TY - JOUR A1 - Berndt, Dominik A1 - Muggli, Josef A1 - Heckel, Robert A1 - Rahiman, Mohd Fuad A1 - Lindner, Matthias A1 - Heinrich, Stephan A1 - Plöchinger, Heinz A1 - Schreiner, Rupert T1 - A Robust Miniaturized Gas Sensor for H₂ and CO₂ Detection Based on the 3ω Method JF - Sensors N2 - Gas concentration monitoring is essential in industrial or life science areas in order to address safety-relevant or process-related questions. Many of the sensors used in this context are based on the principle of thermal conductivity. The 3ω-method is a very accurate method to determine the thermal properties of materials. It has its origin in the thermal characterization of thin solid films. To date, there have been very few scientific investigations using this method to determine the thermal properties of gases and to apply it to gas measurement technology. In this article, we use two exemplary gases (H2 and CO2) for a systematical investigation of this method in the context of gas analysis. To perform our experiments, we use a robust, reliable sensing element that is already well established in vacuum measurement technology. This helix-shaped thin wire of tungsten exhibits high robustness against chemical and mechanical influences. Our setup features a compact measurement environment, where sensor operation and data acquisition are integrated into a single device. The experimental results show a good agreement with a simplified analytical model and FEM simulations. The sensor exhibits a lower detection limit of 0.62% in the case of CO2, and only 0.062% in case the of H2 at an excitation frequency of 1 Hz. This is one of the lowest values reported in literature for thermal conductivity H2 sensors. KW - 3ω-method KW - CO2 sensor KW - H2 sensor KW - thermal gas sensor Y1 - 2022 U6 - https://doi.org/10.3390/s22020485 N1 - Corresponding author: Dominik J. Berndt VL - 22 IS - 2 SP - 1 EP - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Eiler, Julian A1 - Weber, Stefan A1 - Gerlesberger, Peter A1 - Plöchinger, Heinz A1 - Schreiner, Rupert T1 - Active heat-loss compensated miniaturized pirani sensor chip JF - IEEE Sensors Letters N2 - Due to the limited measuring range of commercial Pirani sensors in lower pressure regimes, attempts are being made to extend the measuring range of the sensors. Our approach to extend the measuring range toward lower pressures is a micro-electromechanical systems (MEMS) Pirani sensor with active heat compensation on the suspensions. The sensor element has the shape of a microhotplate and consists of a nickel heating meander embedded in two silicon nitride layers. The whole structure is built on a silicon wafer. The sensor element is suspended on all four corners of the substrate. On each of the suspensions, there is an additional heating structure that minimizes the heat flux from the hot sensor element toward the substrate. The sensor is driven at a constant temperature through a self-balancing Wheatstone bridge. A constant voltage is applied to the heating structures on the suspensions. It has been demonstrated that with these additional heaters, the sensitivity of the sensor can be increased in the high-vacuum regime. This enables reliable vacuum measurements down to 10−6 mbar. KW - Temperature measurement KW - Heating systems KW - Temperature sensors KW - Sensitivity KW - Pressure measurement KW - Voltage measurement KW - Heat sinks KW - Semiconductor device measurement KW - Noise measurement KW - Bridge circuits Y1 - 2025 U6 - https://doi.org/10.1109/LSENS.2025.3605747 SN - 2475-1472 VL - 9 IS - 10 PB - Institute of Electrical and Electronics Engineers (IEEE) ER -