Windmill Software Ltd
Windows Engineering Software

December 2003

The Newsletter for PC-Based Data Acquisition and Control
Issue 65       December 2003
--------------------ISSN 1472-0221----------------------

Welcome to December's Monitor - our compliments of the 
season to you. In this issue, how Windmill is helping a 
French winery comply with bottling standards. We also 
discuss the importance of dewpoint and humidity 
measurements, and have our bi-monthly exhibition listing. 
The Excel corner is having a Christmas break.

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

* Windmill News: Windmill helps bottle French wine
* Dewpoint temperature and humidity 
* Data acquisition and control exhibitions


HACCP (Hazard Analysis and Critical Control Point) and the BRC 
(British Retail Consortium) protocol require that bottle volume 
is checked for accuracy by the weight method and that 
records of such check are kept.  To comply with this the 
Quality Control department of the Maurel Vedeau S.A. 
winery test their bottling line by weighing a sample of 
bottles before and after they are filled. 

To speed up this process, and eliminate errors, they 
looked for some software which would communicate with 
their Mettler Toledo scales and send the weight results 
to directly to a Microsoft Excel spreadsheet. The 
software had to be low cost and easy to use, and so they 
chose Windmill. Regis Revolu, who implemented the system, 

  "Searching through the web for a cheap interface to 
   link a lab scale directly to Excel, I found with 
   Windmill 4.3 not only the interface I was looking for, 
   but also an easy-to-follow step by step procedure 
   (+ VBA program) which made it most simple to use 
   and implement."

The Solution
One to five empty bottles are identified and weighed. 
After passing down the bottling line they are weighed 
again. A VB application in Excel allows Quality Control 

- Select various details from drop-down lists including: 
  the size of the bottles (75cl, 100 cl, etc), the client 
  for whom the wine is being bottled, the type of wine 
  and the vintage.
- Enter the lot number and wine density

Windmill automatically collects the weight data from the 
scales and sends it to Excel. Excel divides the weight by 
the wine's density and calculates the liquid volume. The 
average volume across the 5 bottles is also calculated. 
Excel checks whether the volumes are as they should be, 
and if not warns the operator of the problem.

On pressing the Record button, the system logs all the 
information for Quality Control records.

As a Monitor subscriber, you can download the Windmill 
Software used in this application for free.
The latest version of Windmill, Windmill 6, is available 

Maurel Vedeau S.A. have kindly made their Excel VB 
application available for download at
Disclaimer: The use of this program is entirely the 
responsibility of the user; neither Maurel Vedeau S.A. 
nor Windmill Software can give any guarantee, nor accept 
any liability, arising from the use of this program.

For other applications of Windmill see

For more on Mettler Toledo balances see


The Significance of Dewpoint Temperature

Dewpoint temperature impacts on much more than heating, 
ventilation and cooling considerations. It plays a major 
role in 
- the attainment of high product yield
- the efficient use of energy in many chemical 
  manufacturing processes
- convective heat transfer
- combustion of fossil fuels and combustion engineering, 
- drying of paper, cardboard, plastics, wood, tobacco, 
  leather, printed goods, textiles and grain
- corrosion phenomena which can result in damage and loss 
  of not only unprotected iron and steel structural 
  components but also improperly stored steel and other 
  metal products.


What is Dewpoint?

The dewpoint, or more precisely the dewpoint temperature, 
is the temperature at which the liquid and gaseous phases 
of a material present in a gas, such as water in air, are 
in equilibrium at a given gas pressure. In other words, 
the dewpoint is the temperature at which the liquid 
water, or dew, evaporates at the same rate at which it 
condenses. Measurements of dewpoint and related humidity 
represent a significant use of temperature sensors, 
usually integral to the device or instrument that reports 
the dewpoint temperature or humidity conditions. 


Dew Forms. Fog and Dew seems

The dewpoint temperature is most comonly observed in 
ambient air and is also called the saturation temperature 
of water vapor in air. If you lower the temperature, dew 
will form as fog or condense on a cooler surface faster 
than it evaporates. This phenomenon is observed, for 
instance in very moist air when the dew appears as fine 
water droplets suspended in air (fog) and on cool 
beverage containers in hot weather conditions. 
Conversely, if one raises the temperature above the 
saturation temperature, dew will evaporate faster than it 
condenses. Fog in air and dew on surfaces will dissapear 
under such conditions. This is commonly seen when dew on 
the ground vanishes as the air warms after a cool night.

The value of the dewpoint depends upon the air 
temperature, since hotter air can hold more water vapor 
per unit volume than can colder air. Likewise, the value 
of the dewpoint at a given air temperature is also a 
function of air pressure.


