ASTM E337 PDF

More D Only the essential features of the psychrometer are specified. Scope 1. In this case, the instrument comprises a wet-bulb thermometer only. The aspirated psychrometer is more accurate than the sling whirling psychrometer see Method B , and it offers advantages in regard to the space which it requires, the possibility of using alternative types of thermometers for example, electrical , easier shielding of thermometer bulbs from extraneous radiation, accidental breakage, and convenience.

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A number in parentheses indicates the year of last reapproval. In this case, theinstrument comprises a wet-bulb thermometer only. The aspirated psychrometer is more accuratethan the sling whirling psychrometer see Method B , and itoffers advantages in regard to the space which it requires, thepossibility of using alternative types of thermometers forexample, electrical , easier shielding of thermometer bulbsfrom extraneous radiation, accidental breakage, and conve-nience.

No other units of measurement are included in thisstandard. Mercury, or its vapor, has been demonstrated tobe hazardous to health and corrosive to materials.

Cautionshould be taken when handling mercury and mercury contain-ing products. 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. For more specificsafety precautionary statements, see 8.

Referenced Documents2. Current edition approved July 1, Published July Originally approvedin Last previous edition approved in as E — 02 The flow may be either transverse or parallel to theaxes of the bulbs.

Acotton wick which connects the covering to a waterreservoir may be provided so that water is fed to the coveringcontinuously by capillarity. The flow is transverseto the axes of the bulbs. Summary of Methods4. With mercury-in-glass thermometers, about 2-min ventilation time is usuallynecessary. Also see Section Significance and Use5. Only the essential features of the psychrometer arespecified. This range may be achieved by providingmore than a single pair of matched thermometers.

Theuncertainty in the reading of the dry-bulb temperature shall benot more than The freeend of each sensor shall be smoothly rounded. If the diameterof the stems is small, compared with that of the sensors, thenboth ends of each sensor shall be smoothly rounded. A seamless sleeve is preferred, but a seam ispermissible, provided that it does not add appreciably to thegeneral roughness which the weave imparts to the surface.

It shall extend onto the stem for such a distance that the errorin the observed wet-bulb temperature due to heat conductionalong the stem does not exceed 0. A method of deter-mining the distance for which the covering must extend ontothe stem is outlined in Annex A2. For mercury-in-glassthermometers with solid stems, a distance of twice the stemdiameter is usually adequate.

However,whenever a wicking is used, the covering shall not be securedbetween the thermometer bulb and the cotton wicking whichconnects the covering to a water reservoir. They shall not subse-quently be touched with the fingers. A wick shall be limp. Surfaces required to have a polishedfinish shall be of a bare metal which will retain its brightness.

The radiation shields, essentially in the form ofparallel plates, can be either polished on the outside andblackened on the inside, or polished on both the inside andoutside surfaces.

The clearance between the wet and dry bulbsand the shields shall be not less than half the overall diameterof the wet bulb. The shields shall be liberally flared outwardsat the inlet to prevent the flow separating from the shields onthe inside vena-contracta effect. The shields may form part ofa duct for the airflow. Asecond shield, outside, is not necessary.

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A number in parentheses indicates the year of last reapproval. Asuperscript epsilon indicates an editorial change since the last revision or reapproval. In this case, theinstrument comprises a wet-bulb thermometer only. All uncertainties are at the 95 confidence level. The aspirated psychrometer is more accuratethan the sling whirling psychrometer see Method B, and itoffers advantages in regard to the space which it requires, thepossibility of using alternative types of thermometers forexample, electrical, easier shielding of thermometer bulbsfrom extraneous radiation, accidental breakage, and conve-nience.

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