The Newsletter for PC-Based Data Acquisition and Control
Issue 111 www.windmill.co.uk October 2007
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* Windmill News: Windmill helps radioactive research
* Excel Corner: Reading X and Y values off Excel Charts
* DAQ News Roundup
Windmill News: Windmill helps radioactive research
Scientists are investigating the flow of radioactive
material through the Yucca Mountain in Nevada. To date
measurements and models have assumed a classical,
steady-state diffusion. The researchers wanted to test
if this was an accurate assumption.
As part of their experiments they took borehole samples,
exposed one face of the rock sample to water or tracer
solution and monitored the liquid uptake over time.
Core samples of varying height to diameter ratios were
used to investigate the shape effect.
They hung the rock sample from a bottom-weighing
analytical balance to measure the weight change during
liquid imbibition. To regularly save the readings to
computer disk, they downloaded the free Windmill
from the Windmill web site.
Windmill logged balance readings and to the computer at
selected time intervals, starting with every second and
increasing the interval as time went on.
The Windmill software helped show that the steady-state
diffusion assumed by previous models cannot be applied
to the Yucca mountain.
Yucca mountain is the site of a proposed storage
facility for radioactive waste.
Q Hu, R P Ewing, L Tomutsa and M J Singleton.
Pore Connectivity, Episodic Flow, and
Unsaturated Diffusion in Fractured Tuff
More Windmill application stories are at
Excel Corner: Reading X and Y values off Excel Charts
This month we were asked how to obtain the Y value on
an Excel XY scatter chart, given that the corresponding
X value was known. There are three approaches to this.
The easiest is to use an Excel add-in that has been
created especially to do this. The second way is to
generate an equation which accurately describes your
data, and use that to calculate your values. Thirdly
you may be able to use Excel's built in functions to
calculate the values.
1. Using an Excel Add-In
An Excel add-in contains code that adds extra
features to Excel. Excel is shipped with a variety
of add-ins, and there are many third-party add-ins
available. One which solves our problem is provided
by Tushar Mehta at
This creates a dialogue box which when you enter an
X value tells you the corresponding Y value, and
vice versa. It also draws dotted horizontal and
vertical lines to the Y and X axes from the
Another add-in is provided by Advanced Systems
Design and Development at
This provides functions to interpolate, extrapolate
and curve fit data rapidly. Use the Interpolate
function to find the Y value at a given X value.
2. Generating an Equation from your XY Scatter Chart
On your XY Scatter chart insert a trendline that
fits your data. Right-click the data series and
select Add Trendline. Click the options tab and
choose to display both the equation and the
R-squared value on the chart. The R-squared value
shows how closely your data fits the equation. A
value of 1 indicates an exact fit. Values far
away from 1 indicate that your calculations
won't be accurate and you should try another
Copy the right-hand part of the equation into a
cell, replacing the x with a reference to the cell
holding your known X value. For example, for a linear
trendline the equation Excel displays might be
y = 1.97x + 0.1. If your known X value was in
cell H8, you would enter:
3. Using Excel's Functions
Excel has a couple of built in functions which you
can use to return Y values.
- For a linear trendline use TREND()
- For an exponential trendline use GROWTH()
Which is the best method to use? I've found that using
one of the add-ins gives the best results.
For more on data acquisition and control using Excel see
DAQ News Roundup
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Smart sheets let gadgets talk through their feet
Flexible, electronic sheets could be embedded in
tables, walls and floors, allowing devices
anywhere in the home to communicate. Plastic
transistors and copper wires that snake through
the sheets allow gadgets placed on them to form
spontaneous connections and swap data.
Source: New Scientist
New Quantum Dot Transistor Counts Individual Photons
A transistor containing quantum dots that can
count individual photons (the smallest particles
of light) has been designed and demonstrated at
the National Institute of Standards and Technology.
The semiconductor device could be integrated
easily into electronics and may be able to operate
at higher temperatures than other single-photon detectors.
Source: National Institute of Standards and Technology
Microwaves offer fat chance to probe supermarket food
Microwaves used for zapping instant meals can also
be used to determine the fat and salt content of
supermarket food, according to research carried
out at two Manchester universities. Constant real-time
monitoring by the microwave sensors during the
production process could help reduce waste, maximise
yield, reduce laboratory testing and save energy.
Source: Manchester University
Proximity Sensor Market in North America Being Won by European Vendors
The North American market for proximity sensors
has increased at a moderate single-digit average
annual growth rate over the last 15 years. However,
during the same period, two European vendors have
each achieved approximately double the annual market
growth rate, and are now the leading suppliers
in the market.
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