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Description  |
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BACKGROUND OF THE INVENTION
For many years both health care professionals and athletic coaches have
recognized that the pulse rate of an individual is a primary source of
information about the current and long-term condition of a person's
physiology. To the health care professional the measurement of pulse rate
is a primary measurement taken at the outset of an examination and is a
parameter which is measured regularly for continuing diagnosis and care.
Hospitals are now well equipped for continuous monitoring of the pulse
rate of patients in cardiac and critical care units. To the athletic coach
and to the occasional and regular athlete, the pulse rate of the athlete
is important and hopefully known. In the past attempts have been made to
produce a portable pulse rate meter which can be carried by or worn by the
athlete to provide current pulse rate information while the athlete is
engaged in strenuous activity such as running. Examples of patents showing
pulse rate meters to be worn or carried by individuals are U.S. Pat. Nos.
3,978,849 to Harold S. Geneen, 4,009,708 to John J. Fay, Jr., 4,058,118 to
Lawrence J. Stupay et al, 4,030,483 to Jack B. Stevens, 4,063,551 to James
Sweeney, and 4,038,976 to Frank M. Hardy et al.
Numerous other patents have issued to inventors of complex pulse rate
meters designed for non-portable hospital and other fixed installation
use. Examples of such equipment are shown in U.S. Pat. Nos. 4,022,192 to
Laukren and 4,018,219 to Hajaiban.
Numerous patents have issued on digital watches and various timing and
display circuitry therefor.
Nowhere in the prior art has it been recognized that by combining a pulse
rate meter with a digital watch, in addition to the normal advantages one
might expect, the resulting instrument has greater contribution than the
sum of its parts. It is believed that in the prior art no one has combined
a watch giving real time with a pulse-rate meter. And more particularly,
no one has used such a combination in which the precise accurate timing
circuitry of the watch is used to provide both timing for the signal
processing and display of pulse information. The additional accuracy
possible allows the display of instantaneous pulse rate on a pulse by
pulse basis unrecognized in the prior art. Further, the prior art does not
recognize that by the simultaneous display of average and instantaneous
values of the wearer's pulse rate, the comparison between instantaneous
and average pulse rate may be accomplished to give a direct indication of
abnormalities, and the exact time of the abnormality occurrence may be
observed.
BRIEF DESCRIPTION OF THE INVENTION
We have discovered that greatly enhanced utility for wrist-borne pulse rate
meters is possible by combining the available technology in digital
watches with improved signal processing to detect the actual instantaneous
pulse rate of the wearer on a pulse by pulse basis, and to simultaneously
calculate and display the average pulse rate over a period of time equal
to "N" pulses. Thus employing our invention the wearer is able to
simultaneously observe his average pulse rate and the last pulse rate.
This allows the wearer to follow the cardiac response to changing work
loads and to detect abnormalities in his pulse rate which otherwise would
be submerged in averaging type circuitry. A simultaneous display of
average and instantaneous pulse rate may show a difference between the two
which is of no significance, for example by movement of the sensor on the
skin or other external interference. On the other hand the display of
instantaneous rate may indicate the existence of premature ventrical
contractions of the heart requiring the attention of the wearer's
physician. The availability of actual time data allows the wearer to know
when deviations occurred and this can be calibrated with the nature of his
activity, the extent of exertion and physical location if later desired.
In accordance with our invention there is the elimination of ambiguity
present in many of the types of digital displays where the common field is
used to display sequentially data of a different nature requiring the user
to first ascertain what data is being displayed followed by an observation
and analysis of the data. The data may have changed between the time that
the first appraisal is made and the second observation, resulting in a
confusing situation.
In accordance with this invention a device which has the general appearance
of a digital watch is employed. On the outer face there are a pair of
windows. One window displays real time in accordance with common practice
for digital watches. The second window, having six digits for data
presentation, allocates three spaces to average pulse value and three
spaces to the instantaneous pulse value. Selector switches, one for the
time record, and the other for the pulse display, are located in the edge
of the watch case for easy access. They are of different shape and
location to allow tactile identification.
