US Patent 7360445 Flow sensor

A flow sensor need not have any special terminal for voltage value supply, and can obtain a ratiometric output function at low cost and small size. A calculation circuit calculates, as a reference voltage Vr, a voltage value Vref of an A/D conversion reference power supply in a fuel injection control unit from a terminal voltage of a temperature sensor, and supplies the reference voltage Vr thus calculated by the calculation circuit to a ratiometric output circuit. As a result, a ratiometric output function can be achieved while making it unnecessary a special terminal used only for the purpose of supplying the voltage value Vref.