Bridge-to-Frequency Converter for Smart Thermal Flow-Sensor

A fully integrated bridge-to-frequency converter is presented as signal-conditioning circuitry for a one-chip smart thermal flow sensor. The converter reads out four separate bridges by means of a multiplexer to realize high sensitivity and directional flow measurement over the full range of 360°. Multiplexer control and output signal are microprocessor compatible. The relative measurement cancels all linear errors. The centre frequency is 10kHz. The sensitivity is 1Hz/(μV/V). A bridge-offset of 10mV/V is allowed. The linearity error is 0.1%. The supply voltage is 5V.