United States Patent 1191
`Karr et a1.
`
`[1 1]
`[45]
`
`4,371,945
`Feb. 1, 1983
`
`[54] ELECTRONIC PEDOMETER
`Lawrence J. Karr, 220 Horizon St.,
`[75] Inventors:
`Venice, Calif. 90291; Gary L.
`Wasserman, 2669 Rambla Paci?co,
`Malibu, Calif. 90265; George R.
`Boehme, Venice, Calif.
`[73] Assignees: Lawrence Joseph Karr; Gary Lee
`Wasserman, both of Marine del Rey,
`Calif.
`[21] Appl.No.: 211,684
`[22] Filed:
`Dec. 1,1980
`[51] Int. Cl.3 ............................................ .. G01C 22/00
`[52] US. Cl. .................................. .. 364/561; 364/410;
`235/92 DN; 235/105; 340/323 R
`[58] Field of Search ........... .. 272/70, 73, 100, BIG. 6;
`364/413, 560, 561, 565, 410; 367/99; 235/92
`DN, 92 MT, 92 PE, 92 CP, 105; 340/323 R
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`3,492,582 1/1970 Heywood ..................... .. 340/323 R
`4,049,954 9/1977 Da Costa Vieira et a1. ..... .. 364/560
`4,053,755 10/1977 Sherrill ........................ .. 235/92 DN
`4,220,996 9/1980 Searcy
`..
`364/561
`4,223,211 9/1980 Allsen et a1.
`235/92 DN
`
`4,283,712 8/1981 Goody .......................... .. 340/3231:
`4,285,041 8/1981 Smith ................................ .. 235/105
`Primary Examfner—-Gary Chin
`Attorney, Agent, or Firm-Reagin & King
`[57]
`ABSTRACT
`A pedometer is disclosed which calculates the distance
`a user walks, jogs or runs by electronically measuring
`the length of each stride taken by the user. Stride length
`is measured using ultrasonic waves. The pedometer
`comprises an ultrasonic generator module which is
`strapped to one leg of the user. An ultrasonic detector
`module is strapped to the other leg of the user. The
`generator module emits pulses of ultrasonic energy
`which are detected by the detector module. A proces
`sor and display module in the form of a wristwatch is
`also provided. The processor module is used to calcu
`late stride length based on the speed of sound and the
`time delay between pulses emitted and detected by the
`leg-mounted modules. The pedometer is capable of
`displaying on a digital display the distance traveled,
`time per unit distance, elapsed time and time of day. The
`pedometer is also programmed to compensate for a
`variety of measurement errors.
`
`15 Claims, 12 Drawing Figures
`
`50
`
`1
`
`

`

`U.S. Patent Feb. 1, 1983
`
`Sheet 1 of7
`
`4,371,945
`
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`US. Patent
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`Feb. 1, 1983
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`U.S. Patent
`
`Feb. 1, 1983
`
`Sheet 3 of7
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`4,371,945
`
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`US. Patent
`
`Feb. 1, 1983
`
`Sheet 4 of 7
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`4,371,945
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`

`

`US. Patent Feb. 1, 1983
`
`Sheet 5 of 7
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`4,371,945
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`

`U.S. Patent Feb. 1, 1983
`
`Sheet 6 of?
`
`4,371,945
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`7
`
`

`

`US. Patent Feb. 1, 1983
`
`Sheet 7
`
`4,371,945
`
`{FROM 200 )
`
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`

