Configuration and methods for manufacturing time-of-flight MEMS mass flow sensor
This invention discloses a mass flow sensor manufactured by applying the micro-electromechanical system (MEMS) process to provide a new and improved mass flow sensor that is a self-calibrated in a time-of-flight manner with configuration to measure the flow velocity directly. The self-calibration of a mass flow rate sensor is achieved by providing an electric pulse to a heater in the flow and determining a temperature variations of the fluid. The method further includes a step of measuring a temperature variation by a temperature sensor disposed at a short distance from the heater. The method further includes a step of correlating the temperature variation measured at the temperature sensor with the temperature variation of the heater to determine a time delay and a corresponding flow velocity.
1. A flow rate sensor disposed in a flow comprising:
a temperature sensor disposed adjacent to a micro-heater; and
a heater controller to provide a heating energy as a modulated sinusoid-waveform electric energy to said micro-heaters for measuring a heat convection and time delay of energy transfer from said micro-heater to said temperature sensor through said heat convection in said flow.
2. The flow rate sensor of claim 1 further comprising:
a processor for receiving an input of said flow velocity to directly determine a flow velocity of said flow.
3. The flow rate sensor of claim 1 wherein:
said heater controller provides said heating energy as a plurality of electric pulses each comprises said modulated sinusoid waveform electric energy an electric pulse to said micro heater.
4. The flow rate sensor of claim 1 wherein:
said heater controller provides said heating energy as said modulated sinusoid-waveform electric energy with a specific frequency to said micro heater.
5. The flow rate sensor of claim 1 further comprising:
a second temperature sensor disposed adjacent to a second micro-heater and said heater controller further provides heating energy to said second micro heater.
6. The flow rate sensor of claim 5 wherein:
said temperature sensor and heater and said second temperature sensor and heater are configured for measuring a upstream to downstream temperature difference substantially independent of a heat conduction in said flow.
7. The flow rate sensor of claim 1 further comprising:
a first independent temperature sensor to measure a temperature of said flow.
8. The flow rate sensor of claim 1 further comprising:
a second independent temperature sensor for integrating into
a control loop of said heater controller.
9. The flow rate sensor of claim 1 wherein:
said flow is conducting in a flow channel having a diameter less than 50 mm.
10. The flow rate sensor of claim 5 wherein:
said flow is conducting in a flow channel having a diameter ≧50 mm.
11. The flow rate sensor of claim 1 wherein:
said temperature sensor and said micro heater are supported on a semiconductor substrate.
12. The flow rate sensor of claim 1 wherein:
said micro heater comprising metal strip composed of gold or platinum.
13. The flow rate sensor of claim 1 wherein:
a distance between said temperature sensor and said micro heater is approximately 2 to 12 micrometers.
14. The flow rate sensor of claim 5 wherein:
a distance between said micro heater and said second micro heater is approximately 50 to 5000 micrometers.
15. The flow rate sensor of claim 1 wherein:
said temperature sensor comprising a metal strip composed of gold or platinum.
16. A method for measuring a flow rate of a flow comprising:
disposing a temperature sensor at a short distance from a micro heater in said flow and providing a heating energy to said heater for measuring a time lag by correlating temperature variations of said temperature sensor and said heater for determining a flow velocity of said flow; and
said step of providing a heating energy to said heater further comprising a step of providing a modulated sinusoid heating energy to said heater and determining a temperature response from a heater temperature variation by applying a lock-in phase amplification technique followed by measuring a ratio of an out-of-the-phase component to an in-phase component for determining a phase lag and determining a flow velocity from said phase lag.
17. The method of claim 16 further comprising a step of:
continuously determining said flow velocity for continuously monitoring a specific heat of said flow.
18. A method for measuring a flow rate of a flow comprising:
disposing a temperature sensor at a short distance from a micro heater in said flow and providing a heating energy to said heater for measuring a time lag by correlating temperature variations of said temperature sensor and said heater for determining a flow velocity of said flow;
continuously determining said flow velocity for continuously monitoring a specific heat of said flow; and
continuously measuring a pressure and applying said specific heat of said flow to continuously monitoring a density and composition of said flow.