Impulse analysis for flow sensor-based fluid control system
A fluid flow control system using flow rate changes to extract additional information from an in-line flow sensor. The system provides the ability to determine a position of a movable flow sensor element of a flow sensor by illuminating a photosensitive pixel array with a light source to create a first set of pixel intensity values introducing an abrupt change to the fluid driving pressure, illuminating the photosensitive pixel array with a light source to create a second set of pixel intensity values, and calculating the difference between the first and second sets of pixel intensity values as a function of pixel position.
1. A flow sensor for a flow control system for controlling flow of a liquid, the flow control system having a flow passageway, the flow sensor comprising:
a sensor element movably positioned in the flow passageway, wherein a position of the sensor element in the flow passageway is responsive to a flow rate of the liquid in the flow passageway and to a viscosity of the liquid, and further wherein the flow rate is responsive to a fluid driving pressure and a systemic flow resistance in the flow control system;
a sensor for generating a signal representative of a position of the sensor element in the flow passageway;
a processor coupled to the sensor for receiving the signal from the sensor before and after an abrupt change in the fluid driving pressure to calculate any one or more of:
the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure;
the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure;
a change in position of the sensor element in the flow passageway;
a rate of change in position of the sensor element in the flow passageway;
the flow rate before the abrupt change in the fluid driving pressure;
the flow rate after the abrupt change in the fluid driving pressure;
a change in the flow rate;
the viscosity of the liquid; and
the systemic flow resistance;
said processor calculating one or both of an axial distance between the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure and a rate of change of position of the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure; and
said processor correlating one or both of said axial distance between the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure and said rate of change of position of the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure with a viscosity.
2. A method for determining flow information in a flow control system, the flow control system for controlling flow of a liquid, the flow control system having a flow passageway, a sensor element movably positioned in the flow passageway, and a sensor for generating a signal representative of a position of the sensor element in the flow passageway, wherein a position of the sensor element in the flow passageway is responsive to a flow rate of the liquid in the flow passageway and to a viscosity of the liquid, and further wherein the flow rate is responsive to a fluid driving pressure and a systemic flow resistance in the flow control system, the method comprising:
introducing an abrupt change in fluid driving pressure;
prior to introducing the abrupt change in fluid driving pressure, sampling the signal from the sensor to obtain a first measurement of sensor element position;
after introducing the abrupt change in fluid driving pressure, sampling the signal from the sensor to obtain a second measurement of sensor element position;
determining a difference between the first measurement and the second measurement;
calculating one or both of an axial distance between the first measurement of sensor element position and the second measurement of sensor element position and a rate of change of position of the sensor element between the first measurement of sensor element position and the second measurement of sensor element position; and
correlating one or both of said axial distance between the first measurement of sensor element position and the second measurement of sensor element position and said rate of change of position of the sensor element between the first measurement of sensor element position and the second measurement of sensor element position with a viscosity.
3. The method of claim 2 , further comprising using said difference between the first measurement and the second measurement to calculate any one or more of:
the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure;
the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure;
a change in position of the sensor element in the flow passageway;
a rate of change in position of the sensor element in the flow passageway;
the flow rate before the abrupt change in the fluid driving pressure;
the flow rate after the abrupt change in the fluid driving pressure a change in the flow rate;
the viscosity of the liquid; and
the systemic flow resistance.
4. The method of claim 2 , wherein the sensor element is an optically transmissive ball.
5. The method of claim 2 , further comprising:
using one or both of the first measurement of sensor element position and the second measurement of sensor element position to determine a rate of flow of the fluid in the flow control system.
6. The method of claim 2 , wherein said correlating is performed by comparing one or both of said axial distance between the first measurement of sensor element position and the second measurement of sensor element position and said rate of change of position of the sensor element between the first measurement of sensor element position and the second measurement of sensor element position with known sensor element behavior for one or more fluids of known viscosity, said known sensor element behavior associated with said known viscosity.
7. The method of claim 6 , further comprising:
inputting fluid identifying information;
determining an expected viscosity based on said fluid identifying information;
comparing said viscosity determined by said correlating with said expected viscosity; and
if said viscosity is not within some predetermined threshold of said expected viscosity, outputting an indication of an error condition.
8. The method of claim 2 , wherein the abrupt change in the fluid driving pressure is an abrupt increase in the fluid driving pressure.
9. The flow sensor of claim 1 , wherein said sensor element is an optically transmissive ball.
10. The flow sensor of claim 1 , further comprising:
said processor using one or both of the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure to determine a rate of flow of the fluid in the flow control system.
11. The flow sensor of claim 1 , wherein said correlating is performed by comparing one or both of said axial distance between the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure and said rate of change of position of the sensor element between the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure and the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure with known sensor element behavior for one or more fluids of known viscosity, said known sensor element behavior associated with said known viscosity.
12. The flow sensor of claim 11 , said processor:
inputting fluid identifying information;
determining an expected viscosity based on said fluid identifying information;
comparing said viscosity determined by said correlating with said expected viscosity; and
if said viscosity is not within some predetermined threshold of said expected viscosity, outputting an indication of an error condition.
13. The flow sensor of claim 1 , wherein the abrupt change in the fluid driving pressure is an abrupt increase in the fluid driving pressure.