User manual

OPERATING INSTRUCTION
Technical changes reserved
0141 0315-199 09/2014
Humidity reference cells
for adjustment of humidity sensors
In order to achieve maximum accuracy, it is recommended that the activity should be carried out in a laboratory room. The measurement and
calibration area should be air-conditioned. The ambient temperature should be within 23 °C ±2 K and relative humidity in the environment should
be within 50 % ±5 % RH.
The closed styrofoam container can also be used to improve the temperature stability. During application, the temperature gradient of the environ
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ment must be <1K/h. And effect of environmental factors like wind blow or direct heat radiation should always be minimised during the application.
The testing space in the reference cells should pick up the sensor head to extent possible and should be tightly sealed from atmosphere. If the
sensor is not compatible with the coupling threads, a suitable adapter must be used.
Unnecessary touching of the reference cell with hands should be avoided, otherwise it takes longer time for thermal stabilisation.
Unnecessary opening for a long time should also be avoided, since this is likely to extend the stabilisation time and reduces the durability of cells.
The reference cells can be used for a large number of times over many years.
The salt solution creates humidity in the test chamber for stabilisation. Apart from this, the solution absorbs or releases water depending on
the humidity level of the laboratory environment.
In European climate, the average relative humidity value is approx. 55 % RH. Therefore, the reference cells normally in average absorb
water for drier values. Thus, with the increase in liquid level, more salt gets dissolved. As soon as no more salt crystals are visible, the cell
becomes unusable and should be replaced.
As soon as the internal compartment is completely lled, the solution in the inner compartment forces out and this can damage the dia
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phragm, the sensor or the sensor housing.
The reference cells release water above relative humidity value of 55 % RH. Because of this, the interior dries up slowly. For correct func
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tioning, the liquid should be still visible. Just when only crystalline salt is visible without any liquid content, the cell becomes unusable and
should be replaced.
The effects described above take place only after opening the cap. Hence, the reference cells should not be unnecessarily opened for a long
time. In order to retain the functional effectiveness of the cells for a long time as much as possible, care should be taken to immediately plug
it back after use. It should be ensured that the gasket on the cap is dry and is effectively performing the sealing function.
In tightly closed condition, the cells have practically unlimited life.
Reference cells, in which the saturation level of solution has gone down, can be sent to us for processing (chargeable service). Mechanically
defective cells, (e.g. damaged diaphragm) can be sent to us for free of charge disposal.
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4.3 Ambient conditions
4.4 Storage conditions and durability
B+B Thermo-Technik GmbH | Heinrich-Hertz-Straße 4 | D-78166 Donaueschingen
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