U.S. patent application number 11/380945 was filed with the patent office on 2006-11-09 for systems and methods of power output measurement.
Invention is credited to Richard Benjamin Knapp, Dylan John Seguin, Roland Jeffrey Wyatt.
Application Number | 20060248965 11/380945 |
Document ID | / |
Family ID | 37392899 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060248965 |
Kind Code |
A1 |
Wyatt; Roland Jeffrey ; et
al. |
November 9, 2006 |
SYSTEMS AND METHODS OF POWER OUTPUT MEASUREMENT
Abstract
The present invention pertains to systems and methods of
individual power output measurement. One embodiment relates to a
pressure sensing device configured to be mounted on the bottom
surface of a shoe. The device includes a sensor, a wireless
communication system, a housing, and a mounting system. A second
embodiment relates to a direct power measurement system including a
pressure sensing device, a computer module, and a display module.
In a bicycling application of the system, the device is mounted on
the bottom surface of a shoe so as to measure applied pressure
between at least one of the rider's shoe and corresponding bicycle
pedal. The computing module mathematically converts the measured
pressure as a function of time to a value of power exerted by the
rider. In addition, the computing module may utilize the measured
pressure as a function of time to compute the rider's cadence
(pedal revolutions per unit of time). Various well-known
communication systems such as RF may be integrated within the
device and computing module to facilitate data transmission.
Similar systems may be used to calculate an individual's power
output during other activities including but not limited to
running, rowing, walking, etc. A third embodiment relates to a
method for calculating individual power output during an athletic
activity. The method includes sensing pressure at a particular
location, calculating or computing power, and displaying power.
Inventors: |
Wyatt; Roland Jeffrey;
(Albany, CA) ; Seguin; Dylan John; (Berkeley,
CA) ; Knapp; Richard Benjamin; (Sebastopol,
CA) |
Correspondence
Address: |
BAKER ASSOCIATES PLLC
470 EAST NINTH AVENUE
SALT LAKE CITY
UT
84103
US
|
Family ID: |
37392899 |
Appl. No.: |
11/380945 |
Filed: |
May 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60678887 |
May 6, 2005 |
|
|
|
Current U.S.
Class: |
73/862.391 |
Current CPC
Class: |
A61B 5/0002 20130101;
A61B 2562/0247 20130101; A61B 5/221 20130101; G01L 3/24 20130101;
A61B 5/6807 20130101 |
Class at
Publication: |
073/862.391 |
International
Class: |
G01L 5/04 20060101
G01L005/04 |
Claims
1. An athletic activity pressure sensing device comprising: a
pressure sensor disposed in a particular location to receive
pressure during an athletic activity, wherein the particular
location is related to the athletic activity, and wherein the
pressure sensor is configured to convert received pressure into
electrical data; a wireless communication system electrically
coupled to the pressure sensor and configured to wirelessly
transmit the electrical data; a housing substantially enclosing the
wireless communication system while facilitating the electrical
coupling between the pressure sensor and the wireless communication
system; and a mounting system configured to mechanically couple the
athletic activity pressure sensing device to an athletic article in
a manner that facilitates the disposal of the pressure sensor at
the particular location.
2. The device of claim 1, wherein the pressure sensor further
includes a top housing, a sensor plate, a bottom housing, and an
electrical coupler, and wherein the top housing, sensor plate, and
bottom housing include a plurality of holes to facilitate a portion
of the mounting system.
3. The device of claim 1 further including a power supply that
provides electrical power to at least one of the pressure sensor
and the wireless communication system.
4. The device of claim 1, wherein the athletic activity is cycling,
the athletic article is a shoe, and the particular location is
between the athletic article and a pedal of a corresponding
bicycle.
5. The device of claim 1, wherein the athletic article is coupled
to a portion of a user's body that is primarily utilized in the
performance of the athletic activity.
6. The device of claim 1, wherein the wireless communication system
is disposed on a printed circuit board mechanically coupled and
housed within the housing, and wherein the wireless communication
system includes a power supply.
