CA1197131A - Flow controller - Google Patents
Flow controllerInfo
- Publication number
- CA1197131A CA1197131A CA000431811A CA431811A CA1197131A CA 1197131 A CA1197131 A CA 1197131A CA 000431811 A CA000431811 A CA 000431811A CA 431811 A CA431811 A CA 431811A CA 1197131 A CA1197131 A CA 1197131A
- Authority
- CA
- Canada
- Prior art keywords
- pressure drop
- flow
- damper
- gate element
- control means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/72—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure
- F24F11/74—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Flow Control (AREA)
Abstract
A flow control system is disclosed having a damper located between an inlet and an outlet wherein the position of the damper controls the flow of fluid between the inlet and the outlet, the damper having a pressure drop thereacross, a pressure drop sensor for sensing the pressure drop across the damper, a processor control responsive to the pressure drop sensor for providing an output having a value dependent upon the damper position which will allow a desired amount of flow between the inlet and the outlet based upon the pressure drop across the damper, and a motor responsive to the output for operating the damper to a position to provide the desired flow.
Description
7~3~l ~v FLOW CONTROLLER
BACKGROUND OF THE I~VE~TION
The present invention relates to a flowcontroller for controlling the flow of fluid between an inlet and an outlet dependent upon the pressure drop across the gate which is controlling the flow. Such a flow ~ontrol arrangement can be used for controlling the amount of air moving through an air conditioning duct, the amount of water or other type fluid moving through a pipe under control of a valve, the amount of humidified air moving through an air conditioning duct under control of a damper, or the like. For purposes herein, flow is defined as the volume of fluid moving through a pipe or duct or the like - per unit time.
In the control of variable air volume boxes, for example, several control approaches havebeenheretofore adopted. Hot wire anemometers, heated thermistors, Pitot tubes and deflecting jet streams have been used by contro1 systems for sensing a characteristic of the fluid moving through the duct which characteristic can be related to flow. All of these systems, while they have heretofore performed satisfactorily, have drawbacks. Typically, the signal processing systems which are required by these types of sensors are complex. For example, in t~e Pitot tube approach, one of the two Pitot tubes senses both velocity pressure and static pressure and the other tube senses static pressure. The static pressure sensed by the second tube must be subtracted from the velocity pressure and static pressure seilsed bythe first tube in order to eliminate static pressure from the sensed signal. Then t~e square root of the velocity pressure must be taken in order to derive a signal related to t~e velocity of the fluid moving through the pipe or duct. Thus, the signal yrocessing which must be performed even before the control system can use it -to control the final end element makes the system overly complicated. Furthermore, the system then controls velocity, that is the rate at which the fluid moves through the duct or pipe, rather than flow.
Moreover, pressure drop is easier to sense and to read than velocity pressure because the typical pressure drop within a box ll varies from a ~ inch water column t~
4 inches of water column whereas velocity pressure can vary from .015 inches wat~r column to 1 inch water column.
Pressure drop also gives a better reading of average flow.
If velocity pressure is used, then several readings across box 11 should be used for developing a signal relating to flow through the box. However, by sensing pressure drop, multiple readings can be eliminated.
Multiple readings may also be necessary with the other types of sensors listed above. For example, fluid moving through a duct may not have a constant velocity profile across the duct. Thus, if velocity is to be sensed~
the sensing must be done at several points so that an average velocity can be determined. Such sensing requires the use of multiple sensors thus increasing ~he c~mple~ity of the system.
Similarly, other types of systems which have been used in the past to sense velocity rather than flow have required the use of a complex signal processing arrangement. It is more desirabie, instead, to maintain a desired flow independent of static pressure changes.
The system which is used to control the flow must be stable and not subject to droop. Fixed speed, floating control systems can have stability problems. Such systems do not provide an output signal which relate to how much the controlling element such as a damper must 3~
move in order to provide the correct control but they rather provide an output having a predetermined speed regaLdless of the size of the error signal.
Proportional control systems, on ~he other hand, will provide an output signal based upon the magnitude of the error signal and thus in effect tells the controlling element how much to move in response to the error signal.
Proportional control systems are stable ~ut suffer rom droop because there mus~ be an error signal, i.e. a difference between the actual condition being s~nsed and the desired condition, in order to hold the load at a position to maintain the conditions at the desired level.
