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PhenoMaster | Hardware Operating Instructions
Oxygen molecules which are located in the sensor cavity are ionized at the negative electrode and
accelerated to the positive electrode. The passage through the electrolyte between the two electrodes
is fast, so that the oxygen partial pressure in the cavity decreases. Additional oxygen molecules have
to diffuse through the diffusion opening into the cavity to compensate for the drop in the partial
pressure. As this diffusion is slow as compared to the movement of the oxygen ions through the
electrolyte, the ionization rate and thus, the electrical current depends on the number of oxygen
molecules diffusing to the electrode. According to Fick’s law, the diffusion through the hole of the
cavity is dependent on the gas concentration.
The oxygen sensor is operated at a higher temperature and moisture that penetrates the measuring
cell can lead to inaccurate measurements. This is why the sample air should always be pre-dried with
the Air Drying Unit.
Technical Data
Measurement range
0.1…25%
Resolution
Inlet side: 10bit AD
Outlet side: 11bit DAC
Accuracy
+/- 0.5% of full scale
Stability
+/- 0.5% of full scale/year
The oxygen sensor of the High-Speed Sensor Unit works according to the paramagnetic principle.
For further instructions, see Hardware Operating Instructions - High-Speed Sensor Unit.
11.2.4.2. CO2 Sensor - Working Principle
The CO2 sensor consists of an infrared light source, a gas cell, a narrow optical filter, and a detector.
The sensor uses the Non-Dispersive InfraRed (NDIR) gas sensing method. CO2 molecules, just like
other molecules, vibrate and rotate at characteristic frequencies in the infrared spectra. This results in
gas-specific absorption spectra, which can be used for identifying and quantifying the composition of
gases. The broad spectrum of the light source is selected via the narrow optical filter to form a strong
and specific absorption band for CO2 and a reference band for high transmission.
Technical Data
Measurement range
0…2%
Accuracy
+/- 2% of full scale
Stability
+/- 2% of full scale
Temperature Sensor
11.2.5.
The temperature sensor is provided for measuring the temperature of the test environment.
NOTICE
- Instrument damage!
The sensor is a sensitive measuring instrument that must be protected against damage.
•
Handle the sensor with care.
•
Do NOT immerse the sensor in water, cleaning liquids, etc.
Cage temperature sensor precalibrated in the factory.
11.2.5.1. Analogous Temperature Sensor
It is a precision integrated-circuit temperature sensor, whose output voltage is linear proportional to
the temperature.