7. A system for measuring athletic power output during an athletic
activity comprising: a pressure sensing device configured to
measure pressure at a particular location, wherein the particular
location is related to the athletic activity, and wherein the
pressure sensing device converts the measured pressure into data
and wirelessly transmits the data; a computing module configured to
wirelessly receive the data and mathematically convert the data
into a value of power output according to a specific algorithm; and
a display module configured to display the power output value,
wherein the display module is disposed in a second location that
allows a user to view the display during the athletic activity.
8. The system of claim 7, wherein the pressure sensing device is
mechanically coupled to an athletic article that is coupled to a
portion of a user's body that is primarily utilized in the
performance of the athletic activity.
9. The system of claim 7, wherein the pressure sensing device
comprises: a pressure sensor disposed in a particular location to
receive pressure during the athletic activity, wherein the
particular location is related to the athletic activity, and
wherein the pressure sensor is configured to convert received
pressure into electrical data; a wireless communication system
electrically coupled to the pressure sensor and configured to
wirelessly transmit the electrical data; a housing substantially
enclosing the wireless communication system while facilitating the
electrical coupling between the pressure sensor and the wireless
communication system; and a mounting system configured to
mechanically couple the pressure sensing device to an athletic
article in a manner that facilitates the disposal of the pressure
sensor at the particular location.
10. The method of claim 7, wherein the computing module is housed
within the pressure sensing device so as to directly calculate
power output at the particular location.
11. The method of claim 7, wherein the athletic activity is
cycling, the particular location is between a shoe and a pedal of a
corresponding bicycle, and the second location is on the handlebars
of the bicycle.
12. The method of claim 7, wherein the computer module further
includes a wireless receiver, a power supply, and a processor.
13. The method of claim 7, wherein the computer module and display
module are housed as a single unit.
14. A method for calculating individual power output during an
athletic activity comprising the acts of: sensing pressure at a
particular location, wherein the particular location is related to
the athletic activity; computing power as a function of time
through the application of a particular mathematical algorithm; and
displaying power to a user in a manner that allows the user to view
the power while performing the athletic activity.
15. The method of claim 14, wherein the act of sensing pressure at
a particular location further includes the acts of: receiving a
force at the particular location; measuring the received force;
converting the measured force into electrical data; and
transmitting the electrical data.
16. The method of claim 14, wherein the act of computing power as a
function of time through the application of a particular
mathematical algorithm further includes the acts of: receiving data
corresponding to the sensed pressure; and calculating power as a
function of time.
17. The method of claim 16, wherein the act of calculating power is
performed continuously so as to continuously update the computed
power.
18. The method of claim 14, wherein the athletic activity is
cycling, the particular location is between the athletic article
and a pedal of a corresponding bicycle, and the power is displayed
on an appropriately accessible area of the corresponding
bicycle.
19. A method of dynamically bracketing a metric during an athletic
activity comprising the acts of: providing a user performing an
athletic activity that affects at least one of heart rate, power
output, muscle fatigue, and body heat; continuously measuring a
metric during the performance of the athletic activity, wherein the
metric is associated with at least one of the performance level of
the user at the athletic activity and the exertion level of the
user; receiving a bracket request from the user at a particular
time during the performance of the athletic activity; assigning a
bracket of metric values corresponding to a set of values
substantially centered around the measured metric value at the
particular time at which the bracket request was received.
20. The method of claim 11, wherein the metric is heart rate.
21. The method of claim 11, wherein the metric is power output.
22. The method of claim 11 further includes the act of alerting the
user if the user falls outside of the assigned bracket of metric
values.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional
application Ser. No. 60/678,887 filed May 6, 2005.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to systems and methods of
power output measurement. In particular the present invention
relates to a power measurement device.
[0004] 2. Background of the Invention and Related Art
[0005] Endurance athletes utilize various metrics to measure their
performance and chart their workouts. These metrics are recorded
and analyzed both during and after workouts. For example, interval
type workouts typically involve multiple sets of intense activity,
semi-intense activity, and rest. The intense activity may be
characterized by a range of metrics which correlate to the desired
intensity for a particular athlete. Likewise, the rest or
semi-intense activity periods may be characterized by a range or
metrics which correlate to the desired restful state for a
particular athlete. One common form of metric measurement includes
an athlete's heart rate. An athlete can utilize specific heart rate
ranges to obtain desired intensity or restful states. Various well
known methodologies exist for analyzing heart rate including the
use of VO.sub.2max, maximum heart rate, age, etc. However, it has
been determined that heart rate alone is not necessarily an
accurate assessment of the amount of work an individual is exerting
at any given time. For example, as an athlete improves or increases
fitness, his/her max heart rate may increase while relative working
heart rate for a particular activity may remain constant. In this
case, conventional heart rate measurement will not accurately
identify an athlete's increased performance. Therefore, it is
necessary to utilize other metric measurements or combinations of
metrics to accurately measure an athlete's work load during a
particular activity.
