-----------------------------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. We only send this newsletter to people who have subscribed -- should you wish to cancel your free subscription please visit http://www.windmill.co.uk/newsletter.html 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 http://www.windmill.co.uk We are happy for you to copy and distribute this newsletter, and use extracts from it on your own web site or publication, providing the above notice is included and a link back to our website is in place. An archive of previous issues is at http://www.windmill.co.uk/newsletter.html and an index of articles at http://www.windmill.co.uk/newsletter.html 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] http://www.windmill.co.uk/ https://www.windmillsoft.com/ Comments: Email:
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