Fluid flow rate measuring apparatus

A fluid flow rate measuring apparatus for measuring a flow rate of fluid, comprising:

• a first heating element disposed in a flow of a fluid;
• a first temperature detecting element proximate the first heating element;
• a second heating element disposed in the flow of the fluid and located a downstream, in direction of the flow of the fluid, relative to the first heating element;
• a second temperature detecting element proximate the second heating element;
• a first fixed resistance connected in series with the first temperature detecting element;
• a second fixed resistance connected in series with the second temperature detecting element and having a resistance equal to that of the first fixed resistance, the first and second temperature detecting elements and the first and second fixed resistances being connected in a bridge circuit;
• a comparator;
• a first switching circuit coupled between an output terminal of the comparator and the first heating element;
• and
• a second switching circuit coupled between the output terminal of the comparator and the second heating element, wherein at a fixed temperature, resistance of the first temperature detecting element is smaller than resistance of the second temperature detecting element.

A fluid flow rate measuring apparatus for measuring a flow rate of fluid, comprising:

• a first heating element disposed in a flow of a fluid;
• a first temperature detecting element proximate the first heating element;
• a second heating element disposed in the flow of the fluid and located downstream, in direction of the flow of the fluid, relative to the first heating element;
• a second temperature detecting element proximate the second heating element and having a resistance equal to that of the first temperature detecting element;
• a first fixed resistance is connected in series with the first temperature detecting element;
• a second fixed resistance is connected in series with the second temperature detecting element;
• the first and second temperature detecting elements and the first and second fixed resistances being connected in a bridge circuit;
• a comparator;
• a first switching circuit coupled between an output terminal of the comparator and the first heating element;
• and
• a second switching circuit coupled between the output terminal of the comparator and the second heating element, wherein resistance of the first fixed resistance is larger than resistance of the second fixed resistance.