`

`1
`
`ELECTRONIC PEDOMETER
`
`4,371,945
`2
`Further, since many prior art pedometers display
`only the number of steps taken, the user must mentally
`convert this data into distance and rate of speed. This
`presents an unwieldly procedure for a user attempting
`to determine instantaneous data while running. This
`condition is further aggravated by the fact that most of
`the prior art pedometers are designed to be waist
`mounted for proper acceleration sensing. When
`mounted in this position it is difficult, if not, impossible
`to see the pedometer display while running. The above
`limitations of the prior art pedometers are even more
`pronounced when the user is attempting to measure
`distance traversed during active sports such as tennis,
`handball and the like.
`Accordingly, it is an object of the present invention
`to provide a new and improved pedometer.
`It is another object of the present invention to pro
`vide a new and improved pedometer which measures
`the length of each stride taken by the user.
`It is still another object of the present invention to
`provide a pedometer which measures stride length by
`electronic means.
`It is still another object of the present invention to
`provide a pedometer which calculates and displays total
`distance traversed, elapsed time and speed on a wrist
`mounted display unit.
`
`20
`
`BACKGROUND OF THE INVENTION
`This invention relates to pedometers and, more par»
`ticularly, to pedometers that determine the distance a
`user walks, jogs or runs by electronically measuring the
`length of strides taken by the user.
`Pedometers have been used for many years by hikers
`and long distance walkers to measure the distance tra
`versed. More recently there has been a resurgence in
`interest in these devices for use in the popular sports of
`jogging and distance running. In these types of sports, a
`measure of the athlete's level of achievement requires
`an accurate determination of distance traversed as well
`as elapsed time. With the advent of digital stop watches,
`accurate measurement of elapsed time over a particular
`course is readily achieved. When the variables of both
`distance and time are made available to the user, the
`user's speed may be computed. This information can
`then be used to pace the user and to evaluate progress in
`an exercise program or sporting event.
`A pedometer for use in the above mentioned sports is
`one which can accurately measure the distance tra
`versed under a number of varying conditions. For ex
`ample, the pattern of a jogger may involve activity from
`slow walking to rapid jogging. A typical jogging path
`may include hills and winding paths. In the case of a
`marathon runner, activity may include motion from
`jogging to sprinting. At high running speeds both of the
`user's feet may be clear of the ground at the same time.
`A pedometer suitable for use during these activities
`must operate accurately over' this wide range of condi
`tions.
`Many prior art pedometers have been developed
`which indirectly measure the distance traversed by the
`user by counting the number of steps taken. The opera
`tion of these prior art devices is based on the assumption
`that the user's stride or distance traversed per step is a
`constant. The total distance traversed by the user is
`computed by counting the number of steps taken and
`multiplying this number by a constant stride distance.
`Prior art pedometers employ a variety of techniques
`for counting the number of steps taken. Most of these
`techniques rely on the fact that the user’s body under
`goes an abrupt change in acceleration each time the
`user's foot contacts the ground. This change in acceler
`ation is detected by any one of a number of acceleration
`sensitive devices. One of the more common techniques
`employed in the prior art pedometers is the use of a
`spring-mounted weight which is coupled to a mechani
`cal counter. At each step, the abrupt change in accelera
`tion causes the weight to exert a force on the spring.
`This spring force is, in turn, used to advance the
`counter.
`The prior art pedometers possess several limitations
`which preclude their widespread use in athletic activi
`ties such as described above. For example, the assump
`tion that stride length is a constant results in large errors
`in distance measurement. It has been found that actual
`stride length may vary considerably as a function of
`terrain and running speed. Another disadvantage of the
`prior art pedometers is that the mechanical means for
`sensing and counting steps has proven unreliable under
`the
`conditions mentioned above. in assay cases
`the prior art devices with either fail to record a step or,
`conversely, will record an excessive number of steps.
`
`SUMMARY OF THE INVENTION
`The foregoing and other objects of the invention are
`accomplished by an electronic pedometer which mea
`sures stride length by electronic means. The pedometer
`also sums the individual stride lengths, compensates for
`measurement errors and displays total distance tra
`versed.
`In the preferred embodiment, stride length is mea
`sured indirectly by means of acoustic waves. This con‘
`cept uses the relatively constant velocity of sound to
`convert a time delay measurement into a distance mea
`surement. The electronic pedometer of the present in
`vention includes three components. ‘
`The ?rst component is a leg-mounted battery oper
`ated ultrasonic generator module. The generator mod
`ule includes an ultrasonic transducer for emitting ultra
`sonic energy. The transducer is in turn driven by an
`ultrasonic oscillator which is keyed to produce a contin
`uous train of narrow pulses of ultrasonic energy at a
`?xed repetition rate. The frequency, pulse width and
`repetition rate of the ultrasonic pulses are all synchro
`nized by a crystal controlled time base also located
`within the generator module. The generator module is
`designed to be strapped to one of the user’s legs so that
`the ultrasonic transducer faces the opposing leg.
`The second component of the electronic pedometer is
`a leg-mounted battery operated ultrasonic detector
`module. The detector module includes an ultrasonic
`microphone for detecting the ultrasonic energy emitted
`from the generator module. The microphone output
`signal is in turn ampli?ed and ?ltered to produce a
`detection signal in response to the output of the ultra
`sonic generator. The detection signal is transmitted via
`a high frequency radio transmitter and antenna to the
`third component of the pedometer as described below.
`In a manner analogous to the ultrasonic generator mod
`ule, the ultrasonic detector module is strapped to the
`user’s other leg so that the microphone faces the trans
`ducer on the
`tag.
`The third component of the electronic pedometer of
`the present invention is a battery operated wrist
`
`35
`
`45
`
`55
`
`60
`
`65
`
`9
`
`

