Abstrict To measure the volume of fluid that has flowed past a point and
to actuate a sampler at certain increments of this volume, a stylus
of a flow meter moves to a distance from the center of rotation
of a rotating function disc, which distance is related to the height
of a float in the fluid stream, with the function disc including
a conductive portion having different arcuate lengths at different
distances from the center of rotation so that, as the disc rotates,
the stylus circumscribes a circle around the function disc at a
distance related to the height of the float and is in contact with
the conductive portion for a period of time that represents the
rate of flow of the fluid that corresponds to the height of the
float. Pulses representing in number the rate of flow of the fluid
during each revolution are applied to a counter while the stylus
contacts the conductive portion which accumulates them to form the
integral with respect to the time of the rate of flow, with the
output from the counter being used to actuate a liquid sampler at
predetermined increments of volume of fluid flowing past the float.
Claims What is claimed is:
1. Apparatus for measuring the rate of flow of a fluid through
a channel, comprising:
means for generating a signal proportional to the height of the
fluid flowing through the channel;
rotatable means;
said rotatable means including information stored in a form that
can be sensed;
means for sensing said information;
means for positioning said means for sensing said information and
said rotatable means with respect to each other in accordance with
the signal from the means for generating a signal proportional to
the height of the fluid flowing through the channel;
said means for sensing including means for generating a plurality
of pulses proportional in number to the rate of flow of fluid through
said channel from said information;
said information on said rotatable means including indicia indicating
a flow rate for at least certain heights of said fluid in said channel
whereby the rate of flow through the channel is corrected for non-linear
distortion; and
means for counting said pulses, whereby a signal is provided indicating
the amount of fluid flowing past said means for measuring the height
of the fluid in a fixed period of time.
2. Apparatus according to claim 1 further including a water sampler
connected to said means for counting said pulses; said counter including
means for activating said water sampler at preset counts of said
counter, whereby said water sampler is actuated at predetermined
increments of volume of fluid flowing past said means for generating
a signal.
3. Apparatus according to claim 2 in which the information is recorded
on said rotatable means as a pattern of light blocking indecia and
portions which do not block light.
4. Apparatus according to claim 2 in which said rotatable means
is a printed disc having the information printed upon it.
Description This invention relates to fluid flow meters.
One class of flow meter obtains a signal indicating a characteristic
of the rate of flow of the fluid such as a mechanical motion from
a float indicating the height of the fluid as it flows through a
weir. This signal is then corrected to compensate for the shape
of the weir and integrated to provide signals indicating the volume
of fluid flowing past the float. The signals from the integrator
may be used to actuate the fluid sampler at periodic increments
of volume of fluid flowing through the fluid meter.
In one type of prior art flow meters of this class, the signal
indicating the rate of flow of the fluid is an analog signal which
is integrated by a mechanical integrator to obtain the volume.
This type of prior art flow meter has several disadvantages, such
as: (1) because of the high friction within the integrator and heavy
weight of its parts, it is relatively inaccurate, being affected
by a large hysteresis as the level of the fluid rises and falls;
(2) the unit is heavy and difficult to handle because of the large
amount of power required and the relatively large and heavy parts
included in it; (3) the unit is expensive because of the large number
of relatively complicated and expensive parts; (4) the unit has
to be supplied with power more frequently and does not run untended
for long periods of time; (5) an excessive number of openings are
required in the meter to handle the various settings and these openings
cause the meter to be damaged after a long period of time by the
corrosive environment in which such meters are often used; and (6)
it is difficult to accommodate the meter to make measurements at
different locations because a correction must be applied to the
initial measurements and this correction is different for some locations,
thus requiring a different relatively expensive and difficult to
fabricate mechanical cam for such different locations.
Accordingly, it is an object of this invention to provide a novel
method and apparatus for measuring the rate of flow of fluids.
It is a further object of the invention to provide a novel method
and apparatus for actuating a liquid sampler.
It is a still further object of the invention to provide a novel
method and apparatus for measuring the volume of the fluid flowing
past a point.
It is a still further object of the invention to provide a novel
method and apparatus for generating a digital signal representing
a first variable such as the rate of flow of a fluid from an analog
signal representing a second variable related to the first variable
such as the height of the fluid as it flows at the rate to be determined.
