The sample gas (low 0₂ content) flows at a constant rate through the inside of the sensor regulated at 650 °C. The exterior of the sensor is exposed to the ambient air (approx. 21% O₂) and functions as a reference electrode.

The different O₂ concentrations cause a diffusion of oxygen through the ceramic sensor material. The oxygen molecules are thereby ionized. The energy created in this manner (U, equation 1) corresponds to the potential difference between the two electrodes 3, 4.

Depending on the application, a catalytically inactive ZrO₂ sensor (CIZ) or a catalytically active sensor (CAZ) can be used.

Catalytically inactive ZrO₂ sensor (CIZ)

Contacts and electrode surface inside the pipe are made of a specially developed material, which largely prevents catalytic oxidation of H₂, CO and CH₄.

Catalytically active ZrO₂ sensor (CAZ)

The catalytically active sensor has the same general design as the CIZ. Only the electrode material (Pt) is different. Moreover, the sensor type has a great diagonal sensitivity in the case of measurable carrier gas components.

OXYMAT 64, mode of operation

Measuring effect

U = U_A + RT/4F (In [O₂,air] - In [O₂] (equation 1)
U measuring effect
U_A asymmetric voltage (voltage, at [O₂] = [O₂,air]
T ceramic temperature
[O₂,air] O₂ concentration in the air
[O₂] O₂ concentration in sample gas

Note

The sample gas must be fed into the analyzer free of dust. Condensation should be avoided. Therefore, gas modified for the measurement tasks is necessary in most application cases.

Important features

• Four measurement ranges freely parameterizable, all measurement ranges linear
• Galvanically isolated measurement value output 0/2/4 through 20 mA (also inverted) and as per NAMUR
• Automatic measurement range changeover selectable; possibility of remote switching
• Measurement value can be saved during adjustment
• Wide range of selectable time constants (static/dynamic noise suppression); i.e. the response time of the device can be adapted to the respective measurement task
• Easy to use thanks to menu-driven operation
• Low long-term drift
• Two control levels with their own authorization codes for the prevention of accidental and unauthorized operator interventions
• Automatic, parameterizable measurement range adjustment
• Operation based on the NAMUR recommendation
• Monitoring of the sample gas (via pressure switch)
• Customer-specific device versions, such as:
  • Customer acceptance
  • TAG labels
  • Drift recording
• Ease of use thanks to a numerical membrane keyboard and operator guide
• Smallest measurement span 0 to 10 vpm O₂
• Internal pressure sensor for correction of the influence of sample gas pressure fluctuations.

Diagonal gas effect

Catalytically active sensor (CAZ)

Very large diagonal gas effect of all combustible carrier gases. Thus not suitable for use with combustible carrier gases!

Catalytically inactive sensor (CIZ)

There is only a slight diagonal gas effect in the case of carrier gases with concentration in the range of the O₂ concentration. H₂, CO and CH₄ only have a nominal effect on the combustible carrier gas components.

Examples of typical diagonal gas offsets on a catalytically inactive sensor

The listed deviations depend on the exemplar and can deviate up to ± 0.2 vpm. The actual deviation must be determined individually or the error will be eliminated through a corresponding calibration measure (displacement of the diagonal gas offset).