Abstrict The electronic nutating disc flow meter is suitable for measuring
different liquids with varying viscosities. This meter is best suited
for measuring medium viscosity fluids of 10 to 450 centipoise. This
flow meter includes a microprocessor to correct for the nonlinearity
of fluid flow. The memory in the microprocessor contains three calibration
curves with accompanying lookup table information. CAL A is preset
at the factory for thin viscosity fluids. CAL B is preset at the
factory for medium viscosity fluids and CAL C can be field calibrated.
The calibration curves can be plotted with up to five points per
curve.
Claims What is claimed is:
1. An electronic nutating disc flow meter for measuring volumetric
fluid flow comprising:
a. a housing defining a central chamber, said housing having an
axially aligned inlet and outlet to permit fluid communication with
said central chamber, said housing formed from a composite material;
b. a metering assembly including a wobble disc positioned in said
central chamber, said metering assembly defining an internal circular
passageway having an inlet and an outlet, said inlet of said metering
assembly in fluid communication with said inlet of said housing
and said outlet of said metering assembly in fluid communication
with said central chamber of said housing, said wobble disc having
a protruding drive pin extending through an aperture in said metering
assembly;
c. a free floating signal generator disc positioned in said central
chamber between said metering assembly and said housing, said signal
generator disc formed from a composite material having a friction
reducing component and including a plurality of ferrous, non-magnetized
slugs positioned about the circumference, said signal generator
disc engaging and being rotated by said drive pin as the fluid passes
through the electronic nutating disc flow meter along the following
flow path: fluid enters through said inlet of said flow meter and
passes into said inlet of said metering assembly through said internal
passageway causing said wobble disc to nutate and exiting through
said outlet of said metering assembly, passing through said central
chamber and exiting through said outlet of the flow meter;
d. sensor means located outside of said central chamber and isolated
from the fluid for detecting movement of said slugs as said signal
generator disc rotates in said central chamber, said sensor means
sending a pulsed signal each time a slug passes by said sensor means;
e. computer means including means for storing data defining a calibrated
nonlinear relationship between a K-factor of the meter and a corresponding
volumetric flow rate of the meter, said computer means, response
to the sensor signal and the relationship data in the storing means,
for determining volumetric fluid flow through the electronic nutating
disc flow meter and for generating a volumetric signal representative
of the determined volumetric fluid flow; and
f. means, responsive to the volumetric signal, for displaying a
fluid volume corresponding to the determined volumetric fluid flow
2. The apparatus of claim 1 wherein said computer means comprises
first register means for accumulating said signals over a fixed
unit of time, second register means to periodically receive the
accumulated total from said first register means, storage means
for storing lookup table information, selection means to select
lookup table information, means for calculating the incremental
volume of fluid flow over said fixed unit of time and means for
accumulating batch and cumulative fluid volumes; and wherein said
displaying means comprises means for alternatively displaying said
batch and said cumulative fluid volumes.
3. The apparatus of claim 1 wherein the storing means includes
a plurality of lookup tables defining the calibrated relationship
between the K-factor of the meter and the corresponding flow rate
of the meter.
4. The apparatus of claim 3 wherein each of said lookup tables
are defined by at least three calibration points.
5. The apparatus of claim 3 wherein at least one of said lookup
table can be field calibrated with at least three calibration points.
6. The apparatus of claim 1 wherein said friction reducing component
for said composite material for said signal generator disc is PTFE.
7. The apparatus of claim 1 wherein said friction reducing component
for said composite material for said signal generator disc is carbon.
8. The apparatus of claim 1 wherein said friction reducing component
for said composite material for said signal generator disc is molybdenum
disulfide.
9. The apparatus of claim 1 wherein there no more than ten ferrous
non-magnetized slugs positioned about the circumference of said
free floating signal generator.
10. The apparatus of claim 8 wherein the gap between said sensor
means and said ferrous, non-magnetized slugs is in the range of
0.097 inches to 0.173 inches.
11. The apparatus of claim 9 wherein said ferrous, non-magnetized
slugs are formed from ferrite.
12. The apparatus of claim 1 wherein said displaying means can
be axially adjusted for the viewing convenience of the user.
13. The apparatus of claim 1 wherein said displaying means is a
liquid crystal display (LCD).
14. The apparatus of claim 1 further comprising:
means, responsive to operator input, for selecting a particular
relationship between the K-factor and its corresponding volumetric
flow rate; and
wherein the computer means includes means for calculating the flow
rate based on the particular relationship selected by the operator.
15. The apparatus of claim 14 wherein said means for storing comprises
an electrically erasable, programmable read-only memory (EEPROM)
for storing a lookup table defining a relationship between the K-factor
and its corresponding flow rate.
16. The apparatus of claim 14 wherein the computer means includes
means for determining the closest point in the table corresponding
to the K-factor and for determining the flow rate based thereon.
17. The apparatus of claim 16 wherein said computer means includes
means for interpolating between points in the table to approximate
the flow rate.
18. The apparatus of claim 1 further comprising means for switching
responsive to the sensor means to provide a signal having one level
when the sensor means detects a slug passing thereby and for providing
a signal having another level when no slug is detected.
19. The apparatus of claim 18 wherein said switching means comprises
a bi-polar transistor for providing a zero volt signal when no slug
is detected and for providing a voltage signal when a slug is detected.
20. An electronic flow meter for measuring volumetric fluid flow
comprising:
a. a housing defining a central chamber, said housing having an
inlet and an outlet permitting fluid communication with said central
chamber;
b. a metering assembly positioned in said central chamber, said
metering assembly defining an internal circular passageway having
an inlet and an outlet, said inlet of said metering assembly in
fluid communication with said inlet of said housing and said outlet
of said metering assembly in communication with said central chamber
of said housing, said metering assembly driving a device in response
to fluid flow through said metering assembly;
c. means for sensing movement of said device and generating a sensing
signal in response to said movement;
d. computer means including means for storing information defining
a calibrated nonlinear relationship between the sensing signal of
the meter and its corresponding volumetric flow rate of the meter,
computer means, responsive to the sensing signal and the relationship
in the storing means, for determining a volumetric fluid flow through
the flow meter and for generating a volumetric signal representative
of the determined volumetric fluid flow; and
e. means, responsive to the volumetric signal, for displaying a
fluid volume corresponding the determined volumetric fluid flow.
21. The apparatus of claim 20 wherein said means for storing includes
means for storing a plurality of tables, each table representing
a calibrating curve defining a calibrating nonlinear relationship
between the sensing signal and its corresponding volumetric flow
rate and having at least two points therein.
22. The apparatus of claim 20 further comprising:
means, responsive to operator input, for selecting a calibrating
curve defining a calibrated nonlinear relationship between the sensing
signal and its corresponding volumetric flow rate; and
wherein the computer means includes means for calculating the flow
rate based on the operator selected calibrating curve.
23. The apparatus of claim 22 wherein said means for storing means
comprises an electrically erasable programmable read-only memory
(EEPROM) for storing a lookup table defining a relationship between
the K-factor and its corresponding flow rate.
24. The apparatus of claim 22 wherein the computer means includes
means for determining the closest point in the table corresponding
to the K-factor and for determining the flow rate based thereon.
25. The apparatus of claim 24 wherein said computer means includes
means for interpolating between points in the table to approximate
the flow rate.
26. The apparatus of claim 20 wherein said metering assembly includes
a wobble disk positioned in said central chamber, said wobble disk
having a protruding drive pin extending through an aperture in said
metering chamber; and further including a free-floating signal generator
disk positioned in said central chamber between said metering assembly
and said housing, said signal generator disk formed from a composite
material having a friction-reducing component and including a plurality
of ferrous, nonmagnetized slugs positioned about the circumference,
said signal generated disk engaging and being rotated by said drive
pin as the fluid passes through the electronic nutating disk flow
meter along the following flow path: fluid enters through said inlet
of said flow meter and passes into said inlet of said metering assembly
through said internal passageway causing said wobble disk to nutate
and exiting through said outlet of said metering assembly passing
through said central chamber and exiting through said outlet of
the flow meter.
27. The apparatus of claim 26 wherein said sensing means comprises
a pickup coil means located outside of said central chamber and
isolated from the fluid for detecting movement of said slugs as
said signal generator disk rotates in said chamber, said sensor
means sending a sensing signal each time the slug passes by said
sensor means.
28. The apparatus of claim 27 further comprising means for switching
responsive to the sensor means to provide a signal having one level
when the sensor means detects a slug passing thereby and for providing
a signal having another level when no slug is detected.
29. The apparatus of claim 28 wherein said switching means comprises
a bi-polar transistor for providing a zero volt signal when no slug
is detected and for providing a voltage signal when a slug is detected.
30. The apparatus of claim 20 wherein said computer means further
comprises means for accumulating said signals over a fixed unit
of time, second register means to periodically receive the accumulated
total from said first register means, storage means for storing
lookup table information, selection means to select lookup table
information, means for calculating the incremental volume of said
fluid flow over said fixed unit of time and means for accumulating
said batch in cumulative fluid volumes; and wherein said displaying
means comprises means for alternatively displaying said batch in
said cumulative fluid volumes.
31. The apparatus of claim 20 further comprising an electrically
erasable, programmable read only memory (EEPROM) for storing a lookup
table defining a relationship between a K-factor and its corresponding
flow rate.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The electronic nutating disc flow meter (sometimes hereinafter
flow meter) is suitable for measuring different liquids with varying
viscosities. This flow meter is suitable for measuring thin viscosity
liquids having a centipoise of less than 9 such as water. However,
this flow meter is best suited for measuring medium viscosity liquids
of 10 to 450 centipoise. This flow meter is often used to measure
agricultural chemicals including, but not limited to, liquid herbicides,
liquid pesticides and liquid fertilizers and may be field calibrated
for greater accuracy with specific liquids. This flow meter includes
a microprocessor to correct for the nonlinearity of fluid flow.
