BARTEC BENKE HYGROPHIL H 4230-12 Ex Zone II, Руководство по эксплуатации, Страница: 10 / 112

System description
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Operating Instructions HYGROPHIL® H 4230-12 BA 060207
1.3.1 Measuring chamber
The venturi system and the water cylinder with the humidity sensors are ac-
commodated in the measuring chamber.
To begin with, the air to be measured flows through a venturi nozzle, in
which the gas flow rate is determined by measuring the difference in pres-
sure. Located close to the nozzle is a sensor that measures the dry tempera-
ture. When it leaves the nozzle, the air takes the form of a laminar jet, re-
ferred to as the impact jet, and hits the water surface of the measuring cell.
The sensor that measures the humid temperature (HT) is positioned at the
centre of the measuring cell. The temperature values that are recorded are
made available to the electronics unit and further processed there.
The measuring cell is constantly fed with water from the storage tank by a
hose pump. The water level in the measuring cell is monitored by a sensor.
The pressure in the measuring chamber is likewise measured using a sen-
sor. It is used to correct the measurement results and monitor the equip-
ment. The measuring chamber is followed by the ejector. Currents of air are
used here to create negative pressure in order to pump the measurement
gas through the system. The pumping rate of the ejector is controlled using a
proportional valve, with the help of the gas flow rate measurement in the
venturi nozzle. As a result, the gas flow rate remains constant at around
14 l/min.
Excess water, together with the measurement gas and compressed drive air,
is pumped out of the equipment via the ejector. It leaves the equipment
through a connection at the bottom.
Measuring chamber
Water sensor
Tube pump
Ejector
Pressure control
module