BARTEC BENKE HYGROPHIL H 4230-12 Ex Zone II, Руководство по эксплуатации, Страница: 8 / 112

System description
2
Operating Instructions HYGROPHIL® H 4230-12 BA 060207
1.2 Measurement principle
HYGROPHIL
®
H 4230 works in accordance with the principle of psychromet-
ric gas humidity measurement, measuring the difference in temperature be-
tween two measurement sensors. The difference in temperature results from
the fact that one of the two temperature sensors is moistened. Heat is re-
moved from it by means of evaporation. Using the difference between the
„humid temperature“ and the „dry temperature“ it is possible to determine
various humidity measurement variables precisely based on fixed mathemat-
ical relations. This measurement principle gives rise to a high degree of pre-
cision and reproducibility, corresponds to the secondary standard method in
accordance with DIN 50012 and does not require any calibration. It is one of
the most reliable methods used to measure gas humidity.
Usually, however, this measurement procedure is subject to limits if the gas
temperature exceeds 100 °C or if the gas to be measured is impure. On a
conventional type of humidity sensor, deposits have a detrimental effect on
the evaporation rate and falsify the measurement result.
These limitations are eliminated in this measuring unit that has been further
developed to form an „impact jet psychrometer“. The system can be used for
an extended period of time without failure even at high temperatures and
high humidity levels and for highly polluted or aggressive gases.
1.3 Structure of the humidity meas-
urement system
The measuring chamber and electronics unit are accommodated in stainless
steel enclosures flanged together, each with a door that can be opened sep-
arately.
The water tank is attached to the exterior of the enclosure.