2. Description of the Prior Art
Fluid meters typically have some mechanical drive element immersed
in the flow path of the fluid, such as a nutating disc, a paddlewheel
or a turbine. Fluid flowing through the meter causes movement of
the mechanical drive element immersed in the flow. This mechanical
movement or rotational speed is generally proportional to the rate-of-flow
of the fluid, so that by sensing the rotational speed a fluid meter
can determine flow rate and/or volume. Unfortunately, the rotational
speed of the mechanical drive element is not directly proportional
to the flow. For example, doubling the flow rate will not double
the rotational speed of the nutating disc in the flow meter. Furthermore,
the rate of change is not constant throughout the useful flow range
of the electronic nutating disc flow meter. This nonlinearity is
well known to those skilled in the art. A graph known as a "K-Factor"
plot clearly indicates the curved-line relationship between fluid
flow rate and rotational speed of the mechanical drive element.
Most importantly, nonlinearity becomes more pronounced for viscous
fluids which creates instrument error.
Various attempts have been made to correct for this nonlinearity
and thus improve the ultimate accuracy of fluid meters. See for
example, U.S. Pat. No. 4306457; 4581946; 3965341; 4593365
and 4885943.
The present invention is typically installed in agricultural fluid
delivery systems; however, it is not limited to agricultural applications.
Scienco, Inc. of Memphis, Tenn., currently sells an electronic nutating
disc flow meter, the model SEM-20. The Scienco meter is typically
mounted at or near the pump in an agricultural fluid delivery system.
The Fill-Rite Division of the Tuthill Corporation of Fort Wayne,
Ind., also sells an electronic nutating disc flow meter, the model
810 digital meter. The Fill-Rite meter is typically mounted in-line
and adjacent to the dispensing nozzle in an agricultural fluid delivery
system. The Scienco and the Fill-Rite meters have a single calibration
curve which is defined by a single point. Both of these products
should be field calibrated to ensure accuracy when dealing with
viscous agricultural fluids.
Both the Scienco and the Fill-Rite meters use one or more magnets
which are immersed in the fluid stream and which are rotated by
the nutating disc. One or more reed switches are isolated from the
fluid flow and close a circuit each time the magnet rotates by the
reed switch. The differences between the Scienco and the Fill-Rite
meters and the present invention are discussed in greater depth
in the Information Disclosure Statement filed concurrently herewith.
SUMMARY OF THE INVENTION
Modern agricultural chemicals are typically sold as concentrates
which must be diluted with water before being applied to a crop
or field. In a typical agricultural delivery system, a plastic storage
tank containing a concentrated fluid, such as a herbicide, is mounted
on a delivery truck or at a stationary location away from the field
where the crops are grown. In order to apply the herbicide to the
field, the concentrate must be dispensed from the storage tank to
a vessel which is mounted on a tractor or an implement which is
towed by the tractor. The delivery truck can be driven to the tractor
in the field or the tractor must be driven to the stationary location
to fill the on-board vessel with the concentrated agricultural fluid
and water.
In a typical agricultural application, the farmer must dispense
a specific amount of the concentrated fluid from the supply tank
to the on-board vessel on the tractor or implement. Water is then
added to the vessel to achieve the desired rate of dilution. Because
of the strength of concentrated agricultural fluids, the specific
amount which is dispensed into the on-board vessel becomes important
to the farmer. In the case of a herbicide, if too little of the
concentrate is metered into the on-board vessel, weeds may continue
to grow and adversely effect crop yield. If too much of the herbicide
concentrate is metered into the on-board vessel, it may kill the
crop. In addition, herbicides such as Roundup.RTM. by Monsanto are
rather expensive, costing at retail approximately $56.00 per gallon.
In a typical agricultural fluid delivery system, a pump is mounted
on a storage tank and is connected via a flexible hose to a dispensing
nozzle. The typical agricultural dispensing nozzle is a ball valve
having a handle with 90.degree. of throw. Typically, the ball valve
does not have an automatic shut-off similar to gasoline dispensing
nozzles.
In the case of the Scienco meter, it is mounted on or near the
pump and is connected to the flexible hose; it is remote from the
dispensing nozzle. In the case of the Fill-Rite meter and the present
invention, they are mounted in-line between the dispensing hose
and the nozzle. The inlet port and the outlet port of the present
invention are axially aligned on opposing sides of the housing which
facilitates in-line plumbing between the dispensing nozzle and the
hose. The present invention weighs approximately 1.66 pounds and
therefore does not add an excessive amount of weight to the dispensing
nozzle. The present invention utilizes a compact design which is
approximately four inches in length, four inches in width and three
inches thick, exclusive of porting, which facilitates mounting adjacent
to the dispensing nozzle. It is convenient to have a meter mounted
adjacent to the dispensing nozzle because it is easier for the operator
to read the volume display.
When the operator is pumping fluid from the storage tank to the
on-board vessel, the present invention gives a real time display
of the volume of fluid which has actually been pumped. When the
desired volume has been transferred, the dispensing nozzle can be
manually shut off by the operator and the tank can be filled with
water as required for diluting the concentrate.
The present invention includes a batch totalizer or register, which
is analogous to a trip odometer in an automobile, and a cumulative
totalizer or register which is analogous to the fixed odometer of
an automobile. The batch totalizer can be reset to zero after a
tank has been filled. The cumulative totalizer cannot be reset and
gives a cumulative volumetric total of all fluid which has flowed
through the meter until there is a battery change. The present invention
uses three calibration curves referred to as "CAL A",
"CAL B", and "CAL C". CAL A is for thin viscosity
fluids having a centipoise of less than 9. CAL B is for medium viscosity
fluids from 10 to 450 centipoise, like agricultural herbicides,
and CAL C is for field calibration.
The calibration curves A and B are factory loaded with five points
per curve and are locked into memory. Calibration curve C can be
field calibrated with up to five points on the curve.
The present invention utilizes a lightweight, sturdy, compact design
which facilitates mounting near the dispensing nozzle. The present
invention is accurate and economical to mass produce due to its
unique design which includes use of a microprocessor. The present
invention is self-contained and battery powered for easy field operation.
Low power requirements allow a long service life for the battery
making frequent battery changes unnecessary.
The invention comprises an electronic flow meter for measuring
volumetric fluid flow. A housing defines a central chamber, the
housing having an inlet and an outlet permitting fluid communication
with said central chamber. A metering assembly is positioned in
said central chamber, the metering assembly defining an internal
circular passageway having an inlet and an outlet. The inlet of
the metering assembly is in fluid communication with the inlet of
the housing and the outlet of the metering assembly is in communication
with the central chamber of the housing, the assembly driving a
device in response to fluid flow through the metering assembly.
Means sense movement of the device and generate a sensing signal
in response to the movement. Computer means, responsive to the sensing
signal, determines a volumetric fluid flow through the flow meter
and generates a volumetric signal representative of the determined
volumetric fluid flow. Means store a plurality of calibrating curves
defining a relationship between the sensing signal and its corresponding
flow rate. Means, responsive to the volumetric signal, display a
fluid volume corresponding to the determined volumetric fluid flow.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features, advantages
and objects of the present invention are attained and can be understood
in detail, more particular description of the invention, briefly
summarized above, may be had by reference to the embodiments thereof
which are illustrated in the appended drawings.
It is noted, however, that the appended drawings illustrate only
typical embodiments of this invention and are therefore not to be
considered limiting of its scope, for the invention may admit to
other equally effective embodiments.
FIG. 1 is an isometric view of the electronic nutating disc flow
meter.
FIG. 2 is a top plan view of the electronic nutating disc flow
meter shown in FIG. 1.
FIG. 3 is a bottom plan view of the electronic nutating disc flow
meter shown in FIG. 1.
FIG. 4 is an exploded isometric view of the electronic nutating
disc flow meter shown in FIG. 1.
FIG. 5 is a top plan view of the electronic nutating disc flow
meter with the coverplate removed, exposing the signal generator
disc metering assembly in the central chamber.
FIG. 6 is a section view of the electronic nutating disc flow meter
line 6--6 of FIG. 2.
FIG. 7 is an exploded isometric view of the signal generator disc
and the metering assembly.
FIG. 8 is a bottom plan view of the signal generator disc.
FIG. 9 a section view of the signal generator disc along the line
9--9 of FIG. 8.
FIG. 10 is a top plan view of the top shell of the metering assembly.
FIG. 11 is a section view of the top shell of the metering assembly
along the line 11--11 of FIG. 10.
FIG. 12 is top plan view of the wobble disc.
FIG. 13 section view of the wobble disc along the line 13--13 of
FIG. 12.
FIG. 14 is top plan view of the bottom shell of the metering assembly.
FIG. 15 is a section view of the bottom shell of the metering assembly
along the line 15--15 of FIG. 14.
FIG. 16 is a section view of the electronic nutating disc flow
meter along the line 16--16 of FIG. 2 showing the wobble disc inclined
toward the inlet in the start position.
FIG. 17 is a section view of the electronic nutating disc flow
meter along the line 16--16 of FIG. 2. The wobble disc has advanced
90.degree. in a clockwise direction from the start position shown
in FIG. 17 and is inclined toward the letter B in FIG. 5.
FIG. 18 is a section view of the electronic nutating disc flow
meter along the line 16--16 of FIG. 2. The wobble disc has advanced
180.degree. from the start position shown in FIG. 16 and is now
inclined toward the outlet.
FIG. 19 is a section view of the electronic nutating disc flow
meter along the line 16--16 of FIG. 2. The wobble disc has advanced
270.degree. from the start position shown in FIG. 16 and is now
inclined toward the letter D in FIG. 5.
FIG. 20 is a section view of the electronic nutating disc flow
meter along the line 20--20 of FIG. 2.
FIG. 21 is an enlarged section view of the dome switch taken from
FIG. 18.
FIG. 22 is an enlarged section view of the liquid crystal display
and pickup sensor taken from FIG. 20.
FIG. 23 is an enlargement of the illuminated liquid crystal display
of the nutating disc flow meter.
FIG. 24 is a graph plotting K-Factors versus flow rates for a viscous
fluid and water passing through the electronic nutating disc flow
meter.
FIG. 25 is bottom plan view of the coverplate with the circuit
board attached.
FIG. 26 is a partial block diagram, in schematic form, illustrating
the electronics of the electronic nutating disc flow meter.
