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41
Equilibrium Relative Humidity of Selected
Saturated Salt Solutions from 0 to 100°C
Temp Lithium
Magnesium
Sodium
°C
Chloride Chloride Chloride
0
11.23 ± 0.54
33.66 ± 0.33
75.51 ± 0.34
5
11.26 ± 0.47
33.60 ± 0.28
75.65 ± 0.27
10
11.29 ± 0.41
33.47 ± 0.24
75.67 ± 0.22
15
11.30 ± 0.35
33.30 ± 0.21
75.61 ± 0.18
20
11.31 ± 0.31
33.07 ± 0.18
75.47 ± 0.14
25
11.30 ± 0.27
32.78 ± 0.16
75.29 ± 0.12
30
11.28 ± 0.24
32.44 ± 0.14
75.09 ± 0.11
35
11.25 ± 0.22
32.05 ± 0.13
74.87 ± 0.12
40
11.21 ± 0.21
31.60 ± 0.13
74.68 ± 0.13
45
11.16 ± 0.21
31.10 ± 0.13
74.52 ± 0.16
50
11.10 ± 0.22
30.54 ± 0.14
74.43 ± 0.19
55
11.03 ± 0.23
29.93 ± 0.16
74.41 ± 0.24
60
10.95 ± 0.26
29.26 ± 0.18
74.50 ± 0.30
65
10.86 ± 0.29
28.54 ± 0.21
74.71 ± 0.37
70
10.75 ± 0.33
27.77 ± 0.25
75.06 ± 0.45
75
10.64 ± 0.38
26.94 ± 0.29
75.58 ± 0.55
80
10.51 ± 0.44
26.05 ± 0.34
76.29 ± 0.65
85
10.38 ± 0.51
25.11 ± 0.39
90
10.23 ± 0.59
24.12 ± 0.46
95
10.07 ± 0.67
23.07 ± 0.52
100
9.90 ± 0.77
21.97 ± 0.60
Humidity and Quality Indices (Comfort Indices)
Everybody knows how environmental conditions affect the human feeling of good health: particular
values of temperature, humidity and air velocity turn out to be unpleasant if not unbearable to most
people. Whereas it is easy to quantify the relationship between the measurement of a single variable
and its effects on human beings, it is much more difficult to provide an indication of the combined
effect deriving from all of the variables.
For this reason, different valuation systems have been introduced to get the formulation of the cli-
mate quality indices (
Comfort Indices
).
The DO9847 provides two indices:
Discomfort Index
and
Net Index
. The first one depends on
temperature and relative humidity only, while the second one is related to air velocity, as well.
These two indices can be displayed only if the instrument is connected to a temperature/humidity
combined probe (such as, for example, an HP472AC probe). Discomfort Index and Net Index are
included in the group of variables identified by number 3: A3, B3 or C3, according to whether the
probe is connected either to A, B or C input, respectively. An example of instrument setup to dis-
play the Net Index is detailed on page 35.
The Net Index also depends on air velocity, as stated in the definition given in the following pages.
If the instrument is connected to a hot-wire anemometric omni-directional probe (model AP471 S2),
the air velocity measurement will be used to calculate the index. Should no probe be connected, the
air velocity value will be considered zero and its contribution negligible.
