Patent ID: 8794082
Filing Date: 2014-08-05
Classification: G01F

Abstract:
1. A MEMS time-of-flight thermal mass flow meter comprising: a micromachined time-of-flight (TOF) thermal mass flow sensor; an insertion type of flow channel package; and a single frequency drive functionality circuit; wherein, said micromachined time-of-flight thermal mass flow sensor has a suspending membrane to provide a heat insulated region for device operation; said micromachined time-of-flight thermal mass flow sensor has a first micro-thermistor in a serpentine pattern disposed on a top surface of said suspending membrane and functioning as a micro-heating element; said micromachined time-of-flight thermal mass flow sensor has a second micro-thermistor in a serpentine pattern disposed on said top surface of said suspending membrane, which is in parallel with and a definite distance from said micro-heating element and functioning as a micro-sensing element; said micromachined time-of-flight thermal mass flow sensor has four open slots on said suspending membrane, which are located in parallel on each side of said micro-heating element and said micro-sensing element to isolate lateral heat conduction for the purpose of enhancing measurement accuracy; said single frequency drive functionality circuit contains four basic building circuitries including a heater-driving generator circuit; a sensing signal conditioning circuit; a pre-phase-lag detector circuit; and a micro-controller circuit; said single frequency drive functionality circuit provides a sinusoidal heat wave with a certain frequency to elevate a temperature of micro-heating element; and said sinusoidal heat wave is carried away by a flowing media and causes a phase shift of said sinusoidal heat wave when said sinusoidal heat wave arrives on said micro-sensing element.