Principle Of Operation - Siemens OXYMAT 64 Operating Instructions Manual

2.3

Principle of operation

Principle of operation
The measuring cell consists of a ZrO
sample gas (with a low O
regulated at 650 °C. The exterior of the sensor is exposed to the ambient air (approx. 21%
O ). The two sides of the ZrO
2
electrodes. This produces a stable electrochemical cell. The exterior of this sensor is
exposed to the ambient air (approx. 21% O
different diffusion of the oxygen into the ceramic sensor material. A quantity of oxygen atoms
is ionized equivalent to the oxygen concentration at the electrodes.
A different partial pressure exists due to the differences in concentration on the two sides.
Since ZrO
the lower partial pressure.
A gradient in the oxygen ions is produced across the thickness of the ZrO
leads to a potential difference between the two platinum electrodes in accordance with
equation (1).
The inclusion of crystal lattice faults by doping the ZrO
originally to prevent the formation of cracks in the ceramic material - increases the diffusion
ability of the O
Catalytically active ZrO
The electrode material is made of platinum (Pt). This type of sensor therefore has a large
cross-sensitivity in the presence of flammable components in the residual gas.
Catalytically inactive ZrO
The catalytically inactive sensor has the same basic design as the CAZ auf. However, the
contacts and the electrode surface inside the cylinder are made of a specially developed
material which largely prevents catalytic oxidation of H
OXYMAT 64
Operating Instructions, 06/2008, A5E00880383-03
content) flows at a constant rate through the inside of the sensor
2
membrane are coated with thin platinum films which serve as
2
is electrically conductive at 650 °C, there is a migration of ions in the direction of
2
ions in the ZrO lattice.
2 2
sensor (CAZ)
2
sensor (CIZ)
2
membrane arranged as a cylinder (tubular). The
2
). The different O
2
material with Y
2
, CO and CH
2
Description
2.3 Principle of operation
concentrations also cause a
2
membrane which
2
O and/or CaO -
2 3
.
4
13