It is a still further object of the invention to provide a method
and apparatus for calculating a variable such as the rate of flow
of a fluid from an analog value such as the height of a stream of
the fluid and simultaneously converting the variable into a digital
signal using the same equipment for both the conversion and the
calculation.
It is a still further object of the invention to provide a method
and apparatus for obtaining a digital signal representing the rate
of flow of a fluid from a mechanical motion representing another
related characteristic of the fluid.
It is a still further object of the invention to provide a novel
method and apparatus for enabling a flow meter to be easily and
economically adapted to measure the rate of flow of the fluid under
different conditions requiring a different calculation for the flow
rate.
It is a still further object of this invention to provide a novel
flow rate meter which is especially light in weight, accurate, has
low hysteresis in operation and is economical to construct and operate.
In accordance with the above and further objects of the invention,
a flow rate meter is provided having: (1) fluid characteristic measuring
apparatus for obtaining a signal containing information indicating
the rate of flow of a fluid and also other irrelevant information
such as the nonlinear distortion of the information indicating rate
of flow caused by a weir as described more fully hereinafter; (2)
a function operator for removing the irrelevant information from
the signal and for converting the signal to a form easily processed;
and (3) a calculator section for integrating the signal with respect
to time to provide another signal indicating the volume of liquid
that has flown past a given point.
One type of fluid characteristic measuring apparatus for obtaining
a signal containing information representing the rate of flow of
the fluid includes a float positioned in stream of the fluid and
attached to a shaft to impart an angular displacement to the shaft
representing the changes in the height of the float. However, there
are other types of apparatuses that may be used with the invention
to generate signals containing information representing the rate
of flow of the fluid. These apparatuses generally develop a signal
that includes errors due to nonlinear distorting of the information
as well as the information representing the rate of flow of the
fluid.
To remove the distortion from the signal, the function operator,
in one embodiment, includes a shaft, a function disc and a movable
electric contact stylus, with the contact stylus having one end
mounted to the shaft and having its other end movably positioned
in intimate contact with and movable with respect to the function
disc. The function disc rotates at constant angular velocity such
that the end of the stylus that is in intimate contact with the
rotating disc assumes a position a distance from the center of rotation
of the rotating function disc that is related to the distorted signal
containing the rate of flow information. As the function disc rotates,
the end of the movable electrical contact stylus describes circles
on the face of the disc having radii related to the magnitude of
the signal.
The function disc includes a conductive portion and shaped such
that, in each circular path of the stylus, the ratio of the arc
length of the conductive portion to total length of the circle is
the same as the ratio of the function of the signal that represents
the rate of flow of the fluid to the full scale rates of the apparatus
so that the time the stylus is in contact with the conductive portion
during each revolution of the rotating function disc is proportional
to the rate of flow of the fluid. In one embodiment the conductive
portion is energized with periodic electrical pulses from a pulse
generator and in another embodiment the pulse generator is turned
on when the stylus is in contact with the conductive portion and
turned off when it is not in contact with the conductive portion.
In both of these embodiments, a series of periodic electrical pulses
are made available when the stylus is in contact with the conductive
portion. The rotating function disc is conveniently prepared by
conventional printed circuit techniques from computer generated
information on a plastic disc and a separate disc may be substituted
for each set of different measuring conditions.
In another embodiment, the function disc includes a portion that
passes light and a portion that blocks light rather than conductive
and nonconductive portions and a light sensing device is radially
positioned with respect to the disc by the shaft rather than an
electrical contact stylus. The light passing portion is periodically
energized by a lamp on the opposite side of the disc, which lamp
is periodically illuminated so that the light sensing device receives
light pulses when it is opposite to the light passing portion.
To convert the signal that is proportional to the rate of flow
of the fluid into a form easily processed, the function operator
includes a pulse generator connected in the one embodiment to a
brush that electrically energizes the conductive portion of the
rotating function disc with periodic pulses so that the movable
contact stylus is energized by periodic electrical pulses when it
is in contact with the conductive portion of the rotating function
disc and not at other times and in another embodiment the pulse
generator is turned on when the movable contact stylus is in contact
with the conductive portion and turned off when it is not in contact
with the conductive portion. In still another embodiment, the pulse
generator is electrically connected to the lamp to periodically
energize the light sensor when it is opposite to the light passing
portions of the rotating function disc. Accordingly, the number
of pulses applied to the movable contact stylus generated by the
pulse generator or generated by the light sensor in each complete
revolution of the rotating function disc is proportional to the
rate of flow of the fluid.