FIG. 27 illustrates the steps employed by the microprocessor when
calculating volume in the electronic nutating disc flow meter.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 the electronic nutating disc flow meter is
generally identified by the numeral 1. (For the sake of brevity
the electronic nutating disc flow meter may sometimes hereinafter
be simply referred to as the flow meter 1.) The housing 8 includes
a base 10 and a cover plate 12. The housing 8 defines an internal
central chamber 14 better seen in FIG. 4. The base 10 is connected
to the coverplate 12 by a first bolt 16 a second bolt 18 a third
bolt 22 and a fourth bolt 24. The base 10 includes an inlet port
26 and an outlet port 28 which permit fluid communication with the
central chamber 14.
The base 10 and the coverplate 12 are formed from a composite material
which for manufacturing convenience is injection molded. Various
composite materials are suitable for this application; however,
Applicants have determined that in the best mode the composite material
is approximately 70 percent polyester, 20 percent glass fiber, and
10 percent carbon. The carbon is added to the composite material
to reduce friction with other components and to provide a small
amount of electrical conductivity to dissipate electric static buildup
caused by the flowing fluids. Failure to dissipate static buildup,
may interfere with operation of the electronic components, including
the microprocessor described herein. Other materials which have
chemical resistance to herbicides in addition to polyester may also
be suitable for construction of the base 10 and the coverplate 12
such as nylon and PET (Polyethylene Terephthalate), which are within
the scope of this invention.
Mounted on top of the coverplate 12 is a faceplate 30. The faceplate
30 is attached to the coverplate 12 by a first screw 32 a second
screw 34 a third screw 36 and a fourth screw 38. A self-adhesive
decal 40 is applied to the faceplate 30. A clear window 42 is included
in the decal 40. The window 42 allows the operator to view a liquid
crystal display which is described hereinafter. The orientation
of the coverplate 12 and the faceplate 30 can be adjusted for the
convenience of the operator. To change the orientation, simply remove
the four bolts, 16 18 22 and 24 and remove the coverplate 12.
It can be reassembled in any of four fixed positions to suit the
operator. As shown in FIG. 1 the coverplate 12 and the faceplate
30 are adjusted to be read from the position of the letter B in
FIG. 5. The coverplate 12 and the faceplate 30 can be repositioned
to be read from the position of letter A in FIG. 5 from the position
of letter C, or from the position of letter D.
The decal 40 covers a first dome switch 44 which is marked "Display"
and may hereinafter sometimes be referred to as the Display button
and a second dome switch 46 which is marked "Calibrate"
and which may sometimes hereinafter be referred to as the Calibrate
button. The dome switch 44 and the second dome switch 46 extend
slightly above the surface of the faceplate 30 and create a slight
protrusion in the decal 40. The structure and operation of these
dome switches will be discussed hereinafter. For manufacturing convenience,
the faceplate 30 is injection molded and is formed from amorphous
nylon, water clear and UV stabilized. Other materials such as copolyester
and acrylic could also be used to form the faceplate and are within
the scope of this invention.
Attached to the top of the faceplate 30 is a removable battery
cover 48. The battery cover 48 is attached to the faceplate 30 by
screws 32 34 50 and 52. A seal 124 is captured between the battery
cover 48 and the faceplate 30. The battery cover 48 may be easily
and conveniently removed by the operator in the field to replace
the battery 54 by simply removing the four screws 32 34 50 and
52. The battery cover 48 is injection molded for manufacturing convenience
and is manufactured from the same composite materials as the base
10 and the coverplate 12. The battery 54 is located immediately
below the battery coverplate 48 as will be better seen in FIG. 4.
The electronic nutating disc flow meter 1 is typically connected
in an agricultural fluid delivery system which includes the following
components which are not shown in the drawings. A storage tank will
typically contain a large quantity of concentrated liquid. An electric
pump will be mounted on the tank for dispensing the agricultural
liquid into an on-board vessel. In a typical application, the tank
may be mounted in a truck or a fixed location for dispensing a liquid
into another on-board vessel typically mounted on a tractor or attached
to an implement being drawn by a tractor. The truck will either
go to the tractor in the field or the tractor will go to the fixed
location for filling. A flexible hose which may typically be in
the range of 10 to 14 feet long is connected from the pump to the
inlet port 26 of the electronic nutating disc flow meter 1. The
inlet snout 56 protrudes from the base 10 defining the inlet port
26. For the convenience of the operator, a direction arrow 58 is
formed on the exterior of the inlet snout 56 to indicate proper
flow direction. The outlet snout 60 defines the outlet port 28 and
is connected to a dispensing nozzle. The dispensing nozzle is typically
a ball valve actuated by a handle with 90.degree. of operational
throw. The typical agricultural dispensing nozzle is not the same
as a typical dispensing nozzle for use with fuels such as gasoline.
A typical gasoline nozzle has an automatic shut off which is not
present in the typical agricultural dispensing nozzle.
In FIG. 2 the inlet snout 56 and the outlet snout 60 are axially
aligned on opposing sides of the base 10 to facilitate in-line plumbing
in the agricultural fluid delivery system. As previously discussed,
the inlet snout 56 is connected to a hose, not shown in the drawing,
and the outlet snout 60 is connected to a dispensing nozzle, not
shown in the drawing. This in-line plumbing arrangement allows the
operator to look through the window 42 of the faceplate 30 while
he is dispensing agricultural fluids and simultaneously operate
the dispensing nozzle. The operator does not have to look back at
the pump which may be mounted some distance away on the tank. Various
operational and display functions of the electronic nutating disc
flow meter 1 are selected by the operator by manipulation of the
first dome switch 44 which is marked with the word "Display"
on the decal 40 and the second dome switch 46 which is marked with
the word "Calibrate" on the decal 40. The faceplate 30
is connected to the coverplate 12 by screws 32 34 36 and 38.
The battery cover 48 is connected to the faceplate 30 by the screws
32 34 50 and 52.
FIG. 3 shows the bottom of the base 10 which includes a plurality
of ridges 62 which provide structural rigidity and strength to the
base 10. Bolts 16 18 22 and 24 connect the base to the coverplate
12.
FIG. 4 is an exploded view of the flow meter 1. Starting at the
bottom, a housing 8 includes the base 10 and the coverplate 12.
The housing 8 defines a central chamber 14 which has an inlet port
26 and a outlet port 28 allowing fluid communication between the
central chamber 14 and the exterior of the housing 8. The base 10
is connected to the coverplate 12 by bolts 16 18 22 and 24. An
aperture 64 is formed in the base 10 and allows the bolt 16 to pass
through the base 10. The bolt threadably engages a female receptacle
110 formed in the coverplate 12. Another hole 66 is also formed
in the base 10 allowing the bolt 18 to pass through the base 10
and threadably engage a female receptacle 68 in the coverplate 12.
Another hole 70 is formed in the base 10 allowing the bolt 22 to
pass through the base 10 and threadably engage a female receptacle
116 in the coverplate 12. Another hole 72 is formed in the base
10 which allows the bolt 24 to pass through the base 10 and threadably
engage a female receptacle 74 in the coverplate 12.
A metering assembly is generally identified by the numeral 76 and
includes a wobble disc 78. The metering assembly 76 defines an inlet
port 80 and a plurality of openings which will be collectively referred
to as the outlet port 82. An O-ring 84 is sized to fit around the
inlet snout 86 of the inlet port 80 and seat in the O-ring groove
192. A clip 88 holds the metering assembly together and positions
it inside of the central chamber 14. A slight recess 90 is formed
on the interior of the housing 8 to receive the clip 88 and to prevent
it from rotating as fluid passes through the central chamber 14.
In actuality, there are three other clips better seen in FIG. 5
which stabilize the metering assembly 76 within the central chamber
14. Likewise, there are three other recesses on the interior of
the housing 8 to receive each of these three retaining clips. The
phantom lines show how the retaining clip engages the circumferential
lip 92 of the metering assembly 76.
A signal generator disc is generally identified by the numeral
94. A plurality of slugs 199 are placed about the circumference
of the signal generator disc 94.
The coverplate 12 has an upper recess 13 formed therein and a circular
recess 96 which extends below the level of the upper recess 13.
The circular recess 96 is sized and arranged to receive the pickup
coil which will be discussed hereinafter. The bottom of the coverplate
12 includes a circular protrusion 98 which engages a circular seat
100 on the interior of the base 10. The protrusion 98 includes an
O-ring groove 102 which receives an O-ring 104 which provides a
fluid seal between the coverplate 12 and the base 10 preventing
leakage of any fluids which may flow through the central chamber
14 of the flow meter 1.
The faceplate 30 includes a hole 106 which allows the screw 38
to pass through the faceplate and engage a female threaded receptacle
74 in the coverplate 12. Another hole 108 is formed in the faceplate
30 to allow the screw 32 to pass through the faceplate and engage
the female threaded receptacle 110 in the coverplate 12. Another
hole 112 is formed in the faceplate 30 which allows the screw 34
to pass through the faceplate 30 and engage a female threaded receptacle
68 in the coverplate 12. Another hole 114 is formed in the faceplate
30 to allow the screw 36 to pass through the faceplate 30 an engage
the female threaded receptacle 116 in the coverplate 12.
A portion of the faceplate 30 is recessed to form a battery retainer
118 which receives the battery 54. In the preferred embodiment,
the battery 54 is a 9 volt transistor battery. Connectors 120 extend
from the circuit board and are connected to a terminal 122 which
connects with the battery 54 which provides power to drive the microprocessor
and LCD.
The battery cover 48 is connected to the faceplate 30 by the screws
32 34 50 and 52. A seal 124 is positioned between the battery
cover 48 and the faceplate 30 to isolate water and other fluids
from the electrical chamber 21. The electrical chamber 21 is defined
by the battery cover 48 the faceplate 30 and the upper recess
13 formed in the coverplate 12.
There is a hole 126 in the battery cover 48 and an axially aligned
hole in the seal 124 which permit the screw 50 to pass through the
battery cover 48 and the seal 124 and threadably engage a female
receptacle 128 in the faceplate 30. Likewise, there is another hole
130 in the battery cover 48 which is axially aligned with another
hole 132 in the seal 124 allowing the screw 52 to pass through the
battery cover 48 and the seal 124 and threadably engage a female
receptacle 134 in the faceplate 30.
There is an additional hole 136 in the battery cover 48 which is
axially aligned with another hole 138 in the seal 124 to allow the
screw 34 to pass through the battery cover 48 the seal 124 and
the faceplate 30 to threadably engage the female receptacle 68 in
the coverplate 12. There is another hole 140 in the battery cover
48 which is axially aligned with a hole 142 in the seal 124 to permit
the screw 32 to pass through the coverplate 48 the seal 124 and
the faceplate 30 and threadably engage the female receptacle 110
in the coverplate 12.
