.3  152    88.9
  Feb   130.5  70.3   82.3
  For a true 3D chart forget Excel and choose an analysis
  package like FAMOS.

Further Reading
Microsoft's Examples of Excel Chart Types

Our Excel Charting Tips

* Copyright Windmill Software Ltd
* Reprinting permitted with this notice included
* For more articles see

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Windmill Software Ltd, PO Box 58, North District Office,
Manchester, M8 8QR, UK
Telephone: +44 (0)161 833 2782
Facsimile: +44 (0)161 833 2190
E-mail: [email protected]


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