Proportional control systems are also generally thought to be linear and, therefore, the am~unt of correction is linearly related to offset. The problem of using this type of approach in flow control is ~h~t, in flow control, the amount of correction needed is not constant and varies wit'n the pressure drop and the desired flow.
A third control approach which has been adopted in prior art systems is to provide a variable speed floating control system in which the speed of the actuator movement is dependent upon the amount of deviation between the sensed condition and the desired condition. miS t~pe of system provides integral control WlliCh results in a less ~5 complex system and elLminates droop.
The present invention eliminates many of these disadvantages and adopts many ofthe advantages byproviding essentially a proportional control system having variable gain. Thus, the system is stabl~, linear and does not suffer from droop.
SUMMARY OF THE INVENTION
Thus, the present invention provides a flow control system having a gate element located between an inlet and ~n outlet wherein the position of the gate element ~7~3~
controls the flow of fluid between the inlet and the outlet, the gate element having a pressure drop thereacross, a pressure drop sensor for sensing the pressure drop across the gate element, a processor control responsive to the pressure drop sensor for providing an output signal having a value dependent upon the gate element position which will allow a desired amount of flow between the inlet and the outlet based ùpon the pressure drop across the gate element, and a motor responsive to the output signal for operating the gate element to a position to provide the desired flow.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages will become more apparent from a detailed consideration of the invention when taken in conjunction with the drawings in - w:~ich the single figure of the drawing shows a schematic diagram of the present invention.
DETAILED DESCRIPTION
The system according to the present invention is shown in the drawing controlling a variable air volume box il in an air conditioning system which receives inlet air from inlet duct 12 and discharges outlet air from - outlet duct 13. It should be recognized, however, that the system according to the present invention can be used in humidification systems and valvin~ systems such that either the gate element 14 is a d~mper such as that shown in the drawing or a valve plug or similar valve mechanism in the case of a valve system.
As shown in the drawing, s~atic pressure sensing t~be 15 is located upstream of damper 14 and static pressure sensing tube 16 is located downstream of damper 14. S~atic pressure sensing tubes lS and 16 are connected to transducer 17 which transduces the differential pressure between static pressure sensors 15 and 16 into an electrical signal and 3~
converts the electrical signal into a digi~al signal for supply to microprocessor controller 18.
Based upon the pressure drop signal which it receives from transducer 17, microprocessor controller 18 will determine the position of damper 14 which will provide for the desired flow through box 11. Thus, microprocessor controller 18 issues a control signal to stepper motor 19 for driving damper 14 to the position for providing the desired flow through box 11.
An equation can be written to describe the flow through box 11 dependent upon the particular box chosen.
For example, if box 11 is chosen to be a Metalaire box, then the following equation is a good approximation of the flow of air moving through the box as a function of t'ne pressure drop across damper 14:
FLOW(CFM) - ~sin (3+45) - sin 45D~Kl ~ (1) where 9 is the angle of the damper between its position as snown in thè drawing and its normal closed position shown. by dached l.ine 21, ~1 is a constant term which depends upon the design parameters of box 11, ~P is the pressure drop across damper 14 as sensed by the circuit 15-17, and FLOW is the flow of the air or fluid moving through box 11 from inlet 12 to outlet 13 as a function of cubic feet per minute. Equation 1 can be rewritten as:
. LOW
sin (~+45~) = X~ + .707. (2) Simplifying Equation 2, the anglP ~ at which damper 14 must be moved in order to achieve the desired flow can be given by the expression:
FLOW
30 ~ = sin 1 (K~ .707) _ 45~. (3) ! ( "
3~
This expression then determines the damper angle for ~he desired flow.
In a thermostatically controlled system, the desired flow canbe provided bya thermostat sensing circuit.
~nus, in the drawing, thermostat 22, which may be electric or electronic but is s~own as a pnèumatic thermostat, provides a pneumatic output signal to transducer 23 which converts the pneumàtic signal into a digital signal fox supply to microprocessor controller 18. Thus, the desired flow can be given by the expres~ion:
FLOW = K2~T (4) where K2 is a constant term dependent upon box parameters.
