In an embodiment an electro-thermal device includes a heater, a readout circuit, a digital controller having a first input coupled to a first output of the readout circuit and a digital sigma-delta modulator having a first input coupled to an output of the digital controller and an output coupled to the heater.

A microneedle probe for measuring a sap flow in a plant is disclosed, the microneedle probe including: a substrate; and a sensor unit which is installed on the substrate, generates heat, and measures a temperature that changes in accordance with a sap flow.

The method for calculating concentration ratio includes: (a) heating a gas sensor element to a temperature at which both of two gas components introduced in a gas sensor element react, and maintaining the temperature for a predetermined period to measure an electrical resistance value of the gas sensor element; (b) heating the gas sensor element to a temperature at which only any of the two gas components reacts, and maintaining the temperature for a predetermined period to measure an electrical resistance value of the gas sensor element; and (c) calculating a concentration ratio of the two gas components based on a combination of the electrical resistance value in (a) and the electrical resistance value in (b).

A microneedle probe for measuring a sap flow in a plant is disclosed, the microneedle probe including: a substrate; and a sensor unit which is installed on the substrate, generates heat, and measures a temperature that changes in accordance with a sap flow.

A microneedle probe for measuring a sap flow in a plant is disclosed, the microneedle probe including: a substrate; and a sensor unit which is installed on the substrate, generates heat, and measures a temperature that changes in accordance with a sap flow.

A fluid sensor for sensing a concentration or composition of a fluid, the sensor comprising: a semiconductor substrate comprising a first etched portion; a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises a first dielectric membrane located over the first etched portion of the semiconductor substrate; a first heating element located within the first dielectric membrane; and a second heating element; wherein the first heating element is arranged to thermally shield the second heating element from ambient temperature changes; wherein the first heating element or the second heating element is configured to operate as a temperature sensing element; wherein the first heating element is configured to operate in a constant temperature or constant resistance mode; wherein the second heating element is configured to operate in a constant current or constant voltage mode or constant power mode; and wherein the sensor is configured to determine a thermal conductivity of the fluid using the temperature sensing element to determine said concentration or composition of the fluid.

In an embodiment an electro-thermal device includes a heater, a readout circuit, a digital controller having a first input coupled to a first output of the readout circuit and a digital sigma-delta modulator having a first input coupled to an output of the digital controller and an output coupled to the heater.

An oxygen sensor is provided in which an insulative coating using an exterior resin material made of insulative resin is applied to a self-heating oxygen sensor element made of a ceramic sintered body housed in a case, and in which waterproof cloths with air permeability are attached using resin adhesives so as to cover openings that connect to air holes on end parts of the case. This allows provision of a gas sensor for use both in air and in liquid having insulating property, waterproof property, and thermal safety.

An oxygen sensor is provided in which an insulative coating using an exterior resin material made of insulative resin is applied to a self-heating oxygen sensor element made of a ceramic sintered body housed in a case, and in which waterproof cloths with air permeability are attached using resin adhesives so as to cover openings that connect to air holes on end parts of the case. This allows provision of a gas sensor for use both in air and in liquid having insulating property, waterproof property, and thermal safety.

A gas leak detector cartridge includes a cartridge housing that is removably installed in a handheld device. The cartridge housing includes a sensor that detects a presence of a contaminant in a sample gas and is connected to a printed circuit board. The cartridge housing also includes a pump positioned in a manifold and introduces a sample gas to the sensor. The sensor is at least partially inserted into the manifold that includes the pump.