HEAT FLOWMETER

摘要

The object of the present invention is to provide a thermal flow meter with a simple structure capable of measuring with high precision the flow rate of a fluid in a regular flow rate range and capable of measuring also excessively large flow rates outside of the regular flow rate range. The thermal flow meter comprises heating means (Rh) for increasing the temperature in the vicinity of a temperature-sensitive element on a sensor chip (1) that is provided with a pair of temperature-sensitive elements (Ru and Rd) to a particular temperature above the temperature of a fluid that flows along the sensor chip, first flow rate calculating means (6) for calculating the flow rate of the fluid from a temperature difference that is detected by the pair of temperature-sensitive elements, second flow rate calculating means (7) for calculating the flow rate of the fluid from the driving energy of the heating means, and output controlling means (5) for outputting the flow rate calculated by the second flow rate calculating means instead of the flow rate calculated by the first flow rate calculating means when the flow rate calculated by the first flow rate calculating means exceeds a flow rate threshold value.