FIG. 5 is a top plan view of the electronic nutating disc flow
meter 1 with the coverplate 12 removed. The signal generator disc
94 is positioned on top of the metering assembly 76. The arrow in
the drawing generally indicates the clockwise direction of rotation
of the signal generator disc 94.
The metering assembly 76 is held in place in the central chamber
14 by a plurality of retaining clips. Retaining clip 88 engages
the circumferential lip 92 of the metering assembly 76. The recess
90 on the interior of the base 10 holds the retaining clip 88 in
place. A second retaining clip 150 likewise engages the circumferential
lip 92 of the metering assembly 76. The retaining clip 150 fits
in a recess 152 formed on the interior of the base 10. A third retaining
clip 154 engages the circumferential lip 92 of the metering assembly
76. The retaining clip 154 fits in a recess 156 on the interior
of the base 10. A fourth retaining clip 158 engages the circumferential
lip 92 of the metering assembly 76. The retaining clip 158 is held
in place by a recess 160 on the interior of the base 10. The retaining
clips 88 150 154 and 158 together exert downward pressure on the
circumferential lip 92 holding the metering assembly together and
stabilizing its position in the central chamber 14.
The flow path of fluid through the flow meter 1 is as follows.
Fluid enters through the inlet port 26 of the housing 8 and passes
through the inlet port 80 of the metering assembly 76. The passage
of fluid through the metering assembly 76 causes the wobble disc
78 to nutate or wobble to and fro which causes the signal generator
disc 94 to rotate in a clockwise fashion as shown by the direction
arrow in the drawing. The nutating motion of the wobble disc 78
is transferred to the signal generator disc 94 through a drive pin
162 which protrudes from the wobble disc 78 through an aperture
164 in the metering assembly 76. After the fluid has flowed through
the metering assembly 76 it exits through a plurality of openings
generally identified as the outlet port 82. The fluid then passes
through the central chamber 14 and exits the flow meter 1 through
the outlet port 28.
Referring to FIG. 6 the flow meter 1 is shown in section view
fully assembled with all components in place. The battery cover
48 fits on top of the faceplate 30 which fits on top of the coverplate
12 which engages the base 10. The battery coverplate 48 the faceplate
30 and the upper recess 13 in the coverplate 12 together define
an electrical chamber 21 which is isolated from fluid flow through
the central chamber 14.
The coverplate 12 and the base 10 create a housing 8 which defines
a central chamber 14 through which fluid flows. The signal generator
disc 94 and the metering assembly 76 are positioned in the central
chamber 14 and are immersed in fluid flowing through the flow meter
1. The O-ring 104 mounted on the circular protrusion 98 of the coverplate
12 seals against the circular seat 100 on the interior of base 10
forming a fluid tight seal for the central chamber 14.
A downward facing shoulder 99 is formed about the lower perimeter
of the coverplate 12. An upward facing shoulder 101 is formed about
the upper perimeter of the base 10. When assembled, the shoulder
99 of the coverplate 12 abuts the shoulder 101 of the base 10.
A downward facing shoulder 97 is formed about the lower perimeter
of the faceplate 30. An upward facing shoulder 103 is formed about
the upper perimeter of the coverplate 12. When assembled the shoulder
97 of the faceplate 30 abuts the shoulder 103 of the base 10.
The metering assembly 76 is held in place by a series of clips
88 150 154 and 158. The clips engages the circumferential lip
92 which partially encircles the metering assembly 76. The clips
are held in place by a plurality of recesses in the base 10. Clip
88 engages recess 90 clip 154 engages recess 156. The top of the
clips engage the bottom 87 of the circular protrusion 98 of the
coverplate 12 to hold the clip in place and prevent unwanted movement
resulting from fluid flow through the central chamber 14. The bottom
of the clips engage an upward facing circular shoulder 163 formed
in the base 10. The coverplate 12 is secured to the base 10 by four
bolts, two of which are shown in this figure. Bolt 24 passes through
the hole 72 in the base 10 and threadably engages a female receptacle
74 in the coverplate 12. Bolt 18 passes through the hole 66 in the
base 10 and threadably engages the female receptacle 68 in the coverplate
12.
The electrical chamber 21 contains the circuit board 166 the battery
54 the liquid crystal display (LCD) 168 and the pickup coil . The
electrical chamber 21 is isolated from fluid flow through the central
chamber 14. The battery cover 48 is held in place by four screws,
one of which, 34 is shown in this view. Screw 34 passes through
hole 136 in the battery cover and hole 138 in the seal 124 and threadably
engages the female receptacle 68 in the coverplate 12. The faceplate
30 is likewise held in place by four screws, one of which, 38 is
shown in this view. Screw 38 passes through hole 106 in the faceplate
30 and threadably engages the female receptacle 74 in the coverplate
12.
Referring to FIG. 7 the metering assembly is generally identified
by the bracket and the numeral 76. The signal generator disc is
generally identified by the numeral 94. The metering assembly includes
a top shell 174 which is sized and arranged to engage a bottom shell
176. The wobble disc 78 which may also from time to time be referred
to as a nutator disc, fits in between the top shell 174 and the
bottom shell 176 of the metering assembly 76. The wobble disc 78
includes a drive pin 162 which protrudes from the central spherical
core 178. A radial slot 180 extends from the outer circumference
of the central spherical core 178 to the outer circumference of
the wobble disc 78. The central spherical core 178 engages and nutates
in a first circular journal 182 in the bottom shell 176. The central
spherical core 178 engages and nutates in a second circular journal
165 formed in the top shell 175 better seen in FIG. 11.
A stabilizing vane 184 is formed in the bottom shell 176 and fits
loosely in the slot 180 of the wobble disc 78. The top 186 of the
stabilizing vane 184 touches the interior wall 173 of the top shell
174 thus capturing the wobble disc 78 causing it to nutate as fluid
passes through the metering assembly. The bottom shell 176 includes
an inlet snout 188 which combines with a similar inlet snout 190
protruding from the top shell 174 to define an inlet port 80 for
the metering assemble 76. An O-ring groove 192 encircles the snouts
188 and 190 and receives O-ring 84.
The top shell 174 includes two openings, 194 and 196 which together
with similar openings 234 and 236 in the bottom shell 176 define
the outlet port 82 of the metering assembly 76. The metering assembly
76 and the wobble disc 78 define an internal circular passageway
77 through which fluid flows in the metering assembly 76. As the
wobble disc 78 nutates, the drive pin 162 rotates in a clockwise
circular arc causing the signal generator disc 94 to rotate in a
clockwise fashion as shown by the direction arrow in the drawing.
FIG. 8 is a bottom plan view of the signal generator disc 94 and
the slugs 199. There are ten specific slugs 200 202 204 206
208 210 212 214 216 and 218 positioned about the circumference
of the signal generator disc 94. In the preferred embodiment the
slugs which will be generically identified by the numeral 199 are
formed from ferrite. The slugs 199 are non-magnetized to avoid any
pickup of rust or metal debris from the fluid. A central drive shaft
220 protrudes from the bottom face 222 of the signal generator disc
94. A keyway 224 is formed in the central drive shaft 220. The drive
pin 162 engages in the keyway 224 of the signal generator disc 94.
When fluid passes through the flow meter 1 it causes the wobble
disc 78 to nutate thus causing the drive pin 162 to rotate in a
circular arc which causes the signal generator disc 94 to rotate
in a clockwise direction.
The top surface 226 of the signal generator disc 94 will from time
to time be in rotational contact with the bottom surface 228 of
the coverplate 12 causing friction. The signal generator disc 94
is a free floating apparatus emersed in the fluid stream passing
through the central chamber 14 of the flow meter 1. The fluid will
reduce the degree of friction between the signal generator disc
94 and the coverplate 12; however, care needs to be taken regarding
selection of proper components to minimize the amount of friction
and thus maximize accuracy and the serviceable life of the flow
meter 1. The signal generator disc is formed from a composite material
which should include a friction reducing component such as PTFE.
Other friction reducing materials may also be suitable in this application
such as carbon or molybdenum disulfide. In the preferred embodiment,
Applicant has determined that a suitable composite material for
the friction generator disc is 55% polyester, 30% glass beads and
15% PTFE. It may be possible to form the signal generator disc entirely
from PTFE or some other similar material which is also within the
scope of this invention. Applicant recommends that the ferrous slugs
be recessed approximately 0.010 to 0.015 inches from the top surface
226 of the signal generator disc to allow for uninterrupted wear
during the life of the flow meter 1.
Applicant has also determined that the gap between the pickup coil
170 and the top of the ferrous slugs 199 is optionally in the range
of 0.097 inches to 0.173 inches when ten slugs are used. This gap
is identified by the bracket and the letter Z in FIG. 20. The size
of the gap may vary from this range depending on the number and
size of slugs actually used.
FIG. 10 is a top plan view of the top shell 174 of the metering
assembly 76. The circumferential lip 92 encircles a portion of the
top shell 174. The drive pin 162 protrudes through a central aperture
164 in the top shell 174. A plurality of reinforcing ridges 230
radiate from the central aperture 164. A first hole 194 and a second
hole 196 are formed in the top shell 174 and together with similar
holes 234 and 236 in the bottom shell 176 form the outlet port 82
of the metering assembly 76. The inlet snout 190 protrudes from
the top shell 174 and together with the inlet snout 188 define an
inlet port 80.
FIG. 11 is a section view along the line 11--11 of the top shell
174. The circumferential lip 92 includes a channel 232 which is
formed throughout the entirety of the circumferential lip 92. The
drive pin 162 extends through the central aperture 164. The upper
surface of the central spherical core engages the second circular
journal 165 found in the top shell 174.
FIG. 12 is a top plan view of the wobble disc or the nutator disc
78. A central spherical core 178 is formed in the center of the
disc to support and hold the protruding drive pin 162. The core
178 engages second circular journal 165 in the top shell 174 and
the journal 182 in the bottom shell 176. A radial slot 180 extends
from the outer circumference of the central spherical core 178 to
the outer circumference of the wobble disc 78. The slot 180 loosely
engages the stabilizing vane 184 thus preventing the wobble disc
78 from spinning inside the metering assembly 76 as fluid passes
from the inlet 80 to the outlet 82. The clearance between the slot
180 and the stabilizing vane 184 is loose enough to permit the wobble
disc 78 to freely nutate in response to fluid flow.
