Patent ID: 8225652

Claim:
A thermal flow meter comprising: a sensor chip provided with a pair of temperature-sensitive elements; a heater increasing an ambient temperature in a vicinity of the pair of temperature-sensing elements on the sensor chip by a particular temperature above a temperature of a fluid flowing along the sensor chip; a first flow rate calculator calculating a flow rate of the fluid from a temperature difference detected by the pair of temperature-sensing elements; a second flow rate calculator calculating a flow rate of the fluid from a driving energy of the heater that heats the ambient temperature by the particular temperature above the temperature of the fluid; and an output controller outputting the flow rate calculated by the second flow rate calculator, instead of the flow rate calculated by the first flow rate calculator, when the flow rate calculated by the first flow rate calculator exceeds a flow rate threshold value that is set in advance, wherein the output controller is provided with a switching circuit that selectively outputs the flow rates in accordance with control of the output controller.