5
w ith in th e C a lib r a 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 r a tio n C h e c k C h a m b e r a n d S a tu r a te d S a lt S o lu tio n a r e
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 in ta in a c o n s ta n t
r e 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 r a 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 m a in ta in a c o n s ta n t re la tiv e
h u m id ity o f 7 5 % (a t 2 5 ° C ) a n d k e e p s th e p ro b e in a re a d y -to -u s e
c o n d itio n .
A S T M F 2 1 7 0 r e q u ir e s c a lib r a tio n to b e v e r ifie 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 itiv e
(+ ) s id e 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 r a 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
P o s i T e c t o r A p p
o r a
P o s i T e c t o r A d v a n c e d
g a g e b o d y a n d
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 r e s e n t e n v ir o n m e n t) . P r o b e s s h o u ld r e p o r t a
re la tiv e h u m id ity w ith in 2 % o f th e h u m id ity v a lu e lis te d in Ta b le 1
fo r th e c o r r e s p o n d in g te m p e r a tu r e . To s im p lify th e v e r ific a tio n
p r o c e s s , w e r e 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
P o s i T e c t o r A p p
o r
P 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 r m in e s w h e th e r a p r o b e is r e a d in g
w ith in to le ra n c e .
P ro b e s s h o u ld b e a llo w e d to a c c lim a te fo r a t le a s t 2 4 h o u rs w ith in
th e C a lib ra tio n 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 tio n b e fo re
c a lib ra tio n is c h e c k e d .
It is im p o r ta n t to m a in ta in a c o n s ta n t te m p e r a tu r e 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 r a tu r e flu c tu a tio n fo r th e C a lib r a 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 tr a c te d
fr o m
Ta b le
A 1 .1 ,
E q u ilib riu m R e la tiv e H u m id ity Va lu e 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 tio n s (A S T M E 1 0 4 )
Example Tolerance Calculation:
A t 2 5 ° C , th e S o lu b le S a lt S o lu tio n r e la tiv e h u m id ity r a n g e is
7 5 .3 % ± 0 .2 . In c lu d in g th e ± 2 % r e la tiv e h u m id ity to le r a n c e
s p e c ifie d 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 tio n (B o v e d a ) is c o m p le te ly
d r y, it w ill s o lid ify. T h e y s h o u ld b e r e p la c e d w h ile th e r e is s till
m o is tu re p re s e n t a n d b e fo re th e y a re c o 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