FIG. 13 is a section view of the wobble disc 78. The central spherical
core 178 protrudes both above and below the horizontal axis of the
disc. The drive pin 162 is firmly embedded and captured in the spherical
core 178. Applicants recommend that the drive pin 162 be formed
from stainless steel or some other material suitable for a harsh
chemical environment.
FIG. 14 is a top plan view of the interior of the bottom shell
176 of the metering assembly 78. In the center of the bottom shell
176 a journal 182 is formed to receive and engage the bottom surface
of the central spherical core 178 of the wobble disc 78. A stabilizing
vane 184 protrudes from the bottom shell 176. A first hole 234 and
a second hole 236 are formed in the bottom shell 176 and together
with the holes 194 and 196 in the top shell 174 define the outlet
82 of the metering assembly 76. An inlet snout 188 extends from
the bottom shell 176. The inlet snout 190 and the inlet snout 188
together define the inlet port 80 of the metering assembly 76. A
circular ridge 238 extends from the lower circumferential lip 92
and engages the channel 232 in the upper circumferential lip 92
of the top shell 174 to provide mechanical alignment and sealing
between the top shell 174 and the bottom shell 176. Fluid flow through
the internal circular passageway 77 is indicated by the flow arrows
in FIG. 14.
FIG. 15 is a section view of the bottom shell 176 along the line
15--15 of FIG. 14. The stabilizing vane 184 protrudes from the bottom
shell 176 and the upper edge 186 engages the interior surface 173
of the top shell 174 creating a circular passageway 77 from the
inlet 80 to the outlet 82 in the metering assembly.
An O-ring groove 192 is formed about the inlet snouts 188 and 190
to effect a seal between the metering assembly 76 and inlet port
26 of the base 10.
FIGS. 16 17 18 and 19 will show one complete revolution of the
signal generator disc 94 and one complete nutation of the wobble
disc 78. This series of drawings will also show the flow path of
fluid through the flow meter 1 and the metering assembly 76. In
FIG. 16 the drive pin is inclined towards the inlet port 26 which
will henceforth be referred to as the start position. FIG. 17 shows
the wobble disc 78 advanced 90.degree. in a clockwise direction
from the start position of FIG. 16. FIG. 18 shows the wobble disc
78 advanced 180.degree. in a clockwise direction from the start
position and FIG. 19 shows the wobble disc 78 advanced 270.degree.
in a clockwise direction from the start position.
FIG. 16 is a section view of the electronic nutating disc flow
meter 1 taken along the line 16--16 of FIG. 2. The base 10 and the
coverplate 12 form a housing 8 which defines a central chamber 14.
The inlet snout 56 protrudes from the base 10 and defines an inlet
port 26. The outlet snout 60 protrudes from the base 10 and defines
an outlet port 28. Fluid enters the flow meter 1 as indicated by
the directional arrow in the drawing through the inlet port 26
passes through the central chamber 14 and exits through the outlet
port 26 as shown by the arrow in the drawing.
The coverplate 12 includes an upper recess 13 a circular protrusion
98 and a bottom surface 228. The circular protrusion 98 includes
a circumferential O-ring groove 102 which receives the O-ring 104.
The interior portion of the base 10 includes a circular seat 100
and an upward facing shoulder 101 The coverplate 12 and the circular
protrusion 98 define a downward facing shoulder 99. When assembled
the coverplate 12 fits into the base 10 with the shoulder 99 abutting
the shoulder 101 causing the O-ring 104 to seal against the circular
seat 100. The O-ring and the coverplate 12 together with the base
10 form a fluid tight central chamber 14 which isolates fluid flow
from the electrical chamber 21.
The metering assembly 76 is positioned in the central chamber 14
with the signal generator disc 94 positioned between the metering
assembly 76 and the coverplate 12
The inlet snout 190 of the top shell 174 and the inlet snout 188
of the bottom shell 176 are inserted into the inlet port 26. The
O-ring 84 forms a seal between the inlet port 26 and the metering
assembly 76 as shown in the drawing. Fluid therefore passes from
the inlet port 26 of the housing 8 into the inlet port 80 of the
metering disc 76.
As shown in FIG. 16 the wobble disc 78 and the drive pin 162 are
tilted downward toward the inlet port 26 of the housing 8. The drive
pin 162 is tilted in the direction of the letter A in FIG. 5 which
is identified as the start position. Fluid enters the inlet port
26 of the base 10. The fluid then enters the inlet port 80 of the
metering assembly 76. As the fluid passes into the internal circular
passageway 77 within the metering assembly 76 it encounters the
stabilizing vane 184 as shown by the flow arrow M in FIG. 14. The
stabilizing vane 184 extends from the floor of the bottom shell
176 to the ceiling of the top shell 174 thereby urging fluid into
a clockwise flow path through the internal circular passageway 77
of the metering assembly 76. As the fluid moves in the clockwise
flow path to the position indicated by the flow arrow N in FIG.
14 it causes the wobble disc 78 to nutate inside the internal circular
passageway 77 of the metering assembly 76. The wobble disc 78 moves
from the start position shown in FIG. 16 to a more advanced position
shown in FIG. 17.
In FIG. 17 the drive pin 162 has now rotated in a clockwise direction
90.degree. from the start position of FIG. 16 and is now tilting
toward the letter B shown in FIG. 5. As the drive pin has advanced
90.degree. from the start position, the signal generator disc has
also been rotated 90.degree. from its initial start position shown
in FIG. 16.
The central spherical core 178 of the wobble disc 78 bears against
the journal 182 of the bottom shell 176 and against the second circular
journal 165 of the top shell 174. The drive shaft 220 of the signal
generator disc 94 defines a circular shoulder 221 which abuts a
circular shoulder 163 in the upper surface of the top shell 174.
In FIG. 18 the fluid has advanced through the circular passageway
77 of the metering assembly 76 and has now moved to the position
shown by the arrow 0 in FIG. 14. As the fluid moves through the
circular passageway 77 it forces the wobble disc 78 to nutate into
the position shown in this Figure. The drive pin 162 has now advanced
180.degree. from the start position shown in FIG. 16 and is tilting
toward the letter C in FIG. 5. The signal generator disc has likewise
advanced 180.degree. in a clockwise rotation from the original position
shown in FIG. 16.
In FIG. 19 the wobble disc 78 has advanced 270.degree. from the
initial start position shown in FIG. 16. The drive pin 162 is inclined
toward the letter D in FIG. 5. The fluid has now advanced through
the internal circular passageway 77 of the metering assembly 76
as shown by the flow arrow P in FIG. 14.
As the fluid continues to advance through the circular internal
circular passageway 77 it impacts the stabilizing vane 184 as shown
by the flow arrow Q in FIG. 14. The fluid is forced through the
holes 234 and 236 in the bottom shell 176 as indicted by the flow
arrow R. Fluid likewise exits the internal circular passageway 77
through the holes 194 and 196 in the top shell 174.
As the fluid exits the outlet port 82 it forces the wobble disc
78 to continue to nutate and to return to the start position originally
shown in FIG. 16 which likewise causes the signal generator disc
94 to complete a 360.degree. rotation in the central chamber 14.
For each revolution of the signal generator disc 94 ten slugs will
pass under the pickup coil 170. As fluid continues to flow through
the flow meter 1 the wobble disc 78 continues to nutate thus driving
the signal generator disc 94 in a continuous clockwise direction
as long as fluid is flowing through the metering assembly 76. At
maximum flowrates of 20 gpm, the signal generator disc 94 may be
rotating at approximately 1200 rpm.
The complete flow path of the fluid is as follows. Fluid enters
the flow meter 1 through the inlet port 26. The fluid then passes
through the inlet port 80 of the metering assembly 76. As the fluid
enters the metering assembly it impacts the stabilizing vane 184
as shown by the flow arrow M in FIG. 14. The stabilizing vane 184
acts as a wall which isolates the inlet 80 from the outlet 82 and
together with the top shell 174 and the bottom shell 176 define
the interior circular passageway 77 of the metering assembly 76.
The fluid then flows through the internal circular passageway 77
in the metering assembly 76 as generally indicated by the flow
arrows N, O, and P in FIG. 14. As the fluid passes through the internal
circular passageway 77 in the metering assembly 76 it causes the
wobble disc 78 to nutate as shown in FIG. 16 17 18 and 19. The
fluid then encounters the stabilizing vane 184 as shown by the flow
arrow Q in FIG. 14. The fluid is then forced to exit the internal
circular passageway 77 through the holes 234 and 236 in the bottom
shell 176 and the holes 194 and 196 in the top shell 174. The fluid
then enters the central chamber 14 and passes out of the flow meter
1 through the outlet port 28.
As fluid passes along this flow path, the wobble disc 78 nutates
in the internal circular passageway 77 of the metering assembly
76. The nutation of the wobble disc 78 causes the drive pin 162
to rotate in a circular arc which drives the signal generator disc,
causing it to be rotated in a clockwise direction as long as fluid
is flowing through the flow meter 1. When the fluid flow stops through
the flow meter 1 the wobble disc 78 ceases to nutate and the signal
generator disc 94 stops rotation.
FIG. 20 is a cross-section of the electronic nutating disc flow
meter 1 along the line 20--20 of FIG. 2. In this figure, the nutating
disc 78 and the drive pin 162 are positioned at the same angle as
shown in FIG. 19. In other words, the drive pin is advanced 270
from the initial start position as shown in FIG. 16. A ferrous slug
204 is positioned immediately below the pickup coil 170. This sensor
means 170 sends a signal each time one of the ferrous slugs passes
underneath the sensor 170. In other words, when the signal generator
disc 94 has made one complete revolution, each of the ferrous slugs
will have passed under the pickup coil 170 once and the sensor will
accordingly have sent 10 signals or pulses as each of the ferrous
slugs has passed underneath the sensor 170.
FIG. 21 is an enlargement of the first dome switch 44 taken along
the line 21 of FIG. 18. As previously discussed, there are two dome
switches mounted in the faceplate 30 which are identical in structure.
