Abstract: A sensor for sensing direction of fluid-flow, the sensor comprising: a heating element; a first active temperature sensing element; and a processor; wherein the processor is configured to: receive a first signal corresponding to a first sensed temperature from the first active temperature sensing element; and determine a direction of fluid-flow based on a difference between the first sensed temperature and a threshold value. A method for sensing direction of fluid-flow and a method for manufacturing a sensor are also described.

Abstract: A method for controlling a fluid-flow sensor in the presence of a flowing fluid, the method comprising: applying an electrical bias to the heater element of the fluid-flow sensor, determining a phase of the flowing fluid, and modifying the electrical bias according to the phase of the flowing fluid. A controller for a fluid-flow sensor is also described.

Abstract: A fluid sensor for sensing a concentration or composition of a fluid, the sensor comprising a first temperature sensing element located on or within a first dielectric membrane and a second temperature sensing element located on or within a second dielectric membrane. An output circuit is configured to measure a differential signal between the first temperature sensing element and the second temperature sensing element. The fluid sensor comprises a first region configured to be exposed to the fluid, and a second region configured to be isolated from the fluid, where the first dielectric membrane is located in the first region, such that in use, the first dielectric membrane is exposed to the fluid, and wherein the second dielectric membrane is located in the second region such that in use, the second dielectric membrane is isolated from the fluid.

Abstract: We disclose herein a flow sensor comprising: a first substrate comprising an etched portion, a dielectric region located on a first side of the first substrate, wherein the dielectric region comprises at least one dielectric membrane located over the etched portion of the first substrate, a sensing element located on or within the dielectric membrane, and a second substrate adjoining a second side of the first substrate. The first side of the first substrate and the second side of the first substrate are opposite sides. The first substrate and the second substrate cooperate to form a sensing channel through the flow sensor.

Abstract: A fluid sensor for sensing a concentration or composition of a fluid, the sensor comprising: a semiconductor substrate comprising a first etched portion and a second 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, and a second dielectric membrane located over the second etched portion of the semiconductor substrate; two temperature sensing elements on or within the first dielectric membrane and two temperature sensing elements on or within the second dielectric membrane; an output circuit configured to measure a differential signal between the two temperature sensing elements of the first dielectric membrane and the two temperature sensing elements of the second dielectric membrane; wherein the first dielectric membrane is exposed to the fluid and the second dielectric membrane is isolated from the fluid.

Abstract: There is disclosed herein a flow sensor comprising: a first substrate comprising an etched portion; a dielectric layer located on the first substrate, where the dielectric layer comprises at least one dielectric membrane located over the etched portion of the first substrate; a first heating element and a second heating element located on or within the dielectric membrane; and a controller coupled with the first heating element and the second heating element. The first heating element and the second heating element are arranged to intersect one another within or over an area of the dielectric membrane. The controller is configured to: take a measurement from the second heating element; determine a calibration parameter using the measurement from the second heating element; take a measurement from the first heating element; and determine a flow rate through the flow sensor using the determined calibration parameter and the measurement from the first heating element.

Abstract: We disclose herein a flow sensor assembly comprising a first substrate, a flow sensor located over the first substrate, a lid located over the flow sensor, a flow inlet channel, and a flow outlet channel. A surface of the flow sensor and a surface of the lid cooperate to form a flow sensing channel between the flow inlet channel and the flow outlet channel, and a surface of the flow sensing channel is substantially flat throughout the length of the flow sensing channel.

Abstract: We disclose herein a flow and thermal conductivity sensor comprising a semiconductor substrate comprising an etched portion, a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises at least one dielectric membrane located over the etched portion of the semiconductor substrate and a heating element located within the dielectric membrane. The dielectric membrane comprises one or more discontinuities located between the heating element and an edge of the dielectric membrane.