`

`BRIEF DESCRIPTION OF THE DRAWINGS
`Fi?. i is a perspective view showing the various
`components of the electronic pedometer of the present
`invention;
`FIG. 2 is a perspective view showing a user wearing
`the electronic pedometer of the present invention;
`FIG. 3 is a block diagram illustrating the structure
`and operation of the generator module of the present
`invention;
`FIG. 4 is a block diagram illustrating the structure
`and operation of the detector module of the present
`invention;
`FIG. 5 is a block diagram illustrating the structure
`and operation of the processor and display module of
`the present invention;
`FIG. 6 is a graphic example of the distance between
`the feet of a user as a function of time;
`FIG. 7 is a table listing the time of detection of the
`ultrasonic pulses by the detection module for the exam
`ple of FIG. 6;
`FIG. 8 is a cross-sectional view of the legs of the user
`of FIG. 2 showing the leg interstices; and
`FIGS. 9-12 are flow charts showing the program and
`operation of the preferred embodiment of the present
`invention.
`
`15
`
`25
`
`4,371,945
`3
`4
`mounted processor and display module. This unit in
`the speci?cation when taken in conjunction with the
`cludes a high frequency radio receiver tuned to receive
`drawings in which like reference numerals refer to like
`the RF output signal of the transmitter located in the
`elements in the several ?gures.
`detector module. The output signal from the receiver is
`a reproduction of the detection signal from the detector
`modu'ie.
`detection signai is in turn connected‘ to an
`input terminal of a microprocessor. The microprocessor
`is programmed to perform all of the necessary logic and
`arithmetic operations to convert the detection signal
`into a distance measurement. Both the receiver and
`microprocessor are synchronized by a crystal con
`trolled time base. The time base is also used by the
`microprocessor to calculate elapsed time and time of
`day.
`Output signals from the microprocessor are displayed
`on a multi-digit digital display. The display is mounted
`within a wrist-mounted housing in a con?guration simi
`lar to that of a digital wristwatch. Pushbutton operated
`switches are provided to start, stop and reset the accu
`mulation of time and distance data. The switches also
`enable the display to show time of day, elapsed time,
`distance in miles or kilometers and time per unit dis
`tance. The operation of the electronic pedometer of the
`present invention is as follows.
`The user straps the generator and detector modules
`to each leg so that the ultrasonic transducer and micro
`phone face each other when the legs are adjacent each
`other. The processor and display module is wrist
`mounted. The leg-mounted modules are energized by
`actuating their individual power switches. The pedome
`ter of the present invention measures distance by detect
`ing the time delay between the time the generator mod
`ule emits a pulse of ultrasonic energy and the time this
`energy is detected by the detector module. Since the
`speed of sound is constant for constant temperature, the
`above described time delay is proportional to the dis
`tance between the generator and detector modules.
`The microprocessor is programmed to automatically
`synchronize a logic signal to coincide with the occur
`rence of the pulses of ultrasonic energy emitted from
`the generator module. This synchronization is possible
`because both the microprocessor and the generator
`module are individually controlled by matched crystal
`controlled time bases. When the microprocessor is
`properly synchronized, it calculates the time delay be
`tween the generation of the ultrasonic pulses and the
`detection of these pulses. As described above, this time
`delay represents the distance between the user’s feet.
`The microprocessor converts the time delay data into
`signals which represent the stride distance of the user
`for each step taken.
`The microprocessor is also programmed to compen
`sate for a variety of errors in the measurement of dis
`tance traversed. For example, the microprocessor com
`pensates for the variations of the speed of sound as a
`function of ambient temperature. The processor also
`includes an algorithm for leaping. This algorithm is
`based on the fact that a runner will have a tendency to
`take leaping steps in which both feet are clear of the
`ground. Under these conditions, the distance traversed
`by the runner exceeds his stride length. The processor
`determines a leaping compensation factor as a function
`of runner velocity and stride frequency and adjusts the
`distance calculation accordingly. The processor can
`also compute and display time per unit of distance and
`elapsed time.
`These and other objects, features and advantages of
`the invention will become apparent from a reading of
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`Referring to FIG. 1 there is shown a perspective
`view of the generator module 12, the detector module
`14 and the processor and display module 16 of elec
`tronic pedometer of the present invention. The ultra
`sonic generator module 12 includes a housing 18 which
`may be formed of plastic and which is fastened to an
`adjustable leg strap 20. The strap 20 is designed to per
`mit the module 12 to be mounted to the leg of the user
`of the electronic pedometer and may be formed of an
`elastic material having an adjustable fastening means
`such as Velcro. The plastic housing 18 contains elec
`tronic circuitry, an ultrasonic transducer and a battery
`power source which form the components of the gener
`ator module 12 described hereinafter. A power switch
`22 is also provided to connect the battery power source
`to the electronic circuitry of the module 12. The ultra
`sonic transducer may be in the form of a capacitive or
`piezoelectric disk. This disk is mounted within the hous
`ing 18 in a manner which permits the ultrasonic energy
`to be emitted in a direction opposite to the side of the
`housing 18 which is mounted to the strap 20. The trans
`ducer is in turn covered by a screen or mesh 24 'which
`serves to protect the transducer from dust and mechani
`cal impact.
`Similarly, the ultrasonic detector module 14 consists
`of a plastic housing 26 which is fastened to an adjustable
`leg strap 28. The leg strap 28 is similar in form to the leg
`strap 20 of the module 12. The housing 26 of the module
`14 contains electronic circuitry, an ultrasonic micro
`phone and a battery power source which form the com
`ponents of the ultrasonic detector module 14 as de
`scribed hereinafter. The ultrasonic microphone may be
`in the form of a capacitive or piezoelectric disk. In a
`manner similar to the construction of the module 12,
`this disk is mounted within the housing 26 in a manner
`which permits detection of ultrasonic energy from a
`
`30
`
`60
`
`10
`
`

