-------------------------Monitor------------------------ The Newsletter for PC-Based Data Acquisition and Control Issue 80 www.windmill.co.uk March 2005 --------------------ISSN 1472-0221---------------------- Welcome to our 80th issue. We hope you find it useful, but should you wish to cancel your subscription to Monitor you can do so at http://www.windmill.co.uk/newsletter.html CONTENTS ======== * Windmill News: ComDebug Helps Product Development * Tensiometers and Computerised Irrigation * Excel Corner: Average Values per Hour ________________________________________________________ ________________________________________________________ Windmill News: ComDebug Helps Product Development ________________________________________________________ The Colour Vision Systems company manufactures fruit sorting equipment which is tailored specifically to a customer's needs. When developing a new product they used ComDebug as a short-cut to understanding the control of Telemecanique Altivar variable speed drives. This helped them write dedicated drive communication software in-house, to control VSDs fitted to their machinery. The ComDebug software they used has extensive trouble-shooting capabilities for communicating with almost any RS232, RS422, RS485 or Modbus serial device. What's more, it's free. Download your copy at http://www.windmill.co.uk/serial.html Further Reading: ================ ComDebug http://www.windmill.co.uk/serial.html Other Applications of Windmill http://www.windmill.co.uk/software.html#applications Colour Vision Systems http://www.cvs.com.au/ ________________________________________________________ ________________________________________________________ Tensiometers and Computerised Irrigation ________________________________________________________ Water management is very important in agriculture. Accurately monitoring soil moisture allows precise irrigation. This maximises crop quality, reduces nutrient run-off and saves water. One way to measure soil moisture is with a tensiometer. This comprises a sealed, water-filled, chamber with a porous ceramic tip; a vacuum gauge or pressure sensor; and, in a switching tensiometer, a contact relay. The tensiometer senses and registers the suction force created by the plant pulling water from the soil. When the soil is drying, water flows from the tensiometer chamber across the porous tip into the soil. When the soil is re-wetted, the vacuum which was created inside the chamber during water removal pulls water back from the soil through the porous tip into the tensiometer. The tensiometer's pressure sensor registers the associated pressure changes. A switching tensiometer can automatically control irrigation - not just sense soil moisture. When the vacuum pressure in the chamber reaches a pre-set "dry" reading, a contact relay closes allowing irrigation. When the soil returns to the desired moisture level, the switch opens stopping irrigation. Of course, the switch has to be connected to something. For example, when the switch closes it might complete a circuit to a solenoid valve which opens and allows water to be applied to the soil. Alternatively, you can use a PC to control irrigations. With a PC and software like Windmill, you can also record all irrigations. You can do this either by monitoring the state of the relay of a switching tensiometer, or by taking readings from the pressure transducer. A new log file can be created each day or each week if necessary. The data is easily imported into a database like Access or a spreadsheet like Excel. A computerised system can also record and display temperature, humidity, wind, rainfall and other data. Some tensiometers you can connect directly to the PC's COM port. Others will need an interface fitted to the PC before you can take readings. Further Reading =============== Windmill COMIML: driver needed to communicate with the tensiometer https://www.windmillsoft.com/daqshop/rs232-modbus.html Windmill Logger http://www.windmill.co.uk/logger.html ________________________________________________________ ________________________________________________________ Excel Corner: Average Values per Hour ________________________________________________________ Assume you are continually logging data over several days, and importing the data into Excel. You want to find out the average value for each hour. Windmill collects data in this format Time Temp seconds celsius 16:40:00 18.63 16:45:00 18.42 16:50:00 18.40 16:55:00 18.21 17:00:00 18.15 17:05:00 17.96 17:10:00 17.88 17:15:00 17.82 17:20:00 17.80 To find average readings each hour you need to: 1. Extract the hour from each time reading. To do this use =HOUR(A3), where A3 is the cell reference of the first time stamp. Place this formula in cell C3, then drag it down to the bottom of the data table. 2. Create a named range called "Hour" for the values in column C. 3. Create a named range called "Data" for the data values. 4. Sum all temperatures for a specific hour. For example, for 4 o'clock use =SUMIF(Hour,"=16",Data) Place this in column D 5. Count occurances of the specific hour with =COUNTIF(Hour,"=16") Place this in column E 6. Divide the Sum by the Count to reach the average. For example, =D3/E3 or, if you want to miss out columns D and E use =SUMIF(Hour,"=16",Temperature)/COUNTIF(Hour,"=16") 7. Repeat steps 4, 5 and 6 for the 23 other hour values. Further Reading =============== For tips on using Excel with Windmill see http://www.windmill.co.uk/excel/ For tips on creating ranges in Excel see http://www.windmill.co.uk/monitor53.html http://www.windmill.co.uk/monitor55.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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