System description
4
Operating Instructions HYGROPHIL® H 4230-10 Serie A BA 030520
1.3.1
Measuring chamber
The venturi system and the water cylinder with the humidity sensors are
accommodated 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
pressure. Located close to the nozzle is a sensor that measures the dry
temperature. When it leaves the nozzle, the air takes the form of a laminar
jet, referred 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
sensor. It is used to correct the measurement results and monitor the
equipment. 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.
