Issue 14: Standards
WINDMILL NEWS: PROGRAMMING TOOLS LAUNCHED
Conforming to standards is essential for trade. But how do you find the standards you need? Read on to find how various bodies interact, and where to look for standards' specifications.
The International Electrochemical Commission (IEC) and ISO are two of the most important international standards bodies. The IEC covers electrical and electronic engineering, with ISO covering all other technical fields. ISO comprises a federation of national standards bodies, such as the American National Standards Institute, the Bureau of Indian Standards, the British Standards Institution and Standards Australia. ISO and IEC co-operate on a joint basis with the International Telecommunication Union (ITU). ITU is part of the United Nations and its members are governments.
So how do you find which standards apply in your industrial field or geographical area? Starting with ISO - their catalogue lists both published standards, and draft standards in the later stages of development. They have a very good search facility for the catalogue in English or French.
Once you've found the appropriate standard you can buy it from your country's ISO member. A list of all members is at http://www.iso.ch/addresse/membodies.html. If your country is not a member of ISO, contact the ISO Central Secretariat - see http://www.iso.ch/infoe/contact.htm.
Can't find what you're looking for at ISO? For electrotechnical fields (including electronics, magnetics, electroacoustics and energy production) visit the IEC site. You can search for standards and buy them on-line.
IEC's standards represent the core of the "World Trade Organization's Agreement on Technical Barriers to Trade". Historically, though, their standards take years to conclude. To remedy this for fast moving technologies, they're promoting the Industry Technical Agreement (ITA). Any group of interested parties may create an ITA - it is up to industry players to agree amongst themselves. Once published it is like a de facto standard. However, it is not an international standard as it does not pass through the same consensus procedure. To find out more contact the IEC Central Office.
For telecommunications see ITU's site. You can browse through their standards and order on-line.
Other Organisations: IEEE and ISA
One organisation I haven't yet mentioned is the IEEE Standards Association. This is a "world leader in the development and dissemination of voluntary, consensus-based, industry standards involving today's leading-edge electrotechnology". For breaking news on IEEE standards they issue an electronic news bulletin. Past bulletins are available on-line.
Another useful body is the International Society for Measurement and Control (ISA). Their web site includes a complete listing of their standards, and their InTech magazine brings discussion and news of their own and other organisation's standards.
The standards produced by the international organisations mentioned above are recommendations - voluntary not mandatory. How do they sit with regional standards, which may be legally implemented? Let's take the British Standards Institute as an example (which operates in over 90 countries). A British Standard is prefixed by BS. If it is an ISO standard as well, it would also carry an ISO number. As Britain is also a member of the European Union, it may also carry an EN prefix. For example, in 1979 BSI published the BS5750 quality standard. In 1987 the standard was adopted by ISO and the code became ISO 9000. In 1994 this became BS EN ISO 9000.
Moving on to European Union standards. The Central site for European standards is http://www.newapproach.org/.
This is a good place to look for EU Directives. Directives define the essential requirements that goods must meet when they are placed on the market. Three European standards bodies have the task of drawing up the corresponding technical specifications to meet the Directive's requirements. These are the European Committee for Standardisation (CEN), the European Committee for Electrotechnical Standardisation (CENELEC) and European Telecommunications Standards Institute (ETSI). They each work with the International Organisations: CEN with ISO, CENELEC with IEC and ETSI with ITU.
Directives are mandatory for member countries and exporters to the EU. The Pressure Directive, for example, becomes legally enforceable this month (September).
Other Sources of Information
The World Standards Services Network contains links to international, regional and national standardisation bodies, including those that develop standards in specialised subject areas.
There is a mailing list for the discussion of standards in the SCADA industry, run by Ian Wiese. To subscribe send an e-mail to email@example.com
This month's Visual Basic Corner gives hints on using our new 32-bit IML Tools, and the 16-bit IML Toolkit which they replace. Both these packages let you send and receive data values directly from the hardware (as opposed to going through Windmill's DDE Panel).
As always, the VB Corner is only useful if you wish to write your own applications using Visual Basic. You can use the free Windmill 4.3 programs, or Windmill 6, without any programming at all. (Neither the IML Tools nor the IML Toolkit are free. They both cost 195 pounds - around 320 dollars or 305 euros - and are available from our on-line shop.)
So, onto the IML Tools and Toolkit. They greatly speed-up your programming task by providing a collection of methods and functions. The three which you would use most often let you
- Configure your hardware simply by sending it a file
- Read data from an input channel
- Send data to an output channel
First let's deal with the hardware configuration. The Windmill application called SetupIML scans your hardware and creates a default configuration file, with the extension IMS. You can then use SetupIML to edit the file, tailoring the system to your needs. For example, you can give channels meaningful names and set their engineering units. You can create a library of files, ready for immediate use in your programs. No more tedious communicating with the low-level features of your hardware.
Using the 32-bit IML Tools (Windmill 6)
The new IML Tools comprise an Active X control. Once you've installed and registered the control, you can use it in your VB project. You simply select Components from your Projects menu, and check the IMLcontrol box. You can then place the control on your form and use its properties and methods in your code.
To read from a channel, for example, you'd use
IMSLoadFile(FileSpec$)We have a complete example, which you can download of how to
- Display the readings from 2 analogue inputs, taken once per second, in label controls.
- Create a text control to allow the value of an analogue (or digital) output channel to be varied.
- Change the value on the analogue output when the text in the control is changed.
Using the 16-Bit IML Toolkit (Windmill 4.3)
The IML Toolkit provides dynamic link libraries that you access in your program.
To read a channel, for example, you'd use this function
Declare Function IML_ReadChannel Lib "IMLKIT.DLL" (ByVal ChanName As String, ByVal ChanValue As String)The reading is returned from the channel in ChanValue. For more information see http://www.windmill.co.uk/tools.html. The IML Toolkit also provides DLLs for C and LabVIEW.
Future VB Corners
Next month's VB Corner explains how to use DDE to control Windmill applications from your own code. You can do this with the free Windmill programs, without any extra purchases. November and December Corners will cover using HTML pages for your user interface.
Our other Visual Basic articles are in:
- Monitor # 13, Using DDE to get data from your instrument into your VB Program
- Monitor # 15, Controlling Windmill programs from Visual Basic code
- Monitor # 16, Using an HTML page to generate the user interface for your Visual Basic application
- Monitor # 18, Displaying data from Windmill in an HTML page
- Monitor # 21, Other Visual Basic resources
Copyright 1999 Windmill Software Ltd. All rights reserved. This newsletter may be distributed in its entirety. However, individual sections may not be reproduced without the prior written agreement of Windmill Software Ltd.
To receive Monitor every month please fill in your email address below. We will not pass your address to any third parties.
You will receive an e-mail asking you to confirm your subscription. On doing so you will be sent details of how to download the free software. If you don't receive this e-mail please contact firstname.lastname@example.org.
You can read an archive of previous issues on our Data Acquisition Intelligence site.
You can cancel your free subscription at any time - just return to this page or follow the instructions in the newsletter.