Fluid flow rate measuring apparatus

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

• a first heating element which is disposed at an upstream side in a direction of flow of the fluid;
• a first temperature detecting element which is formed in the vicinity of the first heating element;
• a second heating element which is disposed at a downstream side in the direction of flow of the fluid;
• a second temperature detecting element which is formed in the vicinity of the second heating element;
• a first fixed resistance which is connected to the first temperature detecting element in series;
• a second fixed resistance which is connected to the second temperature detecting element in series and has a resistance value equal to that of the first fixed resistance;
• a bridge circuit which is formed by the first and second temperature detecting elements and the first and second fixed resistances;
• a comparator;
• a first switching circuit which is provided between an output terminal of the comparator and the first heating element;
• and
• a second switching circuit which is provided between the output terminal of the comparator and the second heating element;
• wherein at a specific temperature, a resistance value of the first temperature detecting element is smaller than that of the second temperature detecting element.

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

• a first heating element which is disposed at an upstream side in a direction of flow of the fluid;
• a first temperature detecting element which is formed in the vicinity of the first heating element;
• a second heating element which is disposed at a downstream side in the direction of flow of the fluid;
• a second temperature detecting element which is formed in the vicinity of the second heating element and has a resistance value equal to that of the first temperature detecting element;
• a first fixed resistance portion which is connected to the first temperature detecting element in series;
• a second fixed resistance portion which is connected to the second temperature detecting element in series;
• a bridge circuit which is formed by the first and second temperature detecting elements and the first and second fixed resistance portions;
• a comparator;
• a first switching circuit which is provided between an output terminal of the comparator and the first heating element;
• and
• a second switching circuit which is provided between the output terminal of the comparator and the second heating element;
• wherein a resistance value of the first fixed resistance portion is larger than that of the second fixed resistance portion.