Pressure differential flow meter including a constriction device that can create multiple areas of constriction

A pressure differential flow meter comprising:

• a constriction device,
• (A) wherein the constriction device is capable of creating at least a first area of constriction and a second area of constriction;
• (i) wherein the first area of constriction has a cross-sectional area that is less than the cross-sectional area of the second area of constriction;
• (ii) wherein the pressure differential is within a range when the fluid velocity flowing through the second area of constriction is within a second fluid velocity range;
• and
• (iii) wherein as the fluid velocity through the second area of constriction decreases to about the minimum velocity of the second fluid velocity range, the constriction device creates the first area of constriction;
• and
• (B) wherein at least a portion of the constriction device moves to create the first area of constriction and the second area of constriction.

A method of determining the flow rate of a fluid using a pressure differential flow meter comprising:

• flowing the fluid through the flow meter, wherein the flow meter comprises:
• (A) a constriction device,
• (i) wherein the constriction device is capable of creating at least a first area of constriction and a second area of constriction;
• (a) wherein the first area of constriction has a cross-sectional area that is less than the cross-sectional area of the second area of constriction;
• (b) wherein the pressure differential is within a range when the fluid velocity flowing through the first area of constriction is within a first fluid velocity range and when the fluid velocity flowing through the second area of constriction is within a second fluid velocity range;
• (c) wherein as the fluid velocity through the first area of constriction increases to about the maximum velocity of the first fluid velocity range, the constriction device creates the second area of constriction;
• and
• (d) wherein as the fluid velocity through the second area of constriction decreases to about the minimum velocity of the second fluid velocity range, the constriction device creates the first area of constriction;
• and
• (ii) wherein at least a portion of the constriction device moves to create the first area of constriction and the second area of constriction;
• and
• (B) a flow rate computing device.