Provided is a physical quantity detection device capable of improving noise performance of a flow rate detection unit as compared with the related art. The physical quantity detection device 20 includes a plate-like chip package 208 that is arranged to protrude from the flow path of the measurement target gas and has a width W along the flow direction of the measurement target gas. The chip package 208 includes a flow rate detection unit 205, an accelerating flow path 208c, a measurement surface 208a, a non-measurement surface 208b, and a separation flow portion 208d. The cross sectional area of the accelerating flow path 208c is reduced, and the flow rate detection unit 205 is arranged. The separation flow portion 208d partitions the second sub-passage 234b into a measurement flow path facing the measurement surface 208a and a non-measurement flow path facing the non-measurement surface 208b. In the width direction Dw of the chip package 208, the end portion 208ce of the accelerating flow path 208c and the end portion 208de of the separation flow portion 208d are separated from each other.

A thermal flowmeter for measuring the mass flow rate of a medium in a measuring tube, includes: a measuring tube having a measuring tube wall; a sensor having four probes that project into the measuring tube from a main sensor body; and an electronic measuring/operating circuit designed to operate at least three probes and to generate and provide flow measurement values by operating the probes, each probe having a main probe body and an active probe body, the active probe body designed to heat the medium, to determine the temperature of the medium and/or to influence a flow of the medium in the measuring tube, wherein the main probe bodies span a rhombus on a surface of the main sensor body, and the rhombus is defined by centroid points of cross-sections of the main probe bodies.

A sensor support portion supports a physical quantity sensor. A flow path housing portion forms a measurement flow path, which accommodates a support tip end portion of the sensor support portion. The sensor support portion includes a support front surface, which includes a front fixed portion away from the support tip end portion and fixed to an inner surface of the flow path housing portion. The physical quantity sensor includes a sensor exposure surface exposed from the support front surface. A separation distance between an end portion of the front fixed portion and an end portion of the sensor exposure surface is smaller than a separation distance between the end portion of the sensor exposure surface and the support tip end portion.

To obtain a physical-quantity detection device that reduces a variation in mounting position in a main passage. A physical-quantity detection device 20 of the present invention is inserted into and disposed in a main passage 22, and includes a flange 211 fixed to a seat surface 103 of the main passage 22, and the flange 211 includes a press-fitting portion 281 for positioning with respect to a seat surface 103 side.

A flow rate measurement system outputs a measurement value which represents a magnitude of a flow rate and a flow direction of a fluid that flows through a particular main passage. The system includes a bypass passage disposed in the main passage, a detection unit disposed in the bypass passage that outputs a detection value corresponding to a magnitude of a flow rate and a flow direction of the fluid flowing through the bypass passage, and a calculation unit that, by using the detection value, calculates the measurement value by compensating as needed for a delay in the change in flow rate in the bypass passage with respect to the change in flow rate in the main passage. The compensation is based on whether a change of flow direction has occurred in the main passage or the bypass passage.

A flow meter includes: a flat substrate; a housing that houses the substrate and has an open in at least one surface; a cover that covers the substrate and covers an open surface of the housing; a support that supports the substrate and is in contact with the cover and the substrate; and a fixing unit that connects the substrate and the housing, in which, in a first region and a second region formed by dividing the substrate into two parts at a center in a longitudinal direction, the support is disposed in the first region, and the fixing unit is disposed in the second region.

A physical quantity sensing device is installed to a circuit board and is configured to output a signal, which corresponds to a physical quantity of air flowing through a physical quantity measurement passage. A physical quantity measurement passage inlet, which is communicated with the physical quantity measurement passage, includes a first inner surface and a second inner surface. A second distance, which is measured from the physical quantity sensing device to the second inner surface in a plate thickness direction of the circuit board, is larger than a first distance, which is measured from the circuit board to the first inner surface in the plate thickness direction of the circuit board.

A housing includes a measurement passage through which a part of air flowing in a main passage flows. A sensor assembly is fixed on the housing and includes a circuit board. A detection element configured to output a signal in response to a flow rate of air flowing in the measurement passage and an electronic component configured to drive the detection element are mounted on the circuit board. An outer edge of the circuit board has a fractured part with a fractured shape and a cut part having a surface roughness smaller than that of the fractured part. The fractured part at the outer edge of the circuit board is not arranged in the measurement passage but provided at a position excluding the measurement passage.

A gas flow control system for delivering a plurality of gas flows. The gas flow control system has a gas flow path extending from a gas inlet to first and second gas outlets. First and second flow restrictors are operably coupled to the gas flow path. First and second valves are operably coupled to the gas flow path such that when both first and second valves are in a fully open state, flows of gas from the first and second gas outlets are split according to the impedances of the first and second flow restrictors.

A physical quantity measuring device detects a physical quantity of gas flowing in a flow passage. The physical quantity measuring device includes a sensor element that outputs a detection signal according to the physical quantity, a case that is provided to the flow passage and houses the sensor element, and a protrusion that protrudes from a passage wall surface facing the flow passage. The case includes a measurement chamber that houses the sensor element and an inflow port that is configured to cause a part of gas flowing in the flow passage to flow into the measurement chamber therethrough. The protrusion is configured to guide gas flowing along the passage wall surface toward the inflow port.