The under face of the case includes a pulse transducer. In one embodiment
the pulse transducer is an electro-mechanical device such as a
piezoelectric crystal. When the transducer is an electro-mechanical
device, the watch must be worn on the volar surface of the wrist but
lateral to the tendon cord bundles. In the sub pollex depression, the
pulse of the radial artery may be obtained. The ulnar pulse may be
obtained on the opposite side of the tendon cord bundle from the radial
artery.
In the preferred embodiment the pulse transducer is a light source such as
an LED centrally located and encircled by a light detector such as a photo
diode. A pair of light blocking rings integral with a lower case face
isolate the photo detector from direct view from the light source and from
view of the ambient light when the lower face is in contact with the
wearer's body e.g. the wrist. In the employment of the light backscatter
sensing described above, the watch is worn on the lateral surface of the
wrist so that the sensors can respond to the pulse induced changes in the
arteriolar and capillary beds in the subcutaneous tissues.
The circuitry accomplishing the improved results of this invention employs
a common oscillator which is used to drive both the timing circuitry and
display circuitry. The timing circuitry for the watch constitutes well
known dividers, counters, a multiplexer and driving circuitry. The display
similarly is one of the well known types of LED or liquid crystal. This
display is commonly found in watches of the digital type.
The pulse signal processing circuitry of this invention is driven by the
same oscillator used in the watch timing functions and includes a
circuitry for developing a trigger signal for each pulse of the wearer and
for converting the train of clock beats into a stored frequency count in
pulses per minute. The last read pulse rate is stored and the values of
the last "N" pulse rates are stored. The last pulse rate is displayed via
the multiplexer and display. The average of the last "N" rates is
determined via a divide by "N" circuit and is likewise displayed via the
multiplexer and the display.
Where six digits of time information are desired for example, hour, minutes
and seconds, six-digit display is used for time. Employing this invention
six digits are required for a display of average and instantaneous pulse
rates. Thus two identical six-digit displays are employed in this
invention. The time functions are presented in a 3.times.2 digital display
and the pulse rates are presented in a 2.times.3 digital display.
A novel infra-red source-detector combination is disclosed employing a
concentric arrangement of light source and detector and light blocking
bosses surrounding each.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a front face view of the combined digital watch and pulse rate
meter of this invention with the straps shown in fragmentary form;
FIG. 2 is a rear view of the invention of FIG. 1;
FIG. 3 is a side elevational view thereof;
FIG. 4 is a rear face view of an alternate embodiment of this invention;
FIG. 5 is a side elevational view of the alternate embodiment of FIG. 4;
FIG. 6 is a fragmentary sectional view of the sensor portion of the
embodiment of FIGS. 1 through 3 taken along line 6--6 of FIG. 2;
FIGS. 7 and 8 constitute a block diagram of the circuitry of this
invention; and
FIG. 9 is a layout diagram for FIGS. 7 and 8.
DETAILED DESCRIPTION OF THE INVENTION
This invention is embodied in a combination wristwatch pulse rate meter in
the form best seen in FIG. 1. There, the combination of this invention
generally designated 10 is all enclosed within a watch type case 11 having
a front face region 12 with a pair of windows 13 and 14. Each of the
windows 13 and 14 contain display means, for example, LED, liquid crystal,
or other type of visual display commonly used in digital watches. In the
preferred embodiment each have a six-digit display which may be similar
for purposes of minimization of types of parts utilized in the
manufacture. Since it is preferred that the time display has multiple
selectable time displays--typical labeling under the time displays is as
disclosed. The time functions preferred to be available on demand include:
Date--Day and hour
Hours, Minutes, Seconds and elapsed time
Minutes, Seconds, 0.01 seconds.
In the window 14 again a six-digit display is used but in this case the
first three digits display the average pulse rate and the legend
indicating the average is located on the front face 12 below the window
14, more particularly below the first three digits space, and the last
three digits display the instantaneous pulse rate and is so identified by
legend on the face 12. The use of two separate displays is advantageous in
that it presents the actual time of the reading and less confusing
readout, particularly for the jogger or one who is wearing this invention
for medical reasons. Time always appears in one window and pulse rate in
the other.