The pulses from the contact stylus pulse generator or light sensor
are applied to a counter, which integrates the rate of flow of the
fluid with respect to time by counting the pulses. The output taps
of the counter are used to actuate a liquid sampling device at predetermined
increments of volume of the flow of the liquid.
It may be understood from the above description that the flow meter
of this invention has several advantages, such as: (1) it is inexpensive
because of its simplicity and small number of parts; (2) it is light
in weight and easy to handle because its parts are light and a relatively
small power supply is sufficient; (3) it is highly accurate since
it has few moving parts and these are light in weight and operate
with little friction; (4) it operates for a relatively long period
of time without being reset; (5) it is durable and able to resist
corrosive environments in which it may be used because it has few
openings; and (6) it is easily adjusted for different uses by replacing
the function disk.
The above-noted and other features of the invention will be better
understood from the following detailed description when considered
with reference to the accompanying drawings in which:
FIG. 1 is a simplified perspective view of a flow meter according
to an embodiment of the invention;
FIG. 2 is a simplified diagramatic view, partly in perspective,
of the moving parts of the flow meter of FIG. 1; and
FIG. 3 is a diagramatic view of the principal electrical parts
of the flow meter of FIG. 1.
In FIG. 1 there is shown a perspective view of a flow meter 10
mounted in operating position with respect to a weir 12 to monitor
the flow of fluid therethrough, with the flow meter 10 including
a float assembly 14 and a metering assembly 16.
The metering assembly 16 includes a housing 18 which contains and
protects the operating parts of the metering assembly 16. The housing
18 consists of corrosion resistant materials such as plastic and
stainless steel and is liquid tight to protect the internal operating
parts. The top is of transparent plastic so that the controls can
be observed from the top as will be hereinafter more fully explained.
To mount the housing 18 a vertical mounting plate 20 is fastened
to one side of the housing 18 and includes near the edges of its
vertical sides four elongated vertically arranged slots, two of
which are shown in FIG. 1 at 22A and 22B. The slots are adapted
to receive fasteners such as bolts by which the vertical mounting
plate 20 and therefore the housing 18 are mounted to a vertical
wall, which may be one wall of the weir 12 as shown in FIG. 1. The
elongated slots permit the mounting plate 20 and housing 18 to be
positioned at different selected vertical heights, which provides
one manner of calibration as will be described more fully hereinafter.
To provide the basic indications from which the flow meter 10 calculates
the rate of flow of the fluid, the float assembly 14 includes a
float arm 26 and a float 24 resting within a body of water flowing
through the weir 12 with the float arm 26 being connected at one
end to the float 24 and at the other end to a meter input shaft
28. The float arm 26 extends in a direction transverse to the meter
input shaft 28 so that, as the float 24 rises and falls with the
level of the fluid within the weir 12 the meter input shaft at
28 rotates in a first direction as the float rises and in a second
direction as the float falls.
The weir 12 is a conventional V-notch weir having vertical walls,
two of which are shown at 30 and 32 with the wall 30 supporting
the vertical mounting plate 20 and the wall 32 being a vertical
retaining wall connected to the wall 30 and having a V-shaped notch
at 34 so that the retaining wall 32 creates a water head in which
the float 24 floats and permits the water to flow through the V-notch
34.
Although in FIG. 1 the float assembly 14 and the weir 12 are shown
cooperating with the metering assembly 16 to provide basic measurements
from which the metering assembly determines the rate of flow of
fluid, other conventional arrangements may be used to provide basic
indications. For example, a still well may be used with a different
type of float, actuated from a pulley in a conventional manner.
Moreover, mechanisms which do not utilize a float at all may be
used such as: (1) echo ranging devices which determine the height
of the water by timing ultrasonic sound vibrations or electromagnetic
radiations that are reflected from the surface of the water; or
(2) pressure measuring apparatuses which measure the pressure required
to bubble fluid to the surface of the water or the pressure created
in the direction of the flow of the fluid.