Substitutin~ Equation 4 into Equation 3, the damper angle as a function of both temperature and pressure can be given by the expression:
~T
~ ~ = sin~l ( 2 ~ .707) _ 45~. (5) "~, Kl~
Microprocessor controller 18 can then be set up for determining the damper angle to provide the proper flow as a function of thedeviation ofthe actual temperature from the desired temperature, QT, and the pressure drop ~P across damper 14. In effect then, the thermostat determines the desired flow. Microprocessor 18 issues a signal, ~, to stepper motor 19 to maintain this desired flow even though static pressure fluctuates. The signal 9then is the damper position which will provide the desired flow.
An alternative to using ~he Equation 5 is to provide a curve fit for box 11 which involves a looXup ~able for each ~T which will provide damper angle ~ as a function of the pressure drop across damper 14.
- ( ( ~7~3~
Thus, microprocessor con~roller 18 provides an output signal to stepper motor 19. This output signal has a value representing the damper position which will result in the desired flow through box 11 as a function of the pressure drop across damper 14.
BACKGROUND OF THE I~VE~TION
The present invention relates to a flowcontroller for controlling the flow of fluid between an inlet and an outlet dependent upon the pressure drop across the gate which is controlling the flow. Such a flow ~ontrol arrangement can be used for controlling the amount of air moving through an air conditioning duct, the amount of water or other type fluid moving through a pipe under control of a valve, the amount of humidified air moving through an air conditioning duct under control of a damper, or the like. For purposes herein, flow is defined as the volume of fluid moving through a pipe or duct or the like - per unit time.
In the control of variable air volume boxes, for example, several control approaches havebeenheretofore adopted. Hot wire anemometers, heated thermistors, Pitot tubes and deflecting jet streams have been used by contro1 systems for sensing a characteristic of the fluid moving through the duct which characteristic can be related to flow. All of these systems, while they have heretofore performed satisfactorily, have drawbacks. Typically, the signal processing systems which are required by these types of sensors are complex. For example, in t~e Pitot tube approach, one of the two Pitot tubes senses both velocity pressure and static pressure and the other tube senses static pressure. The static pressure sensed by the second tube must be subtracted from the velocity pressure and static pressure seilsed bythe first tube in order to eliminate static pressure from the sensed signal. Then t~e square root of the velocity pressure must be taken in order to derive a signal related to t~e velocity of the fluid moving through the pipe or duct. Thus, the signal yrocessing which must be performed even before the control system can use it -to control the final end element makes the system overly complicated. Furthermore, the system then controls velocity, that is the rate at which the fluid moves through the duct or pipe, rather than flow.
Moreover, pressure drop is easier to sense and to read than velocity pressure because the typical pressure drop within a box ll varies from a ~ inch water column t~
4 inches of water column whereas velocity pressure can vary from .015 inches wat~r column to 1 inch water column.
Pressure drop also gives a better reading of average flow.
If velocity pressure is used, then several readings across box 11 should be used for developing a signal relating to flow through the box. However, by sensing pressure drop, multiple readings can be eliminated.
Multiple readings may also be necessary with the other types of sensors listed above. For example, fluid moving through a duct may not have a constant velocity profile across the duct. Thus, if velocity is to be sensed~
the sensing must be done at several points so that an average velocity can be determined. Such sensing requires the use of multiple sensors thus increasing ~he c~mple~ity of the system.
Similarly, other types of systems which have been used in the past to sense velocity rather than flow have required the use of a complex signal processing arrangement. It is more desirabie, instead, to maintain a desired flow independent of static pressure changes.
The system which is used to control the flow must be stable and not subject to droop. Fixed speed, floating control systems can have stability problems. Such systems do not provide an output signal which relate to how much the controlling element such as a damper must 3~
move in order to provide the correct control but they rather provide an output having a predetermined speed regaLdless of the size of the error signal.
Proportional control systems, on ~he other hand, will provide an output signal based upon the magnitude of the error signal and thus in effect tells the controlling element how much to move in response to the error signal.
Proportional control systems are stable ~ut suffer rom droop because there mus~ be an error signal, i.e. a difference between the actual condition being s~nsed and the desired condition, in order to hold the load at a position to maintain the conditions at the desired level.
Proportional control systems are also generally thought to be linear and, therefore, the am~unt of correction is linearly related to offset. The problem of using this type of approach in flow control is ~h~t, in flow control, the amount of correction needed is not constant and varies wit'n the pressure drop and the desired flow.
