Flow sensor having an intermediate heater between two temperature-sensing heating portions

A flow sensor for sensing a flow rate of a fluid, comprising:

• a first heating portion, provided at a first position in a flow of the fluid, for heating the fluid and for outputting a voltage in response to a temperature of the first position;
• a second heating portion, provided at a second, downstream position in the flow of the fluid, for heating the fluid and for outputting a voltage in response to a temperature of the second position, the first position and the second position being spaced from each other in a direction parallel to the flow of the fluid;
• and
• an intermediate heater, provided between the first heating portion and the second heating portion, for heating the fluid at an intermediate position between the first position and the second position.