HD31
- 26 -
V1.6
4.3
R
ELATIVE HUMIDITY AND TEMPERATURE COMBINED PROBES
The relative humidity and temperature combined probes use a capacitive sensor for the meas-
urement of relative humidity and a Pt100 sensor for the measurement of temperature. By con-
necting a relative humidity and temperature
combined probe, the instrument can display, be-
sides the two primary quantities, the following derived humidity quantities as well:
•
Saturated vapor pressure (Svp) in hPa
•
Partial vapor pressure (Pvp) in hPa
•
Mixing ratio in g/kg (vapor grams in 1 kg of dry air)
•
Enthalpy in J/g
•
Absolute humidity in g/m
3
(vapor grams in 1 cubic meter of dry air)
•
Dew point Temperature (Td)
•
Wet bulb Temperature (Tw)
•
Discomfort index (DiscIdx)
•
NET index (NetIdx)
Note
:
the calculation of the derived quantities is made taking into consideration a ba-
rometric pressure fixed value equal to 1013.25 hPa.
For measuring, place the probe avoiding areas where fast temperature variations may occur
creating condensation. The measurement in no condition of fast temperature variations is al-
most immediate. On the contrary, if fast temperature variations occur, you have to wait the
sensors and the probe body to reach thermal balance in order to obtain accurate measure-
ments.
See paragraph 13.3 at page 94 for the calibration of relative humidity and temperature com-
bined probes.
4.3.1
D
ISCOMFORT INDEX AND
NET
INDEX
Environmental conditions affect our physiological well-being status: particular values of tem-
perature, humidity and air speed are perceived as unpleasant or even intolerable. While it is
easy to quantify the relationship between well-being status and the measure of each variable
taken separately, it is even more complex to provide an indication about their combined effect.
For this reason, different evaluation systems have been introduced leading to the formulation
of climate qualitative indices (
Comfort Indices
).
The two indices provided by the instrument are the
Discomfort Index
and
the
NET
index
(Net Effective Temperature). The first one depends only on temperature and relative humidity,
while the second one takes into consideration air speed as well. If an anemometric probe is
connected to the instrument, the speed measurement detected is used for the calculation of
the Net Index; if there is no probe connected, air speed is set equal to zero and its contribu-
tion is not taken into account.
Discomfort index:
3
.
46
)
3
.
14
99
.
0
(
100
81
.
0
+
−
•
•
+
•
=
T
H
T
DI
with T = temperature in °C
H = relative humidity in %
On the basis of the value provided by the discomfort index, climate conditions are defined from
comfortable to unsustainable:
Comfortable
Slightly
uncomfortable
Uncomfortable
Very
uncomfortable
Unsustainable
68
70 75
80 86
Summary of Contents for HD31
Page 6: ...HD31 6 V1 6 2 DESCRIPTION Fig 2 1 instrument description...
Page 149: ...HD31 149 V1 6 NOTES...
Page 150: ...HD31 150 V1 6 NOTES...
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