ASTM_D_3631_-_99_2011.pdf

Designation:D363199(Reapproved 2011)Standard Test Methods forMeasuring Surface Atmospheric Pressure1This standard is issued under the fixed designation D3631;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 These methods cover the measurement of atmosphericpressure with two types of barometers:the Fortin-type mercu-rial barometer and the aneroid barometer.1.2 In the absence of abnormal perturbations,atmosphericpressure measured by these methods at a point is valideverywhere within a horizontal distance of 100 m and a verticaldistance of 0.5 m of the point.1.3 Atmospheric pressure decreases with increasing heightand varies with horizontal distance by 1 Pa/100 m or lessexcept in the event of catastrophic phenomena(for example,tornadoes).Therefore,extension of a known barometric pres-sure to another site beyond the spatial limits stated in 1.2 canbe accomplished by correction for height difference if thefollowing criteria are met:1.3.1 The new site is within 2000 m laterally and 500 mvertically.1.3.2 The change of pressure during the previous 10 min hasbeen less than 20 Pa.The pressure,P2at Site 2 is a function of the known pressureP1at Site 1,the algebraic difference in height above sea level,h1 h2,and the average absolute temperature in the spacebetween.The functional relationship between P1and P2isshown in 10.2.The difference between P1and P2for each 1 mof difference between h1and h2is given in Table 1 and 10.4 forselected values of P1and average temperature.1.4 Atmospheric pressure varies with time.These methodsprovide instantaneous values only.1.5 The values stated in SI units are to be regarded as thestandard.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Specific safetyprecautionary statements are given in Section 7.2.Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3249 Practice for General Ambient Air Analyzer Proce-duresIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units(SI):The Modern Metric System3.Terminology3.1 Pressure for meteorological use has been expressed in anumber of unit systems including inches of mercury,millime-tres of mercury,millibars,and others less popular.Thesemethods will use only the International System of Units(SI),asdescribed in IEEE/ASTM SI 10.3.1.1 Much of the apparatus in use and being sold reads inother than SI units,so for the convenience of the user thefollowing conversion factors and error equivalents are given.3.1.1.1 The standard for pressure(force per unit area)is thepascal(Pa).3.1.1.2 One standard atmosphere at standard gravity(9.80665 m/s2)is a pressure equivalent to:29.9213 in.Hg at 273.15 K760.000 mm Hg at 273.15 K1013.25 millibars14.6959 lbf/in.2101325 Pa or 101.325 kPa3.1.1.3 1 Pa is equivalent to:0.000295300 in.Hg at 273.15 K0.00750062 mm Hg at 273.15 K0.01000000 millibars0.000145037 lbf/in.20.000009869 standard atmospheres3.2 standard gravityas adopted by the International Com-mittee on Weights and Measures,an acceleration of 9.80665m/s2(see 10.1.3).3.3 The definitions of all other terms used in these methodscan be found in Terminology D1356 and Practice D3249.1These test methods are under the jurisdiction of ASTM Committee D22 on AirQualityand are the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved Oct.1,2011.Published October 2011.Originallyapproved in 1977.Last previous edition approved in 2007 as D3631-99(2007).DOI:10.1520/D3631-99R11.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.Summary of Methods4.1 The instantaneous atmospheric pressure is measuredwith two types of barometers.4.2 Method A utilizes a Fortin mercurial barometer.Themercury barometer has the advantage of being fundamental inconcept and direct in response.The disadvantages of themercury barometer are the more laborious reading procedurethan the aneroid barometer,and the need for temperaturecorrection.4.3 Method B utilizes an aneroid barometer.The aneroidbarometer has the advantages of simplicity of reading,absenceof mercury,no need for temperature compensation by theobserver,and easy detection of trend of change.The maindisadvantages of the aneroid barometer are that it is notfundamental in concept as the