A dead weight tester apparatus uses unknown traceable weights to apply pressure to a fluid for checking the accuracy of readings from a pressure gauge. A dead weight tester (DWT) is a calibration standard method that uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston. Deadweight testers are so called primary standards[citation needed] which means that the pressure measured by a deadweight tester is defined through other quantities: length, mass and time. Typically deadweight testers are used in calibration laboratories to calibrate pressure transfer standards like electronic pressure measuring devices.
Dead weight tester, Type PD23, Nagano Keiki Co., Ltd.
In general there are three different kind of DWT's divided by the medium which is measured and the lubricant which is used for its measuring element :
gas operated gas lubricated PCU's
gas operated oil lubricated PCU's
oil operated oil lubricated PCU's
All three systems have their own specific operational demands. Some points of attention :
Gas-gasedit
Make sure that the PCU is clean. This is a very important issue as the PCU's operation is sensitive to contamination. Also when connecting a DUT, make sure that the DUT does not introduce contamination in the measuring system.
Gas-oiledit
Lubricant of the PCU 'leaks' in the gas-circuit of the DWT. For this reason there is a small reservoir incorporated in the system. Before commencing a calibration it is a good practice to purge this reservoir. If the reservoir is full, oil will be introduced in critical tubing and will cause an uncontrollable oil-head.
Oil-oiledit
When connecting an oil filled DUT on an oil DWT make sure that the DUT oil will not contaminate the DWT oil. If in doubt. Incorporate a small volume between DUT and DWT and manipulate pressure in such a matter that the oil flow is directed to the DUT. For high accuracy measurement, friction can be lowered by rotation of the piston.
See alsoedit
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deadweight, tester, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, novembe. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Deadweight tester news newspapers books scholar JSTOR November 2019 Learn how and when to remove this message A dead weight tester apparatus uses unknown traceable weights to apply pressure to a fluid for checking the accuracy of readings from a pressure gauge A dead weight tester DWT is a calibration standard method that uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston Deadweight testers are so called primary standards citation needed which means that the pressure measured by a deadweight tester is defined through other quantities length mass and time Typically deadweight testers are used in calibration laboratories to calibrate pressure transfer standards like electronic pressure measuring devices Dead weight tester Type PD23 Nagano Keiki Co Ltd Contents 1 Formula 1 1 Absolute pressure with vacuum reference 1 2 Gauge pressure 1 3 Nomenclature 2 Piston cylinder design 2 1 Gas gas 2 2 Gas oil 2 3 Oil oil 3 See also 4 References 5 External linksFormula editThe formula on which the design of a DWT is based basically is expressed as follows p F A Pa where p reference pressure Pa F force applied on piston N A effective area PCU m2 To be able to do accurate measurements this formula has to be refined Absolute pressure with vacuum reference edit p m gl aee 1 rarm oo P d tA 20 0 1 ap ac t 20 1 pnom lp rN2 ra gl h pvac Gauge pressure edit pe m gl aee 1 rarm oo P d tA 20 0 1 ap ac t 20 1 pnom lp rN2 ra gl h Nomenclature edit p absolute pressure at reference level Pa pe gauge pressure at reference level Pa m total true mass load kg gl local acceleration due to gravity N kg ra ambient air density kg m3 rm average density mass load kg m3 P d t surface tension effect N rN2 density of pressure medium kg m3 h reference level offset DWT DUT m pvac vacuum residual pressure Pa A20 0 PCU effective area at p 0 and 20oC m2 ap linear thermal expansion coefficient piston oC 1 ac linear thermal expansion coefficient cylinder oC 1 t temperature of PCU oC lp elastic deformation coefficient PCU Pa 1 pnom nominal line pressure Pa pe gauge pressure applied to PCU Pa p absolute pressure applied to PCU Pa PCU Piston Cylinder Unit 1 Piston cylinder design editIn general there are three different kind of DWT s divided by the medium which is measured and the lubricant which is used for its measuring element gas operated gas lubricated PCU s gas operated oil lubricated PCU s oil operated oil lubricated PCU s All three systems have their own specific operational demands Some points of attention Gas gas edit Make sure that the PCU is clean This is a very important issue as the PCU s operation is sensitive to contamination Also when connecting a DUT make sure that the DUT does not introduce contamination in the measuring system Gas oil edit Lubricant of the PCU leaks in the gas circuit of the DWT For this reason there is a small reservoir incorporated in the system Before commencing a calibration it is a good practice to purge this reservoir If the reservoir is full oil will be introduced in critical tubing and will cause an uncontrollable oil head Oil oil edit When connecting an oil filled DUT on an oil DWT make sure that the DUT oil will not contaminate the DWT oil If in doubt Incorporate a small volume between DUT and DWT and manipulate pressure in such a matter that the oil flow is directed to the DUT For high accuracy measurement friction can be lowered by rotation of the piston See also edit nbsp Wikimedia Commons has media related to Deadweight testers Blaise Pascal Pascal unit Calibration Force gauge Piezometer Pressure measurement Pressure sensor Vacuum engineeringReferences edit Fluke Corporation Pressurements PressCal Deadweight Tester Software PDF Retrieved 21 November 2019 External links edithttp www euramet org index php id calibration guides Retrieved from https en wikipedia org w index php title Deadweight tester amp oldid 1177292996, wikipedia, wiki, book, books, library,
