-------------------------Monitor------------------------ The Newsletter for PC-Based Data Acquisition and Control Issue 65 www.windmill.co.uk December 2003 --------------------ISSN 1472-0221---------------------- Welcome to December's Monitor - our compliments of the season to you. In this issue, how Windmill is helping a French winery comply with bottling standards. We also discuss the importance of dewpoint and humidity measurements, and have our bi-monthly exhibition listing. The Excel corner is having a Christmas break. We hope you find the newsletter useful, but should you wish to cancel your subscription please do so at http://www.windmill.co.uk/newsletter.html CONTENTS ======== * Windmill News: Windmill helps bottle French wine * Dewpoint temperature and humidity * Data acquisition and control exhibitions ________________________________________________________ ________________________________________________________ WINDMILL NEWS: WINDMILL HELPS BOTTLE FRENCH WINE ________________________________________________________ HACCP (Hazard Analysis and Critical Control Point) and the BRC (British Retail Consortium) protocol require that bottle volume is checked for accuracy by the weight method and that records of such check are kept. To comply with this the Quality Control department of the Maurel Vedeau S.A. winery test their bottling line by weighing a sample of bottles before and after they are filled. To speed up this process, and eliminate errors, they looked for some software which would communicate with their Mettler Toledo scales and send the weight results to directly to a Microsoft Excel spreadsheet. The software had to be low cost and easy to use, and so they chose Windmill. Regis Revolu, who implemented the system, commented: "Searching through the web for a cheap interface to link a lab scale directly to Excel, I found with Windmill 4.3 not only the interface I was looking for, but also an easy-to-follow step by step procedure (+ VBA program) which made it most simple to use and implement." The Solution ============ One to five empty bottles are identified and weighed. After passing down the bottling line they are weighed again. A VB application in Excel allows Quality Control to - Select various details from drop-down lists including: the size of the bottles (75cl, 100 cl, etc), the client for whom the wine is being bottled, the type of wine and the vintage. - Enter the lot number and wine density Windmill automatically collects the weight data from the scales and sends it to Excel. Excel divides the weight by the wine's density and calculates the liquid volume. The average volume across the 5 bottles is also calculated. Excel checks whether the volumes are as they should be, and if not warns the operator of the problem. On pressing the Record button, the system logs all the information for Quality Control records. As a Monitor subscriber, you can download the Windmill Software used in this application for free. The latest version of Windmill, Windmill 6, is available from https://www.windmillsoft.com/daqshop/rs232-modbus.html Maurel Vedeau S.A. have kindly made their Excel VB application available for download at http://www.windmill.co.uk/mv/mtscale1.xls Disclaimer: The use of this program is entirely the responsibility of the user; neither Maurel Vedeau S.A. nor Windmill Software can give any guarantee, nor accept any liability, arising from the use of this program. For other applications of Windmill see http://www.windmill.co.uk/software.html For more on Mettler Toledo balances see http://www.windmill.co.uk/mettler.html ________________________________________________________ ________________________________________________________ DEWPOINT TEMPERATURE AND HUMIDITY ________________________________________________________ The Significance of Dewpoint Temperature ======================================== Dewpoint temperature impacts on much more than heating, ventilation and cooling considerations. It plays a major role in - the attainment of high product yield - the efficient use of energy in many chemical manufacturing processes - convective heat transfer - combustion of fossil fuels and combustion engineering, - drying of paper, cardboard, plastics, wood, tobacco, leather, printed goods, textiles and grain - corrosion phenomena which can result in damage and loss of not only unprotected iron and steel structural components but also improperly stored steel and other metal products. * What is Dewpoint? ================= The dewpoint, or more precisely the dewpoint temperature, is the temperature at which the liquid and gaseous phases of a material present in a gas, such as water in air, are in equilibrium at a given gas pressure. In other words, the dewpoint is the temperature at which the liquid water, or dew, evaporates at the same rate at which it condenses. Measurements of dewpoint and related humidity represent a significant use of temperature sensors, usually integral to the device or instrument that reports the dewpoint temperature or humidity conditions. * Dew Forms. Fog and Dew Disappear...it seems =========================================== The dewpoint temperature is most comonly observed in ambient air and is also called the saturation temperature of water vapor in air. If you lower the temperature, dew will form as fog or condense on a cooler surface faster than it evaporates. This phenomenon is observed, for instance in very moist air when the dew appears as fine water droplets suspended in air (fog) and on cool beverage containers in hot weather conditions. Conversely, if one raises the temperature above the saturation temperature, dew will evaporate faster than it condenses. Fog in air and dew on surfaces will dissapear under such conditions. This is commonly seen when dew on the ground vanishes as the air warms after a cool night. The value of the dewpoint depends upon the air temperature, since