The first dome switch 44 is identified by the phrase "Display"
on the decal 40. The second dome switch, generally identified by
the numeral 46 is identified by the term "Calibrate"
on the decal 40. A circular plastic plunger 250 is positioned in
a circular aperture 252 in the faceplate 30 underneath of the decal
40. The plastic plunger 250 is free to move up and down within the
circular aperture 252 in response to finger pressure on the decal
40. On the reverse side 31 of the faceplate 30 there is a circular
protrusion 254. An elastomer cap 256 is sized and arranged to fit
around the circular protrusion 254. The elastomeric cap 256 has
an internal cone 258 which tends to urge the plunger 250 into an
upward position as shown in the drawing. Attached to the bottom
of the cone 258 is a circular carbon contact 260. Beneath the contact
260 is the circuit board 166. As shown in FIG. 21 the first dome
switch 44 is in the open position. If the operator wishes to close
the first dome switch he puts his finger over the decal 40 and pushes
the plunger 250 downward which depresses the cone 258 causing the
carbon contact 260 to engage two contacts on the circuit board 166
thus closing the circuit. The second dome switch 46 is identical
in structure to the first dome switch 44 previously described. Those
skilled in the art will readily understand and recognize the operation
and features of these two dome switches.
FIG. 22 is an enlargement along the line 22 of FIG. 20. The liquid
crystal display (LCD) 168 and the operation thereof are known to
those skilled in the art and will not be repeated herein for the
sake of brevity. The LCD 168 is positioned in a rectangular recess
262 formed in the reverse side 31 of the clear faceplate 30. The
decal 40 has a clear rectangular window 42 formed therein which
allows the operator to observe the LCD 168 through the faceplate
30. An upper rectangular gasket 264 separates the LCD 168 from the
recess 262 of the faceplate 30. A backplane gasket 266 supports
the bottom side of the LCD 168.
As known to those skilled in the art, the LCD 168 has a plurality
of contact points 268 along one edge of the LCD and a plurality
of additional contact points 270 along the opposing edge of the
LCD 168. The electrical connection between the contact points on
the LCD 168 and the circuit board 166 is accomplished by a first
elastomeric connector 272 which is sometimes referred to as a Zebra
strip and a second elastomeric connector 274. The elastomeric connectors
272 and 274 are known to those skilled in the art and will be described
only briefly herein. Running lengthwise through the elastomeric
connector 272 is a plurality of conductive fibers 276 which form
an electrical connection between the contact points 268 on the LCD
168 and corresponding contact points, not shown, on the circuit
board 166. The elastomeric connector 274 has a similar configuration.
The pickup coil 170 will be briefly described. A central cylindrical
magnet 278 is secured in a plastic spool 280. The magnet is made
of Alnico 8HE material and is fully saturated. Wrapped around the
plastic spool 280 is a coil 282 of copper wire. Applicant recommends
6000 turns of copper wire which is 45 gauge. Wrapped around the
exterior circumference of the copper coil is nylon insulating tape
284. The size and strength of this sensor 170 are largely a matter
of manufacturing convenience. Other similar sensors of different
sizes are within the scope of this invention. The leads to the coil
are connected to the circuit board for sending a signal each time
a ferrous slug passes underneath the pickup coil 170. After the
circuit board 166 has been installed in the faceplate 30 the entire
electrical package is potted to approximately the level indicated
by the line 288. The potting helps prevent deterioration of the
electrical circuit due to moisture and other environmental influences.
FIG. 23 shows the LCD 168 with all digits and flags fully illuminated
solely for purposes of illustration. In actual field operation,
the LCD 168 would never fully illuminate all of the digits and flags
as shown in FIG. 23.
The LCD 168 will display up to six digits and the decimal will
automatically move to the right as required to display large totals.
The maximum total digital display using this LCD is "999999".
For purposes of illustration, each digit is displaying the number
eight and a decimal point is illuminated to read "8.8.8.8.8.8.".
Positioned above the row of digits is a row of flags which indicate
which calibration curve has been selected, i.e. CAL A, CAL B or
CAL C. Positioned below the row of digits is a row of flags which
indicate which totalizing register is being displayed, i.e. TOTAL
1 or TOTAL 2.
When not in operation, the electronic nutating disc flow meter
1 goes into a sleep mode which causes the LCD 168 to generate a
blank display. The flow meter 1 will wake up when fluid flow begins
or anytime the dome switch 44 is actuated. Hereinafter the dome
switch 44 will be referred to as the Display button 44. When fluid
flow begins through the flow meter 1 a small rotor symbol 300 is
illuminated in the lower left hand corner of the LCD 168 The flow
meter has two registers or totalizers which accumulate the volume
of fluid passing through the flow meter 1. "TOTAL 1" is
a batch totalizer that is resettable, and "TOTAL" 2 is
a cumulative totalizer that is non-resettable. The batch totalizer
is used to determine the total volume of fluid that is being dispensed
on a per tank basis. After one tank has been filled, the batch totalizer
can be reset to zero before going to the next tank. The cumulative
totalizer is non-resettable and measures the total volume of fluid
flow through the flow meter 1 from its date of installation until
there is a battery change.
The LCD 168 alternates between Total 1 the batch totalizer, and
Total 2 the cumulative totalizer. When Total 1 has been selected
the LCD will illuminate the following information: "TOTAL 1".
When Total 2 has been selected the LCD 168 will display the following:
"TOTAL 2 LOCKED". Regardless of which total is being displayed,
both totalizers will be operational and will accumulate the volume
of fluid which is passing through the flow meter 1. To erase the
memory of the batch totalizer, the operator depresses the Display
button and holds it for three seconds at which time the display
on the LCD 168 will change to zero.
The flow meter 1 has three separate calibration curves for different
viscosity fluids. Calibration curve A is for thin viscosity fluids
which are less than 9 centipoise. Calibration curve B is for medium
viscosity fluids which are approximately 10 to 450 centipoise, like
most agricultural herbicides. The calibration points for curve A
and B are locked in at the factory and cannot be adjusted by the
operator. Calibration C can be field calibrated by the operator.
Calibration curve C can be calibrated with one or more data points
to establish the parameters of the curve. In order to select calibration
A, B, or C, the operator depresses the dome switch 46 which will
hereinafter be referred to as the Calibration button. While holding
the Calibration button down he momentarily depresses the Display
button 44 which causes the LCD 168 to alternate between the calibration
curves A, B, or C.
If the operator selects calibration curve A, the LCD 168 will display
the following information: "CAL A PRESET"; if the operator
selects calibration curve B, the LCD 168 will display: "CAL
B PRESET". If the operator selects calibration curve C, the
LCD 168 will display: "CAL C". The calibration data is
retained during the computer sleep mode and during battery changes.
If the operator decides to field calibrate curve C, the following
sequence must be initiated. First, the operator must select curve
C as previously described, by depressing and holding the Calibrate
button and by momentarily depressing the Display button until the
LCD 168 displays "CAL C". Then the operator must depress
and hold the Calibrate button 46 and the Display button 44 for
three seconds, at which time, the LCD 168 will display on the top
line "CAL C", and in place of the numerals it will display
"CAL-P0". When the calibrate button 46 and the Display
button are released, the LCD 168 will then begin blinking and will
display on the top line "CAL C" and in place of the digits
"CAL-P1". The flow meter 1 is now ready for loading the
first field calibration point. The previous field calibration curve
will be erased when the new curve is stored in memory.
If the operator elects to install a one point field calibration
curve, the following procedure is utilized. The operator momentarily
depresses and releases the Calibrate button 46 which will cause
the LCD 168 to quit blinking and display: "CAL-P1". At
this time, the operator should fill an accurate five unit container
with fluid in one smooth stream. Care should be taken to start and
stop the flow quickly. This calibration run should last at least
10 seconds. After dispensing five units, the operator presses and
releases the Calibrate button 46. The LCD 168 then blinks "CAL-P2".
The first calibration point has now been stored in memory. The operator
has now established a one point calibration curve. To exit this
procedure, the operator presses and releases the Calibrate button
and the Display button simultaneously, at which time the display
will return to the digital format.
If the LCD 168 blinks a "no" on the upper line after
an attempt to enter a field calibration point, then the procedure
was a failure and it must be repeated.
If the operator chooses a multiple point calibration curve with
up to five calibration points, the following procedure is used.
First the operator selects Calibration curve C, as discussed hereinabove.
The LCD 168 will display "CAL-P0" the operator must then
press and release the Calibrate button, at which time the LCD 168
will quit blinking and will display "CAL-P1". At this
time, the operator should fill an accurate five unit container with
fluid in one smooth stream. Care should be taken to start and stop
the flow quickly. After the operator has dispensed five units, he
must press and release the Calibrate button. The LCD 168 will then
blink "CAL-P2". The first calibration point has been stored
in memory.
The five unit container must be emptied. The operator must momentarily
depress the Calibration button and the display will stop blinking.
The meter is now ready to receive its second calibration point.
The operator must now adjust the system to a different flow rate
and re-fill the aforementioned five unit container with fluid in
one smooth stream. After dispensing five units, he must press and
release the calibrate button. The LCD will then blink "CAL-P3".
The second calibration point has been stored in memory.
The aforementioned sequence can be repeated using different flow
rates so that a maximum of five calibration points can be stored
in memory. To exit the calibration procedure, the operator presses
and releases the Calibrate and Display button simultaneously. The
LCD 168 will then return to the numerical format. A blinking "No"
indicates a bad calibration, and the procedure must be repeated.
FIG. 24 is a graph which plots flow rate in gallons per minute
on the horizontal axis and the K-Factor in pulses per gallon on
the vertical axis. K-Factor is defined as the number of pulses or
signals generated by a meter per gallon of fluid passing through
the meter. Curve A is a five point curve for water passing through
the flow meter 1. The K-Factor for water various from approximately
590 pulses per gallon, to approximately 610 pulses per gallon, depending
on the flow rate through the flow meter 1.
If the operator wished to measure the flow rate of water through
the flow meter 1 he should select calibration curve A for thin
viscosity fluids. Water has a centipoise of one. Although the flow
meter 1 can be used to measure water, Applicants recommend that
it be used primarily for medium viscosity fluids such as agricultural
herbicides for the greatest degree of accuracy.
