Bridge - Output - to - Frequency Converter for Smart Thermal Air - Flow Sensors

AbsfructA fully integrated bridge-output-to-frequency converter has been realized as signal-conditioning circuitry for a onechip smart thermal maskflow sensor. The frequency converter reads out four separate mistor bridges of the air-flow sensor in order to realize high sensitivity and direftional flow measurement over the fd angle range of 360". The converter selects the sensor bridges individually by means of a microprocessorcontrolled analog multiplexer. The flow velocity and direction are also calculated by the micropmcesaor. The relative measurement cancels all W-order errors. The center frequency is 10 kHz and the sensitivity 1 IW@VN). A bridgeoffset of 10 mVN is allowed, and the linearity error is 0.1%.