COSA Xentaur Hygrocontrol Type 72 - Manual (Page 11)

Series 72 Manual page 7
To assure the easiest handling and highest accuracy, the solutions are
enclosed in glass ampoules, which should be opened only before usage.
Opening is simplified by the weakened middle part of the ampoules. Once
opened the solutions may catch humidity from or give humidity to their
environment - so the time of usage is restricted and they should be used for one
calibration only.
6.4. Calibration Chamber
The calibration chambers we are supplying under No. 1810 (or 4716 for 12 mm
diameter probes) are hermetically sealed chambers which consist of three
parts:
1) main part with thread for coupling with probe tip
2) removeable bottom to put the solution in
3) O-ring to give tight connection between parts 1) and 2).
The chamber is made from Aluminium to achieve
a) temperature equilibrium
b) simpliest cleaning procedure.
Mechanical dimensions of the chamber are optimized to form a closed body
without edges. By this form a quick and stable atmosphere of the desired rel.
humidity over the solution is guaranteed.
6.5. Usage of Saturated Salt Solutions
There exist a number of different salts where the rel. humidity over the surface
of their saturated solutions is known and reported by organisations like NBS or
DIN. Lately the temperature dependencies and accuracies of this solutions were
verified - so series 72 transmitters are able to be tested and calibrated with
these solutions too. As preparation and handling of these saturated solutions
require knowledge and care, we do not provide these directions in this manual.
If you need any help in this matter, please contact our technical staff.
6.6. Temperature Equilibrium
Due to the temperature dependency of rel. humidity over salt solutions, you
should assure a constant temperature of 22°C with deviations of not more than
1°C. This can be done by placing the probe in an area free from draughts, direct
sunlight, radiators and any other factor that might cause temperature
fluctuations. Place the instrument on an insulating base such as polystyrene
and assure that the instrument, calibration chamber and solutions are
conditioned to the same temperature before starting the calibration.
6.7. Mounting the Calibration Device
First remove the filter from the tip of the probe. The chamber may now be
screwed to the thread of the probe. The bottom of the chamber is removeable
and it is here that the textile pad and the solution are to be placed. To avoid
improper humidity values, always clean the bottom of the chamber thoroughly,
use new pads, and new solutions.