Curve E represents Roundup.RTM. herbicide, a Monsanto product,
at 40.degree. Fahrenheit. The K-Factor varies from approximately
615 to 670 depending on the flow rate. Curve C represents Roundup.RTM.
herbicide at 60.degree. Fahrenheit. The K-Factor likewise varies
from approximately 600 to 650 pulses per gallon. Curve B also represents
Roundup.RTM. herbicide at 80.degree. Fahrenheit with a K-Factor
which varies from approximately 600 to 655 pulses per gallon.
Curves B, C and E are based on empirical test data for the herbicide
Roundup.RTM. at various temperatures.
In order to prepare a factory calibration curve for the electronic
nutating disc flow meter, Applicants generate a hypothetical curve
D which is a rough average between the three actual curves, B, C
and E for Roundup.RTM.. If the electronic nutating disc flow meter
will be sold to a specific user, who is known to use Roundup.RTM.
herbicide as the predominate chemical, factory CAL B will be loaded
with the curve D shown on FIG. 24.
If the purchaser or intended user of the flow meter 1 is known
to use other specific herbicides, other factory calibration curves
can be installed in the flow meter for other specific agricultural
chemicals. For example, if the user is known to use Ciba Giegy chemicals,
such as Dual.RTM. herbicide, a specific factory calibration curve
can be specially loaded for this particular brand of herbicide in
CAL B.
FIG. 25 is a back plan view of the faceplate 30 with the circuit
board 166 in place. Along the perimeter of the bottom of the faceplate
30 is a downward facing shoulder 97 which engages an upward facing
shoulder 103 formed on the upper perimeter of the coverplate 12.
There are four holes, 106 108 112 and 114 formed in the faceplate
30 to allow screws to connect the faceplate 30 to the coverplate
12. A first female receptacle 128 and a second female receptacle
134 are formed in the faceplate 30. They respectively receive screws
50 and 52 for securing the battery cover 48 to the faceplate 30.
Formed as a integral part of the faceplate 30 is the battery holder
118. The battery 54 is supported in the battery holder 118. The
battery 54 connects to a terminal 122 which connects to the circuit
board 166 via the connectors 120. A rim 310 protrudes from the reverse
side 31 of the faceplate 30. The rim is sized to receive the circuit
board 166 which is held in place by screws 312 314 316 and 318.
The circuit board 166 is approximately three inches in length and
two inches in width, weighing less than one ounce with the pickup
coil 170 the connectors 120 and terminal 122 in place. This design
allows the flow meter 1 to be relatively compact and light weight
to facilitate installation adjacent to the dispensing nozzle. After
the circuit board 166 has been installed a potting material is poured
over the circuit board and is contained by the rim 310 to further
protect the circuitry. The pickup coil 170 is tall enough to protrude
beyond the level of the potting material.
The microprocessor 320 is positioned on the left hand side of the
circuit board 166. Applicant uses a Mitsubishi M50930 an 8-bit,
single-chip CMOS microprocessor. It has 4096 bytes of permanent
memory in the ROM (Read Only Memory) and 128 bytes of memory in
the RAM (Random Access Memory). The main operating program, the
permanent memory and all programing instructions are permanently
burned into the ROM. The RAM contains the background totalizer,
the batch register, the cumulative register and generally performs
all mathematical calculations using the formulas which will be described
herein. A EEPROM 322 is mounted on the right side of the circuit
board (electrically erasable programmable read only memory). To
the far right of the circuit board is EEPROM programming interface
connection 324 which allows the factory to program the EEPROM as
desired.
After each flow meter 1 has been manufactured it is placed on a
ballistic calibrator in the factory for testing. Due to manufacturing
tolerances each individual unit varies slightly from other units
previously manufactured. Testing on the ballistic calibrator allows
the factory to electronically adjust and compensate for these manufacturing
differences.
At the end of the production line is a ballistic calibrator. After
each unit comes off the production line, it is placed on the ballistic
calibrator and Stoddard brand solvent, which approximates water,
is pumped through each electronic nutating disc flow meter. The
ballistic calibrator empirically determines a five point K-Factor
curve for each specific unit based on the amount of solvent which
is pumped through the flow meter. This five point K-Factor curve
is loaded onto a floppy disc. This disc is transferred to a personal
computer which is connected to a translation station which connects
to the EEPROM programming interface 324.
This special five point curve would be ideal for a specific fluid,
such as Stoddard brand solvent or water, both of which have a low
viscosity, i.e. 1 or 2 centipoise. This specific curve is acceptable,
but not ideal for the entire range of thin viscosity fluids, i.e.
1 to 9 centipoise. To improve accuracy, the curve which has been
empirically determined on the ballistic calibrator is altered, by
a ratio, to a curve that better approximates a range of fluids between
1 to 9 centipoise. This altered curve is loaded in to the EEPROM
as CAL A for thin viscosity fluids of less than 9 centipoise.
The empirically derived curve is altered a second time by a different
ratio, to a curve that better approximates a range of fluids between
10 to 450 centipoise. This altered curve is into the EEPROM as CAL
B for medium viscosity fluids of 10 to 450 centipoise.
It has been determined that for a given unit the difference between
the K-Factor curve for Stoddard brand solvent, and the K-Factor
curve for thin viscosity fluids and the K-Factor curve for medium
viscosity fluids varies by a typical offset or ratio curve. The
personal computer has in its memory a series of offset values for
the thin viscosity fluid range and a different set of offset values
for the medium-viscosity fluid range. This information may sometimes
be referred to as the Calibration Curve Offset Table. This data
could be empirically derived by one skilled in the art for this
or other designs.
For standard production this personal computer selects offset data
from the Calibration Curve Offset Table, as appropriate for the
thin-viscosity fluid range, and uses the offsets to modify the empirically-derived
K-Factor curve from the ballistic calibrator. This yields a calculated,
modified cal curve appropriate for the thin-viscosity fluid range,
which curve is then programmed into the EEPROM of the electronic
nutating disc flow meter, as previously described, as the standard
production CAL A. This electronic adjustment sequence allows the
factory to correct for slight manufacturing differences between
each individual unit.
In addition, for standard production, the personal computer selects
offset data from the Calibration Curve Offset Table, as appropriate
for medium-viscosity fluid range, and uses the offsets to modify
the empirically-derived K-Factor curve from the ballistic calibrator.
This yields a calculated, modified cal curve appropriate for said
medium-viscosity fluid range, which curve is then programmed into
the EEPROM of the electronic nutating disc flow meter, as previously
described, as the standard production CAL B. This electronic adjustment
sequence allows the factory to correct for slight manufacturing
differences between each individual unit.
The computer also has various sets of data for specific brands
of thin viscosity fluids or medium viscosity fluids for custom programming.
For example, there is a data table for Avadex BW.RTM. brand herbicide,
a Monsanto product and another data table for ERADICANE EXTRA.RTM.
brand herbicide, an ICI product, both of which are thin viscosity
fluids. For custom production, the personal computer selects offset
data from the Calibration Curve Offset Table, as appropriate for
a specific brand of thin viscosity fluid, and uses the offsets to
modify the said empirically derived K-Factor curve from the ballistic
calibrator. This yields a calculated, modified cal curve appropriate
for the specific brand of thin viscosity fluid, which curve is then
programmed into the EEPROM of the electronic nutating disc flow
meter, as previously described, as custom CAL A. This electronic
adjustment sequence allows the factory to correct for slight manufacturing
differences between each individual unit.
In addition, for custom programming, the personal computer selects
offset data from the Calibration Curve Offset Table, as appropriate
for specific brands of medium viscosity fluid, and uses the offsets
to modify the empirically derived K-Factor curve from the ballistic
calibrator. For example, there is a data table for Roundup.RTM.
brand herbicide, a Monsanto product, another for Dual.RTM. brand
herbicide, a Cibi Giegy product, etc. This yields a calculated,
modified cal curve appropriate for the specific brand of medium
viscosity fluid, which curve is then programmed into the EEPROM
of the electronic nutating disc flow meter, as previously described,
as custom CAL B. This electronic adjustment sequence allows the
factory to correct for slight manufacturing differences between
each individual unit for specific fluids.
It is also within the scope of this invention to load into the
EEPROM various custom curves such as a thin viscosity calibration
without a medium viscosity calibration, a medium calibration without
a thin viscosity calibration, multiple thin viscosity calibrations,
or multiple medium viscosity calibrations. The advantage is better
accuracy.
Referring to FIG. 26 a partial block diagram in schematic form
illustrating the electronics of the flow meter 1 according to the
invention is illustrated. A signal generator disk 94 having a plurality
of ferrous slugs 199 therein is positioned in the central chamber
14. Signal generator disk 94 is rotated by movement of the fluid
through the flow meter inducing a sensing signal in pickup coil
170 each time a slug 199 passes in proximity to the coil 170. Amplifier
310 amplifies and filters the sensing signal generated by coil 170
and uses the amplified signal to control the operation of a bi-polar
transistor 320. In particular, bi-polar transistor 320 is switched
on and off in response to detection or no detection of a ferrous
slug 199 by coil 306 in order to provide a square wave pulse to
a microprocessor 320 having either a value of six volts (VCC) when
a slug 199 is in proximity to the coil 306 and zero volts when no
slug is present.
System oscillator 340 generates an oscillating signal which is
used as a clock to drive microprocessor 320 as well as used by the
other circuits for timing. The microprocessor 320 is driven by a
voltage regulator 350 which provides a constant system voltage VCC
for driving the microprocessor 320. This microprocessor periodically
drives the EEPROM 322. EEPROM 322 includes information such as lookup
tables, algorithms or other information which defines the relationship
between a K-factor and its corresponding flow rate. This information
is programmed at the factory prior to installation. Operator controls
370 including first dome switch 44 hereinafter display button,
and second dome switch 46 hereinafter calibrate button, are used
by the operator to control the display, calibration or other operation
of the flow meter 1 according to the invention. In addition, an
EEPROM programming interface 324 may be provided to permit external
calibration or control of microprocessor 320 and to permit additional
information to be dumped or otherwise programmed into EEPROM 322.