hotter air can hold more water vapor per unit volume than can colder air. Likewise, the value of the dewpoint at a given air temperature is also a function of air pressure. * Humidity, It's Not All Relative =============================== The dewpoint or saturation temperature also is described as the 100% relative humidity (RH)condition; when air holds 100% of the moisture that it possibly can. The RH of air is defined technically as the ratio of the water vapor pressure to the vapor pressure of saturated air at the same temperature. But it is measured in many different ways, ranging from horse hairs to special electronic sensors. The moisture content of air can also be characterised in terms of the absolute humidity (AH) or humidity ratio, the weight of water vapor in the air per unit weight of dry air at the same temperature (pounds per pound or kilos per kilo). Just from the brief descriptions above it can be appreciated that there are three different measurement variables described, dewpoint temperature, relative humidity and absolute humidity, which can each independently represent the same water-vapor-in-air condition. To complicate matters even further, a time- honoured method to measure the moisture conditions in air has been to measure the dry bulb and the wet bulb temperature of the air. * Heat is Involved..of course =========================== Then it starts getting a little complex. Since it takes heat input to evaporate liquid water and since water vapor releases heat when it condenses, there is an obvious energy content in a given mass of moist air. The energy content depends upon the temperature and the amount of moisture present. This involves costs when one is trying to remove the moisture from something like grain or a wet web of paper using a flow of air. Increasing the air temperature can enable faster drying, but it requires heat to increase the air temperature. That means some fuel must be expended at a cost. Similarly when, for comfort reasons, one needs to cool the air below the dewpoint temperature by flowing air over a cold surface. It costs fuel and money to cool the surface and "soak up" the heat that the condensing water liberates, not to mention the cost of moving the air. So, the total heat content of air depends upon its moisture content. The energy relation is described as the enthapy per unit weight, BTU/Lb or J/Kg. It is also important to note, that almost inevitably each of the three variables, when described, is paired with the air temperature value. For example, a statement that the relative humidity is 65% means much more when the current air temperature is also given. Of course, under such conditions the air temperature is higher than the dewpoint temperature since the air is not saturated. * It's All Related and Described (by Equations, Tables and Charts and Available in Software) ======================================================== Needless to say, there are well established relationships between the four variables. The relationships can be described in terms of equations, in numerical tables and graphically. One of the most commonly used methods, until the advent of low cost computers with programs relating the parameters, was the psychrometric chart. It is still widely used and takes several forms. Almost complicating the matter of measuring the properties of air (or any other gas) containing moisture further still are the facts of independent methods for measuring each of the variables described above and several different device types to perform each variable measurement. Since temperature sensors are used either directly or indirectly in most of these measurements, they are considered a unique use or application of temperature sensors. * By Ray Peacock, industrial physicist and founder of Temperatures.com, Inc. Ray teaches an industrial temperature measurement course for ISA (the Instrumentation, Systems and Automation Society) and can be contacted at [email protected] or via the http://www.temperatures.com/ website. Further Reading: Monitor Issue 23: Using a PC to Monitor Weather http://www.windmill.co.uk/monitor23.html Monitor Issue 5: How to Use Your PC to Measure Temperature http://www.windmill.co.uk/thermocouple.html For more on computerised humidity measurement please contact Windmill Software on [email protected] ________________________________________________________ ________________________________________________________ DATA ACQUISITION AND CONTROL EXHIBITIONS ________________________________________________________ Continuing our bi-monthly listing of exhibitions and conferences related to data acquisition and control. ICISIP - 2004 4-7 January Le Royal Meridien Chennai India International conference on intelligent sensing and information processing. http://www.icisip.org/ Measurement Science Conference 12-16 January Disneyland Hotel Anaheim California USA Founded in 1970 to promote education and professionalism in measurement science and related disciplines. http://www.msc-conf.com/ Sicon/04 27-29 January 2004 InterContinental Hotel New Orleans USA Sensors for industry conference, focusing on sensors for defense and security. Organised by ISA and the Instrumentation and Measurement Society of IEEE. http://www.siconference.org/ mtec 2004 11-12 February NEC Birmingham UK Addresses all aspects of sensor, measurement and instrumentation technology. http://www.mtec-info.co.uk/ Southern Manufacturing 2004 18-19 February Thorpe Park, Surrey, UK http://www.industry.co.uk/ CHIFA 2004 3-6 March Guangzhou Canton China 8th international factory automation and instrument exhibition. http://www.merebo.com/ Automaticon 23-26 March Warsaw Poland International fair for measurement and control http://www.world-fima.com/ml ________________________________________________________ * 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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