While many different types of arrangements may be used to provide
the basic data concerning the flow rate, particular benefits are
obtained by using devices which measure the height of the liquid
and provide indications of this height to the metering assembly
16.
In FIG. 2 there are shown, in a simplified diagrammatic perspective
view, the float assembly 14 and the operating parts of the metering
assembly 16 as they are connected together for operation.
The metering assembly 16 includes a function operator section 36
and a calculating section (not shown in FIG. 2) with the function
operator section being connected to the float assembly 14 through
the meter input shaft 28 to receive the basic measurements indicating
rate of flow of the fluid and to the calculating section within
the electronic portion 38 to which it provides a signal indicating
the amount of fluid that has passed the float. As will be explained
in greater detail hereinafter with reference to FIG. 3 the calculating
section uses this information to generate actuating signals such
as signals to start a water sampler.
To operate on the basic measured data by a function, the function
operator section 36 includes a function disc assembly 40 and an
operator assembly 42 with the function disc 44 and an electrical
motor 46 connected to the function disc 44 through an output shaft
48 to rotate the function disc. The function disc 44 is a rotatable
plastic disc having a conductive portion 45 on one surface, with
the conductive portion being shaped to provide a desired function
as more fully explained hereinafter. The operator assembly 42 includes
the meter input shaft 28 a moving contact stylus 50 and a stationary
contact stylus 52.
To operate on the function disc assembly 40 the moving contact
stylus 50 of the operator assembly 42 is electrically conductive,
having its moving point in intimate contact with the function disc
44 and its other end mounted for rotation with the shaft 28 so that
as the shaft 28 rotates from angular position to angular position
in response to changes in the position of the float 24 the point
of the moving stylus 50 moves to different radial distances from
the shaft 48 and hence describes different circles on the function
disc 44 as the function disc 44 is rotated by the electrical motor
46 which different circles each represent a different position
of the float 24.
To provide a stored function to the operator assembly to remove
the distortion from the basic information, the conductive portion
45 of the function disc 44 is arranged so that the function represented
thereby has a length of a radius from the shaft 48 as its independant
variable an arc of a circle on the conductive portion 45 at that
distance as its dependant variable so that the distance of the point
of the moving stylus 50 from the shaft 48 corresponds to the angle
of the meter input shaft 28 and hence to the height of the float
24 and the time during a rotation of the disc that the point of
the moving stylus 50 contacts the conductive portion of the disc
44 represents the rate of flow of the liquid corresponding to this
height of the float 24.
To convert the signal represented by the time the movable stylus
50 is in contact with the conductive portion 45 of the function
disc to signals that are easily used for calculations, the fixed
contact stylus 52 has one end in contact with the conductive portion
45 of the function disc 44 and the other end electrically connected
in circuit with the moving stylus 50 so that a circuit is completed
when both the moving contact stylus 50 and the stationary contact
stylus 52 are contacting the conductive portion of the function
disc 44. The stylus 52 makes contact with the conductive portion
of the function disc 44 at a location where there is a continuous
annular conductive portion with a center about the shaft 48 so that
the fixed contact stylus 52 is always in electrical contact with
a conductive portion of the function disc 44. With this arrangement,
the portion of the time that a circuit is completed between the
moving contact stylus 50 and the stationary contact stylus 52 corresponds
to the function represented by the conductive portion 45 of the
disc 44 and therefore the flow rate of the fluid.
Instead of having a conductive portion 45 the function disc 44
may include a portion that passes light. In this embodiment, the
stylus 50 includes a light sensor at its tip and the reverse side
of the function disc is periodically illuminated to provide the
same digital output as when a conductive portion is used but without
as much wear or friction between the parts.
To enable the shaft 28 to rotate freely and to prevent damage to
the operating parts of the metering assembly 16 the input shaft
28 near its end that is connected to the float arm 26 passes through
a seal 54 in the housing 18 with other space-apart portions of
the shaft 28 being rotatably mounted within first and second bearings
56 and 58.
