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- Englisch (26) (entfernen)
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- Coulometric sensors (4)
- Hydrogen detection (4)
- Electronic nose (3)
- Ion mobility spectrometer (3)
- Multivariate data analysis (3)
- Product adulteration (3)
- Spice mixtures (3)
- Trace humidity measurement (3)
- ANOVA (2)
- Calibration (2)
Organisationseinheit der BAM
A silicon MIS-structure prepared with thin layers of the super-ionic conductor LaF3 and Pd is used to detect hydrogen. The sensor is able to detect hydrogen in a concentration range from below one ppm to the lower flammable limit in air which is 4 vol.-%. The chip operates at room temperature which results in an extremely low energy consumption compared to other hydrogen sensors. Only once per day a short heating pulse is necessary to reactivate the sensor chip. In cooperation with the BAM, a long-term experiment was carried out. The duration of the measurement was about three months, with a hydrogen exposure every two weeks. The sensor signal remained stable over the measured period.
Five miniaturized sensors based on dew-point,
capacitance or resistance measurement were tested for the
detection of humidity in compressed gases.
The dew-point sensors with optical or dielectric detection of
condensation were used at gas pressures up to 3 MPa in
dew-point range of -20 to 70°C and show no systematic
deviation and an uncertainty of dew-point temperature
mostly less than 1 K. The LiCl sensor has also a low
uncertainty but exhibit a systematic deviation to higher
values of dew-point. Capacitive polymer sensors can
indicate also a dew-point, even down to -70 °C and have an
uncertainty of about 1 to 2 K. The oxide sensor works in the
dew-point range of -10 to 20°C and has a signal what
exponential decreases with increasing gas pressure up to 10
MPa.
All types of sensor can be applied in compressed gases at
least up to 3 MPa, but their different change of sensor signal
due to the gas pressure has to be considered.
A hydrogen sensor based on a silicon Metal/Solid Electrolyte/Insulator/Semiconductor (MEIS) structure with thin layers of the super-ionic conductor LaF3 and Pd gate metal was investigated in a hybrid structure on a resistance heater mounted on a ceramic substrate. The sensor was operated at room temperature, however, a short heating impulse once a day ensures a fast and reproducible dynamic behavior. The sensor was characterized in the concentration range typical for alarm levels up to 40% of the lower flammability limit and shows a logarithmic dependency of the sensor signal from the hydrogen concentration and a mean sensitivity of about 140 mV/decade. The response time (t90) is about 8 s. In a long term test for a period of three month, the sensor was exposed to hydrogen every two weeks. The sensor signal was shown to be stable in dynamic behavior, sensitivity and signal difference.