Abstract. In this paper, the first steps towards integrating a mass sensing system into an existing miniaturized ceramic DSC (differential scanning calorimetry) chip are presented. A vibration setup is developed based on the mass-dependent change in frequency of the DSC chip as an oscillating cantilever. A simulation model reveals that the resolution of the measurement can be improved by reducing the chip thickness. In this study, different measurement methods (acoustic, optical, and piezoresistive) are investigated. Three complete measurement systems are set up and evaluated with regard to their integration in the DSC chip. All presented measurement methods show promising results and already allow mass measurements with a resolution of 100 µg.

Due to increasingly stringent limits for NOx emissions, there is now more interest than ever in cost-effective, precise, and durable exhaust gas sensor technology for combustion processes. This study presents a novel multi-gas sensor with resistive sensing principles for the determination of oxygen stoichiometry and NOx concentration in the exhaust gas of a diesel engine (OM 651). A screen-printed porous KMnO4/La-Al2O3 film is used as the NOx sensitive film, while a dense ceramic BFAT (BaFe0.74Ta0.25Al0.01O3–δ) film prepared by the PAD method is used for λ-measurement in real exhaust gas. The latter is also used to correct the O2 cross-sensitivity of the NOx sensitive film. This study presents results under dynamic conditions during an NEDC (new European driving cycle) based on a prior characterization of the sensor films in an isolated sensor chamber with static engine operation. The low-cost sensor is analyzed in a wide operation field and its potential for real exhaust gas applications is evaluated. The results are promising and, all in all, comparable with established, but usually more expensive, exhaust gas sensors.

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Abstract. The temperature-dependent properties of sensor films for measuring the concentration of various gas components affect, to a large extent, the sensor characteristics of planar gas sensors. Therefore, it is important to know the temperature distribution of the gas-sensitive films of such sensors precisely. Using screen-printed thermocouples and a thermal-imaging camera, two principles for determining the temperature profile of gas sensors inside of a protection cap are shown and compared in this study. The data agree well, and the results can be used in future to determine the influences of varying flow and temperature conditions on the temperature profile of a sensor and to reduce such effects by adapting the periphery, e.g., by designing appropriate protection caps.

The selective detection of different gas components will remain of huge importance in the future, either in the ambient air or in flue gases, e.g., for controlling purposes of combustion processes. The focus here is on the development of a highly selective ammonia sensor that will be exemplarily used in the flue gas of biomass combustion plants with catalysts for nitrogen oxide reduction. Such applications require a robust sensor design, in this case, based on a ceramic substrate. The gaseous ammonia is detected with the help of a zeolite film, whose selective adsorption properties towards ammonia are already intensively being used in the field of flue gas catalysis. The adsorption and desorption of ammonia on the gas-sensitive zeolite film lead to changes in the dielectric properties of the functional material. Using an interdigital electrode (IDE) structure below the zeolite film, the capacitance was determined as a measure of the ammonia concentration in the gas. In this context, the fabrication of all layers of the sensor in the thick film with subsequent laser patterning of the IDE structure enables a cost-efficient and effective method. The functionality of this sensor principle was extensively tested during measurements in the laboratory. A high and fast response to ammonia was detected at different sensor temperatures. In addition, very low cross-sensitivities to other gas components such as water (very low) and oxygen (zero) were found.