Additionally, the system includes a liquid crystal display 168 driven
by microprocessor 320 for indicating to the operator either information
relative to the programming operations which are occurring or the
present flow rate or batch flow rate. Microprocessor 320 includes
drivers for controlling the display of LCD 168. Optionally, the
electronics may be provided with an input (PULSIN) for externally
inputting sensing signals to the bipolar transistor 320 and an FET
395.
The flow meter 1 is designed to ensure that the microprocessor
320 operates at a low power level. This allows use of a small 9
volt transistor battery while maintaining adequate battery lifetime.
The CMOS (Complementary Metal Oxide Silicon) circuitry power requirements
as used in the Mitsubishi microprocessor 320 and operational amplifier
310 are known to be a small fraction of that of comparable NMOS
(N-Channel Metal Oxide Silicon) or bipolar circuitry (1/100 typical).
CMOS circuitry also allows the use of relatively high-value resistors
for pull-up and similar functions, thereby further reducing the
system's overall power requirements. The flow meter 1 takes full
advantage of CMOS circuitry including the use of a CMOS microprocessor
320 and operational amplifier 310.
All microprocessor based circuits require the presence of a clock
signal which is a high-frequency signal used to keep all of the
microprocessor's internal functions synchronized. A typical clock
frequency for the Mitsubishi microprocessor 320 would be 4 MHZ.
The flow meter 1 uses a lower frequency of 480 KHz, while still
maintaining adequate operating characteristics. Supply current is
reduced accordingly.
The CMOS Mitsubishi microprocessor 320 has special operating modes
which help to achieve power reduction (this is not unique to Mitsubishi;
microprocessors from other vendors often have similar modes). These
modes are called the "WAIT" mode and the "STOP"
mode. In these modes, certain normal operating functions of the
microprocessor 320 are switched off, thus reducing power usage.
The STOP mode is the more drastic of the two, since essentially
all functions are halted. This includes the clock, the LCD, the
timers, and all instruction processing. The STOP mode reduces power
consumption, from normal operation, by a factor of over 100. The
microprocessor 320 invokes STOP mode when the flow meter 1 is in
the sleep state.
The WAIT mode is an intermediate mode, during which only instruction
processing is stopped; the display, clock, and timers continue in
normal operation. The WAIT mode reduces power consumption, from
normal operation, by a factor of about 10.
It is important to understand that both of these reduced-power
modes are programmable, which means that careful program design
will maximize their effectiveness. STOP mode is automatically invoked
if the flow meter 1 is inactive for a period of time exceeding five
minutes (the unit falls "asleep").
The WAIT mode is intermingled with normal operation in such a way
that WAIT mode is invoked during all times when the unit is not
actually doing foreground processing as shown in FIG. 27. Thus there
will typically be about a 40% duty cycle, i.e., full power mode
is used about 40% of the time, with WAIT mode taking the remaining
60%.
Use of an EEPROM 322 is desirable in a flow meter to retain calibration
data and other seldom-changed customization parameters, but there
is a power-consumption penalty. The EEPROM 322 used in the flow
meter 1 is manufactured by Catalyst Semiconductor, Inc. of Santa
Clara, Calif. and is a model CAT59C11 although other brands of EEPROM
may be suitable and are within the scope of this invention. This
EEPROM 322 is rated by the manufacturer to consume a normal operating
current of as much as 5 milliamperes. This is a large current for
a battery powered system and would reduce battery life if energized
on a continual basis.
However, the microprocessor 320 does not need to consult the EEPROM
322 on a continuous basis. The program supplies power to the EEPROM
322 only for brief intervals when access is actually required The
EEPROM 322 is powered for just under 0.5 second out of each 60 seconds.
This is a duty cycle of about 0.8% which means that instead of 5
milliamperes, the EEPROM 322 imposes an extra burden of only about
0.04 milliamperes (normally even less, since the manufacturer's
rating is usually conservative).
CALCULATION OF VOLUMETRIC FLUID FLOW
As previously discussed, the present invention has two K-Factor
curves which are factory loaded and permanently stored in the memory
of the EEPROM 322; CAL A is for thin viscosity fluids and CAL B
is for medium viscosity fluids. In FIG. 24 curve D is the factory
curve which is loaded in the EEPROM for the herbicide Roundup.RTM..
This specific herbicide is relatively viscous and is approximately
175 centipoise at 60.degree. F. Other K-Factor curves can be loaded
into the EEPROM at the factory as CAL B, depending on the intended
use of the flow meter 1. For example, if the factory knows that
the intended user of the flow meter 1 typically applies Dual.RTM.
herbicide to his crops, a K-Factor curve can be loaded which is
specific for this brand. If the intended use is unknown, a generic
K-Factor curve is loaded as CAL B at the factory.
The following example will explain how the microprocessor 320 calculates
volumetric fluid flow. This example will use the K-Factor curve
D of FIG. 24 and assumes that it has been factory loaded into the
EEPROM as CAL B.
Referring to FIGS. 26 and 27 the process executed by microprocessor
320 according to the invention will be described. The steps described
in block diagram 27 may sometimes be described as foreground processing.
The accumulation of pulse counts during a one second period of time
in the background totalizer may sometimes be described as background
processing. Initially, the following data is factory loaded into
the EEPROM 322 for purposes of calculating flow volume.
First, the operator must select CAL A, CAL B or CAL C by using
operator controls 370. In this example, CAL B has been selected.
The data in Table 1 is transferred from the EEPROM 322 to the RAM
in the microprocessor 320. In order to calculate the volume of fluid
flowing through the electronic nutating disc flow meter, the following
formula is used:
NDV is the new value of the delta volume which is added at one
second intervals to the batch register and the cumulative register
within the RAM. NPR is the new pulse rate in pulses per second.
COEFA(b) is a coefficient selected from Table 1 under the column
listed COEFA. DPR is the delta pulse rate in pulses per second.
COEFB(b) is a coefficient selected from Table 1 under the column
COEFB. The K-Factors are the five calibration points on curve D
of FIG. 24.
In FIG. 26 the new pulse rate (NPR) is generated at one second
intervals. The signal generator disc 94 will be spinning in a clockwise
direction as liquid is passing through the flow meter 1. The pickup
coil 170 sends out a signal each time one of the ferrous slugs 199
passes underneath the sensor 170. The signal produced by the pickup
coil 170 is in the neighborhood of 20 to 25 millivolts, and is transferred
to an operational amplifier 310 were the signal is boosted to approximately
five volts. The operational amplifier 310 also filters out high
frequency signals for greater accuracy. The operational amplifier
310 generates a signal which selectively drives bipolar transistor
300 as a switch which, when closed, applies VCC to pin 27/INT1 to
microprocessor 320 to generate pulses each time a slug 199 is detected
by sensor 170. The pulses are then accumulated in a background totalizer
in the RAM in the microprocessor 320. The microprocessor 320 has
a clock which measures time in one half second increments. The new
pulse rate (NPR) is the total number of pulses accumulated in the
background totalizer for a one second period of time.
The batch register and the cumulative register in the RAM use BCD
numbers (Binary Coded Decimals) whereas the background totalizer
uses binary numbers.
The microprocessor 320 calculates a new delta volume (NDV) each
second while fluid is flowing through the flow meter 1 using the
aforementioned formulae and automatically adds the new delta volume
to the batch register and the cumulative register each second, thus
providing real time information to the operator. The operator therefore
will observe the amount of liquid that is actually flowing through
the dispensing nozzle on the LCD 168. The value on the LCD 168 will
change at one second intervals and will be incrementally increased
as a new delta volume is added to the batch register and the cumulative
register.
In order to better understand how the new delta volume is calculated,
the following examples will be given. Assume a new pulse rate (NPR)
of 60. This is generated as indicated in FIG. 26 by the signal generator
disc 94 which rotates in a clockwise fashion as fluid passes through
the flow meter 1. The signal is sensed by the pickup coil 170 it
is amplified and filtered, and accumulated in the background totalizer
as a binary number for a one second period of time. The new pulse
rate is converted into binary coded decimals in the foreground totalizer
in the RAM by step 402. The data in Table 1 has been previously
transferred by step 404 from the EEPROM 322 to the RAM for this
calculation sequence by selection of CAL B, by the operator by using
the operator controls 370. Assuming that NPR equals 60 the microprocessor
320 will determine that this pulse rate is bracketed between calibration
point two and calibration point three in Table 1. The program will
then select at step 408 the next lower one second pulse count value
(PR) which in this case is 54.6. At step 410 microprocessor 320
executes the program to then fetch or lookup COEFA(b) from the Table,
which in this example is 0.00153. The microprocessor 320 will then
calculate the baseline data volume (BDV) at step 412 by multiplying
the NPR times COEFA(b) which in this case will be 60.times.0.00153=0.0918.
At step 414 microprocessor 320 compares the NPR to the PR to determine
if the NPR is exactly the same as a table pulse rate (PR). In this
example, the NPR is 60 and there is no identical pulse rate (PR)
in Table 1. However, if the new pulse rate (NPR) had been identical
to a pulse rate of the table, the product (0.0918) which is a base
line delta volume, and would be incrementally added to the batch
register by step 416 and to the cumulative register by step 418
in the RAM. Obviously, the NPR does not equal the PR in very many
situations.
Continuing with the example, if step 414 determines that the NPR
is not equal to one of the pulse rates (PR) in the data table the
microprocessor 320 executes step 420 and subtracts the next lower
table value from the NPR to produce a delta pulse rate, i.e. 60-54.6=5.4.
The program will then execute step 422 to fetch or lookup the corresponding
coefficient B from the data table which in this case is 0.00036.
The program then executes step 424 and multiples the delta pulse
rate times coefficient B to yield the incremental delta volume in
gallons. The microprocessor 320 then adds the base line delta volume
to the incremental delta volume which yields the new delta volume
at step 426. The new delta volume is added to the batch register
at step 428 and to the cumulative register at step 430. The process
then returns to start so that it occurs once each second, therefore
providing the operator with real time data concerning the volume
of fluid dispensed through the flow meter 1. In our example, this
takes on the following values, assuming NPR=60:
In this example, 0.09374 gallons will be added to the batch register
and the cumulative register in the RAM which will display the new
volume on the LCD 168. When the battery is changed all data in the
RAM is lost. The batch register and the cumulative register in the
RAM therefore go to zero when the batteries are changed. The calibration
curve data is stored in the EEPROM 322 and is not lost when the
batteries are changed. |