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DAVID W. SPITZER'S E-ZINE
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TECHNICAL AND MARKETING SERVICES
FOR INSTRUMENTATION SUPPLIERS AND END-USERS
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The field effect transistors are designed such that charge must build up on the gate to allow current to flow from the drain to the source. The gate is coated with silicon nitride or aluminum oxide that selectively adsorbs hydrogen ions from solution thus developing a positive charge on the gate.
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The overwhelming majority of centrifugal pumps need to overcome the static pressure in the piping system. Assume the liquid is being pumped to an atmospheric tank located six meters above the pump. This means that a pump speed of approximately 77 percent (square root of 0.6 per the second Affinity Law) is required to overcome the static head in the discharge pipe and initiate flow. There will be no flow at the 50 percent pump speed. Pump speed requirements will be even higher if the tank is pressurized and/or if flow with pipe friction is considered.
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Coriolis mass flowmeters have good accuracy and have the advantage of measuring mass flow directly without having to compensate for density. Positive-displacement flowmeters also measure accurately but do not inherently compensate for density, so independent temperature compensation may be advisable in some applications. In general, there appears to be a trend away from positive-displacement flowmeters (traditionally used in this service) toward the application of Coriolis mass flowmeters.
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ABOUT SPITZER AND BOYES, LLC
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In addition to over 35 years of experience as an instrument user, consultant, and expert witness, David W Spitzer has written over 10 books and 250 articles about flow measurement, level measurement, instrumentation, and process control. David (with Walt Boyes) is the author of seven Consumer Guides to various industrial flow and level technologies. David teaches his flow measurement seminars in both English and Portuguese.
Spitzer and Boyes, LLC provides engineering, technical writing, training seminars, strategic marketing consulting, distribution consulting, and expert witness services worldwide, and can be contacted at +1.845.623.1830 or www.spitzerandboyes.com.
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