To provide a visual indication of the height of the liquid in the
weir 12 a liquid height reference assembly 60 is provided having
a liquid height reference pointer 62 and a liquid height reference
scale 64. The liquid height reference pointer 62 is mounted at one
end to the meter input shaft 28 and points at its other end to markers
on the liquid height reference scale 64 with the central portion
of the liquid height reference pointer extending radially outwardly
from the shaft 28 so that the pointer moves along the liquid height
reference scale, pointing to different marks on it, as the meter
input shaft 28 rotates from angular position to angular position.
While the function-operator section 36 utilizes a function disc
44 having a conductive portion or a light passing portion indicating
the desired function, obviously other types of function-operating
apparatuses can be used. To be suitable, a function-operating apparatus
must be able to remove the irrelevant information and either provide
a signal that can be easily integrated or that can be converted
to a signal that can be easily integrated.
However, because of its simplicity, the function disc 44 has particular
advantages in the fluid meter 10 described herein. One advantage
is that a function disc can be prepared using existing printed circuit
techniques. Accordingly, different function discs may be inexpensively
made available to provide the necessary function for different shaped
weirs or for other modifications to the equipment that require a
change in the function. Moreover, the function can be computer generated.
A second advantage is that the function disc is easily replaceable
and may be conveniently ordered and shipped by mail because of its
compact size and light weight. A third advantage is that only a
small amount of power is required to drive the function disc.
In FIG. 3 there is shown a simplified diagrammatic view of the
electronic portion 38 cooperating with the function disc 44 and
including a fixed frequency pulse generator 66 a counter 68 and
a switch 70 with the fixed frequency pulse generator 66 being part
of the function operator section and the counter 68 being the principal
part of the calculating section. The switch 70 connects the outputs
of the counter 68 to a recorder 71 and a water sampler 73.
The fixed frequency pulse generator 66 is electrically connected
to the fixed contact stylus 52 and the counter 68 is electrically
connected to the moving contact stylus 50 or the pulse generator
66 is always connected to the counter 66 and activated or deactivated
by an electrical connection through the styli 50 and 52. With this
arrangement, fixed frequency clock pulses are applied from the fixed
frequency pulse generator 66 to the fixed contact stylus 52 and
to the moving contact stylus 50 through the conductive portion of
the function disc 44 which applies them to the counter 68. In the
alternative, the fixed frequency pulse generator may be connected
to a gas discharge lamp 69 in an embodiment in which the function
disc 44 includes a transparent portion 45 and a light sensor is
connected to the counter 68.
The counter 68 includes a plurality of outputs, each of which is
connected to a different fixed contact of the multiple position
switch 70. The moving contact of the multiple position switch 70
is moved to a selected position to determine the number of counts
applied from the fixed frequency pulse generator 68 through the
function disc 44 before an output signal from the flow meter 10
is provided to a controlled device and recording equipment. The
controlled device may, for example, be a water sampler 73 which
is activated to draw a sample of liquid from a body of the liquid
each time that a pulse is applied to it through the switch 70.
In assembling the flow meter 10 the function disc 44 is prepared
with the proper function 45 to accommodate the location of the liquid
level sensing apparatus, which in the preferred embodiment is a
float assembly. In the preferred embodiment, the function disc receives
information from the operator section 42 which indicates the level
of the liquid in the weir 12 and converts this information into
signals indicating the rate of flow of the liquid through the body
of water containing the weir. For a V-notch weir and a float of
the type shown in FIG. 1 the rate of flow of the liquid is proportional
to the change in the level of the fluid raised to the five halves
power. However, other types of measuring arrangements require a
different function and a different function plate must be formed
for each different function.
Function plates for different applications of the flow meter 10
are easily fabricated using printed circuit techniques. The appropriate
function is prepared by a computer and a conductive material is
applied to a plastic disc by photographic techniques in accordance
with any of the many prior art methods for performing this operation.
Sometimes the actual environments for measuring the rate of flow
are relatively standardized, so that a relatively few different
function discs will satisfy a large number of applications for the
flow meter. However, different function discs may be easily substituted
within a given flow meter and be economically shipped from place
to place so that the flow meter 10 is well adapted for use in making
measurements in a number of different locations.