`

`4,371,945
`6
`5
`invention. Included within the generator module 12 is a
`direction opposite to the side of the housing 26 which is
`battery power source 56, a crystal controlled time base
`mounted to the strap 28. The ultrasonic microphone is
`58, a narrow pulse generator 60, an ultrasonic oscillator
`protected by a mesh or screen 29. A power switch 30 is
`and driver 62 and an ultrasonic transducer 64. The crys
`provided to energize the electronics within the module
`tal controlled time base 58 includes a quartz crystal
`14. Included as part of the ultrasonic detector module
`frequency standard and a series of frequency dividers to
`14 is a VHF antenna 32 which is embedded in the leg
`produce highly accurate clock signals at the output
`strap 28.
`terminals 01 and 02 of the time base 58. The output
`Also shown in FIG. 1 is the processor and display
`terminal 01 of time base 58 is connected to the clock
`module 16. The module 16 includes a housing 34 which
`input terminal CLK of the pulse generator 60. The pulse
`may be formed of plastic or metal. The housing 34 is
`generator 60 is con?gured to produce a pulse train
`fastened to an adjustable wrist strap 36. Mounted within
`signal at the output terminal of the generator 60 which
`the housing 34 are a digital display 38 and pushbutton
`consists of equally spaced narrow pulses shown as sig
`actuated switches 40, 42, 44 and 46. Also located within
`nal 66 in FIG. 3. In the preferred embodiment the pulses
`the housing 34 are electronic components used for cal
`are spaced precisely thirty milliseconds apart and each
`culating and displaying the output data of the electronic
`pulse has a width of four hundred microseconds.
`pedometer, a battery power source for energizing the
`The output terminal of the pulse generator 60 is con
`electronics of the module 16 and a speaker for generat
`nected to the input terminal IN of the oscillator and
`ing a variety of audio tones. A VHF antenna 48 is pro
`driver 62. The output terminal 02 of the time base 58 is
`vided which is positioned within the adjustable wrist
`connected to the clock input terminal CLK of the oscil
`band 36. From the above description of the module 16,
`lator and driver 62. The oscillator and driver 62 is de
`it can be seen that the form of the module 16 resembles
`signed to produce an ultrasonic waveform at its output
`that of a digital wristwatch. It is contemplated that
`terminal OUT in response to a pulse appearing at the
`fabrication methods similar to those for producing digi
`input terminal IN of the oscillator and driver 62. The
`tal Wristwatches will be used to construct the module
`output terminal OUT of the oscillator and driver 62 is in
`16. These fabrication processes are well known to those
`turn connected to drive the ultrasonic transducer 64.
`skilled in the art.
`The transducer 64 generates ultrasonic energy in re
`The display 38 of the module 16 is divided into two
`sponse to the output signal from the oscillator 62. This
`independent legends as shown in FIG. 1. Thus, display
`ultrasonic energy radiates from the front surface of the
`38 is capable of simultaneously displaying two vari
`housing 18 of the generator module 12 as shown in FIG.
`ables. The variables to be displayed are selected by
`1. In the preferred embodiment the frequency of the
`operating the pushbutton actuated switches 40, 42, 44
`ultrasonic oscillator is 40 kilohertz.
`and 46 in a predetermined sequence. The variables
`The time base 58, the pulse generator 60 and the
`which may be displayed by the modules 16 include time
`oscillator and driver 62 all receive their operating volt
`of day, elapsed running time, distance traversed and