[0006] One particularly useful metric measurement involves
calculating the amount of power or work an athlete is generating as
a function of time. An increase in power output directly translates
to an increased athletic performance. Likewise, a decrease in power
output translates to a decreased athletic performance. The
measurement of instantaneous power has become popular for certain
activities, including cycling. Power output has been determined to
be a more accurate measurement of an athlete's performance and is
therefore a more useful metric for analysis and improvement.
[0007] Unfortunately, it is difficult to accurately measure an
athlete's power output. Power is a function of force, and many
sports involve the application of force in a variety of directions.
In addition, few athletes are willing to wear or equip heavy force
measurement devices. In cycling, well known existing devices have
attempted to calculate power output as a function of pedal cadence.
This measurement scheme is inherently inaccurate because the power
necessary to pedal at a particular cadence depends tremendously
upon the surface over which the bicycle is traveling. For example,
a steep hill requires more power per pedal stroke than a flat or
downhill grade. Likewise, systems that attempt to extrapolate power
measurements from heart rate are inherently flawed because they do
not account for the increased power output that often accompanies
an increase in fitness.
[0008] Accordingly, there is a need in the industry for an
efficient and accurate system of power output measurement.
SUMMARY OF THE INVENTION
[0009] The present invention pertains to systems and methods of
individual power output measurement. One embodiment relates to a
pressure sensing device configured to be mounted on the bottom
surface of a shoe. The device includes a sensor, a wireless
communication system, a housing, and a mounting system. A second
embodiment relates to a direct power measurement system including a
pressure sensing device, a computer module, and a display module.
In a bicycling application of the system, the device is mounted on
the bottom surface of a shoe so as to measure applied pressure
between at least one of the rider's shoe and corresponding bicycle
pedal. The computing module mathematically converts the measured
pressure as a function of time to a value of power exerted by the
rider. In addition, the computing module may utilize the measured
pressure as a function of time to compute the rider's cadence
(pedal revolutions per unit of time). Various well-known
communication systems such as RF may be integrated within the
device and computing module to facilitate data transmission.
Similar systems may be used to calculate an individual's power
output during other activities including but not limited to
running, rowing, walking, etc. A third embodiment relates to a
method for calculating individual power output during an athletic
activity. The method includes sensing pressure at a particular
location, calculating or computing power, and displaying power.
[0010] These and other features and advantages of the present
invention will be set forth or will become more fully apparent in
the description that follows and in the appended claims. The
features and advantages may be realized and obtained by means of
the instruments and combinations particularly pointed out in the
appended claims. Furthermore, the features and advantages of the
invention may be learned by the practice of the invention or will
be obvious from the description, as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In order that the manner in which the above-recited and
other advantages and features of the invention are obtained, a more
particular description of the invention briefly described above
will be rendered by reference to specific embodiments thereof which
are illustrated in the appended drawings. Understanding that these
drawings depict only typical embodiments of the invention and are
not therefore to be considered limiting of its scope, the invention
will be described and explained with additional specificity and
detail through the use of the accompanying drawings in which:
[0012] FIG. 1 illustrates an exploded view of a pressure sensing
device configured to be mounted on a shoe in accordance with one
embodiment of the present invention;
[0013] FIG. 2 illustrates a perspective view of a biking shoe with
a pressure sensing device attached in accordance with a power
output measuring system embodiment of the present invention;
[0014] FIG. 3 illustrates a perspective view of the biking shoe of
FIG. 2, further illustrating the exploded attachment of a sensor
cover;
[0015] FIG. 4 illustrates a perspective view of the assembled
pressure sensing device and sensor cover illustrated in FIGS. 2 and
3;
[0016] FIG. 5 illustrates a perspective view of a pressure sensing
device incorporated into a sock in accordance with an alternative
device embodiment of the present invention; and
[0017] FIG. 6 illustrates a perspective view of one embodiment of a
power output measuring system for a bicycle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The present invention pertains to systems and methods of
individual power output measurement. One embodiment relates to a
pressure sensing device configured to be mounted on the bottom
surface of a shoe. The device includes a sensor, a wireless
communication system, a housing, and a mounting system. A second
embodiment relates to a direct power measurement system including a
pressure sensing device, a computer module, and a display module.
In a bicycling application of the system, the device is mounted on
the bottom surface of a shoe so as to measure applied pressure
between at least one of the rider's shoe and corresponding bicycle
pedal. The computing module mathematically converts the measured
pressure as a function of time to a value of power exerted by the
rider. In addition, the computing module may utilize the measured
pressure as a function of time to compute the rider's cadence
(pedal revolutions per unit of time). Various well-known
communication systems such as RF may be integrated within the
device and computing module to facilitate data transmission.
Similar systems may be used to calculate an individual's power
output during other activities including but not limited to
running, rowing, walking, etc. A third embodiment relates to a
method for calculating individual power output during an athletic
activity. The method includes sensing pressure at a particular
location, calculating or computing power, and displaying power.
While embodiments of the present invention are directed at systems
and methods of power output measurement, it will be appreciated
that the teachings of the present invention are applicable to other
areas.
[0019] The following terms are defined as follows:
[0020] Metric--A numerical value relating to a particular
measurement. For example, speed, heart rate, power output, cadence,
stroke, etc.
[0021] Pressure Sensor--A device configured to measure the amount
of applied pressure at a particular point or area, wherein the
measured pressure is converted into an electrical data signal.
[0022] Shoe--An article that covers a user's foot and possibly a
portion of a user's lower leg. A shoe may be composed of both
flexible and rigid materials and combinations thereof. A shoe may
be designed to achieve specific performance characteristics
consistent with a particular sport. For example, a cycling shoe is
generally rigid so as to maximize force transfer between a rider
and a bicycle.
[0023] Wireless communication system--Any system capable of
transmitting data wirelessly between two or more points. For
example, a radio transmitter may be used to convert and transmit
electrical signals across a radio frequency to a radio
receiver.
[0024] Mounting system--An attachment system for mechanically
coupling one item to another. For example, a mounting system is
used in accordance with embodiments of the present invention to
couple a pressure sensing device to a user and/or an athletic
article.
[0025] Reference is initially made to FIG. 1, which illustrates an
exploded view of a pressure sensing device configured to be mounted
on a shoe in accordance with one embodiment of the present
invention, designated generally at 100. The pressure sensing device
100 includes a sensor 110, a housing 120, a wireless communication
system 190, and a mounting system 180 (shown in both FIGS. 1 and
3). The sensor 110 further includes a top sensor housing 104, a
sensor plate 106, a bottom sensor housing 108, and an electrical
coupler 102. The illustrated sensor plate 106 is a force sensing
resistor (FSR). Force sensing resistors are uniquely suited for
athletic force measurement due to their dimension and weight
characteristics. The electrical resistance at the electrical
coupler 102 of the sensor plate 106 is directly related to the
amount of pressure or force applied upon the FSR. The sensor 110
further includes a plurality of holes 112 which facilitate a
portion of the mounting system 180, as illustrated in FIG. 3. The
holes 112 may be arranged to be consistent with a universal 3-hole
Look.TM. style mount. The top and bottom sensor housing 104, 108
effectively cover the majority of the sensor plate 106. This
covering system protects the sensor plate 106 from damage without
substantially affecting the measurement of applied pressure. The
covering or sandwiching arrangement of the top sensor housing 104,
sensor plate 106, and bottom sensor housing 108 allows pressures to
be directly transmitted from one of the top and bottom sensor
housing 104, 108 to the sensor plate 106. However, pressure can
only be sensed between two objects. For example, if a force is
applied upon the top sensor housing 104, the bottom sensor housing
must be coupled to another object to oppose the force such that
pressure can be sensed. The process of pressure measurement will be
described in more detail below.
[0026] The housing 120 is configured to protect portions of the
device that may otherwise be damaged by exposure or incidental
contacts. The illustrated housing 120 includes an enclosure 124, a
cap 122, an o-ring 128, and a cover 126. The enclosure 124 provides
a cavity in which portions of the wireless communication system 190
may be housed. In addition, the enclosure 124 and the cap 122
facilitate portions of the mounting system 180 that allow the
device 100 to be coupled to articles for use in measuring
particular pressure values. The o-ring 128 and cover 126 are
positioned to cover and seal a back opening of the enclosure 124.
The back opening of the enclosure, allows for access and assembly
of the printed circuit board 194.
[0027] The illustrated mounting system 180 includes two attachment
members 182 configured to extend through a portion of the housing
120 for the purpose of attaching the device to an article (not
shown). In addition, the mounting system 180 includes three other
attachment members 184 (illustrated in FIG. 3) which extend through
a sensor cover 152 and the sensor 110 for further attachment to an
article. The illustrated mounting system 180 may further include
the use of adhesive or other chemical coupling system to be used in
place of or in conjunction with the attachment members 182. In the
illustrated embodiments of FIGS. 2-4, the article is a shoe 205.
Various other mounting systems may be used in accordance with the
present invention including quick-release type systems that would
allow for efficient attachment and release of the device 100 to an
article.
[0028] The wireless communication system 190 is electrically
coupled to the sensor 110 via the electrical coupler 102. The
wireless communication system 190 is configured to wireless
transmit data corresponding to the pressure applied upon the sensor
110. The illustrated wireless communication system 190 further
includes a printed circuit board 194 and a power supply 192. The
power supply may include batteries that are configured to be
rechargeable without removal from the device 100. The printed
circuit board 194 includes various electrical components including
but not limited to a transmitter, an antenna, a processor, a DC
converter, etc. The printed circuit board 194 may further include a
microprocessor that performs one or more mathematical computations
on the measured pressure such as a mathematical conversion to
measure power. The printed circuit board 194 further includes a
coupler for facilitating the electrical coupling with the sensor
110. The transmitter may be configured to transmit the data
utilizing any wireless data medium including but not limited to
radio frequency, microwave, magnetic coupling, infrared, etc. In
addition, the printed circuit board 194 is shaped to conform to the
internal dimensions of the housing 124 and to facilitate the
electrical coupling with the sensor 110. In addition, the power
supply 192 and corresponding circuitry on the printed circuit board
194 are arranged in a manner that will also conform to the internal
dimensions of the housing 124.
[0029] One embodiment of the electrical operation of the pressure
sensing device 100 and accompanying power measurement system (not
illustrated) is described for demonstrative purposes. The sensor
110 is powered by a constant current source such as the power
supply 192. In response to pressure, the sensor 110 produces a time
varying voltage that is amplified by a standard op-amp amplifier.
An output voltage from the sensor 110 is split into three streams
that are eventually transmitted to a microcontroller. The first
stream computes RMS, the second stream produces a pulse stream that
is proportional to the frequency of the output voltage, and the
third stream is directly transmitted to the microcontroller. The
microcontroller samples the three streams every 1/10 of a second
and counts the number of pulses that occur every second after a
sensed pressure. This data is then buffered as 10 bit data and
wirelessly transmitted using a Zigbee.TM. RF standard. A receiver
module may receive the signal and display the data on an LCD
display screen. The receiver module may also be configured to
receive multiple signals from a plurality of pressure sensing
devices. Likewise, the wireless components may form a mesh network
that allow for various devices to interface with one another. In
addition, the receiver module may be equipped with a USB
microcontroller to facilitate directly interfacing and transmitting
data to a personal computer. Various other electrical
configurations may be utilized in accordance with the present
invention.
[0030] Reference is next made to FIGS. 2-4, which illustrate a
perspective view of a biking shoe with a pressure sensing device
attached in accordance with a power output measuring system
embodiment of the present invention, designated generally at 200.
The biking shoe may also be referred to as an athletic article. The
illustrated shoe 205 is a cycling shoe, and the illustrated
pressure sensing device 100 is the pressure sensing device 100
described with reference to FIG. 1. However, other shoe and
pressure sensing device combinations may be practiced in accordance
with the present invention. The sensor cover 152 is shaped three
dimensionally to cover the exposed surfaces of the sensor 110. In
addition, the sensor cover 152 includes a plurality of holes
positioned to correspond to the holes of the sensor 110. Three
attachment members 184 may then be extended through the sensor
cover 152, the sensor 110, and into a receiving boss on the shoe
205, as part of the mounting system 180. Various seals and couplers
may also be utilized to prevent water or debris from contacting the
sensor. It should be noted that the sensor cover 152 must be
coupled to the shoe 205 in a manner that allows for effective force
transfer so as to not affect the measured pressure upon the sensor
110. A cleat or bicycle pedal attachment system may be incorporated
into the sensor cover 152 or other portion of the device 100 so as
to minimize weight. In addition, various calibrations may be
necessary to optimize the performance of a particular shoe and
pressure sensing device combination.
[0031] Reference is next made to FIG. 5, which illustrates a
perspective view of a pressure sensing device 310 incorporated into
a sock 305 in accordance with an alternative device embodiment of
the present invention, designed generally at 300. The sock 305 is
an alternative article which may be used for attachment of a
pressure sensing device 310 in accordance with the systems and
methods of the present invention. Various sports such as cycling,
running, etc. require athletes to exert forces by their feet onto
the ground or another athletic article such as a bicycle pedal.
Therefore, the measurement of pressure at the bottom of a user's
leg 315 may be applicable in determining power output during
particular athletic activities. The pressure sensing device 310 is
positioned at approximately the ball of the user's foot for the
most efficient measurement of exerted forces by a user. In
addition, the bottom of the sock 305 may include a rigid or
semi-rigid surface to assist in coupling and stabilization of the
pressure sensing device 310 in relation to the remainder of the
sock 305. Various pressure sensing devices 310 may be used in
conjunction with a sock including but not limited to the pressure
sensing device illustrated and described with reference to FIG.
1.
[0032] Reference is next made to FIG. 6, which illustrates a
perspective view of one embodiment of a power output measuring
system for a bicycle, designated generally at 400. The power
measurement system includes pressure sensing devices 410 and a
computing and display module 405. The pressure sensing devices 410
are positioned in a particular location between the rider 415 or
user's shoe and the pedals of the bicycle. This location has been
determined to effectively measure pressure for purposes of
calculating power output of the user while cycling. The bicycle
further includes a frame 420, two tires 425, a seat 430, and a pair
of pedals 435. The pressure sensing devices 410 wirelessly transmit
data to the computing and display module relating to the pressure
and/or power output applied at each of the pressure sensing devices
410. It should be noted that alternative embodiments may utilize a
single pressure sensing device 410 between only one of the rider's
415 shoes and pedal 435. The computing/display module 405 is
positioned on the handlebars of the bicycle but may also be
positioned on the user's wrist or the bicycle stem to allow for
efficient visual recognition by the user. The computing/display
module 405 calculates power output of the user while cycling by
receiving data from the pressure sensing devices 410 and converting
or computing power in a display format such as a numerical metric
or visual graph. It has been determined that the pressure
measurements at the particular locations will exhibit a cyclic
characteristic that is consistent with the pedal cadence and can
therefore be used to calculate and display cadence in addition to
power output. Although illustrated for purposes of measuring a
cyclist's power output, the teachings of the illustrated system are
applicable to other athletic activities.
[0033] A further embodiment (not illustrated) refers to a method of
dynamically bracketing a metric during an athletic activity. An
athlete who is performing an athletic activity may often wish to
hold a metric within a particular range so as to maximize
performance. However, this range may not be quantifiable before or
after the athletic activity. Therefore, it is necessary to
dynamically bracket the metric during the athletic activity. The
method includes continuously monitoring at least one metric
associated with the athlete's athletic performance or exertion
level. For example, heart rate and power output may be continuously
monitored and displayed to the athlete. Upon recognition of a
useful situation, the athlete makes a bracket request to a computer
module. The method then assigns a bracket or set of metric values
corresponding to a set of values substantially centered around the
measure metric value at the particular time at which the bracket
request was received. Various well known electrical systems and
methods may be employed in the execution of this method in
accordance with the present invention.
[0034] Thus, as discussed herein, the embodiments of the present
invention relate to a system of power output measurement. The
present invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes that come within the meaning and
range of equivalency of the claims are to be embraced within their
scope.
* * * * *