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8.6.5
C
ALIBRATING THE RELATIVE HUMIDITY SENSOR
In HD35ED…TC and HD35ED…TV models with high accuracy R.H. sensor, the sensor can be cali-
brated in the two points 75% RH and 33%RH.
Before starting the calibration procedure, it’s better to
check
if a new calibration is necessary,
with the aid of 75.4%RH and 33%RH saturated solutions: a calibration will be performed only
if an error of a few humidity points in one of the two calibration points is detected.
The sensor can be calibrated in both points or in one point only.
Preliminary operations before calibration:
Check that the chamber with the saturated saline solutions contains at the same time:
• solid state salt,
• liquid solution or wet salt, in particular for the 75%RH solution.
The instrument and the saturated solutions to be used for this operation must be placed in a
stable temperature environment for the whole calibration period. Wait for at least a couple of
hours with a stable temperature so that the instrument and the saturated solutions reach a
thermal balance with the environment before starting the calibration procedure. In order to ob-
tain a good calibration, it is crucial that the probe and the solution have the same temperature.
Bear in mind that plastic material is a bad heat conductor.
Calibration should be performed at a temperature ranging within 15 and 30°C.
Calibration procedure:
1.
Unscrew the probe protection grid and screw the M12×1 threaded ring.
Avoid any contact of the sensitive element with your hands or other objects or liquids.
If
some liquid has formed inside the measuring chamber, dry it with a clean absor-
bent paper towel
.
2.
Unscrew the cap of the saturated solution. Screw the threaded ring with the probe on the
saturated solution container and wait for at least 30 minutes.
3.
Access the menu with the administrator password and select the item
CAL_MENU
. Press
ENTER
to confirm.
4.
Select the item
RH_75%_CAL
to calibrate the point 75%RH or
RH_33%_CAL
to calibrate the
point 33%RH. Press
ENTER
to confirm.
5.
The blinking value of the saturated solution at the temperature measured by the probe is
displayed.
SET
75.2
24.5
°C
Note
: the suggested calibration value is not updated if the measured temperature changes
after starting calibration. If necessary, set manually the calibration value to the value of the
saturated solution at the measured temperature using
/
keys (see table 8.6.1 below).
6.
Press
ENTER
to confirm the value, the instrument stores the calibration and returns to the
calibration submenu.
7.
Remove the threaded ring with the probe from the container of the saturated solution and
close the container with the solution.
