Isolde Simon

Bio: Isolde Simon is an academic researcher from Bosch. The author has contributed to research in topics: Thermal conductivity & Surface micromachining. The author has an hindex of 5, co-authored 15 publications receiving 757 citations.

Micromachined metal oxide gas sensors: opportunities to improve sensor performance

Abstract: This review deals with gas sensors combining a metal oxide based sensing layer and a substrate realized by using micromachining. It starts by giving an overview of the design principles and technology involved in the fabrication of micromachined substrates examining thermal and mechanical aspects. Both kinds of micromachined substrates, closed-membrane-type and the suspended-membrane-type, are discussed. The deposition of the sensing layer is complicated by the mechanical fragility of the micromachined substrates. Different approaches used for the formation of the sensing layer such as thin film and thick film deposition techniques are reviewed. Finally, the gas sensing function of the sensitive layer is analyzed and various ways for extracting the information are presented with respect to the improvement of sensor performance brought by this new approach.

Thermal and gas-sensing properties of a micromachined thermal conductivity sensor for the detection of hydrogen in automotive applications

Abstract: This work describes the design and characterization of a micromachined thermal conductivity sensor for detection of hydrogen in automotive fuel cell systems. Thermal and gas-sensing properties are investigated via simulations and experiments. The manufactured sensors consist of a thin dielectric membrane as carrier structure for a platinum heater and temperature sensor. Membrane and heater size were varied to examine their influence on sensitivity, power consumption and thermal response. Based on a sensor element with a membrane size 1.5 mm ×1.5 mm a hydrogen sensor prototype with a detection limit of 0.2% hydrogen in air was achieved.

Sensor module having a sensor element surrounded by a heating element

Abstract: A sensor module having a heating structure and a sensor element is described. The heating structure surrounds the sensor element so that heat dissipation through a frame is largely prevented. This yields a greater measuring accuracy of the sensor module. In particular, interfering influences due to a temperature dissipation through the mount frame are thereby prevented.

Temperature sensing device for detecting an acceleration or shock provided with a heating unit, and associated method

Abstract: A sensor is used for measuring the motion of a fluid in relation to a heating device. A temperature-measuring means is provided in such a way that the temperature of the fluid is measured at a measuring location as a function of the motion of the fluid, as a measuring location, the location of the heating device or its immediate vicinity being provided.

Sensor mit einer Heizeinrichtung und Verfahren

Abstract: Es wird ein Sensor (1) und ein Verfahren vorgeschlagen, wobei der Sensor der Messung der Bewegung eines Fluids relativ zu einer Heizeinrichtung (30) dient, wobei Temperaturmessmittel (30, 31) derart vorgesehen sind, in Abhangigkeit der Bewegung des Fluids die Temperatur des Fluids an einem Messort zu messen, wobei als Messort der Ort der Heizeinrichtung oder in ihrer unmittelbaren Nahe vorgesehen ist.

Hydrogen Sensors - A review

Abstract: Hydrogen sensors are of increasing importance in connection with the development and expanded use of hydrogen gas as an energy carrier and as a chemical reactant. There are an immense number of sensors reported in the literature for hydrogen detection and in this work these sensors are classified into eight different operating principles. Characteristic performance parameters of these sensor types, such as measuring range, sensitivity, selectivity and response time are reviewed and the latest technology developments are reported. Testing and validation of sensor performance are described in relation to standardisation and use in potentially explosive atmospheres so as to identify the requirements on hydrogen sensors for practical applications.

The role of morphology and crystallographic structure of metal oxides in response of conductometric-type gas sensors

Abstract: This review paper discusses the influence of morphology and crystallographic structure on gas-sensing characteristics of metal oxide conductometric-type sensors. The effects of parameters such as film thickness, grain size, agglomeration, porosity, faceting, grain network, surface geometry, and film texture on the main analytical characteristics (absolute magnitude and selectivity of sensor response (S), response time (τres), recovery time (τrec), and temporal stability) of the gas sensor have been analyzed. A comparison of standard polycrystalline sensors and sensors based on one-dimension structures was conducted. It was concluded that the structural parameters of metal oxides are important factors for controlling response parameters of resistive type gas sensors. For example, it was shown that the decrease of thickness, grain size and degree of texture is the best way to decrease time constants of metal oxide sensors. However, it was concluded that there is not universal decision for simultaneous optimization all gas-sensing characteristics. We have to search for a compromise between various engineering approaches because adjusting one design feature may improve one performance metric but considerably degrade another.

Higher-order chemical sensing.

Abstract: 6.2. Orthogonality versus Independence 584 6.3. Cross-sensitivity and Diversity 585 6.4. Multiple Roles of Redundancy 585 7. Data Preprocessing 586 7.1. Baseline Correction 586 7.2. Scaling 587 7.2.1. Global Techniques 588 7.2.2. Local Techniques 588 7.2.3. Nonlinear Transforms 588 8. Drift Compensation 588 8.1. Univariate Drift Compensation 589 8.2. Multivariate Drift Compensation 589 9. Feature Extraction from Sensor Dynamics 591 9.1. Transient Analysis 591 9.1.1. Oversampling Procedures 592 9.1.2. Ad hoc Transient Parameters 593 9.1.3. Model-Based Parameters 593 9.1.4. Comparative Studies 595 9.2. Temperature-Modulation Analysis 596 10. Multivariate Calibration 599 10.1. Multiway Analysis 599 10.2. Dynamical Models 602 11. Array Optimization 604 11.1. Sensor Selection 604 11.2. Feature Selection 605 11.3. Optimization of Excitation Profiles 607 12. Conclusion and Outlook 608 13. References 609

Metal-Organic Frameworks for Sensing Applications in the Gas Phase

Abstract: Several metal-organic framework (MOF) materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O2, CO2, C3H8, NO, H2, ethanol and methanol in the gas atmosphere and under different test gas humidity conditions. Different sensor configurations were studied in a frequency range of 1 Hz -1 MHz and time-continuous measurements were performed at 1 Hz. The materials did not show any impedance response to O2, CO2, C3H8, NO, or H2 in the gas atmospheres, although for some materials a significant impedance decrease was induced by a change of the ethanol or methanol concentration in the gas phase. Moreover, pronounced promising and reversible changes in the electric properties of a special MOF material were monitored under varying humidity, with a linear response curve at 120 °C. Further investigations were carried out with differently doped MOF materials of this class, to evaluate the influence of special dopants on the sensor effect.