In FIG. 1 the time is registered as 7 hours, 30 minutes and 0 seconds while
a typical pulse rate for one engaged in athletic activity is displayed in
the lower window 14. The instrument 10 registers an average rate of 122
pulses per minute with an instantaneous or last pulse at a rate of 119
pulses per minute.
In addition to the desirability of dual independent space for time and
pulse information, simultaneous display of average pulse rates and
instantaneous pulse rate is of significant importance. Prior art pulse
rate meters using less precise circuitry employ averaging to avoid
displaying an abnormality related to either patient movement relative to
the transducer or errors in signal processing. In accordance with this
invention, the simultaneous display of average and instantaneous pulse
rate provides three important sets of information; the two values
displayed plus the simultaneous comparson of the two. The average pulse
rate is important in showing the trend over a number of cycles and will
tend to change less dramatically. Thus a jogger can watch his pulse climb
from start of activity towards the limit he or his doctor has set.
Any abnormality in any one pulse is clearly displayed in the right three
digits of the pulse rate display. Its displacement from the average rate
indicates the abnormality to the wearer at the same instant he is
observing the average rate. The abnormality may indicate a premature
ventricular contraction of the heart about which the wearer should be
concerned based upon his doctor's evaluation, or it may be due to some
abnormality of movement of the watch on the wrist or due to some abrupt
change in the activity of the user.
Thus, the average value and the instantaneous value both bear significant
information and the comparison of the two values made possible by this
simultaneous display in the same window provides additional significant
information to the wearer. The time display is simultaneously available.
Thus, time of occurrence is observable as well.
The combination of this invention preferably includes three controls--15,
16, and 17 as follows:
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Function Positions
______________________________________
Watch Switch Date or time Display off
15 selection Date on
Time on
Pulse Switch Pulse Sensor and
(1) Sensor and
Rate 16 Display Condition
Display OFF
(2) Sensor and
Display ON
(3) Sensor OFF
Display locked
Timer or
Switch Control Stop (1) Timer OFF/Reset
Stop 17 Watch Timer and
Display OFF
Watch Display (2) Timer ON
Display ON
(3) Timer OFF
Display Locked ON
to fast recording.
______________________________________
The timer function is useful particularly for one doing timed exercises or
jogging but is not mandatory. It employs the accurate timing circuitry of
the watch and uses its display as well. To aid in eliminating any
ambiguity in the nature of the reading, the timer switch 17 further
produces the display of a decimal point ahead of the hundredths position.
This signal plus the rapid change of the last two positions (hundredths of
a second) gives the user a clear indication that the timer fraction is
being displayed in the time window 13.
Switch 15 will have three fixed positions to select the time function
display mode and pulse mode for setting or adjusting time functions.
The combination 10 is held on the wearer's body by a pair of straps 20 and
21 which may be ordinary watch straps in the preferred embodiment of this
invention since all powering, sensing and control features of this
invention are contained within the case 11.
Now referring to FIGS. 2-5, which are side and under side views of the
invention of FIG. 1, the typical relationship of the straps 20 and 21 to
the case 11 are more clearly apparent, and in these views the transducer
portion on the underside of the case 11 may be seen. This transducer
structure is contained within a boss region 22 of substantial diameter in
order to provide a relatively large area of intimate contact with the
user's wrist. This will insure both comfortable wearing and sufficient
contact for obtaining an accurate pulse indication by either a pulse
transducer of the pressure type contained therein shown in FIGS. 4 and 5,
or by the preferred embodiment employing an infra-red source-detector
combination as best shown in FIG. 2.
Watch straps must provide adjustable tension in as much as the sensors must
be forced into the flesh of the wrist for a reading. This situation may be
uncomfortable over a prolonged period of time and the strap may include
provision for release of pressure during normal wearing.
A suitable detector is the type CLT 2160 photo diode produced by Clairex
Electronics, Inc., of Mount Vernon, New York 10550.
