Vol. 6 No. 1 Subject: Flow Measurement News Date: 2-25-04 From: McCrometer, "The Flow Measurement Specialists" ........ http://www.mccrometer.com ........ ******************************************* This newsletter is e-mailed by McCrometer monthly to subscribers worldwide. It consists of flow measurement information of interest for professionals in this field. For More information on our complete line of flowmeters go to: <http://www.mccrometer.com> ******************************************* McCrometer Newsletter – February 2004 Special Notice - McCrometer is pleased to announce the addition of guest authors for our monthly newsletter. This month we feature David W. Spitzer, PE. David has over 25 years experience in many facets of instrumentation, process control, electrical, and utility engineering, including conceptualization, estimating, design, construction, startup, operation, troubleshooting, and teaching. Alongside Walt Boyes, they own and operate Spitzer and Boyes LLC, serving both the profit and not-for-profit business sectors. Flowmeter Performance (excerpt from The Consumer Guide to Magnetic Flowmeters) By David W. Spitzer The purpose of installing a flowmeter system is to measure flow accurately in a reliable manner. Whereas issues dealing with physical properties, process parameters, electronic features, and interconnections are often considered extensively, the quantification of the expected measurement quality of the installed flowmeter can be virtually neglected. Often, relatively little emphasis is given as to how well the flowmeter will perform its intended purpose. Adding to the confusion are the differences in the manner in which performance is expressed and the incomplete nature of the available information. Nonetheless, the quality of flow measurement should be a prime concern. Accuracy Statements The performance of a flowmeter is quantified by means of its accuracy statements. One must understand not only which parameter is being described, but also the manner in which the statement is expressed. In flow measurement, parameters are commonly described in terms of a percentage of the actual flow rate, a percentage of the full scale flow rate, and/or a percentage of the meter capacity. These terms are mathematically related so it is possible to convert one to another. Note that other terminology may be used to express these concepts. When this occurs, confirm exactly what the other terms mean in order to correctly relate them to the terms used in this report. A percentage of rate statement describes a parameter that is in error by a constant percentage of the actual measurement. In the measurement of 0-100 units measured with an accuracy of 1 percent of rate, the absolute error can be calculated as: Flow Absolute Error (1% rate) 100 units 1% of 100 = 1.00 unit 50 “ 1% of 50 = 0.50 “ 25 “ 1% of 25 = 0.25 “ 10 “ 1% of 10 = 0.10 “ In contrast, a percentage of full scale statement describes a parameter that is in error by a constant amount regardless of flow rate. In the measurement of 0-100 units measured with an accuracy of 1 percent of full scale, the absolute error can be calculated as: To find out more about McCrometer's line of flow meters, including the V-Cone(r), Wafer-Cone(r), the V2-Municipal(tm), Water Specialties Propeller Meter(tm), Mc(r) Propeller, Ultra Mag(r), and SK(r) Variable Area Meters, please contact McCrometer at 951-652-6811 or visit our website at www.mccrometer.com ******************************************* Copyright 2003 McCrometer If you have comments or suggestions for newsletter topics you would like to see, please address them to: Bob Peters or Richard Steven mailto:newscomment@mccrometer.com ********************************************************************************* Know anyone looking for a steady dose of flow measurement information? ********************************************************************************* To subscribe send e-mail to mailto:news-request@mccrometer.com with a keyword SUBSCRIBE in the subject field. To unsubscribe, send e-mail to mailto:news-request@mccrometer.com with a keyword REMOVE in the subject field. ********************************************************************************* To subscribe or unsubscribe online, please go to our website at: http://www.mccrometer.com/subscribe.htm ********************************************************************************* Distributed by McCrometer "The Flow Measurement Specialists" http://www.mccrometer.com