`age V1 at their terminals Vcc and GND respectively.
`average time per unit of distance. Time of day is dis
`The operating voltage V1 is supplied from the battery
`played in units of hours, minutes and seconds. Distance
`source 56 whenever the switch 22 is closed. Operation
`measurements may be displayed in units of miles or
`of the circuit of the generator module 12 thus described
`kilometers.
`is as follows.
`The pushbutton switches 40, 42, 44 and 46 also pro
`After the user straps the ultrasonic generator module
`vide additional logic functions. They are used to set the
`12 to one leg, the user actuates the switch 22 providing
`time of day and they are also used to select the elapsed
`power to the electronic circuitry shown in FIG. 3. The
`time mode and to select the distance calculating mode
`crystal controlled time base 58 provides clock signals to
`of operation of the electronic pedometer of the present
`both the pulse generator 60 and the oscillator and driver
`invention. In addition, the switches 40, 42, 44 and 46
`62. The pulse generator 60 generates the output signal
`provide the capability of starting and stopping the accu
`45
`66 shown in FIG. 3. The signal 66 consists of a continu
`mulation of elapsed time and distance traversed. The
`ous series of narrow pulses occurring at the points in
`switches 40, 42, 44 and 46 are also used to reset the
`time T1, T2, T3, T4, T5, etc. In the preferred embodi
`elapsed time and distance traversed.
`ment, the time between pulses is thirty milliseconds.
`Referring now to FIG. 2 there is shown a perspective
`Therefore, T1 represents thirty milliseconds, T2 repre
`view of a user 50 wearing the electronic pedometer of 50
`sents sixty milliseconds, T3 represents ninety millisec
`the present invention. As shown in FIG. 2, the ultra
`onds, etc.. As each pulse is generated by the pulse gen
`sonic generator module 12 is mounted to the left leg 54
`erator 60, a corresponding pulse of ultrasonic energy is
`of the user 50 by means of the adjustable strap 20. The
`produced by the transducer 64. Thus the transducer 64
`module 12 is positioned so that the housing 18 contain
`radiates ultrasonic pulses which also occur every thirty
`ing the ultrasonic transducer faces the opposing or right
`milliseconds.
`leg 52. Similarly, the ultrasonic detector module 14 is
`The interpulse spacing within the signal 66 is accu
`strapped to the right leg 54 by means of the strap 28.
`rately controlled by the crystal controlled time base 58.
`The module 14 is oriented so that the housing 26 faces
`The ultrasonic generator module 12 continues to radiate
`the opposing or left leg 52. Thus when the user’s legs 52
`pulses of ultrasonic energy as long as the switch 22 is
`and 54 are adjacent each other, the ultrasonic trans
`closed. The transducer 64 is configured so that it radi
`ducer and ultrasonic microphone mounted in modules
`ates a generally hemispheric pattern of ultrasonic en‘
`12 and 14, respectively, are facing each other. Also
`ergy from its surface.
`shown in FIG. 2 is the processor and display module 16
`Referring now to FIG. 4 there is shown a block dia
`mounted to the wrist of the user 50 in the same manner
`gram illustrating the operation of the detector module
`as a wristwatch.
`14 of the present invention. As shown in FIG. 4 the
`Referring now to FIG. 3 there is shown a block dia
`circuitry of the detector module 14 includes a battery
`gram illustrating the operation of the electronic cir
`power source 68 which supplies power to a terminal V2
`cuitry within the generator module 12 of the present
`
`60
`
`25
`
`30
`
`35
`
`40
`
`55
`
`65
`
`11
`
`

