MIL-HDBK-1110
in ASTM E 667, Clinical Thermometers (Maximum Self-Registering,
Mercury-in-Glass). One thermometer has a clean "sock" or "wick"
on it that is wetted with water. Air is circulated around the
thermometers by the motorized fan or by whirling the hand-held
sling psychrometer. Whirling should be with a steady, medium
speed. Both thermometers should be read periodically and the
airflow (whirling) continued until the reading becomes constant.
The "wet" bulb thermometer temperature will be lowered
by evaporation of the water on the sock. The evaporation rate is
related to the relative humidity and barometric pressure.
Psychrometric tables relate temperature depression (difference
between "dry" and "wet" bulb readings) to relative humidity and
dew point. These standard tables, available from suppliers of
psychrometers, cover the range from 23.0 to 30.0 inches
barometric pressure. The effect of barometric pressure is
relatively small; if it is unknown, use the 30.0-inch pressure
table near sea level and the 29.0-inch pressure table at high
elevations.
10.3.7
Wind Meter. A pocket-size wind meter is available for
determining wind speed in miles per hour and velocity of air
moving across a spray booth. Spraying on days with excessive
winds can cause overspray or dry spray problems.
10.3.8
Moisture Meter. Meters are available for determining
the moisture content of wood, plaster, concrete, or other
materials. Some are nondestructive, while others require contact
pins to be driven into the surface. An alternate non-destructive
procedure for determining if too much moisture is present in
cementitious surfaces is described in ASTM D 4263.
10.3.9
Wet Film Gage. Gages for determining paint wet film
thickness are available in different types, two of which are
described in ASTM D 1212 and one in ASTM D 4414. All are
destructive in that they disturb the paint and require touching
up the film.
10.3.9.1 Notched Metal Gage. The most widely used type of wet
film thickness gage, described in ASTM D 4414, consists of a thin
rigid metal notched gage, usually with four working faces. Each
of the notches in each working face is cut progressively deeper
in graduated steps. The gage with the scale that encompasses the
specified thickness is selected for use. To conduct the
measurement, the face is pressed firmly and squarely into the wet
paint immediately after its application. The face is then
carefully removed and examined visually. The wet film thickness
is the highest scale reading of the notches with paint adhering
to it. Measurements should be made in triplicate. Faces of
gages should be kept clean by removing the wet paint immediately
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