COSA Xentaur Hygrocontrol Type 86 Ex - Manual (Page 24)

4.3 Withstanding Chemical Attack
Our sensors are wellknown for their resistance against most chemical
attacks. To give the user some informations over the additional errors
which are arising from some chemicals, we listed our experiences over the
last 10 years. (See the table at the end of this manual).
Be aware, that the given concentrations are valid for a single chemical in
normal atmosphere (room temperature) only. As temperature has to be
taken into consideration too, you cannot expect to get proper predictions
out of the table - please contact our technical staff for more informations.
4.4 Protection of Transmitter Electronics
To give highest protection against the surrounding atmosphere, our
transmitter housings are according to IP 65. Avoid atmospheres of more
then 80 %RH, as condensation could occur with rapid temperature
changes.
4.5 Influence of Temperature on Humidity
To detect rel. Humidity, the sensor has to be in equilibrium with the
atmosphere - this cannot be done spontaneously! It is up to you, to choose
a position of the sensor, where the equilibrium may be reached as quick
as possible. Take into consideration that also Temperature has a great
influence on rel. Humidity! At Room Temperature and 50 %RH, a
temperature change of 1°C will cause a change of rel. Humidity by 3%.
This is the reason, why all instruments use a combination of Humidity and
Temperature Sensors for detection of rel. Humidities. Only if Temperature
has stabilized, proper values of rel. Humidity may be expected.
Different tube materials of sensors have an influence on temperature
stabilisation by their different thermal mass and conductivity. SS-316 tubes
predict higher times to achieve equilibrium of temperature as PTFE or PP
tubes - be aware of this problem and choose a proper material.
Avoid errors by unproper installation of the sensor as for example:
- Influence by Heat: direct Sun, Heaters, unknown Air Streems etc.
- Influence by Water: Vapors, dropping or spraying Water etc.
- Influence by Pollution: Dust, Aerosoles, Chemicals etc.
4.6 Humidity Measurements over Ice
Don't forget that our sensors are calibrated for conditions of vapor
pressure over liquid water. If you are measuring rel. Humidities over ice,
you will get an error which is strictly dependent on the difference of
saturation pressure of vapor over ice compared with the saturation
pressure of vapor over chilled water. The following table shows the results
of a measurement of saturated vapor over ice at different temperatures
below zero.
HYGROCONTROL Manual for Type 86 Ex Page
23