9 Technical Data
83
9.1.2
Measurement principle for O
2
using magnetic pressure method
If oxygen, which is paramagnetic gas is in an uneven magnetic field, it is attracted to the stron-
ger portion of the magnetic field increasing the pressure in that portion.
Generally, the pressure increase can be shown in the equation below:
U
P =
H
2
• X • C
H: Magnetic field strength
X: Magnetization factor of paramagnetic component (O
2
)
C: Concentration difference between paramagnetic component (O
2
)
and
carrier gas (O
2
)
The pressure increase at this time is taken out from the magnetic field using a non-paramag-
netic gas such as nitrogen. It is detected by a capacitor microphone detector and then con-
verted into electric signals.
Carrier gas uses air, which does not require any cylinder gas.
The magnetic field uses electromagnet of AC drive, and the signal is processed as AC
signals, contributing to a stable measurement value.
Fig. 65 Schematic diagram of measurement principle for MPA
Sample gas
Magnet
Magnetic field cell
Carrier gas (Air)
Measured value of O
2
