Embodiments described herein include systems and methods for detecting flow of a fluid. One embodiment of a system includes a flow body, a thermal tube sensor housing, and a computing device. In some embodiments, the flow body includes an inlet for receiving the fluid and an outlet for expelling the fluid, the thermal tube sensor housing includes a sensor tube that includes a first connection portion and a second connection portion, and the sensor tube is configured with a cross position where a first portion of the sensor tube crosses paths with a second portion of the sensor tube, reducing a thermo-siphoning effect.

A physical quantity measurement device includes a housing forming a through flow path, and a measurement flow path branching from the through flow path. A physical quantity sensor is provided in the measurement flow path. An inner surface of the housing includes an inlet ceiling surface and an inlet floor surface which face each other and define an inlet through path that is between and connects an inlet of the through flow path and an inlet of the measurement flow path, The inlet ceiling surface includes a ceiling inclined surface that extends from the inlet of the through flow path and is inclined with respect to the inlet floor surface. A distance between the ceiling inclined surface and the inlet floor surface gradually decreases in a direction from the inlet of the through flow path toward an outlet of the through flow path.

A physical quantity measurement device includes a housing forming a through flow path, and a measurement flow path branching from the through flow path. A physical quantity sensor is provided in the measurement flow path. An inner surface of the housing includes an inlet ceiling surface and an inlet floor surface which face each other and define an inlet through path that is between and connects an inlet of the through flow path and an inlet of the measurement flow path, The inlet ceiling surface includes a ceiling inclined surface that extends from the inlet of the through flow path and is inclined with respect to the inlet floor surface. A distance between the ceiling inclined surface and the inlet floor surface gradually decreases in a direction from the inlet of the through flow path toward an outlet of the through flow path.

Several types of flow apparatus are disclosed including bypass parts, mass flow meters, and mass flow controllers are disclosed. A bypass unit includes a bypass part that is a plate-like member and a pair of external connection parts that is a pair of plate-like members laminated on two principal surfaces of the bypass part, respectively. The bypass part includes one first member or a laminated object of the first members. The first member is a sheet-like member in which a first inlet hole, a first outlet hole, and a groove, which makes these holes communicate with each other are formed. A second inlet hole and a second outlet hole are formed in the external connection part. The first inlet hole and the second inlet hole are configured to airtightly communicate, and the first outlet hole and the second outlet hole are configured to airtightly communicate with each other.

A collar is provided for use with a fluid flow sensor to reduce condensation of a moist gas flowing through the fluid flow sensor. The collar comprises a body defining an interior that defines an airspace between the collar and the housing of the fluid flow sensor when the collar is positioned on the fluid flow sensor. The collar also includes a heat source secured to the body and adapted to heat air contained within the airspace to consequently heat the housing of the fluid flow sensor and the interior surfaces of the sensor to reduce condensation of the moist gas.

Traditional flow sensors include an upstream resistive sensor element, a downstream resistive sensor element and an intervening heater resistive element. To help reduce the size and/or cost of such flow sensor, it is contemplated that the heater resistor may be eliminated. When so provided, the space required for the heater resistive element, as well as the corresponding heater control circuit, may be eliminated. This can reduce the cost, size and complexity of the flow sensor. Coupling a resistive sensor element of such flow sensor to ground through a low temperature coefficient of resistance (TCR) resistor can reduce the variation of span of an output of the flow sensor which can improve resolution and accuracy of such sensor.

The present invention provides a thermal flowmeter having good measurement accuracy by reducing deviation in the flow velocity distribution of a gas under measurement flowing through an auxiliary passage. An auxiliary passage 330 for taking in a portion of a gas under measurement IA flowing through a main passage 124 has a curved passage 32a that bends toward a flowrate measurement element 602. The curved passage 32a has a resistance portion 50 formed therein that applies resistance to the flow of the gas under measurement IA flowing through the outer peripheral side CO of the curved passage 32a so that the pressure loss of the gas under measurement IA flowing through the outer peripheral side CO is high compared to that of the gas flowing through the inner peripheral side CI of the curved passage 32a.

The present invention provides a thermal flowmeter having good measurement accuracy by reducing deviation in the flow velocity distribution of a gas under measurement flowing through an auxiliary passage. An auxiliary passage 330 for taking in a portion of a gas under measurement IA flowing through a main passage 124 has a curved passage 32a that bends toward a flowrate measurement element 602. The curved passage 32a has a resistance portion 50 formed therein that applies resistance to the flow of the gas under measurement IA flowing through the outer peripheral side CO of the curved passage 32a so that the pressure loss of the gas under measurement IA flowing through the outer peripheral side CO is high compared to that of the gas flowing through the inner peripheral side CI of the curved passage 32a.

A connection terminal is on a flange of a thermal flow meter. A terminal connection part has a first and a second bent part. The first bent part is bent from a first direction to a second direction. The second bent part has is bent from the first bent part to a third direction. The first and second bent parts are formed such that when connection pin parts of a plurality of the connection terminals and terminal connection parts of the plurality of connection terminals are projected onto a first imaginary plane, an imaginary line L extending along a first direction passing through the projection areas of each of the terminal connection parts of the plurality of connection terminals passes between the projection areas of the connection pin parts from among the connection pin parts of the plurality of connection terminals, that are positioned on both sides.

A connection terminal is on a flange of a thermal flow meter. A terminal connection part has a first and a second bent part. The first bent part is bent from a first direction to a second direction. The second bent part has is bent from the first bent part to a third direction. The first and second bent parts are formed such that when connection pin parts of a plurality of the connection terminals and terminal connection parts of the plurality of connection terminals are projected onto a first imaginary plane, an imaginary line L extending along a first direction passing through the projection areas of each of the terminal connection parts of the plurality of connection terminals passes between the projection areas of the connection pin parts from among the connection pin parts of the plurality of connection terminals, that are positioned on both sides.