| 摘要 |
A thermal type flowmeter for measuring a flow rate of a fluid which is equipped with a thermo-sensitive resistor provided within a fluid passage and arranged to heat when being energized. The flowmeter includes an electric power adjusting element provided in series to the thermo-sensitive resistor so as to adjust an electric power to be supplied to the thermo-sensitive resistor in accordance with a current inputted to its input terminal and a constant current source circuit connected to said input terminal of the electric power adjusting element to supply a predetermined constant current to the input terminal of the electric power adjusting element. A control circuit outputs an adjustment signal to adjust an energization electric power to the thermo-sensitive resistor so that the thermo-sensitive resistor has a predetermined temperature, and a current adjusting circuit connected to the input terminal of the electric power adjusting element divides the constant current from the constant current source circuit in accordance with the adjustment signal from the control circuit so as to adjust the input current to the electric power adjusting element. This arrangement can reduce the minimum operating voltage for the flowmeter because the input current of the electric power adjusting element can be obtained from the constant current source circuit. <IMAGE> <IMAGE> |
