Abstrict A flow meter for use in scuba diving is disclosed. The device has
a coil or, alternatively, two coils separated by a predetermined
distance and sensors for measuring induced electromotive force.
The device is provided with a switch to enable it to be activated.
The switch also acts to disable the device and allow compass operation.
An embodiment of the device including a compass and a processor
allows for navigation functions to be performed.
Claims What I claim is:
1. A portable device for measuring fluid flow of a conductive fluid
and for assisting navigation of a diver comprising:
a) a waterproof housing;
b) a DC power supply for providing power to the device disposed
within the housing;
c) a coil disposed within the housing to allow the conductive fluid
outside the housing to flow proximate the coil on at least a side
thereof for generating a measurable field;
d) a switch for providing DC power from the power supply to the
coil in a first mode of operation and for preventing DC power from
being supplied to the coil in a second mode of operation;
e) a first conducting sensor and a second conducting sensor disposed
outside the housing for sensing the measurable field and for providing
a first signal and a second signal, respectively, corresponding
to the sensed measurable field;
f) measuring means coupled to receive the first signal and the
second signal and for determining a measurement of fluid flow rate
in dependence upon at least an aspect of the first signal and the
second signal and for providing a third signal in dependence upon
the measurement; and
g) display means for displaying information indicative of fluid
flow rate in dependence upon the third signal.
2. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 further comprising a
second coil disposed within the housing to allow the conductive
fluid outside the housing to flow proximate the second coil on at
least a side thereof for contributing to the measurable field.
3. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 2 wherein the waterproof
housing forms an opening having an aft end and a fore end, the fore
end in fluid communication with the aft end and wherein the two
coils are disposed within the waterproof housing on different sides
of the opening to allow water, outside the housing, to flow therebetween.
4. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 3 wherein the coils are
connected in series.
5. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 wherein the fluid is
water.
6. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 wherein the waterproof
housing including the circuitry therein has an overall density substantially
the same as water.
7. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 wherein the switch is
electronically activated by the measuring means.
8. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 wherein the power supply
is a 9 volt battery.
9. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 wherein the measuring
means comprises a differential amplifier for amplifying a difference
between the first signal and the second signal and for providing
an amplified signal; an analogue to digital converter for converting
the amplified signal into a digital value; and a processor for converting
the digital value into a measurement of fluid flow.
10. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 9 wherein the measuring
means further comprises a memory means containing a look up table
for converting the digital value to a measurement of fluid flow.
11. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 9 further comprising means
for measuring time and means for multiplying a measured time and
a measured flow rate.
12. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 further comprising means
for measuring time and means for multiplying a measured time and
a measured flow rate.
13. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 1 further comprising:
g) a compass for determining an orientation of the device and for
providing a fourth signal; and
h) a processor means for receiving the third signal and the fourth
signal and for providing a fifth signal in dependence upon both
the third signal and the fourth signal to the display means;
wherein the display means also displays information in dependence
upon the fifth signal.
14. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 13 further comprising
means for storing information in dependence upon the third signal
and the fourth signal.
15. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 14 wherein the means for
storing information in dependence upon the third signal and the
fourth signal is for storing information relating to water current,
current direction, and diver speed.
16. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 15 wherein the processor
means is for calculating a direction in which a diver is to swim
in order to substantially reach a predetermined destination from
a predetermined origin and for providing the fifth signal in dependence
upon the calculated direction.
17. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 13 further comprising
means for storing information in dependence upon the third signal,
the fourth signal and the fifth signal relating to water current,
current direction, diver speed, diver direction, and past measured
and calculated values; wherein the processor means is for receiving
the third signal and the fourth signal and for calculating an approximate
location for the diver in dependence upon the third and fourth signals
and stored information; and wherein the fifth signal is provided
in dependence upon the third and fourth signals and the calculated
approximate location to the display means.