Centrally located within the detector 23 is a secondary boss 22A, and an
infra-red source 24 which may, for example, be a light emitting diode such
as type SSL 55 CF of the General Electric Company, which provides
emissions in the near infra-red region.
The circular detector array 23 surrounding the infra red source 24 insures
a detection of the change in optical backscatter of the subcutaneous
arteriolar and capillary bed of the wearer with each heart contraction and
resultant pulse of oxygenated blood. The boss 22 serves to isolate the
infra-red detector from ambient light. The boss 22A prevents direct
transmission of light between source 24 and detectors 23. The coaxial
arrangement of these three elements provides a relatively large contact
surface area resulting in not only effective sensing of a pulse rate but
minimum discomfort to the wearer. The circular array of the detector 23
allows the detection of pulses in a substantial arteriolar-capillary bed
within the hemispherical region denoted in FIG. 6 for increased signal to
noise ratio and energy utilization. In FIG. 3 in partial cross-section,
two sections of a single circular apertured disc photo-detector, 23a, are
shown. The single photo-detector 23a, or the circular array 23 of FIG. 2
allows integration of the backscatter field which serves the dual purpose
of increasing signal sensitivity and reducing position dependence of the
pulse meter.
An alternate, less preferred transducer is illustrated in FIGS. 4 and 5.
There boss 32, similar to boss 22, is present however, a pressure
transducer 33 constitutes the pulse source in direct contact with the
wrist of the wearer. The transducer 32 may be of the piezoelectric or
other type well known in the art.
DESCRIPTION OF THE CIRCUITRY
The circuitry of this invention which provides for the combinatiion of
time, average pulse rate and instantaneous pulse rate information is
represented in accordance with the preferred circuitry as shown in block
diagram form in FIGS. 7 and 8.
Now referring to FIGS. 7 and 8 in conjunction with FIGS. 1 through 6 for
reference, the basic timing element of this invention is an oscillator
100, for example a crystal oscillator operating at a suitable frequency,
for example 2.sup.21 Hz. There are precision oscillator crystals mass
produced for watch circuits with nominal frequencies of 2.sup.15 Hz and at
2.sup.16 Hz. The 2.sup.15 Hz is too slow for both precision timing and
computation storage and and is based upon every pulse period. The 2.sup.16
Hz is marginal. The 2.sup.21 Hz is also a mass produced, precision crystal
which may be economically employed. At this frequency there is ample speed
to execute all of the timing, storage, computational, transfer and display
functions. The output of the oscillator 100 is introduced into the
cascaded divider network 101 constituting a plurality of divider steps so
arranged to provide submultiples of the basic frequency. Typical
frequencies of the divider 101 used are 2.sup.10 Hz used to control the
chronometric measurements, 2.sup.3 Hz used to control frequency steering
logic and display logic; 2.sup.9 Hz for use in the pulse signal
acquisition and processing circuit and 2.sup.21 Hz used in the processing
storage and computing of pulse-rates.
The 2.sup.10 Hz signal from the divider 101 is itself introduced in two
series connected converters or dividers 102 and 103; the former,
converting the 2.sup.10 Hz signal to the train of pulses of one
millisecond duration, and the divider 103 providing 0.01 second timing
pulses which are used to drive a hundredth of a second counter 104. The
0.01 second counter 104 is in actuality two cascaded decade counters. Upon
overflow after a count of 99 this counter 104 automatically resets to a
count of 00.
