ASTM_D_6176_-_97_2015.pdf

Designation:D617697(Reapproved 2015)Standard Practice forMeasuring Surface Atmospheric Temperature with ElectricalResistance Temperature Sensors1This standard is issued under the fixed designation D6176;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 This practice provides procedures to measure represen-tative near-surface atmospheric(outdoor air)temperature formeteorological purposes using commonly available electricalthermometers housed in radiation shields mounted on station-ary or portable masts or towers.1.2 This practice is applicable for measurements over thetemperature range normally encountered in the ambientatmosphere,50 to+50C.1.3 Air temperature measurement systems include a radia-tion shield,resistance thermometer,signal cables,and associ-ated electronics.1.4 Measurements can be made at a single level for variousmeteorological purposes,at two or more levels for verticaltemperature differences,and using special equipment(at one ormore levels)for fluctuations of temperature with time appliedto flux or variance measurements.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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.2.Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheresE344 Terminology Relating to Thermometry and Hydrom-etryE644 Test Methods for Testing Industrial Resistance Ther-mometersE1137/E1137M Specification for Industrial Platinum Resis-tance Thermometers3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice,refer toTerminology D1356 and E344.Some definitions are repeatedin this section for the readers convenience.3.1.2 connecting wiresthe wires which run from the ele-ment through the cable end closure and external to the sheath.3.1.3 interchangeabilitythe extent to which the thermom-eter matches a resistance-temperature relationship.3.1.4 inversionthe increase in potential temperature withan increase in height(see 3.1.5 and 3.2.7).3.1.5 lapse ratethe change in temperature with an in-crease in height(see 3.1.4 and 3.2.7).3.1.6 resistance thermometera temperature-measuring de-vice comprised of a resistance thermometer element,internalconnecting wires,a protective shell with or without means formounting,a connection head or connecting wire with otherfittings,or both(see also 3.2.3).3.1.7 resistance thermometer elementthe temperature-sensitive portion of the thermometer composed of resistancewire,film or semiconductor material,its supporting structure,and the means for attaching connecting wires.3.1.8 thermistora semiconductor whose primary functionis to exhibit a monotonic change(generally a decrease)inelectrical resistance with an increase in sensor temperature.3.2 Definitions of Terms Specific to This Standard:3.2.1 ambientthe portion of the atmosphere where the airtemperature is unaffected by local structural,terrain,or heatsource or sink influences.3.2.2 sensorused interchangeably with resistance ther-mometer(see 3.1.6)in this practice.3.2.3 shielda ventilated housing designed to minimize theeffects of solar and terrestrial radiation on a temperature sensorwhile maximizing convective heat transfer between the sensor1This practice is under the jurisdiction ofASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved April 1,2015.Published April 2015.Originallyapproved in 1997.Last previous edition approved in 2008 as D6176 97(2008).DOI:10.1520/D6176-97R15.2For 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 and the passing air,and to protect the sensor from contact withliquid moisture;also known as radiation shield.3.2.4 temperature differentialthe difference between twoor more simultaneous temperature measurements,typicallyseparated vertically at a single location;see 3.1.4 and 3.1.5.3.2.5 temperature variancea statistical measure,the de-viation of individual temperature measurements from the meanof those measurements obtained over a user-defined samplingperiod.3.2.5.1 DiscussionTemperature variance describes tem-perature variability at a fixed point in the atmosphere.Thecovariance of temperature and