A third control approach which has been adopted in prior art systems is to provide a variable speed floating control system in which the speed of the actuator movement is dependent upon the amount of deviation between the sensed condition and the desired condition. miS t~pe of system provides integral control WlliCh results in a less ~5 complex system and elLminates droop.
The present invention eliminates many of these disadvantages and adopts many ofthe advantages byproviding essentially a proportional control system having variable gain. Thus, the system is stabl~, linear and does not suffer from droop.
SUMMARY OF THE INVENTION
Thus, the present invention provides a flow control system having a gate element located between an inlet and ~n outlet wherein the position of the gate element ~7~3~
controls the flow of fluid between the inlet and the outlet, the gate element having a pressure drop thereacross, a pressure drop sensor for sensing the pressure drop across the gate element, a processor control responsive to the pressure drop sensor for providing an output signal having a value dependent upon the gate element position which will allow a desired amount of flow between the inlet and the outlet based ùpon the pressure drop across the gate element, and a motor responsive to the output signal for operating the gate element to a position to provide the desired flow.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages will become more apparent from a detailed consideration of the invention when taken in conjunction with the drawings in - w:~ich the single figure of the drawing shows a schematic diagram of the present invention.
DETAILED DESCRIPTION
The system according to the present invention is shown in the drawing controlling a variable air volume box il in an air conditioning system which receives inlet air from inlet duct 12 and discharges outlet air from - outlet duct 13. It should be recognized, however, that the system according to the present invention can be used in humidification systems and valvin~ systems such that either the gate element 14 is a d~mper such as that shown in the drawing or a valve plug or similar valve mechanism in the case of a valve system.
As shown in the drawing, s~atic pressure sensing t~be 15 is located upstream of damper 14 and static pressure sensing tube 16 is located downstream of damper 14. S~atic pressure sensing tubes lS and 16 are connected to transducer 17 which transduces the differential pressure between static pressure sensors 15 and 16 into an electrical signal and 3~
converts the electrical signal into a digi~al signal for supply to microprocessor controller 18.
Based upon the pressure drop signal which it receives from transducer 17, microprocessor controller 18 will determine the position of damper 14 which will provide for the desired flow through box 11. Thus, microprocessor controller 18 issues a control signal to stepper motor 19 for driving damper 14 to the position for providing the desired flow through box 11.
An equation can be written to describe the flow through box 11 dependent upon the particular box chosen.
For example, if box 11 is chosen to be a Metalaire box, then the following equation is a good approximation of the flow of air moving through the box as a function of t'ne pressure drop across damper 14:
FLOW(CFM) - ~sin (3+45) - sin 45D~Kl ~ (1) where 9 is the angle of the damper between its position as snown in thè drawing and its normal closed position shown. by dached l.ine 21, ~1 is a constant term which depends upon the design parameters of box 11, ~P is the pressure drop across damper 14 as sensed by the circuit 15-17, and FLOW is the flow of the air or fluid moving through box 11 from inlet 12 to outlet 13 as a function of cubic feet per minute. Equation 1 can be rewritten as:
. LOW
sin (~+45~) = X~ + .707. (2) Simplifying Equation 2, the anglP ~ at which damper 14 must be moved in order to achieve the desired flow can be given by the expression:
FLOW
30 ~ = sin 1 (K~ .707) _ 45~. (3) ! ( "
3~
This expression then determines the damper angle for ~he desired flow.
In a thermostatically controlled system, the desired flow canbe provided bya thermostat sensing circuit.
~nus, in the drawing, thermostat 22, which may be electric or electronic but is s~own as a pnèumatic thermostat, provides a pneumatic output signal to transducer 23 which converts the pneumàtic signal into a digital signal fox supply to microprocessor controller 18. Thus, the desired flow can be given by the expres~ion:
FLOW = K2~T (4) where K2 is a constant term dependent upon box parameters.
Substitutin~ Equation 4 into Equation 3, the damper angle as a function of both temperature and pressure can be given by the expression:
~T
~ ~ = sin~l ( 2 ~ .707) _ 45~. (5) "~, Kl~
Microprocessor controller 18 can then be set up for determining the damper angle to provide the proper flow as a function of thedeviation ofthe actual temperature from the desired temperature, QT, and the pressure drop ~P across damper 14. In effect then, the thermostat determines the desired flow. Microprocessor 18 issues a signal, ~, to stepper motor 19 to maintain this desired flow even though static pressure fluctuates. The signal 9then is the damper position which will provide the desired flow.
