5
w ith in th e C a lib ra tio n C h e c k C h a m b e r w h e n n o t in u s e . T h e
C a lib ra tio n C h e c k C h a m b e r a n d S a tu ra te d S a lt S o lu tio n a re
d e s ig n e d in a c c o rd a n c e w ith A S T M E 1 0 4 to m a inta in a c o n s ta n t
re la tiv e h u m id ity. P e r A S T M F 2 1 7 0 , th e C a lib ra tio n C h e c k
C h a m b e r an d S a tura ted S a lt S o lu tio n m a in tain a co n s ta n t re lative
h u m id ity o f 7 5 % (a t 2 5 ° C ) a n d ke e p s the pro b e in a rea d y -to -u s e
c o n d itio n .
A S T M F 2 1 7 0 re q u ire s c a lib ra tio n to b e v e rifie d w ith in 3 0 d a y s
p rio r to u s e . P o w e r-u p th e p ro b e b y in s e rtin g a b a tte ry, p o s itive
(+ ) side u p . P ro b e c a lib ra tio n is v e rifie d b y in s e rtin g a p ro b e in to
th e C a lib ra tio n C h e c k C h a m b e r, c o n n e c tin g to e ith e r th e
o s i T e c t o r A p p o r a o s i T e c t o r A d v a n c e d gage body and
ta k in g a m e a s u re m e n t (a fte r a llo w in g th e p ro b e a t le a s t 1 h o u r to
a c c lim a te to th e p re s e n t e n v iro n m e n t). P ro b e s s h o u ld re p o rt a
re la tive h u m id ity w ith in 2 % o f th e h u m id ity va lu e liste d in Ta b le 1
fo r th e c o rre s p o n d in g te m p e ra tu re . To s im p lify th e v e rific a tio n
p ro c e s s , w e re c o m m e n d u s in g th e C a l C h e c k fu n c tio n o f th e
o s i T e c t o r A p p o r o s i T e c t o r A d v a n c e d . T h e C a l C h e c k
fu n c tio n a u to m a tic a lly d e te rm in e s w h e th e r a p ro b e is re a d in g
w ith in to le ra n c e .
P ro b e s sh o u ld be allow e d to a c c lim a te fo r at lea s t 2 4 h o u rs w ith in
th e C a lib ra tion C h e c k C h a m b e r a n d S o lu b le S a lt S o lu tion b e fo re
c a lib ra tio n is c h e c k e d .
It is im p o rta n t to m a in ta in a c o n s ta n t te m p e ra tu re w ith in th e
C a lib ra tio n C h e c k C h a m b e r. R e la tiv e h u m id ity v a ria tio n d u e to
te m p e ra tu re flu c tu a tio n fo r th e C a lib ra tio n C h e c k C h a m b e r is
s h o w n in Ta b le 1 .
Table 1
E x tra c te d fro m Ta b le A 1 .1 ,
E q u ilib riu m R e la tiv e H u m id ity Value s
fo r S e le c te d S a tu ra te d A q u e o u s S a lt
S o lu tion s (A S T M E 1 0 4 )
Exa ple Tolerance Calculation:
A t 2 5 ° C , th e S o lu b le S a lt S o lu tio n re la tiv e h u m id ity ra n g e is
7 5 .3 % ± 0 .2 . In c lu d in g th e ± 2 % re la tiv e h u m id ity to le ra n c e
s p e c ified in A S T M F 2 1 7 0 , a p ro b e w o u ld b e c o n s id e re d to b e in
to le ra n c e if it m e a s u re d b e tw e e n 7 3 .1 – 7 7 .5 % .
W h e n th e S a tu ra te d S a lt S o lu tion (B o v e d a ) is co m p le te ly
d ry, it w ill s o lid ify. T h e y s h o u ld b e re p la c e d w h ile th e re is s till
m o istu re p re s e n t an d b e fo re the y a re co m p le te ly s o lid .
N O T E :
t ° C t ° F
S o d i u m
C h l o r i d e ( R H % )
5 4 1 7 5 .7 + 0.3
1 0 5 0 7 5 .7 + 0.3
1 5 5 9 7 5 .6 + 0.2
2 0 6 8 7 5 .5 + 0.2
2 5 7 7 7 5 .3 + 0.2
3 0 8 6 7 5 .1 + 0.2
3 5 9 5 7 4 .9 + 0.2
4 0 1 0 4 7 4 .7 + 0.2
4 5 11 3 7 4 .5 + 0.2