`

`. 0
`
`25
`
`4,371,945
`via the switch 30. Also shown in FIG. 4 is an ultrasonic
`microphone 70, the output of which is ampli?ed by
`ampli?er 72. The output terminal of the ampli?er 72 is
`connected to the input terminal of a band pass ?lter 74.
`The output terminal of the ?lter 74 is connected to the
`input terminal of a voltage level detector 76. The output
`terminal of the level detector 76 is in turn connected to
`the input terminal of a VHF radio transmitter 78. The
`radio transmitter 78 is designed to transmit data via the
`antenna 32 to the processing and display module 16 as
`described below. Operation of the electronic circuitry
`of the ultrasonic detector module 14 thus described is as
`follows.
`The user straps the ultrasonic detector module 14 to
`one leg and actuates the power switch 30. As shown in
`FIG. 4, actuation of switch 30 provides voltage to ter
`minal V2 from power source 68. Terminal V2 supplies
`operating voltage to the V56 and GND terminals of the
`ampli?er 72, ?lter 74, detector 76 and transmitter 78.
`The ultrasonic microphone 70 responds to the pulses of
`ultrasonic energy being generated by transducer 64
`strapped to the opposing leg. The microphone 70 gener
`ates an output signal in response to the ultrasonic en
`ergy. This output signal is ampli?ed by ampli?er 72.
`The ?lter 74 is used to eliminate transient noise and
`spurious signals from the signal generated by micro
`phone 70. The band pass ?lter 74 is designed to have a
`center frequency of 40 kilohertz corresponding to the
`frequency of ultrasonic energy emitted by the trans
`ducer 64. The level detector 76 is designed to produce
`an output voltage pulse each time the microphone 70
`detects a pulse of ultrasonic energy from the transducer
`64. The signal appearing at the output terminal of the
`level detector 76 is thus a series of pulses shown as
`signal 80 in FIG. 4. The pulses shown in the signal 80
`occur at the times T1’, T2’, T340 , T4‘, T5‘, etc. which
`correspond to the detection of the ultrasonic pulses
`generated at the times T1, T2, T3, T4, T5, etc., respec
`tively. The pulses appearing at the output terminal of
`the level detector 76 are transmitted via the transmitter
`40
`78 and antenna 32 to the processor and display module
`16.
`Referring now to FIG. 5 there is shown a block dia
`gram illustrating the operation of the electronic cir
`cuitry within the processor and display module 16 of
`the present invention. The circuitry shown in FIG. 5
`includes a battery power source 82 connected to a ter
`minal V3. Also shown is a VHF radio receiver 84 and
`the antenna 48 for receiving the signals transmitted by
`the transmitter 78. The output terminal of the receiver
`84 is connected to input terminal I| of a microprocessor
`86. The microprocessor 86 provides all of the logic and
`arithmetic functions required to calculate and display
`the various outputs of the electronic pedometer of the
`present invention. Input signals to the microprocessor
`86 include a signal from an ambient temperature sensor
`88. The output terminal of the sensor 88 is connected to
