Siemens ULTRAMAT 23 Series Equipment Manual page 29

Paramagnetic oxygen measurement
Figure 3-6
In contrast to other gases, oxygen is highly paramagnetic. This property is used as the basis for
this method of measurement.
Two permanent magnets generate an inhomogeneous magnetic field in the measuring cell. If
oxygen molecules flow into the measuring cell (1), they are drawn into the magnetic field. This
results in the two diamagnetic hollow spheres (2) being displaced out of the magnetic field. This
rotary motion is recorded optically, and serves as the input variable for control of a
compensation flow. This generates a torque opposite to the rotary motion around the two
hollow spheres by means of a wire loop (3). The compensation current is proportional to the
concentration of oxygen.
The calibration point is calibrated using the AUTOCAL function by connecting oxygen
(analogous to calibration of the electrochemical O
technical data, the zero point of the paramagnetic measuring cell must be calibrated with
nitrogen weekly in the case of all measuring ranges < 5% or every two months in the case of all
larger measuring ranges.
ULTRAMAT 23
Equipment Manual, 04/2022, A5E37100388-012
Operating principle of the paramagnetic O sensor
2
sensor). In order to comply with the
2
Description
3.3 Function
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