Windmill Software Ltd
Windows Engineering Software

July 2006

The Newsletter for PC-Based Data Acquisition and Control
Issue 96           July 2006
--------------------ISSN 1472-0221----------------------

Welcome to the latest issue of Monitor. We hope you enjoy 
it, but should you wish to cancel your subscription you 
can do so at

* Windmill Notes: Charting Data
* Why and When to Calibrate Instruments
* DAQ News Roundup

Windmill Notes: Charting Data

When you download the free Windmill package, or buy 
Version 6 of the software, you will find a 
charting program included in the bundle. This is 
called "Windmill Chart".

Chart handles many types of input channel, from many 
types of devices and sensors, including: thermocouples, 
pressure transducers, digital switches, flow meters and 
almost any laboratory instrument with an RS232 port.

To use Chart you just select up to 8 channels of data 
then click the Start button. If you need to see more 
than 8 channels, just start another instance of Chart.

You can chart the same channel in two Chart windows, 
each running at different speeds.  This lets you 
see a detailed short term view in one while the other 
tracks a long term trend.  When doing this it often 
helps to change the title of the Chart window from 
"Windmill Chart" to something more descriptive.  
To do this stop the chart then select Display from 
the menu bar.

Chart's Print option only lets you print a static 
chart. However, if you want a copy of a moving 
chart just Press Alt + PrintScreen.  This will 
copy the chart to the clipboard from where you 
can paste it into your document or spreadsheet.

There are various styles of chart: separated or 
super-imposed traces; grid-lines on or off; choice 
of pen colour for each channel; black or white 
background; alarm indication; and so on.  You set 
these from Chart's Display menu.

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.

Other Windows applications can send commands to Chart 
by means of Dynamic Data Exchange (DDE). For example, 
you could use Excel or a Visual Basic program to start, 
stop and print the chart.  See Chart's Help file for 
the full list of commands it understands and 
information on dynamic data exchange.  You can download 
the latest versions of the Help file from

Chart shows a continuously updating graph of live 
data against time.  If you want to replay previously
logged data as a moving chart you need the Windmill 
Replay program. This will re-run the data and lets 
you fast-forward, rewind and zoom in and out. It also 
display a table of data that, when you double-click 
a point on the chart, shows you the exact 
value of that point. For more on Replay see

For more on Windmill Chart and the other 
Windmill software see
If you prefer to use Excel to chart your data see

Why and When to Calibrate Instruments

Measurement and control devices are sold tested and 
calibrated to international standards.  Over time, 
though, they will lose their accuracy and measurements 
will "drift".  

Drift is a slow variation of a performance characteristic 
such as gain.  

Drift is due to component ageing or environmental changes: 
for example changes in temperature or humidity. It is 
especially significant when you are measuring low-level 
signals (a few microvolts) over long periods of time, or 
in difficult environmental conditions. 

The way to deal with drift is to re-calibrate the 
instrument periodically.  Calibration compares the 
instrument's actual performance to an accuracy standard. 
To do this you may need to return the instrument to the 
manufacturer or receive an on-site visit from them.  
You will then receive a calibration certificate which 
will be valid until the next recommended calibration 
date, often a year later.  The higher the accuracy 
required, the more frequently the instrument will 
need to be calibrated.

Some instruments are able to re-calibrate themselves 
periodically. They measure a reference voltage and 
compensate for offset and gain drifts.  An offset 
drift results in a reading other than zero, for a zero 
condition.  Self-calibration is useful for long term 
monitoring since drifts do not accumulate. You need 
to be careful not to set the re-calibrations too far 
apart as this can lead to small discontinuities in the 
recorded data as the re-calibrations occur. 

Further Reading

Issue 95 of Monitor, Choosing the Right Range and 

Data Acquisition Glossary

DAQ News Roundup

Welcome to our roundup of the latest findings in 
data acquisition and control.  

If you would like to receive more timely DAQ news updates 
then grab our RSS newsfeed at  Read for 
information how.

Tiny radio chip can store video clips
   A memory device the smaller than a grain of rice 
   has been developed by Hewlett Packard Labs.  Called 
   the Memory Spot, the chip makes it possible to attach 
   digital information to any surface, object or document.  
   So a postcard could be accompanied by photos or 
   videos.  The chip is a read-write CMOS memory device, 
   2-4 mm square, with a built-in antenna and 10 ten 
   times faster than Bluetooth.
   Source: Hewlett Packard

Device records smells to play back later
   Engineers at the Tokyo Institute of Technology in 
   Japan are building an odour recorder capable which 
   will record a smell and play it back later.  The 
   system will use 15 chemical-sensing microchips to 
   pick up a broad range of aromas.  These are then 
   used to create a digital recipe from a set of 
   96 chemicals that can be chosen according to the 
   purpose of each individual device.
   Source: New Scientist

Noise Measurement May Boost Wireless Device Performance
   Researchers have developed improved methods for 
   accurately measuring very faint thermal noise caused 
   by random motion of electrons in electronic 
   circuits.  The technique may help improve the signal 
   range, data rate and battery life of wireless 
   Source: National Institute of Science and Technology

Call for Proposals on Standards for Wireless Automation
   ISA's standards committee on wireless systems for 
   automation has issued calls for proposals to encourage 
   a variety of experts to collaboratively create a new 
   series of wireless communication standards for 
   industrial monitoring and control.
   Source: ISA - The Instrumentation, Systems, and Automation Society

* 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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