User Guide

6
Read wet & dry bulb ther-
mom e ters; replace body in
8
Read % relative humidity
as indicated by arrow.
2
In struc tion 0012-9015
4
Pull body
from tube
until body
hangs
free.
5
Use tube
as handle;
whirl body
about 1-½
minutes.
7
Set thermometer readings on
upper two calculator scales.
A D G H I
B G H C F E
2
Fill psy-
chrometer
reservoir
with water.
Replace cap.
3
Be sure
wick covers
“wet” bulb
(the other
bulb is dry).
1
Remove
cap; im-
merse end
of body to
saturate
wick.
OPERATION
APPLICATION
MAINTENANCE
WICK (A) should be kept clean; when dirty,
cut off WICK below WET BULB THER-
MOM E TER (D) and pull clean sec tion out of
END CAP (B) and slide over bulb on WET
BULB THER MOM E TER.
A WICK REPLACEMENT KIT may be pur-
chased separately (refer to parts list). One
or two extra WICKS may be kept in END
CAP and will help retain mois ture longer.
Pack WICKS loosely to allow thor ough wa ter
sat u ra tion and ample wa ter supply to the
WET BULB THER MOM E TER.
THERMOMETERS (D) and (F) are re-
place able by backing off SCREWS (G) and
loos en ing THERMOMETER CLIPS (H). To
sep a rate BODY (C) and TUBE (E), drive
ROLL PIN (I) out of eye in PLUG AND
SWIVEL AS SEM BLY, which then may be
slid out back end of TUBE.
Wet-bulb temperatures should be read fi rst
and as quickly as possible for high est ac-
cu ra cy. Delay in reading may cause er ror. In
addition, the wick must be kept clean, sat u -
rat ed with water, and whirled long enough
to stabilize tem per a tures.
The range of the psychrometer is from 10%
to 100% R.H., for dry-bulb tem per a tures of
30° to 100°F (–5° to 50°C).
In addition to the above instructions,
baro met ric pressure and other factors will
in fl u ence exact relative humidity de ter mi n-
a tions to a very minor degree. For precise
work, use a psychrometric chart or set of
tables such as W.B. No. 235 “Psy chro met ric
Tables for Ob tain ing the Vapor Pres sure,
Relative Hu mid i ty, and Tem per a ture of Dew
Point,” which can be purchased from the
Su per in ten dent of Documents, United States
Gov ern
ment Printing Of fi ce, Wash ing ton,
D.C. The accuracy of the Psy chrom e ter,
how ev er, is sat is fac to ry for all ex cept the
most ex act ing work.
3
In struc tion 0012-9015
3. Holding TUBE, whirl body two to three
revolutions per second (120 to 180 RPM).
4. Continue whirling until temperatures
sta bi lize (1-½ minutes is usually am ple).
5. Immediately read WET BULB THER-
MOM E TER (D) and then DRY BULB
THER MOM E TER (F). (See ap pli ca tion
in struc tions.)
6. Set wet and dry bulb temperatures op-
po site each other on side rule type cal cu -
la tor scales, sliding BODY into TUBE as
re quired.
7. Read % R.H. (percent relative hu mid i ty)
indicated by arrowhead on lower scale.
Before Using:
WICK (A) should be thoroughly sat u rat ed
with wa ter. Remove END CAP (B) and im-
merse PSY CHROM E TER BODY (C) up to
mercury (or red spirit) reservoir on the ther-
mom e ters un til WICK is thor ough ly wet ted.
Fill END CAP with water and re place; tight en
just enough to pre vent leak age.
To Use:
1. Be sure WICK (A) is wet and covers mer–
cury (or red spirit) reservoir on WET BULB
THER MOM E TER (D). Be sure res er voir
on other THER MOM E TER (F) is dry.
2. Pull TUBE (E) clear of BODY so BODY
can swivel.