ASTM D6176-97(2022)

SIGNIFICANCE AND USE 4.1 Applications—Ambient atmospheric temperature measurements can be made using resistance thermometers for many purposes. The application determines the most appropriate type of resistance thermometer and data recording method to be used. Examples of three typical meteorological applications for temperature measurements follow. 4.1.1 Single-level, near-surface measurements for weather observations (1)3, thermodynamic computations for industrial applications, or environmental studies (2). 4.1.2 Temperature differential or vertical gradient measurements to characterize atmospheric stability for atmospheric dispersion analyses studies (2). 4.1.3 Temperature fluctuations for heat flux or temperature, or variance computations, or both. Measurements of heat flux and temperature variance require high precision measurements with a fast response to changes in the ambient atmosphere. 4.2 Purpose—This practice is designed to assist the user in selecting an appropriate temperature measurement system for the intended atmospheric application, and properly installing and operating the system. The manufacturer's recommendations and the U.S. Environmental Protection Agency handbook on quality assurance in meteorological measurements (3) should be consulted for calibration and performance audit procedures. SCOPE 1.1 This practice provides procedures to measure representative near-surface atmospheric (outdoor air) temperature for meteorological purposes using commonly available electrical thermometers housed in radiation shields mounted on stationary or portable masts or towers. 1.2 This practice is applicable for measurements over the temperature range normally encountered in the ambient atmosphere, –50 to +50 °C. 1.3 Air temperature measurement systems include a radiation shield, resistance thermometer, signal cables, and associated electronics. 1.4 Measurements can be made at a single level for various meteorological purposes, at two or more levels for vertical temperature differences, and using special equipment (at one or more levels) for fluctuations of temperature with time applied to flux or variance measurements. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.