Abstract: A flow sensing module with a bypass channel is provided. The flow sensing module may include a body portion and a flow sensor. The body portion may include a main fluid inlet, a main fluid outlet, a main fluid channel extending between the main fluid inlet and the main fluid outlet, a bypass fluid inlet and a bypass fluid outlet each configured to be in communication with the main fluid channel, and a bypass fluid channel extending between the bypass fluid inlet and the bypass fluid outlet. The flow sensor may be disposed in the bypass fluid channel to sense a flow rate of a fluid in the bypass channel. No pressure drop element is disposed in the main fluid channel, so the main fluid channel may have a pressure loss of a very small value. Moreover, linearity and sensitivity of the flow sensing module may also be improved.

Abstract: A flow sensing module with a bypass channel is provided. The flow sensing module may include a body portion and a flow sensor. The body portion may include a main fluid inlet, a main fluid outlet, a main fluid channel extending between the main fluid inlet and the main fluid outlet, a bypass fluid inlet and a bypass fluid outlet each configured to be in communication with the main fluid channel, and a bypass fluid channel extending between the bypass fluid inlet and the bypass fluid outlet. The flow sensor may be disposed in the bypass fluid channel to sense a flow rate of a fluid in the bypass channel. No pressure drop element is disposed in the main fluid channel, so the main fluid channel may have a pressure loss of a very small value. Moreover, linearity and sensitivity of the flow sensing module may also be improved.

Abstract: The present invention provides a MEMS thermal flow sensor or meter for measuring the flow rate of a fluid without need for calibration of the flow sensor for that particular fluid. A response curve is determined by plotting the sensor output voltage against the volume flow rate divided by fluid thermal diffusivity for a calibration fluid of known thermal diffusivity, and storing response curve data in memory. A conversion factor is employed to provide a measure of correct flow rate of an unknown fluid. This conversion factor is derived from the ratio of the thermal time constant of the calibration fluid to the thermal time constant of the measured fluid, the time constants being measured at zero flow. These time constants are stored in memory. This conversion factor in conjunction with the response curve data is utilized by the processor to produce the correct flow rate.

Abstract: A flow element for detecting flow is described. The flow element includes 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, such as being a thousand times greater than the main flow resistance. The flow body further defines a bypass flow inlet and a bypass flow outlet. The bypass flow inlet and the bypass flow outlet fluidly connect the bypass flow path to the main flow path.

Abstract: The present invention provides a MEMS thermal flow sensor or meter for measuring the flow rate of a fluid without need for calibration of the flow sensor for that particular fluid. A response curve is determined by plotting the sensor output voltage against the volume flow rate divided by fluid thermal diffusivity for a calibration fluid of known thermal diffusivity, and storing response curve data in memory. A conversion factor is employed to provide a measure of correct flow rate of an unknown fluid. This conversion factor is derived from the ratio of the thermal time constant of the calibration fluid to the thermal time constant of the measured fluid, the time constants being measured at zero flow. These time constants are stored in memory. This conversion factor in conjunction with the response curve data is utilized by the processor to produce the correct flow rate.