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Issue 18: Process Control, Oil and ActiveX
CONTENTS
Windmill News |
New Year Survey
| Process Control in
the Oil and Gas Industry | VB Corner - Displaying
Measurements on a Web Page
WINDMILL NEWS: EDUCATION SUCCESS WITH WINDMILL!
A new education kit for schools and colleges uses the Windmill Software
demo to explain control technology. (You can download free copies of this
process control demo from https://www.windmill.co.uk/windmill7.html)
The Windmill Graphics software was seen as essential for students'
information technology skills. The software lets them control a process
from their PC screens. By pointing and clicking they can simulate closing
drain valves, filling tanks, starting heating operations, and so on - thus
familiarising themselves with process control.
Other skills taught by the control technology resource include:
- Using level control systems with digital sensors
- Temperature control with digital and analogue sensors
- Monitoring systems
- Data logging
Feedback from teachers indicate that the kit has been universally well
received. It was developed and distributed to schools and colleges by the
Higher Still Development Programme.
For more details of the education programme visit https://www.windmill.co.uk/education.html.
For more details on Windmill Graphics visit https://www.windmill.co.uk/graphics.html.
To purchase a fully working version of Windmill Graphics visit https://www.windmillsoft.com/daqshop/software.html
As an aid to improving our services we would be very grateful if you
could fill in this brief survey. All information is confidential and won't
be passed to any third parties. Miss out any questions you don't want to
answer.
(You'll be
returned to this page after pressing Send Survey.)
The education kit featured in the Windmill News, used examples from the
oil and gas industry to provide real life illustrations of control
technology. Much of the information came from UKOOA, whose web site is
detailed below.
- UK Offshore Operators
Association
- UKOOA is the representative organisation for the UK offshore oil and
gas industry. Making the oil and gas industry more open, accessible and
accountable is the major thrust of their strategy. As one way of
achieving their mission they provide a great deal of education resources
for teachers. Their site also gives a glossary of terms used in the
industry, news headlines and environmental reports detailing issues,
discharges and emissions.
http://www.ukooa.co.uk/
- Institute of Petroleum
- The Institute of Petroleum is another site which provides a range of
educational resources on process control in the oil and gas industry.
It's an independent European centre for the advancement and
dissemination of technical, economic and professional knowledge relating
to the international oil and gas industry. For 60 years it has been one
of the principal independent bodies in Europe. Its objectives include
lifetime learning and to increase the knowledge and understanding of the
oil industry by young people. A large amount educational material
reproduced is on its web site.
http://www.petroleum.co.uk/
- Offshore
Technology
- Another web site in a similar vein is Offshore Technology's. Their
current projects section gives masses of information on individual oil
fields, including process control
details.
http://www.offshore-technology.com/
Last time we
reviewed how to use HTML to provide the layout and user interface for your
VB application. This month we go one step further and look at how we can
get data from Windmill into your HTML page. The title VB Corner is in fact
a misnomer this month. We've written the script for the HTML page in
JavaScript since this is easily used with a web browser such as Internet
Explorer. However, the script could have been written in VBscript and the
same principles apply.
The easiest way to communicate with the Windmill system from a web page
is to use an ActiveX control. Windmill's IML Tools control sets
up your data acquisition hardware or instruments, sends data to them and
reads back data values from them. In this way you are relieved of the
tedious programming task of communicating directly with the hardware. You
can also re-use your code with many different instruments and devices.
For reasons of space we have not included the entire JavaScript code
and sample html page here, but invite you to download it from here.
The examples given assume you are using the IML Tools ActiveX control.
They explain how to display data from 3 measurement channels on a web
page, and update the readings every time a button is pressed.
*
Overview of JavaScript and HTML Coding for Data Acquisition
- Within the <HEAD> of the HTML page we need to:
- Declare
the ActiveX control as an object on the page
- Elsewhere on the HTML page we need to:
- Create a table with
cells identifying where the data should be placed.
- Within the JavaScript part of the page we need to:
- Configure the hardware by loading a file containing all the
configuration details
- Set which channels to read, and the ID of the table elements where
data will be posted
- Within the <BODY> of the HTML page we need to:
- Call the
JavaScript function
- DECLARING AN OBJECT
To declare the control as an object on the
page we use this code
<OBJECT ID="IMLcontrol" WIDTH=64 HEIGHT=63
CLASSID="CLSID:1FCF5582-2A14-11D3-9743-525400DDF830">
<PARAM NAME="_ExtentX" VALUE="1693">
<PARAM NAME="_ExtentY" VALUE="1667">
</OBJECT>
The CLSID allows the page to uniquely identify the component it is
trying to load. It comes from the Windows registry.
- CREATING A TABLE WITH CELLS TO HOLD THE DATA
Each table cell
designated to hold data must be uniquely identified. For example, to
identify a cell as CHAN0 you could use this HTML. <TD><SPAN ID="CHAN0"></SPAN></TD> In
the JavaScript code a line like this will write the reading into the
table cell Chantxt=document.all("CHAN0");
-
- JAVASCRIPT FUNCTION TO CONFIGURE THE HARDWARE
Configuring the
hardware means, for example, specifying engineering units
(oC for example) and setting the expected maximum and
minimum data values for each hardware measurement channel. In a
Windmill system you do this in the SetupIML program, by making choices
from dialogue boxes and then saving a file containing your selections.
This file is called an IMS file. Once you've created an IMS file all
you need to do is send it to the hardware, and the hardware will be
appropriately configured.
To do this in JavaScript you
need to state which file you want to use. So, you need a line looking
like this var IMSfilespec="c:\\wm5\\test.ims"; To load the file
we use x=IMLcontrol.IMSLoadFile(IMSfilespec,IMSname);
So
in a couple of lines we have selected the measurement type, range,
data format, alarm settings, engineering unit conversion and so on,
individually for all channels. (Note, in the full example more lines
are used, as error checking to ensure the IMS file is found is also
included.)
- JAVASCRIPT FUNCTION TO READ AND DISPLAY DATA
The JavaScript and
html examples given in the jan2000.zip file, are
written so that data is read immediately the page is loaded, using the
function: getIMLdata()
After that data is read every time a
user clicks a Refresh button on the web page. Of course, we could
alter the code so that data is refreshed every so many seconds, or
when another event occurs.
- CALLING THE JAVASCRIPT FUNCTIONS
The first function called is to
configure the hardware (which we obviously need to do before we can read
any data). If the hardware configuration function is called initControl,
we do this then with the <BODY onLoad="initControl()"> HTML tag.
It
takes just 45 lines of JavaScript code to display our example of data
from 3 measurement channels. These channels might be, for example, two
thermocouples and one pressure transucer. Alternatively they might be
one weight reading from a balance, one temperature reading and one
humidity reading. In fact, the measurement may come from almost any type
of sensor or instrument.
This concludes our current series
of VB Corners. We hope you enjoyed them. Should you need customised data
acquisition software, written in Visual Basic or other langauges, Windmill Software's team of software
programmers would be pleased to send you a quote for your project.
Our other Visual Basic articles are in:
Do you have a question, comment or suggestion on this newsletter? E-mail
the editor - Jill Studholme - at monitor@windmillsoft.com
Copyright 2000 Windmill Software Ltd. All rights reserved. You may
freely forward this newsletter in its entirety, but please don't reproduce
individual sections without the prior written agreement of Windmill
Software Ltd.
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