초록 ▼

The invention relates to a method and apparatus for linearizing a flow velocity sensor based on pressure difference measurement. According to the method, a difference of two pressure signals is measured from the flow under measurement and is proportional to the square of the flow velocity. The press

The invention relates to a method and apparatus for linearizing a flow velocity sensor based on pressure difference measurement. According to the method, a difference of two pressure signals is measured from the flow under measurement and is proportional to the square of the flow velocity. The pressure difference is measured using a micromechanically manufactured symmetrical capacitive differential pressure sensor based on the force balance principle. The pressure-induced deviation from force balance is compensated for by inducing on the pressure-sensing diaphragm of the differential pressure sensor a force-balance-restoring electrostatic pressure. The amplitude of the force-balance-restoring electrical feedback control signal also acts as the system output signal and is directly proportional to the square root of the difference of the two pressure signals, and thus, a linear function of the flow velocity. According to the invention, the feedback control voltage is a function of the direction of the pressure difference and is applied only to one of the stationary electrodes so that the electrostatic force of attraction thus induced acts counter to the force generated by the pressure difference under measurement, whereby the polarity of the system output voltage signal is dependent on the direction of the flow.

대표청구항 ▼

[ I claim:] [5.] A linearized flow velocity measurement apparatus, comprising:a flow velocity sensor disposed in the flow under measurement, said flow velocity sensor having two pressure outlet ports such that the pressure difference between the two pressure outlet ports is proportional to the squar

[ I claim:] [5.] A linearized flow velocity measurement apparatus, comprising:a flow velocity sensor disposed in the flow under measurement, said flow velocity sensor having two pressure outlet ports such that the pressure difference between the two pressure outlet ports is proportional to the square of the flow velocity;a symmetrical capacitive differential pressure sensor coupled to said flow velocity sensor to receive the outputs of the two pressure outlet ports, said differential pressure sensor including a sensing diaphragm disposed between two stationary electrodes for converting the pressure difference between the pressure outlet ports into an electrical measurement signal by sensing a deviation of the sensing diaphragm from a force balance state, said differential pressure sensor receiving a feedback control signal proportional to the square root of the pressure difference between said two pressure outlet ports; andfeedback control voltage generating circuitry including limiter circuits for selectively applying the feedback control voltage to the stationary electrodes of said differential pressure sensor so that the feedback control signal is applied to only one electrode at a time.