To mount the flow meter 10 for measuring the rate of flow of the
liquid, the vertical mounting plate 20 is positioned adjacent to
a vertical wall, which may be the vertical wall of the weir 12
in front of which the float 24 floats. The vertical mounting plate
is mounted to the wall by means of bolts fastened through the wall
within the slots 22 at such a location that the float 24 rests in
the liquid within the weir area with room to rise and fall with
changes in the liquid level without rising above the bottom surface
of the metering assembly 16 (FIG. 1).
To adjust the metering assembly 16 in vertical height above the
level of the liquid, the bolts are loosened and the metering assembly
is moved upwardly or downwardly, with the bolts sliding within the
elongated vertical slots 22. The position of the metering assembly
may be selected so that the liquid height reference pointer 62 points
to a zero reference mark or other calibration mark on the liquid
height reference scale 64 when the float 24 is floating freely in
the liquid at a selected reference level of the liquid. In this
manner, the liquid height indicator is properly calibrated by positioning
the metering assembly 16 on the vertical wall of the weir.
In operation, the fluid meter 10 first obtains basic indications
from the liquid, which indications contain information concerning
the rate of flow of the fluid and also distortion imparted to the
indications by factors such as the shape of the channel in which
the fluid flows. These indications are operated upon with the function
incorporated within the fluid meter 10 to remove the irrelevant
information and to convert the relevant information into a form
that is easily processed to indicate the rate of flow of the fluid.
The rate of flow of the fluid is then integrated to provide information
concerning the volume of fluid that is flowing and this information
is used to generate control signals that may be used for a variety
of purposes, one of which is to actuate a liquid sampler to draw
a sample from the body of water.
To obtain basic indications containing information about the rate
of flow of the fluid, the float 24 floats within the weir 12. The
liquid level within the weir 12 rises as the rate of flow rises
and falls as the rate of flow falls causing the float 24 to rise
and fall in a manner indicating the rate of flow of the fluid in
the body of water.
The indications containing information about the rate of flow are
imparted to the meter input shaft 28 through the float arm 26 which
rotates radially about the meter input shaft 28 as the float 24
rises or falls, turning the meter input shaft 28 in a manner that
reflects the rate of flow of the liquid.
The rotating of the meter input shaft 28 is not ordinarily directly
proportional to the rate of flow of the fluid because increase or
decrease in the height of the float 24 is also affected by other
irrelevant information such as by the nature of the weir 12. In
a V-notch weir, such as that shown in FIG. 1 the rate of flow of
the fluid is proportional to the changes in the height on the liquid
within the weir to the five halves power.
To remove the irrelevant information, the basic indications containing
information about the rate of flow of the liquid are imparted by
the rotation of the meter input shaft 28 to the moving contact stylus
50 (FIG. 2) which rotates about and with the rotation of the meter
input shaft 28 its outer end moving in intimate contact with the
function disc 44 to assume a different radial distance from the
shaft 48 for each different angular position of the meter input
shaft, thus assuming positions with respect to the function disc
44 which are related to the basic indications containing information
about the rate of flow of the fluid. While the end of the stylus
50 contacts the discs 44 the motor 48 is rotating the function
disc 44 about the shaft 46 so that the moving point of the moving
contact stylus 50 describes circles against the function disc 44
which circles vary in diameter with the basic indications.
Each different radius circle described by the moving end of the
moving contact stylus 50 crosses a different part of the conductive
portion 45 of the function disc 44. The conductive portion of the
function disc 44 is prepared so that each of the different diameter
circles about the shaft 48 corresponds to a different function that,
when operated upon by the operator section 42 removes the irrelevant
information from the indications containing both the irrelevant
information and information concerning the flow rate of the liquid.
To remove the irrelevant information, the conductive portion 45
is arranged so that the time during each revolution of the function
disc 44 that the moving end of the moving contact stylus 50 is describing
an arc across the conductive portion compared to the time of a complete
revolution of the function disk is proportional to the flow rate.
The moving end of the moving contact stylus 50 is positioned by
the meter input shaft 28 to describe the correct diameter circle
on the function disc 44 for each level of the fluid in the weir
12 as the function disc 44 rotates.
To obtain a signal that is easy to process and is proportional
to the flow rate of the liquid, the fixed frequency pulse generator
66 in one embodiment (FIG. 3) applies periodic electrical pulses
to the contact stylus 52 so that the conductive portion of the function
disc 44 is continually energized with periodic electrical pulses.
As the moving end of the moving contact stylus 50 crosses the conductive
portion of the function disc 44 it receives the periodic electrical
pulses from the conductive portion and applies them to the counter
68. In another embodiment, an electrical connection between the
moving contact stylus 50 and the contact stylus 52 through the conductive
portion energizes the pulse generator 66 causing it to apply pulses
directly to the counter 68. Accordingly, the counter 68 receives
a number of pulses that is proportional to the time that the moving
end of the moving contact stylus 50 is describing an arc across
the conductive portion of the function disc 44. Thus, the number
of pulses applied during each revolution of the function disc 44
to the counter 68 represents the flow rate of the liquid.
This process is essentially the same when the function disc 44
includes a light passing portion 45 rather than a conductive portion
with the fixed frequency pulse generator 66 being connected to the
lamp 69 and the counter 68 being connected to the light sensor 50.
To integrate the flow rate of the liquid to provide indications
of the volume of fluid that has flowed past the fluid meter, the
switch 70 is set at a selected one of the fixed contacts connected
to selected ones of the outputs of the counter 68. With the switch
70 in the set position the counter 68 counts the number of pulses
for each revolution of the function plate 44 that represents the
rate of flow of the liquid during the time of that revolution. Since
the function disc 44 rotates at a constant speed, the sum of the
pulses applied to the counter 68 during each revolution represents
the integral of the rate of flow of the liquid with respect to time
and therefore the amount of fluid flowing past the flow meter. When
the counter reaches the output connected to the armature of the
switch 70 a pulse is applied indicating that the selected volume
of liquid has flowed past the fluid meter 10. This signal may be
used to actuate a sampling device to draw a sample from the liquid.
From the above description it can be understood that the fluid
meter has several advantages, such as: (1) it is inexpensive; (2)
it is light in weight and easy to handle; (3) it is highly accurate;
(4) it operates for a relatively long period of time without being
reset; and (5) it is durable and able to resist corrosive environments
in which it may be used.
The fluid meter 10 is economical because it has relatively few
parts and these parts are inexpensive. The integration of the flow
rates is performed by an inexpensive counter. The operation of calculating
the relationship between the basic indications and the actual rate
of flow of the liquid is accomplished by an inexpensive printed
circuit disc and moving stylus arrangement. Moreover, it is inexpensive
to adapt the meter for use in different environments since it is
only necessary to change the function disc, which is a relatively
inexpensive unit and easily replaced, to accommodate different measuring
conditions.
The flow meter 10 is light in weight and easy to handle because
it has few moving parts and does not require any substantial amount
of power. The electrical circuit requires a very low power to operate
and since it consists essentially of a counter and a pulse generator,
both of which may operate at low power levels. There are few moving
parts and these moving parts are very light in weight, thus not
requiring any substantial amount of power. Since a relatively low
power is required a heavy power supply is not necessary and the
apparatus is easy to handle and move.
Because of the low power requirement, the unit may run for a long
period of time without being reset. The primary consideration in
resetting such a unit is the length of time it can run on the power
stored within it.
The fluid meter 10 only has one opening that accommodates a continuously
moving part. This is the opening accommodating the meter input shaft
28. There is also an electrical inlet and an inlet for selecting
the volumes of liquid at which a signal is to be provided. However,
these inlets do not move and may be easily sealed. Because the inlets
are easily sealed and the casings are of corrosion resistent material,
the unit is able to withstand the corrosive environments for long
periods of time.
The fluid meter 10 is also very precise. It is precise because
there is a relatively low amount of friction. The only moving part
is the continuously rotating function disc 44 and the slowly moving
input shaft and movable contact stylus 50 and these parts have very
little friction.
Although a specific embodiment of the invention has been described
in some detail, many modifications and variations in the preferred
embodiment are possible without deviating from the invention. Therefore,
it is to be understood, that within the scope of the appended claims,
the invention may be practiced otherwise than is specifically described. |