In one example in accordance with the present disclosure, a fluid analysis system is described. The fluid analysis system includes a fluidic die. The fluidic die includes a fluid chamber to hold a volume of fluid to be analyzed and an impedance sensor disposed within the fluid chamber. The impedance sensor measures an impedance of the fluid in the fluid chamber. The fluid analysis system also includes an evaluator device electrically coupled to the impedance sensor. The evaluator device determines at least one property of the fluid based on the impedance.

According to one embodiment, a hydrogen sensor is disclosed. The hydrogen sensor includes a capacitor, a gas detector, a heater, and a determiner. The capacitor includes a deformable member that deforms by absorbing or adsorbing hydrogen and varies a capacitance value corresponding to a deformation of the deformable member. The gas detector detects gas based on a capacitance value of the capacitor. The heater heats the deformable member. The determiner determines whether gas detected by the gas detector contains a substance other than hydrogen or not, wherein the gas detector detects the gas during a heating period during which the heater heats the deformable member.

A method of identifying a gas is provided. The method includes providing a gas sensor device comprising at least two stacked metal oxide layers, wherein a change in conductance of the gas sensor device in a presence of a gas varies with a temperature of the stacked metal oxide layers. The method includes bringing the gas into proximity with the stacked metal oxide layers. The method also includes measuring the conductance of the gas sensor device when the gas is in proximity with the stacked layers at multiple temperatures to generate a temperature-conductance profile. The method also includes identifying a gas of interest based on the temperature-conductance profile.

Various embodiments relate to a gas sensor, including: a carrier, an electrode structure; and a sensor layer in contact with the electrode structure, wherein the sensor layer includes or essentially consists of turbostratic graphite.

A gas sensor includes a plurality of sensing resistors that vary in resistance based on ambient temperature and the presence of certain gases, such as CO.sub.2 and H.sub.2O. The responses of each of the sensing resistors vary based on a base temperature of each of the sensing resistors. The base temperatures for each of the sensing resistors and configurations of the sensing resistors are selected to emphasize a response to a gas of interest (e.g., CO.sub.2) while de-emphasizing or canceling contributions from ambient temperature and gases that are not of interest (e.g., H.sub.2O).

We disclose a micro-hotplate comprising a substrate comprising an etched portion and a substrate portion and a dielectric region over the substrate. The dielectric region comprises first and second portions. The first portion is adjacent to the etched portion of the substrate and the second portion is adjacent to the substrate portion of the substrate. The micro-hotplate further comprises a heater formed in the dielectric region, and a ring structure formed within and/or over the dielectric region such that the ring structure is coupled with the first and second portions of the dielectric region.

We disclose herein an environmental sensor system comprising an environmental sensor comprising a first heater and a second heater in which the first heater is configured to consume a lower power compared to the second heater. The system also comprises a controller coupled with the environmental sensor. The controller is configured to detect if a measured value of a targeted environmental parameter is present. The controller is configured to switch on at least one of the first and second heaters based on the presence and/or result of the measured value of the targeted environmental parameter.

A monolithic gas-sensing chip assembly for sensing a gas analyte includes a sensing material to detect the gas analyte, a sensing system including a resistor-capacitor electrical circuit, and a heating element. A sensing circuit measures an electrical response of the sensing system to an alternating electrical current applied to the sensing system at (a) one or more different frequencies, or (b) one or more different resistor-capacitor configurations of the system. One or more processors control a low detection range of the system to the gas, a high detection range of the system to the gas, a linearity of a response of the system to the gas, a dynamic range of measurements of the gas by the system, a rejection of interfering gas analytes by the system, a correction for aging or poisoning of the system, or a rejection of ambient interferences that may affect the electrical response of the system.

Miniature resistive gas detectors incorporate thin films that can selectively identify specific gases when heated to certain characteristic temperatures. A solid state gas sensor module is disclosed that includes a gas sensor, a heater, and a temperature sensor, stacked over an insulating recess. The insulating recess is partially filled with a support material that provides structural integrity. The solid state gas sensor module can be integrated on top of an ASIC on a common substrate. With sufficient thermal insulation, such a gas detector can be provided as a low-power component of mobile electronic devices such as smart phones. A method of operating a multi-sensor array allows detection of relative concentrations of different gas species by either using dedicated sensors, or by thermally tuning the sensors to monitor different gas species.

A sensor is disclosed. The sensor comprises a first substrate; a second substrate positioned relative to the first substrate; a first electrode located between the first substrate and the second substrate, the first electrode formed on the second substrate; a sensing portion covering at least a part of the first electrode and further covering at least a portion of the second substrate; a pad electrode located between the first substrate and the second substrate, wherein the pad electrode is formed on the second substrate and is electrically coupled to the first electrode; and a bonding pad located between the first substrate and the second substrate, wherein the bonding pad is formed on the first substrate and is electrically coupled to the pad electrode.