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35
R
ELATIVE HUMIDITY PROBES
The humidity probes for the DO9847 are of the combined humidity and temperature type: the hu-
midity sensor is of the capacitive type, the temperature sensor is a Pt100. The probes are equipped
with a module with a DIN 8-pole connector inside which is a microprocessor circuit with a perma-
nent memory which stores the calibration data.
By pressing the function keys F1, F2 and F3 corresponding to the indications Xsel, Ysel and Zsel, it
is possible to view the humidity (or one of the derived quantities, as explained below), the tempera-
ture (or one of the derived quantities) detected by the combined probe connected to the inputs of the
instrument, as well as some quality indices: if a combined probe is connected to input A, A1 repre-
sents humidity, A2 represents the temperature measured by the Pt100 sensor of the probe and A3
Discomfort Index and Net Index (see paragraph
Humidity and Quality Indices (Comfort indices)
at
page 41 for a detailed description of index meaning).
The instrument measures the relative humidity, the temperature and, starting from a fixed baromet-
ric pressure value of 1013.25mbar, calculates the following six derived quantities:
1.
Pvp partial vapour pressure (hPa)
2.
g/kg grams of vapour in a kilogram of dry air
3.
g/m
3
grams of vapour in a cubic metre of dry air
4.
J/gr enthalpy
5.
Td dew point (°C)
6.
Tw wet bulb temperature (°C)
7.
Td dew point (°F)
8.
Tw wet bulb temperature (°F)
9.
Svp saturated vapour pressure (hPa)
10.
DiscIndx Discomfort Index
11.
NetIndx Net Index
The first 8 variables, together with relative humidity, form a group of nine variables identified on
the display with the number 1: A1, B1 or C1 depending on whether the relative probe is connected
respectively to input A, B or C of the instrument.
The group composed of the temperature of the Pt100 sensor and of the Svp variable is identified on
the display with the number 2: A2, B2 or C2.
Relative humidity, the Discomfort Index and the Net Index are listed in A3 (as well as in B3 or in
C3).
Selection within each of the three groups is made with the key <9/UNIT> as shown in the example
below.
Suppose that a combined humidity and temperature probe is connected to input A of the instrument
and you want to show the dew point (Td in °C) on the first line of the display, the saturated vapour
pressure (svp) on the second line and the Net index on the third one.
Procedure:
if the display is not set to view A1, A2 and A3 variables, press F1 (Xsel) until you see the indica-
tion
A1
on the first line, press key F2 (Ysel) to see the indication
A2
on the second line and F3
(Zsel) to see the indication
A3
on the third line. At this point, press the key <9/UNIT>:
