Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to an apparatus for measuring
the flow rate of a liquid, and in particular to an apparatus
for measuring the flow rate of an electrically conductive
liquid.
The apparatus is specifically designed for measuring
the flow rate of aqueous solutions of agricultural chemicals,
so that the quantity of chemical applied over a given area
can be accurately calculated. Agricultural chemicals may be
hazardous to the user and to the environment. In order to
avoid crop injury or poor performance because of the
application of incorrect quantities of chemical, it is
important that the flow rate of a crop sprayer be accurately
determined. Existing flow measuring devices are unduly
complicated, often inaccurate and may include moving parts.
The object of the present invention is to overcome
the above-mentioned problems by providing a relatively
simple, compact apparatus for accurately measuring the flow
rate of an electrically conductive liquid.
Accordingly, the present invention relates to an
apparatus for measuring the flow rate of an electrically
conductive liquid comprising container means for receiving a
predetermined quantity of a flowing liquid; electrical power
supply means; computer means connected to said power supply
means; first probe means for initiating operation of the
apparatus when liquid flowing into said container means
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closes a circuit between said first probe means, said power
supply means and said computer means; second probe means
connected to said computer means, whereby when the liquid
closes a circuit between said first and second probe means,
the computer means can determine the flow rate based on the
volume of said container means and the time required to close
the circuit between said first and second probe means; and
display means connected to said computer means for providing
a visual indication of the flow rate.
The invention will be described in greater detail
with reference to the accompanying drawings, which illustrate
a preferred embodiment of the invention, and wherein:
Figure 1 is a schematic, exploded, perspective view
of a container for use in the apparatus of the present
invention;
Figure 2 is a schematic block diagram of an
electrical circuit used in the apparatus of the present
invention;
Figure 3 is a detailed circuit diagram of the
electrical circuit of Fig. 2; and
Figure 4 is a block diagram illustrating the manner
in which the components of Fig. 3 are to be arranged to form
a complete drawing.
It should be noted that in order to simplify
illustration of the invention parts have been omitted from
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the drawings, particularly from Figure 2.
With reference to Fig. 1, one of the basic
components of the apparatus of the present invention includes
a casing 100 defined by a bottom wall 101, a top wall 102, a
rear wall 103, side walls 105 and a front cover plate 106.
An opening 107 is provided in the cover plate 106. The
opening 107 is closed by a window 108, which covers a liquid
crystal display 110, which is mounted on a plate 111. The
plate 111 also carries the remaining circuitry (Figs. 2 and
3), and a power supply, i.e. batteries 112 (Figs. 2 and 3)
are mounted in the casing.
The casing 100 houses a container generally
indicated at 114. The container 114 is defined by a pair of
parallel tubes 116 and 117, which extend upwardly through
openings 118 in the top wall 102 of the casing 100. One of
the tubes 116 is longer than the other tube 117, extending
upwardly beyond the top wall 102.
A first probe 120 (Figs. 2 and 3) extends into the
bottom end of the tube 116. Four additional probes 122, 123,
124 and 125 extend into the tube 117. The bottom ends of the
tubes 116 and 117 are connected by a horizontal tube 127.
Referring to Fig. 2, the probes 120 and 122 to 125
are incorporated into a circuit including a power supply
defined by the batteries 112 (Fig. 3). The batteries 112 are
used to provide power to the remaining elements of the
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circuit, even though the appropriate connecting lines have
been omitted from Fig. 2. This feature of the invention is
described in greater detail hereinafter. The probes 123 to
125 are connected to a microprocessor 129, which is
controlled by a pair of selector switches 130 and 131, and a
tri-state buffer 132. The microprocessor 129 is connected
through a latch 134 to a memory (ROM) 135. The
microprocessor 129 is also connected to a display driver 137
and the liquid crystal display 110. Voltage from the
batteries 112 to the various components of the circuit
including the display driver 137 is controlled by a voltage
regulator 138.
The operation of the apparatus will be described
with reference to Fig. 3. In general terms, the purpose of
the apparatus is to measure the flow rate of an agricultural
chemical through sprayer nozzles. A mathematical combination
of the predetermined volume of the container 114, and the
length of time required to fill the volume between the probes
123, 124 and 125 is used to determine the flow rate. By
entering the spacing between ad~acent nozzles and the
travelling speed of the sprayer, using the switches 130 and
131, respectively, the apparatus can be used to determine the
quantity of liquid per unit area.
Power for the apparatus is provided by two nine volt
batteries 112, which are connected to two diodes 140. The
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diodes 140 protect the circuit of Fig. 3 from reverse power
connection. The negative terminals of the batteries 112 are
connected to ground by line 141. The power and logic levels
from the ground line 141 to the chips defining the
microprocessor 129, the buffer 132, the latch 134, the memory
135, hex buffers 143 for the probes, and the display driver
137 are as follows: pins 7 and 20 of the microprocessor 129;
pin 10 of the buffer 132; pins 1 and 10 of the latch 134;
pins 2, 14 and 22 of the memory 134; pin 8 of the hex buffer
143 and pin 1 of the display driver 137. The nine volt
positive power line extends from the diode 140 to the nine
volt probe 120 in the tube 116. The nine volt positive power
line also supplies power to the hex buffer 143 and the
emitter of a switching transistor 145. -
As water or an aqueous solution of a chemical is
introduced into the longer tube 116, the water flows through
the tube 127 into the tube 117. Thus, the water contacts
both the start probe 122 and the nine volt probe which causes
current to flow through resistors 146 and 147 to ground. The
potential at the pin 7 of the buffer 143 is raised
sufficiently to drive the output pin 6 to a high potential.
The high potential causes current to flow through diode 149
to charge a capacitor 150 to a high potential. A capacitor
152 connected to the resistor 146 of the start probe 122 is
connected from the pin 7 of the buffer 143 to ground to help
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reduce "noise" on the input of the circuit. From the high
potential at pin 6 of the buffer 143 sufficient current flows
through the diode 149 to overcome the draining effect of a
resistor 153. The high potential then causes current to flow
S through a resistor 154 to drive the potential at pin 5 of the
buffer 143 high, which in turn drives the output pin 4 high.
The current from the high potential then flows through a
resistor 156 to the base of a switching transistor 157, and
through the emitter of the transistor to ground. With the
extra current flowing through the base of the transistor 157,
the internal resistance from the collector to the emitter of
the transister is reduced which allows more current to flow
from the nine volt supply line through the transistor 145, a
resistor 158 and the transistor 157 to ground. The extra
current through the base of the transistor 145 allows the
resistance between the collector and emitter of the
transistor to be greatly reduced which permits the current
from the nine volt supply to flow into the emitter of the
transistor 157 and through the collector thereof to the input
of the voltage regulator 138.
With the input voltage at seven volts or higher and
the ground pin of the voltage regulator 138 connected to
ground, the voltage regulator will provide a steady five volt
supply relative to the ground line. The five volt supply is
connected to the pins 5, 6, 26 and 40 of the microprocessor
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129, pin 20 of the buffer 132, pin 20 of the latch 134, pins
1, 27 and 28 of the memory 135, and pin 20 of the display
driver 137 for supplying power to the chips and to the logic
control on some of the chips.
When water is removed from the measuring container
114, i.e. when the tubes 116 and 117 are tilted to empty
them, current flow from the nine volt probe 120 to the start
probe 122 is cut, and the small charge on the capacitor 152
drains to ground through the resistor 147 in milliseconds or
less. With the resistor 147 holding the pin 7 of the buffer
143 low, the output pin 6 of the buffer 143 is also low.
With the diode 149 blocking reverse flow from the charged
capacitor 150, the charge and voltage will slowly drain
through the resistor 153 to ground with some flow through the
15 resistor 154 and the buffer 143 to ground. The charge on the
capacitor 150 remains high enough to keep the pin 5 of the
buffer 143 in the "high" input state and therefore maintains
power for approximately forty to fifty seconds. In other
words, the display still provides a reading even after the
container 114 has been emptied.
When water introduced into the container 114 passes
the start probe 122 and reaches the low probe 123, current
flows through the nine volt probe 120 and the water to the
low probe 123. The current then flows from the low probe 123
25 and through resistors 160 and 161 to ground. A capacitor 163
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connected from pin 14 of the buffer 143 to ground is intended
to reduce the input noise. With current flowing through the
resistors 160 and 161, the potential at the pin 14 of the
buffer 143 is sufficiently high to drive the output pin 15 on
the buffer to a high potential. With a high potential at pin
115 of the buffer 143, current will flow through a resistor
164 to pin 35 of the microprocessor 129, and will change the
input pin 35 from a low potential to a high potential. A
pull down resistor 164(a) reduces the high potential level at
the pin 35 to an acceptable level and helps produce the low
level input.
When the water level rises to the middle or medium
probe 124, current flows from the nine volt probe 120 through
the water to the medium probe 124, and through resistors 166
and 167 to ground. A capacitor 168 connected from pin 11 of
the buffer 143 to ground is intended to reduce the input
noise. With current flowing through the resistors 166 and
167, the potential at pin 11 of the buffer 143 is
sufficiently high to drive the output pin 12 of the buffer
143 to a high potential. With the high potential at the pin
12, the current flows through a resistor 170 to pin 36 of the
microprocessor 129, changing the input pin 36 from a low
potential to a high potential. A pull down resistor 170(a)
reduces the high potential level at the pin 36 to an
acceptable level and helps reduce the low level inputs.
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When the water level reaches the high probe 125,
current flows through the nine volt probe 20 and the water to
the high probe 125. The current then flows from the high
probe 125 through resistors 171 and 172 to ground. A
capacitor 174 connecting pin 9 of the buffer 143 to ground is
intended to reduce the input noise. With current flowing
through the resistors 171 and 172, the potential at the pin 9
of the buffer 143 is sufficiently high to drive the output
pin 10 of the buffer 143 to a high potential. With a high
potential at pin 10 of the buffer 143, the current will flow
through a resistor 175 to pin 37 of the microprocessor 129,
changing the input pin 37 from a low potential to a high
potential. A pull down resistor 175(a) reduces the high
potential level at the pin 37 to an acceptable level and
reduces low level input.
The switch 130 is a binary coded decimal (BCD)
switch connected to the octal tri-state buffer 132, with pull
down resistors 177 on outputs 1, 2, 4 and 8. Pins labelled
"c" are connected to the five volt supply. When the switch
130 is rotated from the 0 to the 9 position, the output from
pins 1, 2, 4 and 8 will change states from high to low and
low to high to give an e~uivalent output from the switch.
The output pins 1, 2, 4 and 8 are connected to pins 11, 13,
15 and 17, respectively of the buffer 132. The same switch
setup is used for the selector switch 131, except that the
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pull down resistors 178 and the output pins 1, 2, 4 and 8 are
connected to pins 2, 4, 6 and 8, respectively of the buffer
132. The switches 130 and 131 are selector switches for
speed and spacing inputs to the buffer 132. The speed in
question is the speed of travel of the sprayer, and the
spacing is the spacing between the sprayer nozzles.
When the speed spacing values are to be read by the
microprocessor 129, a high level input is sent from the
buffer 132 to the pin 31 of the microprocessor 129 which is
in a normally low state, as is the other data select ouput
pin 32. When both pins 31 and 32 are in the low state, pins
1 and 19 of the buffer 132 are in the low state, and drive
the output pins 3, 5, 7, 9, 18, 16, 14 and 12 into a high
impedance. When the pin 31 of the microprocessor 129 goes to
15 a high state, it drives the pin 19 of the buffer 132 to a
high state, permitting the data at pins 11, 13, 15 and 17 to
appear on pins 3, 5, 7 and 9 of the buffer 132. When the pin
32 of the microprocessor 129 goes high, it drives pin 1 of
the buffer 132 high, permitting data on the pins 2, 4, 6 and
20 8 to appear on pins 18, 16, 14 and 12, respectively of the
buffer 132.
When the current from the five volt supply line runs
through a resistor 180 and a zener diode 181, the voltage at
battery drops because of discharge, the supply voltage to the
buffer 143 also drops while the voltage at the pin 3 of the
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buffer 143 remains relatively constant. With a drop in
supply voltage, the high/low threshold also drops and passes
the voltage at pin 3 of buffer 143. Thus, the output pin 2
of the buffer 143 goes to a high state which in turn drives
pin 1 of the microprocessor 129 into a high state through
resistor 182. A resistor 184 connected to ground helps
reduce the voltages at pin 1 to acceptable levels.
Additional switches 186 are connected to input pins
33, 34, 38 and 39 of the microprocessor 129 to pull the input
pins from their naturally high states to low states. The
switches 186 are opened or closed to make four different
selections, namely high or low speed range, high or low
spacing range, large or small tube size, and English or
metric units.
The memory 135 is a read only memory (ROM) chip
containing a program for the microprocessor 129. The data
lines from the microprocessor 129 (pins 12 to 19) are
connected to pins 11 to 13 and 15 to 19, respectively of the
memory 135. The pins 12 to 19 are also connected to the pins
3, 4, 7, 8, 13, 14, 17 and 18, respectively of the latch
134. The latch 134 is a tri-state octal latch. The output
lines from the latch 134 which are address lines appear on
pins 2, 5, 6, 9, 12, 15, 16 and 19 and are connected to pins
10, 9, 8, 7, 6, 5, 4 and 3, respectively of the memory 135.
Four port line pins 21 to 24 of the microprocessor 129 are
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connected to the top address pins 25, 24, 21 and 23,
respectively of the memory 135. The "ALE" line on pin 12 of
the microprocessor 129 is connected to the enable line of the
latch pin 11 of the latch 134. The "PSEN" pin 9 of the
microprocessor 129 is connected to the "CS" pin 20 of the
memory 135. With this arrangement, the microprocessor 129
can read the program from the memory 135.
By using the following connections, the
microprocessor clock can function and run the program: a
capacitor 186 is connected to ground and to pin 2 of the
microprocessor 129, a capacitor 187 is connected to ground
and to pin 3 of the microprocessor 129, and crystal 188 is
connected to pins 2 and 3 of the microprocessor. A capacitor
190 is a reset capacitor, which permits the microprocessor to
reset internal registers before a program starts to run. For
data to be transmitted from the microprocessor 129 to the
display driver 137, the pins 21, 22 and 25 of the latter must
be connected to pins 10, 12 and 24, respectively of the
microprocessor 129. The pin connections illustrated in Fig.
3 between the display driver 137 and the display 110 enable
the driver to operate the display. A capacitor 191 connected
to ground and to pin 19 of the driver 137, and a resistor 192
connected to the five volt supply and to pin 19 of the driver
137 set up the oscillator which operates the driver 137.
When power is applied to the microprocessor 129
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using the automatic turn-on circuitry described hereinbefore,
the microprocessor immediately proceeds through the program
stored in the memory 135. The program automatically monitors
the input from the probe buffers 143 and the selector
switches 130 and 131, and when given correct sequence of
events, mathematically determines the flow rate by using
variables determined by the user, including speed and
spacing, a unit of time determined by the microprocessor and
the predetermined volume of the tube.
When the microprocessor 129 detects a change in the
low buffer input, a timer/counter within the microprocessor
is started. The timer continues counting as the container
114 fills with water until a change in the output of the
medium probe 124 is detected. When the change is detected,
the value of the counter is stored in the microprocessor 129
and the computer continues to count until a change in the
high probe 125 is detected or an overcount occurs. When a
change in the high probe 125 is detected, the count stops and
the count values are stored in the microprocessor 129. For
an overcount with a medium probe count value, and because the
medium probe position is one-half the high probe position,
the count is stopped and the count value is doubled and
stored in the memory. For an overcount with no probe changes
on the medium or high probe, the count is stopped and the
microprocessor 129 outputs an overcount display to the liquid
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crystal display 110.
The microprocessor 129 then examines the switch
positions and determines the values for the speed, spacing,
tube size and units for the display, the microprocessor 129
then determines the exact flow rate or application rate from
the variables of speed, spacing, time measured, units
required and the volume of the tube between the probes. When
the microprocessor 129 has calculated the displayed value,
such value is displayed on the liquid crystal display 110
with the units indicator. The indicators are displayed to
show the units used. If an out of range display is
calculated, the indicators change to show that the display
drive unit is out of the predetermined operating range of the
nozzle checker (the apparatus of the present invention). The
calculated value will remain on the display 110 until the
microprocessor 129 detects a low state on the low buffer 143,
i.e. on the low probe 122. This is effected by dumping water
out of the tubes 116 and 117. The microprocessor 129 will
also reset the timer and clear the display 110 to ready the
apparatus for testing another nozzle.
Finally, the microprocessor 129 will wait until the
automatic shut-off circuit turns the power off in about forty
to fifty seconds if there has been no change in the start
probe input. The hex buffer 143 and the associated sensing
circuit are the only components that are left on. In this
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"off" mode the batteries 112 should last approximately one to
one and one-half years.
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