An alternative to using ~he Equation 5 is to provide a curve fit for box 11 which involves a looXup ~able for each ~T which will provide damper angle ~ as a function of the pressure drop across damper 14.
- ( ( ~7~3~
Thus, microprocessor con~roller 18 provides an output signal to stepper motor 19. This output signal has a value representing the damper position which will result in the desired flow through box 11 as a function of the pressure drop across damper 14.
Claims (24)
1. A fluid flow control system comprising:
a damper located between a fluid inlet and a fluid outlet wherein the position of the damper controls the flow of fluid between said inlet and outlet, said damper having a pressure drop thereacross;
pressure drop sensing means for sensing said pressure drop across said damper;
processor control means responsive to said pressure drop sensing means for providing an output having a flow value dependent upon the damper position which will allow a desired amount of flow between said inlet and outlet based upon said pressure drop across said damper; and, motor means responsive to said output for operating said damper to a position to provide said desired flow.
a damper located between a fluid inlet and a fluid outlet wherein the position of the damper controls the flow of fluid between said inlet and outlet, said damper having a pressure drop thereacross;
pressure drop sensing means for sensing said pressure drop across said damper;
processor control means responsive to said pressure drop sensing means for providing an output having a flow value dependent upon the damper position which will allow a desired amount of flow between said inlet and outlet based upon said pressure drop across said damper; and, motor means responsive to said output for operating said damper to a position to provide said desired flow.
2. The system of claim 1 wherein said pressure drop sensing means comprises a first static pressure sensor located upstream of said damper and a second static pressure sensor located downstream of said damper.
3. The system of claim 2 wherein said pressure drop sensing means comprises a transducer responsive to said first and second static pressure sensors for providing a digital signal representing said pressure drop,
4. The system of claim 3 wherein said processor control means comprises a thermostat for providing a signal for determining said desired amount of flow.
5. The system of claim 4 wherein said processor control means comprises a processor for receiving said digital signal, and a transducer connected between said processor and said thermostat for providing a signal representing said desired amount of flow.
6. The system of claim 5 wherein said motor means comprises a stepper motor responsive to said output from said processor control means for driving said damper to said position.
7. The system of claim 6 wherein said processor comprises a microprocessor for determining on the basis of an equation damper position to produce said desired amount of flow based upon the pressure drop across said damper and a temperature sensed by said thermostat.
8. The system of claim 6 wherein said processor control means comprises a microprocessor having lookup tables for providing said output, said lookup tables comprising a plurality of lookup tables, each lookup table related to a particular temperature sensed by said thermostat and each table having damper angle as a function of said pressure drop.
9. The system of claim 1 wherein said processor comprises a microprocessor for determining on the basis of an equation damper position to produce said desired amount of flow based upon the pressure drop across said damper and a temperature sensed by said thermostat.
10. The system of claim 1 wherein said processor control means comprises a microprocessor having lookup tables for providing said output, said lookup tables comprising a plurality of lookup tables, each lookup table related to a particular temperature sensed by said thermostat and each table having damper angle as a function of said pressure drop.
11. The system of claim 1 wherein said processor control means comprises a thermostat for providing a signal for determining said desired amount of flow.
12. A flow control system comprising:
a gate element located between an inlet and an outlet wherein the position of the gate element controls the flow of fluid between said inlet and outlet, said inlet and outlet having a pressure drop therebetween;
pressure drop sensing means for sensing said pressure drop, processor control means responsive to said pressure drop sensing means for providing an output having a flow value dependent upon the gate element position which will allow a desired amount of flow between said inlet and outlet based upon said pressure drop; and, motor means responsive to said output for operating said gate element to a position to provide said desired flow.
a gate element located between an inlet and an outlet wherein the position of the gate element controls the flow of fluid between said inlet and outlet, said inlet and outlet having a pressure drop therebetween;
pressure drop sensing means for sensing said pressure drop, processor control means responsive to said pressure drop sensing means for providing an output having a flow value dependent upon the gate element position which will allow a desired amount of flow between said inlet and outlet based upon said pressure drop; and, motor means responsive to said output for operating said gate element to a position to provide said desired flow.