`input terminal I2 of microprocessor 86. The sensor 88 is
`used to compensate for temperature variations in the
`speed of sound as described below.
`The pushbutton actuated switches 40, 42, 44 and 46
`are connected to input terminals I3, 14, I5 and I6 respec
`tively of microprocessor 86. As described above, actua
`tion of the pushbuttons 40, 42, 44 and 46 determines the
`mode of operation of the electronic pedometer and also
`provides the start, stop and reset functions. Output
`terminals 01 of a crystal controlled time base 90 is con
`nected to the clock input terminal CLK of microproces
`
`sor 86. The time base 90 is similar to the time base 58
`described above for the ultrasonic generator module 12.
`As shown in FIG. 3, the output terminal 02 of the time
`base 90 is connected to the clock input terminal CLK of
`the receiver 84. The time base 90 is used also to supply
`timing reference signals to the microprocessor 86. The
`time base 90 is also used to stabilize the frequency of the
`receiver 84 in a manner well known to those skilled in
`the art.
`Microprocessor 86 generates a variety of output sig
`nals as follows. Output terminal 01 is connected to a
`speaker 89 which is used to generate a variety of audio
`tones. Output port Op of microprocessor 86 is connected
`to drive the display 38 of the processor and display
`module 16. The display 38, the receiver 84, the micro
`processor 86 and the time base 90 all receive continuous
`operating power at their respective VCC and GND
`terminals from the battery power source 82. The overall
`operation of the electronic pedometer of the present
`invention as described above and illustrated in FIGS. 2,
`3, 4 and 5 is as follows.
`Referring to FIGS. 2, 3 and 4, in combination, it can
`be seen that the transducer 64 of the generator module
`12 emits pulses of ultrasonic energy which radiate from
`the module 12 mounted to the user’s left leg 54, as
`shown in FIG. 2. These ultrasonic pulses occur repeti
`tively at precisely spaced time intervals as shown in the
`signal 66 of FIG. 3. Similarly, the ultrasonic micro
`phone 70 of the detector module 14 detects the ultra
`sonic pulses emitted by transducer 64. The detected
`pulses of ultrasonic energy are converted into the pulse
`train shown in the signal 80 in FIG. 4. The timing data
`contained in the signal 66 and the signal 80 may be used
`to calculate distance between the ultrasonic transducer
`64 and the ultrasonic microphone 70 in the following
`manner.
`The distance between the transducer 64 and the mi
`crophone 70 is determined by measuring the delay be
`tween the time at which a pulse of ultrasonic energy is
`generated by transducer 64 and the time at which that
`pulse of ultrasonic energy is detected by microphone
`70. Referring to signal 66 in FIG. 3, the times T1, T2, T3,
`etc. represent the time at which each ultrasonic pulse is
`generated. Referring to signal 80 in FIG. 4, T'], T'z, T’3,
`etc. represent the times at which these ultrasonic pulses
`are detected by the microphone 78. Therefore, the dif
`ference in time between T1 and T'] represents the delay
`between gene