-------------------------Monitor------------------------ The Newsletter for PC-Based Data Acquisition and Control Issue 68 www.windmill.co.uk March 2004 --------------------ISSN 1472-0221---------------------- Welcome to the March edition of Monitor. This month we've the results of our survey, notes on dealing with alarms in Windmill and a discussion on some of the types of chart available in Excel. We hope you find this issue useful, but should you wish to cancel your subscription please do so at http://www.windmill.co.uk/newsletter.html CONTENTS ======== * Windmill News: The Survey Results * Windmill Notes: Handling Alarms * Excel Corner: Pie, Doughnut, Bubble and Surface Charts ________________________________________________________ ________________________________________________________ Windmill News: The Survey Results ________________________________________________________ Our thanks once again if you returned our January survey. Your comments have made interesting reading and prompted plenty of ideas for the future of Monitor. After our announcement in the last issue that the exhibitions section was to be scrapped, we received a flurry of survey responses in favour of the listings. We've therefore decided to reinstate them, but on a quarterly basis. In the space created we'll run a series of notes on the Windmill programs. We've examined your suggestions for topics you'd like to See discussed, and will endeavour to cover as many of these as possible in future editions. The most popular part of the newsletter was the accounts of how Windmill was being used in the real-world. To include more of these application stories, however, we need your help. When people buy Windmill software, or download it from the web, unless they have a problem we normally don't hear from them again. We therefore don't know how they are using Windmill. If you have found Windmill software useful, and would be happy for us to use your application as an example, please get in touch. Fill in the form at http://www.windmill.co.uk/application.html Meanwhile, you can find a list of previously covered applications at http://www.windmill.co.uk/software.html#applications The Excel corner was a close runner-up in popularity. If you have a question about using Excel with Windmill, or a tip you'd like to share, let us know. Previous Excel notes are archived at http://www.windmill.co.uk/excel/ and http://www.windmill.co.uk/excel/excel-charting.html ________________________________________________________ ________________________________________________________ Windmill Notes: Handling Alarms ________________________________________________________ Windmill lets you set two alarm thresholds on each measurement channel: a warning alarm and a critical alarm. When monitoring temperature for example, you might specify a warning alarm when the reading rose above 27 oC and a critical alarm when it exceeded 33 oC. Alternatively, you could have a warning alarm when a temperature fell below freezing and a critical alarm when it rose above boiling. Use the SetupIML program to set alarm thresholds. SetupIML also lets you set the level when the alarm is to be cancelled. In our first example above, you might choose to keep the warning alarm in place until the temperature returned to below 25 oC. This stops an alarm continually being switched on and off if the temperature is wavering around the alarm threshold. You can choose to output a digital signal when a channel goes into alarm. With suitable hardware this lets you turn on a light, sound a buzzer or activate an autodialler to ring a telephone number with a pre- programmed message. Tip: Every alarm condition you define uses some memory and requires processing time to continually check whether the condition is true or false. To optimise Windmill's performance, therefore, only enable alarms where needed. * How the Windmill Programs Treat Alarms: Display, Control, Logging and Telephoning ========================================= Display ------- The Windmill Logger and DDE Panel programs show warning alarms on a blue background and critical alarms on a red background. Windmill Chart shows alarm levels as tick marks on its axis. It can also show its traces in different colours for no alarm, warning alarm and critical alarm states. Control ------- When a channel goes into alarm, you might want a series of events to occur. We've already mentioned the digital switching, but with the optional Windmill Test-Seq program you can perform much more sophisticated control. Test-Seq interprets a file of commands and controls the other Windows programs, or data acquisition equipment, accordingly. With Test-Seq, for example, you could automatically log at different speeds depending on whether channels are in alarm. Perhaps taking readings every 10 seconds when there are no alarms and every second when there is a channel in alarm. You could also: - Pass control to another part of the test sequence when a specified alarm occurs - Prioritise alarms - Latch alarms so the alarm continues to be reported until Test-Seq instructs differently - Wait until an alarm occurs before continuing with your test sequence program - Wait until all alarms are cleared before continuing with your test sequence program For more on Test-Seq see https://www.windmillsoft.com/daqshop/test-control.html Logging and Telephoning ----------------------- Although the standard Windmill Logger program indicates on screen