Technology
in a single measuring cuvette. This has the advantage that all gas concentrations are measured at exactly the same time.
With gas sensors connected in series, there would inevitably be a time lag, which would cause a significant error in dynamic processes, especially at low gas flow rate. Figure 5: High- resolution IR spectrum of the gases CH4
, CO2
be analysed The
INFRA.sens®
, and CO to has a very high measurement accuracy of
2%. To achieve this, all measurement errors are compensated electronically. These include in particular:
• Temperature compensation between 5°C and 45°C • Air pressure compensation between 600hPa and 1200hPa • Carrier gas dependence between CO2
and CH4
• High long-term stability due to an internal reference measurement.
The use of a gold-plated analysis cuvette also effectively prevents changes in the reflection properties, thereby significantly improving long-term stability. The basic design of the INFRA. sens®
gas measurement module is shown in Figure 6. Figure 7 shows the entire measurement setup.
Humidity measurement The
HUMI.sens®
is based on a capacitive humidity sensor.
This sensor consists of a hygroscopic polymer material in which water vapour from the measured gas is stored. This storage changes the dielectric properties of the polymer material. The polymer material is located between the electrodes of an electrical capacitor and thus also changes the capacitance of the capacitor. The capacitance increases almost linearly with humidity.
An equilibrium is established between the humidity in the measured gas and the humidity in the polymer, which adapts reversibly to varying humidity levels.
Data communication also takes place via an I2 C interface.
Figure 9:
HUMI.sens® for I2
with gas connections and plug contacts C data transmission
Figure 6: Schematic diagram of the
INFRA.sens NDIR gas measurement module. 1. IR emitter, 2. Analysis cuvette (AK), 3. IR detector with preamplifier, 4. Evaluation electronics, 5. Signal outputs (CAN, Modbus, RS232, analogue), 6. Gas output, 7. Gas input
Figure 10: Process log from a batch with activated GreenFlow
Fig. 7:
INFRA.sens with a 100 mm analysis cuvette (AK100) and integrated moisture and oxygen measurement
Oxygen measurement
Oxygen measurement is performed using an electrochemical cell (EC).
In this process, a chemical reaction takes place between the oxygen to be measured and a liquid electrolyte. This reaction releases four electrons per oxygen molecule.
The resulting sensor current increases proportionally with the number of reacting O₂ molecules. This produces a sensor characteristic curve that rises linearly with increasing O₂ concentration.
The O2 electronics via an I2
concentration is transmitted to the
INFRA.sens base C data interface and processed.
Figure 11: Potential savings with the GreenFlow system for different hardening furnaces
Figure 8:
O2.sensD
with gas connections and I2
C data cable
Figure 12: Monthly consumption and savings of a TQ-XL(1200) furnace system
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IET - JANUARY / FEBRUARY 2026
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