-------------------------Monitor------------------------ The Newsletter for PC-Based Data Acquisition and Control Issue 98 www.windmill.co.uk September 2006 --------------------ISSN 1472-0221---------------------- Welcome to September's issue of Monitor: we hope you find it useful. Should you wish to cancel your subscription though you can do so at http://www.windmill.co.uk/newsletter.html CONTENTS ======== * Windmill News: Data Acquisition Glosary Updated * Excel Corner: Resettting a Counter from Excel * DAQ News Roundup ________________________________________________________ ________________________________________________________ Windmill News: Data Acquisition Glosary Updated ________________________________________________________ Thank you to everyone who suggested terms that should be in our data acquisition glossary. Here are some of the new inclusions. Absolute accuracy How closely the measured value approaches the real value. Relative accuracy How accurately a change in signal is measured. Analogue Input An infinitely variable signal connected to a data acquisition system. This is generally a voltage signal. Thermocouples, strain gauge bridge circuits and gas concentration probes, for example, all produce an analogue voltage. Alternatively the signal may be a milliamp current. In this case the data acquisition hardware will convert the current to a voltage before accepting it. Analogue Output A waveform or control signal generated by the data acquisition and control equipment. Digital Input A digital signal going into a data acquisition device. A digital signal has only 2 states. Digital Output A digital signal generated by the data acquisition and control equipment. Software controls each digital output by just one bit - setting the digital line high or low. Calibration The process where a data acquisition device's performance is compared to an accuracy standard, and the performance adjusted as necessary. Current sink The maximum current that data acquisition output channels can dissipate. Current source The maximum current that can be supplied by the data acquisition device for output signals. Decibel A logrithmic measure of the ratio between two quantities. Symbol dB. Dynamic range The ratio of the largest to the smallest signal that can be measured at one time. Normally expressed in Decibels (dB). The maximum signal is generally the analogue-to-digital converter's full scale signal. The dynamic range of a DAQ device is important when both large and small signals are to be measured. Dynamic Range = 20 x log (Max Voltage / Min Voltage) RTU Remote Terminal Unit. A data acquisition device at a remote location which transmits data back to, and accepts commands from, a central PC (or other controller). TCP/IP Transmission Control Protocol/Internet Protocol. Communications protocols used to connect hosts on the internet. Text format Information in the ASCII character set that is unformatted. Each byte in the file contains one character that conforms to the standard ASCII code. For the full glossary, with links to more information and articles, go to http://www.windmill.co.uk/glossary.html ________________________________________________________ ________________________________________________________ Excel Corner: Resetting a Counter from Excel ________________________________________________________ Windmill lets you use Excel to send commands to your data acquisition devices. You can thus use Excel to reset a counter to zero. How you do this depends on your counting equipment. If you have a Microlink device, such as the USB units we sell in our on-line shop (www.windmillsoft.com), then you can reset a counter by sending it a 0. If you have an instrument connected to the PC over RS232, then you can often reset a counter by sending it a command to do so. * To Reset a Microlink Counter.... ================================ 1. Start Windmill DDE Panel and select the Connections menu. Make sure your counter is connected. 2. In Excel enter a 0 into cell A1 and create this macro. Sub DDEpoke() ddeChan = Excel.DDEInitiate("Windmill", "data") Excel.DDEpoke ddeChan, "counter", Range("A1") Excel.DDETerminate (ddeChan) End Sub Where "counter" is the name of your counter channel. 3. Run the macro from Excel. The counter is reset to 0. Note: You can't reset a Microlink 826 to 0. This logs data from utility meters - sending the consumption readings to a PC running Windmill. * To Reset a Counter on an RS232 Instrument... ============================================ 1. Install the free Windmill Software with the LabIML driver or the Windmill CONFIML software (http://www.windmill.co.uk/https://www.windmillsoft.com/daqshop/rs232-modbus.html). 2. With the free software, use ConfIML to configure the driver. Create an extra channel to hold the Reset command. 3. In ConfIML, go to the Channel settings dialogue. - Select your Reset channel and set it as a "Write channel" - Type \V into the Write string box. When you run your Excel macro, the \V will be replaced by the reset command. If the command needs any hidden characters, such as a Return, use the non-printable button to insert these before or after the \V - Save 4. Start SetupIML and create a setup file using the configuration you have just saved. 5. Start Windmill DDE Panel, load the setup file and connect your counter. 6. In Excel, enter the command to reset the counter into cell A1 and then create this macro Sub DDEpoke() ddeChan = Excel.DDEInitiate("Windmill", "data") Excel.DDEpoke ddeChan, "counter", Range("A1") Excel.DDETerminate (ddeChan) End Sub Where "counter" is the name of your counter channel. When you run the macro, the \V command you entered in ConfIML is replaced by whatever is in cell A1 in Excel. For example, to reset a magnetometer counter you might have the command ARC followed by a carriage return. In ConfIML you would enter \V\C013 (\C013 indicates the carriage return). In Excel you would enter ARC into cell A1. When you ran the macro the \V is replaced by ARC and is followed by the carriage return. * Note: If you prefer you can use the AnalogOut program instead of DDE Panel. In this case, for line 2 of your macro, use ddeChan = Excel.DDEInitiate("AnalogOut", "data") For more on using Excel for data acquisition and control, see http://www.windmill.co.uk/excel/ ________________________________________________________ ________________________________________________________ DAQ News Roundup ________________________________________________________ Welcome to our roundup of the latest findings in data acquisition and control. If you would like to receive more timely DAQ news updates then grab our RSS newsfeed at https://www.windmillsoft.com/monitor.xml. Read http://www.windmill.co.uk/newsfeed.php for notes on how to display the news on your own web site, read it via e-mail or through a newsfeed viewer. Swallowable Sensors An ingested wireless capsule that can help clinicians diagnose digestive disorders is ready for patients. The electronic pill is swallowed; it then gathers information about the digestive system as it travels through it, transmitting the information to a receiver worn by the patient. Source: Technology Review http://www.technologyreview.com/ How-To Guide for Removing Data from Storage Media Before ditching or donating that used computer, CD or other data-storage media, sensitive or personal information should be properly "sanitised," according to a new guide from the National Institute of Standards and Technology (NIST). The Guide provides information on techniques to remove data from a wide variety of media types and a decision matrix to determine which technique is best. Source: National Institute of Standards and Technology https://www.nist.gov/ New sensor system detects ocean pollution A new technique developed by UC Irvine scientists mathematically analyses temperature and salinity data collected by sensors in the water along the coast. The scientists found that fluctuations in the sensor data immediately correlate with changes in water quality. This is a far faster way of detecting pollution than collecting water samples. The researchers' equations transform the data into a measurement of the range over which the data naturally fluctuates, and thus immediately flag pollution. Source: University of California, Irvine http://today.uci.edu/news/release_detail.asp?key=1525 Taking measurements inside a hurricane A small aircraft is set to fly through the eye of a hurricane to take the first continuous data on how such storms gain their strength. The craft, called an aerosonde, will measure the temperature, pressure, humidity and wind velocity inside the storm in an effort to help predict changes in hurricane intensity. Source: NewScientist.com news service http://www.newscientistspace.com/ ________________________________________________________ ________________________________________________________ * 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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