Windmill Software Ltd
Data Acquisition Intelligence

Charting and Excel
May 2001

The Newsletter for PC-Based Data Acquisition and Control
Issue 34             May 2001
--------------------ISSN 1472-0221----------------------

Thank you for subscribing to Monitor. This month we're 
focusing on charting and Excel. 

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* Windmill News: New Guide to using Windmill with Excel
* Windmill Charting Tips
* Excel Corner: Charting with Excel

Windmill News: New Guide to using Windmill with Excel

Learn about the ways to get real-world data into Excel. 
From simply importing previously logged data, to fully 
automated collection and analysis in Excel.

Windmill Charting Tips

If you've downloaded the free Windmill Software suite 
you'll have seen our Chart program. Here are a couple 
of tips on using Windmill Chart.

Incorporating the Chart in your Report
  Whilst Chart is the active window, press the Alt and 
  Print Screen keys. This copies the Chart image to the 
  clipboard. Now simply paste the picture of Chart into 
  your Word, Excel or other Windows-based report. This 
  is also useful when printing the Chart, as you can 
  annotate the image as necessary. 

Showing Data Over a Longer Time-Scale
  To show data over a longer time-scale, and thus 
  display more data, just change the "paper speed". For 
  example, if the Chart window is 5 cm wide and your 
  paper speed is 5 cm per second, you will see 5 
  seconds of data. If your paper speed is 5 cm per 
  minute, you will instead see 5 minutes of data.

For more details on Windmill Chart see

Excel Corner: Charting with Excel

Spreadsheets are very useful tools for analysing your 
data. You can average readings over time or number of 
sampling points, or put data directly into reports. You 
can collect data with the free Windmill Logger program 
and after collection has finished import it into your 
spreadsheet. Alternatively you can transfer data as it 
arrives, using dynamic data exchange. For details of how
to do this see

Although this article concentrates on Excel, many of the 
comments here also apply to other spreadsheet programs.

This Excel Corner looks at charting with Excel. But 
first, do you need to use Excel to chart your data? It 
may be that Windmill's free, real-time charting program 
is all that is necessary. Or, for re-running charts 
after collection has finished, you could use the 
Windmill Replay software. This lets you rewind, fast-
forward, zoom in, zoom out and scroll through large 
data files looking for areas of interest. (More 
details on Windmill Replay are at
A third Windmill program, Windmill Graphics, lets you 
display a bar chart of the current data: a 
continuously changing snapshot of the live situation.

So why use Excel to chart data?

1. Windmill Chart and Replay always plot data against 
   time. With Excel you could plot, for example, 
   temperature against depth.
2. Excel offers many different styles of chart - you may 
   decide a stock chart, say, suits your purpose better 
   than the Windmill charts.


Choosing the Type of Excel Chart to Use

Excel provides a multitude of chart styles and it can 
sometimes be confusing which one is the best to use. 
Here we highlight three well suited to data acquisition 
- stock, bar & column and xy scatter.

Stock Chart: Useful for Displaying High, Low and Average 

 A stock chart shows high, low and close data. This is 
 designed for plotting stock market movements, but can be 
 useful when plotting, say, daily temperatures. To plot 
 the temperature range for each day you would have the 
 date in the first column, the highest temperature of the 
 day in the next column, the lowest temperature in the 
 third column, and, for example, the average temperature 
 of the day in the fourth column - replacing the stock 
 market close data.

Column and Bar: Good for Displaying Counts

 Column and bar charts are useful for comparison of 
 discrete measurements made at regular intervals. For 
 example, if you were counting people entering a 
 building, you might use a column chart to show count 
 totals for a series of days or weeks. To display data 
 from several buildings you could use a stacked column 
 chart, where figures for each building are shown as a 
 part of the total column count. 

 A column chart has time on the horizontal x-axis 
 and a bar chart time on the vertical y-axis. If 
 you have too many columns, Excel won't display 
 all the column labels. Displaying data in bars 
 removes this problem.

Line Charts Versus xy Scatter

 You would usually use an xy scatter chart in preference 
 to a line chart. With xy scatter an independent variable 
 is plotted on the x-axis and variables dependent upon 
 this plotted on the y-axis. When you add a trend line, 
 you can see the relationship between the variables. For 
 example you might see a linear relationship between the 
 concentration of a compound in solution and its 
 absorbance of light.

 With Line charts the x values are more like labels than 
 values. They are spaced equally, no matter what their 
 value. Using our above example, suppose you plotted 
 absorbance against the concentration of four solutions 
 of 0, 1, 2 and 6 mM. With xy scatter the line will be 
 straight as the 6mM point is plotted in its correct 
 position 4 units away from the 2 mM point. With a line 
 chart the 6mM point is plotted just 1 unit away from 
 the 2 mM point, giving a steep rise in absorbance and 
 thus non-linear graph. 


Excel Tip of the Month: Quickly Adding New Data to an 
Excel Chart

Suppose you have used Windmill to log rainfall and 
atmospheric pressure data. You import the data file 
into Excel and have 3 columns: Time, Rainfall and 
Pressure. You create a chart plotting rainfall against 
time. You now decide to add the pressure data to the 
- Highlight the pressure column
- Move the mouse pointer over the edge of the 
  highlighted data, so it changes to an arrow
- Click and drag the column onto the chart
Rainfall and pressure are now plotted against time.

This tip courtesy OzGrid Business Applications. More 
charting tips are available on their web site.


* 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
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