REMOVABLE HIGH FLOW IMPEDANCE MODULE IN FLOW SENSOR BYPASS CIRCUIT

1 . A flow element comprising:

a flow body defining a main flow path having a main flow resistance; and

a removable flow module defining at least a part of a bypass flow path having a bypass flow resistance, the bypass flow resistance being much greater than the main flow resistance,

wherein the flow body further defines a bypass flow inlet and a bypass flow outlet, the bypass flow inlet and the bypass flow outlet fluidly connecting the bypass flow path to the main flow path.

2 . The flow element of claim 1 , wherein the bypass flow resistance is greater than one thousand times the main flow resistance.

3 . The flow element of claim 1 , wherein the removable flow module comprises:

a module body having a substrate;

a flow channel etched in the substrate and having an etched inlet opening and an etched outlet opening;

a heater configured to heat fluid flowing through the flow channel; and

at least one film temperature sensor configured to sense temperature of fluid flowing through the flow channel.

4 . The flow element of claim 1 , wherein the substrate is at least one of: semiconductor and glass.

5 . The flow element of claim 1 , further comprising a pressure drop element configured to force a portion of the fluid flowing through the main flow path into the bypass flow path.

6 . The flow element of claim 5 , wherein the pressure drop element is integrated into the flow body.

7 . The flow element of claim 1 , further comprising at least one filter disposed between the main flow path and the part of the bypass flow path defined by the removable flow module.

8 . The flow element of claim 7 , wherein the at least one filter comprises at least one biological filter.

9 . The flow element of claim 1 , wherein the main flow path is a straight path between a flow element inlet and a flow element outlet.

10 . The flow element of claim 1 , wherein the bypass flow path is parallel to the main flow path.

11 . The flow element of claim 1 , wherein the bypass flow inlet defines an inlet interface path having an interface resistance.

12 . The flow element of claim 11 , wherein the bypass flow resistance is greater than fifty times the interface resistance.

13 . The flow element of claim 11 , wherein the inlet interface path is perpendicular to the main flow path.

14 . The flow element of claim 11 , wherein the inlet interface path extends from the main flow path at an angle.

15 . The flow element of claim 1 , further comprising at least one of: a humidity sensor and a barometric sensor.