Components; Sensor - Burkert 8626 Instructions De Service

2.5

Components

2.5.1 Sensor

The flow sensor of the MFC Type 8626 works on the hot-film anemometer principle.
The signal measured depends on the product of the density and the flow velocity
and delivers the mass flow rate directly. Additional parameters such the density must
not be registered and used in a calculation.
In a bridge circuit, the temperature difference between the heating resistor (R
a temperature sensor (R
constant (Fig.3). The necessary bridge current (I) is a measure of the velocity of the
flowing gas.
This constant temperature operating mode protects the sensor from thermal
overload.
.
m
m
Fig.3 Operating principle of the thermal flow sensor
Elements installed upstream for conditioning the flow ensure reproducible flow
modes. Once calibrated, the sensor signal provides information on the overall flow in
the flow channel.
In the MFC Type 8626, the measurement is carried out in the main stream , so that a
very good dynamic ratio is assured.
Because of the configuration of the Pt heating resistor on a glass chip lying along
the flow direction, the sensor is very little affected by contamination.
34
) placed in the flowing medium upstream of it is kept
T
I
I
S
S
R R
T S
R
K
R R
2 1
) and
s
I
I
PID
PID
Type 8626