when channels are in alarm, it doesn't save any additional information about the alarm. For this you need the Windmill Alarm Logger which records alarms, and the action taken, in a file. Whenever Alarm Logger finds a channel that is in alarm, it pops into the foreground of the computer screen and beeps. It can also alert you by playing an audio file through a sound card, switching a digital switch (buzzer, light, etc) or by telephoning an engineer. Alarm Logger software also lets you insert delays between an alarm being registered and an output being switched - useful in reducing the instances of false alarms. If, say, the temperature of a freezer was to momentarily rise when the freezer lid was opened; the alarm would not activate unless the temperature remained over the limit for a certain time. You can tell Alarm Logger that you're aware of the alarm and not to report it again until a set time has passed, so acknowledging the alarm. Operators are asked what action they have taken on the alarm and their comments are recorded. It is easy to run Alarm Logger over an Ethernet network, as it actually consists of three programs: a Setup, a Monitor and a Viewer. The Alarm Setup configures the system, letting you set such things as the time between alarm checks or an advisory message to be displayed when a specific alarm occurs. The Alarm Monitor watches the hardware for alarms. When the Monitor flags an alarm, the Alarm Viewer tells engineers about it. The Setup, Monitor and Viewer programs can be run on different computers around a network. For more on Alarm Logger see http://www.windmill.co.uk/alarm.html ________________________________________________________ ________________________________________________________ Excel Corner: Pie, Doughnut, Bubble and Surface Charts ________________________________________________________ Excel offers many different ways to chart data. In Issue 34 of Monitor we discussed Stock, Column, Bar, Line and xy Scatter charts, and their suitability for data acquisition applications. Today we cover some more chart types with tips on their strengths and weaknesses. For illustrations of these and other Excel chart types see the Microsoft site: http://office.microsoft.com/assistance/preview.aspx?AssetID=HA010346071033&CTT=6&Origin=EC010553071033 Pie Charts ========== A pie chart shows data from one row or column of data. They are good for comparing quantities, letting you see at a glance the relation of each item to the whole. They are also valuable when you want to emphasize the importance of one measurement compared to the rest. If you were monitoring electricity meters at four locations, a pie chart showing the percentage contribution of each to the total consumption might be a good choice. However, the more values you include the more difficult it becomes to compare data, and the more unsuitable a pie chart becomes. It is much easier to examine values that are numerically close with a bar or column chart. Doughnut Chart ============== A doughnut chart is like a pie chart but can contain more than one data series. It has the same drawbacks as a pie chart, but the extra data series make it even more difficult to interpret easily. I've yet to see a set of data collected by Windmill that couldn't be better represented by another choice of chart. Bubble Charts ============= Bubble charts are similar to xy scatter charts. In scatter charts you plot two variables against one another. For example, you might plot latitude on the x axis against longitude on the y axis. With a bubble chart, three variables are represented. Each data point has two values, as in the scatter chart, but is shown as a bubble rather than a point. The size of the bubble indicates the value of a third variable. Suppose, for example, you were a train operator trying to find out on which parts of the track the train wheels were slipping. A device in the train logs latitude, longitude and the duration of the train's wheel slippage. In Excel you plot latitude against longitude and show wheel slippage duration as the bubbles. The largest bubbles show where the problem is the greatest. Surface Charts ============== A surface chart is a 3-dimensional graph which is good for showing the relationship between three variables. It looks like a topographic map with colours showing areas that have similar values. For example, the strength of a material decreases with time and increases with temperature. A surface chart would let you quickly see the combinations of temperatures and time that produce the same strain results. However, Excel's surface charts are not true 3D scatter charts. Excel treats the x and y values as categories and thus expects a grid of data. If you were comparing rainfall in different areas during different months, for example, you would have a grid like this (you need to set your e-mail viewer to courier font to get it to display correctly) Area1 Area2 Area3 Jan 106.3 152 88.9 Feb 130.5 70.3 82.3 etc For a true 3D chart forget Excel and choose an analysis package like FAMOS. Further Reading =============== Microsoft's Examples of Excel Chart Types http://office.microsoft.com/assistance/ Our Excel Charting Tips http://www.windmill.co.uk/excel/excel-charting.html ________________________________________________________ ________________________________________________________ * 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/
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