-----------------------------Monitor-----------------------------
The Newsletter for PC-Based Data Acquisition and Control
Issue 27 www.windmill.co.uk October 2000
-------------------------ISSN 1472-0221--------------------------
Welcome to another edition of Monitor from Windmill Software.
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CONTENTS
========
* Windmill News: Any driver now free with Windmill
* Engineering Units
- History of the different systems of units
- Style conventions and rules for using SI Units
- Why are SI Units the global choice?
* Exhibitions and conferences
_________________________________________________________________
Windmill News:
Any Driver now Free with Windmill
The Windmill data acquisition software suite works with a wide
range of hardware, and thus has a series of hardware drivers.
These include:
- the LabIML driver, which handles most instruments with an RS232
port
- the Modbus drivers, which handle Modbus devices over RS232 or
RS485
- the Harvester driver, which handles Fieldbus networks etc
acting as DDE servers
Previously Windmill was supplied with the LabIML driver and other
drivers were extra. Now, though, our on-line catalogue lets you
choose any driver when you buy Windmill.
https://www.windmillsoft.com/daqshop/software.html
You are not limited to one driver, however. You can connect many
different types of hardware and simply buy the requisite drivers
as the need arises. We've listed more drivers in our catalogue so
it's easy for you to upgrade your system. For details see
https://www.windmillsoft.com/daqshop/software.html
_________________________________________________________________
Engineering Units: SI, Metric, Imperial and American
Just over a year ago, the Mars Climate Orbiter crashed into the
surface of Mars. The main reason was a discrepancy over the units
used. The navigation software expected data in newton second; the
company who built the orbiter provided data in pound-force
seconds. Another, less expensive, disappointment occurs when
people used to British pints order a pint in the USA, only to be
served what they consider a short measure. Again the reason is
confusion over units; this time due to the fact that American
units, although bearing the same names as British Imperial units,
often refer to very different measures.
Why are there different systems of units?
=========================================
In 1824 a British Act of Parliament gave precise definitions to
Imperial units. These included the yard, pound, bushel and
gallon. Six years later an American survey found weights and
measures in various ports differed significantly. This led to the
United States, in 1834, standardising measurements. However,
although these were named after British units, they were not
always the same measures as those used in Britain. The gallon
chosen, for example, was the "Queen Anne wine gallon", which was
already obsolete in Britain.
The most widely used system of units and measures around the
world is the Systeme International d'Unites (SI), the modern form
of the metric system. This originated in France, where in 1790
the French Academy of Science was commissioned to design a new
system of units. They decided that:
- The units should be based on unvarying quantities in nature
- Multiples of units should be decimal
- The base units should be used to derive other units
These principles allowed the metric system to evolve and SI units
have become the fundamental basis of scientific measurement
world-wide.
*
SI Base Units
=============
There are just 7 base units
Quantity Unit Symbol
length metre m
mass kilogram kg
time second s
temperature kelvin K
amount of substance mole mol
electric current ampere A
luminous intensity candela cd
Prefixes are used to indicate powers of ten. They mean that with
only one unit of measurement you can express any measurement from
the smallest to the largest. They each have a short name and
symbol. Large factors have upper case symbols, and small factors
lower case symbols.
For example:
giga 1 000 000 000 G
mega 1 000 000 M
kilo 1 000 k
milli 0.001 m
micro 0.000 001 µ
Style Conventions and Rules for using SI Units
==============================================
General principles for the writing of unit symbols and numbers
were first proposed in 1948. These were subsequently adopted and
elaborated by ISO, the international standards organisation.
1. Unit symbols are printed in roman (upright) type, irrespective
of how the rest of the text is printed.
2. Unit symbols are unaltered in the plural.
3. Unit symbols are written without a final full stop (period)
except for normal punctuation such as at the end of a
sentence.
4. Unit symbols are placed after the numerical value, leaving a
space between the value and the symbol. For example 5 V not
5V.
5. Unit symbols are generally written in lower case letters,
except when the name of the unit is derived from a proper
name. (Note that when the name of a unit which is derived from
a proper name is written out in full, such as ampere or herz,
the name is not capitalised. The only exception to this is
Celsius.)
6. The the given SI unit symbol should be used. The symbol for
second, for example, is s. To use sec or secs is incorrect.
7. Unit symbols and unit names shouldn't be mixed. Metre per
second, not metre/second or metre/s.
Summary of Advantages of SI Units: Why they are the Global Choice
=================================================================
- No conversions: only one unit for each quantity
- No numbers to memorise: derived units are defined algebraically
with no numerical factors
- No long rows of zeros: prefixes are used to indicate powers of
ten
- World standard: all other units, including British Imperial and
American units, are defined by them
- Not static but evolves to take advantage of increasing accuracy
of measurement standards and increasing needs for measurements
*
Further Reading
===============
You can find more information on units on these web sites.
National Physical Laboratory (UK)
http://www.npl.co.uk/npl/reference/
NIST: National Institute of Standards and Technology (USA)
http://physics.nist.gov/cuu/Units/index.html
Bureau International des Poids et Mesures
http://www.bipm.fr/
The Metric System [SI]: A concise reference guide
http://www.subnet.virtual-pc.com/ba424872/Metric.html
Metric Units and Conversion Charts, T Wildi, 1996, IEEE Press.
https://www.amazon.co.uk/exec/obidos/ASIN/0780310500/1286-21
_________________________________________________________________
Exhibitions and Conferences
Every other month we list forthcoming exhibitions and conferences
related to data acquisition and control.
1-2 November
NEMEX, National Energy Management Exhibition
NEC Birmingham UK
Europe's energy managing conference and exhibition. Features
energy saving solutions, climate change levy debate and a series
of workshops.
http://www.nemex-energy.co.uk/
7-9 November
Manufacturing Week 2000
NEC Birmingham UK
As well as incorporating the Design Engineering Show and Vehicle
Engineering & Design, this year's Manufacturing Week also
includes Automation and Production. Over 300 exhibitors plan to
attend.
http://www.manweek.co.uk/
7-9 November
CIM 2000
NEC Birmingham UK
Computers in Manufacturing. A UK exhibition showing the latest IT
innovations.
http://www.cimshow.co.uk/
BIAS
7-11 November
Milan Italy
International exhibition for the automation, industrial
components and instrumentation sectors. It boasts 2,600
exhibiting companies coming from 30 countries, and an estimated
60,000 visitors coming from around seventy countries.
http://www.bias.it/
21-22 November
Instrumentation South East
ExCel London UK
http://www.instrumentation.co.uk/Instse2000.htm
5-10 November
2000 International Mechanical Engineering Congress and Exposition
(ASME)
Walt Disney World Florida USA
The congress aims to provide a program that balances academic,
research and industrial applications. For design, manufacturing
and product engineers.
http://www.asme.org/conf/congress00/
28-30 November
SPS/IPC/Drives
Germany
Exhibition for automation technology. Exhibits include: data
acquisition equipment, sensors and periphery equipment.
http://www.mesago.de/
_________________________________________________________________
* Copyright Windmill Software Ltd
* Reprinting permitted with this notice included
* For more articles see https://www.windmill.co.uk
We are happy for you to copy and distribute this
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included and a link back to our website is in place.
An archive of previous issues is at
https://www.windmill.co.uk/newsletter.html
and an index of articles at
https://www.windmill.co.uk/newsletter.html
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
E-mail: monitor@windmillsoft.com
https://www.windmill.co.uk/
https://www.windmillsoft.com/
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