Humidity, It's Not All Relative

The dewpoint or saturation temperature also is described 
as the 100% relative humidity (RH)condition; when air 
holds 100% of the moisture that it possibly can. The RH 
of air is defined technically as the ratio of the water 
vapor pressure to the vapor pressure of saturated air at 
the same temperature. But it is measured in many 
different ways, ranging from horse hairs to special 
electronic sensors.

The moisture content of air can also be characterised in 
terms of the absolute humidity (AH) or humidity ratio, 
the weight of water vapor in the air per unit weight of 
dry air at the same temperature (pounds per pound or 
kilos per kilo).

Just from the brief descriptions above it can be 
appreciated that there are three different measurement 
variables described, dewpoint temperature, relative 
humidity and absolute humidity, which can each 
independently represent the same water-vapor-in-air 
condition. To complicate matters even further, a time-
honoured method to measure the moisture conditions in air 
has been to measure the dry bulb and the wet bulb 
temperature of the air.


Heat is Involved..of course

Then it starts getting a little complex. Since it takes 
heat input to evaporate liquid water and since water 
vapor releases heat when it condenses, there is an 
obvious energy content in a given mass of moist air. The 
energy content depends upon the temperature and the 
amount of moisture present. This involves costs when one 
is trying to remove the moisture from something like 
grain or a wet web of paper using a flow of air. 
Increasing the air temperature can enable faster drying, 
but it requires heat to increase the air temperature. 
That means some fuel must be expended at a cost.

Similarly when, for comfort reasons, one needs to cool 
the air below the dewpoint temperature by flowing air 
over a cold surface. It costs fuel and money to cool the 
surface and "soak up" the heat that the condensing water 
liberates, not to mention the cost of moving the air.

So, the total heat content of air depends upon its 
moisture content. The energy relation is described as the 
enthapy per unit weight, BTU/Lb or J/Kg.

It is also important to note, that almost inevitably each 
of the three variables, when described, is paired with 
the air temperature value. For example, a statement that 
the relative humidity is 65% means much more when the 
current air temperature is also given. Of course, under 
such conditions the air temperature is higher than the 
dewpoint temperature since the air is not saturated.


It's All Related and Described (by Equations, Tables and 
Charts and Available in Software)

Needless to say, there are well established relationships 
between the four variables. The relationships can be 
described in terms of equations, in numerical tables and 
graphically. One of the most commonly used methods, until 
the advent of low cost computers with programs relating 
the parameters, was the psychrometric chart. It is still 
widely used and takes several forms.

Almost complicating the matter of measuring the 
properties of air (or any other gas) containing moisture 
further still are the facts of independent methods for 
measuring each of the variables described above and 
several different device types to perform each variable 
measurement. Since temperature sensors are used either 
directly or indirectly in most of these measurements, 
they are considered a unique use or application of 
temperature sensors.


By Ray Peacock, industrial physicist and founder of, Inc.  Ray teaches an industrial 
temperature measurement course for ISA (the 
Instrumentation, Systems and Automation Society) and 
can be contacted at or via 
the website.

Further Reading:
Monitor Issue 23: Using a PC to Monitor Weather
Monitor Issue 5: How to Use Your PC to Measure Temperature

For more on computerised humidity measurement please 
contact Windmill Software on


Continuing our bi-monthly listing of exhibitions and 
conferences related to data acquisition and control.

ICISIP - 2004
4-7 January 
Le Royal Meridien Chennai India
International conference on intelligent sensing and 
information processing.

Measurement Science Conference
12-16 January
Disneyland Hotel Anaheim California USA
Founded in 1970 to promote education and professionalism 
in measurement science and related disciplines.

27-29 January 2004 
InterContinental Hotel New Orleans USA 
Sensors for industry conference, focusing on sensors for 
defense and security. Organised by ISA and the 
Instrumentation and Measurement Society of IEEE.

mtec 2004 
11-12 February
NEC Birmingham UK
Addresses all aspects of sensor, measurement and 
instrumentation technology.

Southern Manufacturing 2004
18-19 February
Thorpe Park, Surrey, UK

CHIFA 2004
3-6 March
Guangzhou Canton China
8th international factory automation and instrument 

23-26 March
Warsaw Poland
International fair for measurement and control


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

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and an index of articles at

Windmill Software Ltd, PO Box 58, North District Office,
Manchester, M8 8QR, UK
Telephone: +44 (0)161 834 6688
Facsimile: +44 (0)161 833 2190


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