18. A portable device for measuring fluid flow and for assisting
navigation of a diver as defined in claim 13 further comprising
means for storing information in dependence upon the third signal,
the fourth signal and the fifth signal relating to water current,
current direction, diver speed, diver direction, predetermined destination,
and past measured and calculated values; wherein the processor means
is for receiving the third signal and the fourth signal and for
calculating an approximate location for the diver and an estimated
direction of travel for the diver in dependence upon the third and
fourth signals and stored information; and wherein the fifth signal
is provided in dependence upon the third and fourth signals and
the estimated direction of travel to the display means.
19. A portable device for measuring fluid flow and for assisting
navigation of a diver comprising:
a) a substantially waterproof housing having a handle portion and
a tube portion having an aft end and a fore end in fluid communications,
the tube portion for accepting conductive fluid at the fore end
thereof and for allowing the fluid to pass through the tube portion
and exit at an aft end thereof;
b) a DC power supply disposed within the housing and for providing
power to the device;
c) a pair of coils disposed on different sides of the tube portion
of the housing between the aft end and the fore end thereof for
allowing fluid outside the housing to pass therebetween, said coil
and said fluid for generating a measurable field;
d) a switch for providing power from the power supply to the pair
of coils in a first mode of operation and for preventing power from
being supplied to the pair of coils in a second mode of operation;
e) a first conducting sensor and a second conducting sensor disposed
outside the housing for sensing the measurable field within fluid
passing outside the housing proximate the coils and for providing
a first signal and a second signal, respectively, corresponding
to the sensed measurable field;
f) measuring means coupled to receive the first signal and the
second signal and for determining a measurement of fluid flow rate
in dependence upon at least an aspect of the first and second signals
and for providing a third signal in dependence upon the measurement;
and
g) display means for displaying information indicative of fluid
flow rate in dependence upon the third signal.
Description FIELD OF THE INVENTION
This invention relates generally to fluid flow measurement and
more particularly relates to a portable device for measuring water
flow for use in scuba diving and navigation.
BACKGROUND OF THE INVENTION
Scuba diving has become a very popular sport. In scuba diving an
individuals goes on a dive--submersing themselves under water for
a period of time. Some dives originate and end at a same location.
This is often the case when diving from a boat or a dock. Other
dives originate in a first location and end in a second different
location. In either case, navigation is very important in order
to locate the end location for a dive.
Once under the water, it is difficult to detect motion absent a
fixed landmark such as a sea bed or a coral reef. Divers detect
motion relative to the water in which they are immersed. When diving
in a river or in a significant current, a diver perceives no motion
when moving at the current's speed. Further, a diver's compass makes
no indication of drift due to current unless the diver's orientation
is forced to change.
Electronic flow meters are known for use in boats. A family of
devices is taught by Freund, Jr. et al. in U.S. Pat. No. 4262542.
The devices operate from a DC power source and generate pulses to
drive two coils. Electrodes disposed within the device detect an
induced magnetic field to determine fluid flow. Various electronic
circuitry is used to amplify the induced magnetic field and measure
it. The use of such a configuration allows variations in size and
other factors to provide a family of flow meters for measuring fluid
flow through tubes or pipes. The use of a regularly pulsing (clocked)
flow meter as described in U.S. Pat. No. 4262542 interferes with
the use of a compass in close proximity due to magnetic field interference.
A further electromagnetic flow meter is taught by Ruckel in U.S.
Pat. No. 4727754. The device uses a magnetic core with wire windings.
Such a magnetic core would interfere with a compass used in close
proximity.
OBJECT OF THE INVENTION
It is an object of this invention to provide a means of determining
current speed for scuba divers that does not interfere with compasses
or other scuba diving equipment.
It is an object of this invention to provide a means of determining
an approximate direction of travel.
It is an object of the invention to provide a means of determining
a distance traveled.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a portable device
for measuring fluid flow and for assisting navigation of a diver,
comprising:
a) a waterproof housing;
b) a DC power supply for providing power to the device disposed
within the housing;
c) a coil disposed within the housing to allow fluid outside the
housing to flow proximate the coil on at least a side thereof;
d) a switch for providing DC power from the power supply to the
coil, in a first mode of operation, and for preventing DC power
from being supplied to the coil, in a second mode of operation;
e) a first conducting sensor and a second conducting sensor disposed
outside the housing for sensing electromagnetic fields within fluid
passing outside the housing proximate the coil and for providing
a first signal and a second signal, respectively, corresponding
to sensed electromagnetic fields;
f) measuring means coupled to receive the first signal and the
second signal and for determining a measurement of fluid flow rate
in dependence upon at least an aspect of the first signal and the
second signal and for providing a third signal in dependence upon
the measurement; and
g) display means for displaying information indicative of fluid
flow rate in dependence upon the third signal.
In accordance with the invention there is further provided a portable
device for measuring fluid flow and for assisting navigation of
a diver comprising:
a) a substantially waterproof housing having a handle portion and
a tube portion having an aft end and a fore end in fluid communications,
the tube portion for accepting fluid at the fore end thereof and
for allowing the fluid to pass through the tube portion and exit
at an aft end thereof;
b) a DC power supply disposed within the housing and for providing
power to the device;
c) a pair of coils disposed on different sides of the tube portion
of the housing between the aft end and the fore end thereof for
allowing fluid outside the housing to pass therebetween;
d) a switch for providing power from the power supply to the pair
of coils in a first mode of operation and for preventing power from
being supplied to the pair of coils in a second mode of operation;
e) a first conducting sensor and a second conducting sensor disposed
outside the housing for sensing electromagnetic fields within fluid
passing outside the housing proximate the coils and for providing
a first signal and a second signal, respectively, corresponding
to sensed electromagnetic fields;
f) measuring means coupled to receive the first signal and the
second signal and for determining a measurement of fluid flow rate
in dependence upon at least an aspect of the first and second signals
and for providing a third signal in dependence upon the measurement;
and
g) display means for displaying information indicative of fluid
flow rate in dependence upon the third signal.
The advantages of a system in accordance with this invention are
numerous. For example, measuring water flow helps in navigation
divers and can be performed while allowing regular compass use.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplary embodiment of the invention will now be discussed
in conjunction with the attached drawings in which:
FIG. 1 is a simplified diagram illustrating a problem faced by
swimmers and divers;
FIG. 2 is a schematic block diagram of a flow meter according to
an aspect of the present invention;
FIG. 3 is a detailed drawing of a coil configuration for use in
the present invention;
FIG. 4 is a detailed schematic of a flow meter according to an
aspect of the present invention;
FIG. 5a is a simplified drawing of a housing for a flow meter according
to the present invention;
FIG. 5b is a simplified drawing of a further housing for a flow
meter according to the present invention;
FIG. 6a is a flow diagram indicating a method of using a flow meter
according to the invention;
FIG. 6b is a flow diagram indicating a further mode of operation
of a flow meter according to the invention;
FIG. 6c is a flow diagram indicating a further mode of operation
of a flow meter according to the invention;
FIG. 7 is a simplified drawing of a housing for a navigation console
according to the present invention;
FIG. 8 is a flow diagram indicating a method of using a navigation
console according to the invention;
FIG. 9 is a drawing of a diver with a navigation console according
to the invention in which a first portion of the navigation console
is disposed remotely for a second portion thereof, and
FIG. 10a and FIG. 10b are drawings of a diver's watch including
an embodiment of the present invention therein.
DETAILED DESCRIPTION
A typical problem is illustrated in FIG. 1. A diver wishes to traverse
from point A to point B on opposite banks of a river. Standing at
point A, the diver establishes that point B is due east (as shown
on the compass 2). The diver gets into the water and using a compass,
proceeds due east. Unfortunately, while swimming, the river current
sweeps the diver downstream causing the diver to exit the river
at point C far downstream of an intended exit point. A vector representing
the diver's speed 3 and a vector representing the river current
4 are summed to form a vector representing the diver's actual speed
and direction 5.
Generally a diver estimates a best guess for a course to swim in
order to traverse from point A to point B. The diver swims in that
direction hoping to end up upstream of the desired exit point. The
diver then is able to drift downstream with little effort in order
to exit at a desired location. It would be advantageous for a diver
to measure current flow and diver swim speed in order to better
estimate a course to swim. Devices for measuring fluid flow, as
are available for use in marine or factory applications, are impractical
due to size, power consumption, and due to interference with compass
operation.
A schematic of an embodiment of the invention is shown in FIG.
2. A flow meter for use in scuba diving is portable, sealed, and
has no moving parts (other than switches 10). The device comprises
two coils 11 and 12 connected in series and two sensing plates 13
and 14. The coils are connected from a power supply to ground, the
connection inducing current in the coils thereby inducing a magnetic
field. Optionally, other components may be placed in series with
the coils to control current or filter the DC signal. The sensing
plates 13 and 14 are connected to an amplifier 17 and an amplified
signal is digitized by an analogue to digital conversion circuit
20 and provided to a processor 22. The processor 22 is a simple
micro-controller. Alternatively, the processor is a microprocessor.
The processor in conjunction with memory means 23 converts the digitized
amplified signal into predetermined units of measure and drives
a display means 25 in order to provide a visual indication of the
fluid flow rate.
In use, the device is placed in water and the magnetic field is
induced in the water. As water is generally conductive (as found
in lakes, rivers, . . .), and forms a moving conductor through a
magnetic field. A predetermined distance away, the sensor plates
13 and 14 measure induced electromotive force to determine the flow
rate of the water. The amplifier 17 amplifies a difference between
the sensed electric fields and provides an amplified difference
to the analogue to digital converter 20. A digitized value for the
amplified difference is provided to the processor 22 which transforms
the digitized value into a measure of fluid flow. Generally, the
transformation is in the form of a unit conversion from voltage
difference to feet/second or meters/second. The conversion requires
a linear transform in the form of 1 volt difference=n knots. Alternatively,
the relationship between voltage and flow rate is non-linear. Alternatively
to a transform, a look up table can be used to map measured voltages
onto flow rates.
Referring to FIG. 3 an embodiment of a coil construction in accordance
with the invention, is shown. The coil is formed of enameled copper
wire of a size of 36 AWG. The same physical wire is used to form
both coils and the connection therebetween. Each coil is wound 185
times in a substantially rectangular loop having dimensions of,
for example, 1 cm by 4 cm. The coils employed in this embodiment
are symmetrical and spaced by substantially 1 cm. It is important
to ensure that the gap between the coils allows for any housing
desired and allows for sufficient fluid flow through an inlet in
the housing and between the coils and without substantially distorting
the flow. Alternatively, the wire size, length, and material may
be selected to be different from those set out above. Further, the
shape and dimensions may differ from those set out above.
Referring to FIG. 4 a more detailed schematic of the circuitry
of the present embodiment is shown. Reference values shown are schematic
references and are different from those in other Figures. Switches
SW3 and SW4 allow the magnetic field to be enabled and disabled.
This provides a diver with an ability to use both a compass and
a flow meter during a same dive. A power conditioning circuit 40
ensures accurate current flow to the circuit. The conditioning circuit
40 has a power switch SW1 for the apparatus in order to enable or
disable power supply to the electronic circuitry. The conditioning
circuit 40 also adjusts voltage and current as required. Thirdly,
a sensing circuit 42 is shown. An amplifier U3 receives signals
from each sensing plate 13 and 14 and amplifies a difference therebetween.
A processor U2 having 2 analogue input terminals receives the amplified
signal and a reference signal of, for example, +5 V. Digitizing
of the signal and processing are performed and the result is output
to a dual 7 segment LED D2. Alternatively the output is provided
to an output means in the form of an LCD. In a further embodiment
a compass (not shown) is also included in the circuit and a graphical
display 46 for use therewith.
FIG. 5a shows a housing 32 for use with the invention. The coils
11 and 12 are disposed within the housing 32 on either side of an
opening 35 of substantially 1 cm.times.4 cm. On end sides of the
opening 35 and outside the housing 32 are disposed electromagnetic
sensing plates 13 and 14. In this way, the sensing plates make electrical
contact with conducting fluids in the form of water during operation
of the unit. An LED 27 provides a visual indication of the status
of the main power switch 29. Alternatively, the visual indication
is incorporated into another display means. A display means 25 is
provided for displaying the fluid flow through the device and a
switch 10 activates the coils. Preferably, the switch 10 only activates
the coils while pressed in order not to interfere with compass operation.
An attachment point 31 allows the housing to be fastened to a divers
wet suit or equipment to prevent loss.
Alternatively, a single coil is used with two sensors as shown
in FIG. 5b. The sensors 13 and 14 are disposed outside the housing
32 on either side of the coil and water is allowed to pass along
at least a side of the coil 12 spaced from the coil by the housing
32. The induced voltage in each of the sensors 13 and 14 is compared
to establish a measurement of fluid flow in a fashion analogous
to that used with multiple coils. An advantage of the single coil
embodiment is reduced interference with fluid flow and reduced cost.
A flow diagram for the apparatus is shown in FIG. 6a. The unit
operation begins with power up. Power up is initiated by turning
the switch 29 into an "On" position. Electronic circuitry
is initialized. This step includes delays in power up to prevent
power spiking, processor initialization, program loading, and calibration
when necessary.
The processor polls "coil sense" until a voltage is present.
This allows the processor to establish when the coils 11 and 12
are activated. Alternatively, another means is established for reaching
that determination. Further alternatively, the coils are read whether
or not they have been activated.
According to the flow diagram, when the coils have been activated
(supplied with power), the amplified signal is polled to establish
a digitized value of same. Once a value is present, "coil sense"
is again polled to establish that power is still being provided
to the coils 11 and 12. In the absence of power to the coils, the
circuit assumes a boundary condition in which power to the coils
was provided for a period of time within the sampling period but
not for the entire period. When such is the case, the digitized
signal is not considered a good measurement and the circuit displays
an error--or holds the last value if one is present. When "coil
sense" remains active, the digitized signal value is transformed
via a look up table into an indication of fluid flow in knots. Alternatively,
other units are used. The display locks with the displayed value
for a period of time and then is cleared. Alternatively, during
that time fluid flow measurements are made and a determination of
accuracy of the measurement is made. When inaccurate, the displayed
result is either adjusted accordingly or alternately, displays a
low value and high value of a range of possible measurements. The
device then re-enters a state of polling for coil activation.
The flow diagrams of FIG. 6b and 6c show two further modes of operation
for a device as described above. A common form of diving is drift
diving. In drift diving, after descending to a desired depth, a
diver allows themselves to drift. This form of diving consumes less
energy and, when a substantial current exists, allows a diver to
travel a good distance. In a drift mode, as shown in FIG. 6b, the
device measures drift of a diver. Once water current speed is measured,
the device has an indication of drift speed (true drift it is equal
to the current speed). A timer within a microprocessor used in the
device, measures time. An indication is provided to the device that
drifting is commencing. Upon conclusion, a further indication is
provided. The microprocessor calculates a total drift time and multiplies
the resulting value by the current speed. A drift distance is then
provided to an output means. Alternatively, the drift distance provided
to the output means is provided at predetermined intervals or predetermined
distances. This allows for monitoring of drift distance during drifting.
In a third mode of operation and shown in FIG. 6c, a diver uses
the device to measure swim speed of a diver relative to the water
in which the diver is diving. As shown in the flow diagram of FIG.
6c, a diver enters the water, points the device ahead of the diver,
and swims forward. The device periodically measures water flow speed.
The speed water flows by the diver, is substantially equal to the
diver's swim speed relative to the water and thus, results for water
flow speed are indicative of diver swim speed. The operation of
this mode of the device is based on same principles as the second
mode of operation for the device in which it measures drift. There,
the basis of a measurement of drift is that a diver while drifting
does not move substantially with respect to the water current. In
the third mode of operation, a diver is assumed not to move relative
to the water current absent the diver swimming.
An application of the flow meter in an underwater navigation console
will now be described with reference to FIG. 7. An enclosure is
provided with a handle. On a display portion of the enclosure is
a compass 102 a chronometer 106 and a flow display 108. An inlet
104 at a front end of the enclosure allows water to pass therethrough
and contains the coils and the sensors for use in fluid flow measurement.
Flow measurement readings are displayed on the flow display 108.
A diver can, through input means 110 in the form of knobs and buttons
enter the speed and direction of current, the desired direction
of travel, and diver swim speed. A processor means within the enclosure
calculates and displays a preferred direction for travel 121 on
the compass display along with the desired direction 122 and an
indication of absolute direction in the form of an arrow pointing
north 123.
The console will now be described in operation referring to FIG.
8. The flow diagram is for console use and reflects one method of
using same. A diver wishing to use the console for navigation, enters
the water with the console. The diver selects current flow entry
using the input means 110. A stationary object is located and the
diver maintains a fixed position and points the console into the
current. An actuating button is pressed to measure current flow.
The current flow is shown on the flow display 108 and the current
direction (read immediately before and after the flow measurement
and compared for correctness) is displayed on the compass. When
acceptable, the diver accepts the values. Alternatively, the diver
discards the values and measures the current flow again. The diver
selects diver speed entry. The diver again points the console into
the current and swims into the current. A measurement of the diver's
relative speed is performed by the console. Alternatively, the diver
can face in any direction and the relative speed reading should
be substantially the same. When desirable, this measurement is also
accepted. The flow display can now display current speed or diver
speed. The compass shows North or another predetermined direction.
The diver now enters a direction, and optionally distance to travel.
The processor means calculates an approximate direction in which
the diver should swim in order to reach the desired destination.
Alternatively as shown in FIG. 8 the console dynamically calculates
location based on compass, chronometer, and fluid flow through the
inlet. Using such a method, the flow meter must be isolated from
the compass for example by placing the compass measuring circuit
distant from the flow meter. Alternatively, the flow meter can be
cycled on and off and alternately, the processor means can read
the compass and the flow speed extrapolating between cycles. The
latter will only approximate navigation, but as no navigation tools
currently exist that simplify navigation to this degree, even an
estimate of location is desirable.
Referring to FIG. 9 an embodiment wherein the compass 102 is distant
to the flow meter 50 is shown. A compass 102 is disposed on the
tank of a diver. Alternatively, the compass 102 is disposed on the
belt, flippers, or other diving apparatus. The magnetic field of
the flow meter is designed to minimize the affects on the compass
102. The compass is substantially unaffected by the flow meter magnetics
in its location. The navigation console accepts directional and
flow information at predetermined intervals or, alternatively, when
changes occur. The information is used to calculate diver location
and, for example, to display information indicative of the diver
location to the diver at all times.
Alternatively, the navigation console calculates an approximate
diver location and upon request, the console displays a suggested
direction of swim so as to allow the diver to reach a predetermined
destination. Such a request may be in the form of pressing a button.
Alternatively, the flow meter employed in the navigation console
measures flow in a plurality of orthogonal directions in order to
more accurately calculate diver location. Further alternatively,
the console is designed to be secured to the diver in a manner that
allows substantially accurate calculations while minimizing any
interference to a divers natural motions and hydrodynamics.
Any submersible portable flow meter that does not interfere with
compass operation can be used in a navigation console as herein
described. One advantage of the flow meter described herein is that
it is a sealed unit without moving parts.
An underwater navigation console or a flow meter according to the
present invention may be incorporated into other diving equipment.
In FIGS. 10a and 10b, the invention is incorporated into a diver's
watch. FIG. 10a shows a configuration of a flow meter 1 having two
coils. FIG. 10b shows a configuration of a flow meter 1 having a
single coil. A flow meter according to the present invention could
also be incorporated into a diver's mask wherein the transparent
portion of the mask also acts as a display onto which results are
projected. This functions similar to head up displays for automobiles
and is well known in the design of automobile dashboard systems.
In an embodiment, the switch is electronically controlled and is
actuated by the microprocessor within the device.
Numerous other embodiments may be envisaged without departing from
the spirit and scope of the invention. |