13. The system of claim 12 wherein said pressure drop sensing means comprises a first static pressure sensor located to sense inlet pressure and a second static pressure sensor located to sense outlet pressure.
14. The system of claim 13 wherein said pressure drop sensing means comprises a transducer responsive to said first and second static pressure sensors for providing a digital signal representing said pressure drop.
15. The system of claim 14 wherein said processor control means comprises a thermostat for providing a signal for determining said desired amount of flow.
16. The system of claim 15 wherein said processor control means comprises a processor for receiving said digital signal, and a transducer connected between said processor and said thermostat for providing a signal representing said desired amount of flow.
17. The system of claim 16 wherein said motor means comprises a stepper motor responsive to said output from said processor control means for driving said gate element to said position.
18. The system of claim 17 wherein said processor comprises a microprocessor for determining on the basis of an equation gate element position to produce said desired amount of flow based upon the pressure drop across said gate element and a temperature sensed by said thermostat.
19. The system of claim 17 wherein said processor control means comprises a microprocessor having lookup tables for providing said output, said lookup tables comprising a plurality of lookup tables, each lookup table related to a particular temperature sensed by said thermostat and each table having gate element angle as a function of said pressure drop.
20. The system of claim 12 wherein said processor comprises a microprocessor for determining on the basis of an equation gate element position to produce said desired amount of flow based upon the pressure drop across said gate element and a temperature sensed by said thermostat.
21. The system of claim 12 wherein said processor control means comprises a microprocessor having lookup tables for providing said output, said lookup tables comprising a plurality of lookup tables, each lookup table related to a particular temperature sensed by said thermostat and each table having gate element angle as a function of said pressure drop;
22. The system of claim 12 wherein said processor control means comprises a thermostat for providing a signal for determining said desired amount of flow.
23. A fluid flow control system for controlling the flow of fluid through a duct in which a damper is located, the flow being dependent upon the pressure drop across the damper and damper/duct design parameters, said system comprising:
a damper located within said duct between a fluid inlet and a fluid outlet wherein the position of the damper controls the flow of fluid between said inlet and said outlet, said damper having a pressure drop thereacross; pressure drop sensing means for sensing said pressure drop across said damper;
processor control means connected to said pressure drop sensing means for providing an output signal having a value dependent upon said pressure drop across said damper and said design parameters; and, motor means connected to said pro-cessor control means and responsive to said output signal for operating said damper to a position to provide a desired flow.
a damper located within said duct between a fluid inlet and a fluid outlet wherein the position of the damper controls the flow of fluid between said inlet and said outlet, said damper having a pressure drop thereacross; pressure drop sensing means for sensing said pressure drop across said damper;
processor control means connected to said pressure drop sensing means for providing an output signal having a value dependent upon said pressure drop across said damper and said design parameters; and, motor means connected to said pro-cessor control means and responsive to said output signal for operating said damper to a position to provide a desired flow.
24. A fluid flow control system for controlling the flow of fluid through a duct in which a gate element is located, the flow being dependent upon the pressure drop across the gate element and gate element/duct design parameters, said system comprising: a gate element located within said duct between an inlet and an outlet wherein the position of the gate element controls the flow of fluid between said inlet and said outlet, said inlet and said outlet having a pressure drop therebetween; pressure drop sensing means for sensing said pressure drop; processor control means connected to said pressure drop sensing means for providing an output signal having a value dependent upon said pressure drop and said gate element/duct design parameters; and, motor means connected to said processor control means and responsive to said output signal for operating said gate element to a position to pro-vide a desired flow.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40581482A | 1982-08-06 | 1982-08-06 | |
| US405,814 | 1989-09-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1197131A true CA1197131A (en) | 1985-11-26 |
Family
ID=23605358
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000431811A Expired CA1197131A (en) | 1982-08-06 | 1983-07-05 | Flow controller |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1197131A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1391662A1 (en) * | 2002-08-22 | 2004-02-25 | Richard Gatley | Gas flow control system |
-
1983
- 1983-07-05 CA CA000431811A patent/CA1197131A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1391662A1 (en) * | 2002-08-22 | 2004-02-25 | Richard Gatley | Gas flow control system |
| GB2393799B (en) * | 2002-08-22 | 2006-03-08 | Richard Gatley | Gas flow control systems |
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