Device for measuring flow rate of air

摘要

A device for measuring the flow rate of air includes an electric heater arranged in a path of the air flow and a temperature compensation resistor arranged at a distance from the heater in the path of the air flow, the resistance of the resistor being changed according to the temperature of the air. A selective current supply unit supplied the heater with a current having a current value selected from one of two, large and small, current values. A temperature selection unit selects a plurality of temperature values of the electric heater according to the change of the resistance of the temperature compensation resistor. A current value switching unit switches the current level of the selective current supply under the condition that one of the selected temperature values is attained or maintained. The flow rate of the air is measured by a time measurement unit for measuring the time required for the change of temperature between the plurality of temperature values due to the change of the temperature of the electric heater caused by the switching by the current value switching unit.