The seconds counter 105 is actually two decade counters set to overflow and
reset to 00 after reaching a count of 59. At each overflow and reset a
pulse is sent to the minutes counter 106. Thus counter 104 produces an
output pulse to a seconds counter 105 every 100 pulses constituting one
second. The seconds counter 105 in turn produces one output pulse to a
minutes counter 106 every sixty seconds. The second counter 105 is
actually two decade counters set to overflow and reset to 00 after
reaching a count of 59. At each overflow and reset, a pulse is sent to the
minutes counter 106. The minutes counter in turn produces an output pulse
each sixty counts to an hours counter 107. The hours counter 107 produces
a single output pulse to a day counter 108 once each 24 hours. The day
counter 108 in turn produces an output pulse for each pulse, and this
latter pulse is introduced into the date counter 109 which in turn
provides output pulses once each day to the multiplexer 112. The display
elements must be presented at a rate faster than the normal human flicker
perception which is approximately 16 Hz, or 2.sup.4 Hz. Digital displays
at 64 Hz are perceived as a steady source. Strobe pulses for the
multiplexer 112 are provided by a 2.sup.n Hz strobe and digit driver
circuit 113 which is additionally connected to a strobe source for the
display if required. The multiplexer 112 provides the output of the stored
information introduced by each time function source from 1/100th seconds
through the date counter to the segment decoder and segment driver circuit
114 which is directly connected to the date time display in windows 114 in
FIG. 1. Each of the foregoing aspects of the chronometry circuitry is well
known in the digital watch field and a mre complete understanding of the
selection and operation of such circuitry may be had by reference to a
number of prior patents or publications but particularly the article
entitled "An I.sup.2 L Watch Chip with Direct LED Drive" article entitled
("An I.sup.2 Watch Chip with Direct LED Drive" appearing in the Journal of
Solid State Circuits, Vol. SC-11 No. 6, December 1976 at Page 847 et seq
by Patrick A .Tucci and Louis K. Russell.
PULSE METER
The pulse measuring portions of this invention are all driven by the same
basic oscillator 100 which drives the chronometric system. The basic
timing frequency from the crystal oscillator 100 has been divided into
sub-multiple frequencies 2.sup.9 Hz, 2.sup.11 Hz, and 2.sup.21 Hz in the
divider 101 and are used in the pulse signal portions of the invention.
Signal acquisition employing our preferred embodiment is accomplished in
the block identified as 150, Signal Acquisition. It includes the infra-red
signal source 24 which optionally, in order to save power, may be pulsed
under the control of a pulse power source, 24A. Typically, a duty cycle of
20 percent is suitable at a pulse rate of 2 KHz.
The infra-red detector 23 will detect the backscatter signal emanating from
the wrist of the body portion of the wearer in the form of a 2 KHz signal
modulated in amplitude at the pulse rate of the individual. This signal is
then passed through a suitable amplifier having gain, for example of 1000,
and through a band pass filter BPF typically having a pass band of 1000 Hz
centered at 2 KHz. The signal is then envelope detected in a suitable
detector to provide the pulse wave and filtered through a low pass filter
having a cutoff in the order of 10 Hz to eliminate such interference as 60
cycle hum or other higher frequency signals that might be picked up. The
detected filtered pulse signal is then introduced into signal conversion
circuit 152 which typically includes a pulse square and inverter to
provide an output square wave at the frequency of the wearer's pulse. This
signal is then introduced as the switching signal to a bi-stable
multivibrator 153 having a pair of AND gates, each having one input
coupled to output leads of opposite states of the multivibrator 153. The
second input to each AND gate is a timing signal at a 2.sup.9 Hz
frequency. Each of these AND gates will pass the 2.sup.9 Hz signals to
their respective counter 154 and 155 for the period that the multivibrator
153 is in an ON state associated with that particular AND gate. The
counter 154 termed the Nth period counter, stores the number of 2.sup.9 Hz
pulses which pass through its associated AND gate. Similarly, the counter
155 which is identified as Nth+1 period counter, stores the number of
2.sup.N Hz pulses passing through its associated AND gate when enabled.
When there is no change in the pulse rate between two successive
individual pulses of the wearer, the count in both counters 154 and 155
will be identical. As the pulse rate of the wearer changes, the count in
the counters 154 and 155 will each change accordingly. The change from
pulse rate from counter period to counter period reflects the wearer's
change in pulse rate on a per pulse basis.
Both the counters 154 and 155 are under the control of a counter transfer
and reset logic circuit 156, which is itself under the control of
flip-flop 153. As each counter is loaded via its respective AND gate and
the flip-flop switches to the opposite state, a dump signal is received
from the transferred logic circuit 156 followed by reset applied to that
particular counter. The count in each counter is sequentially introduced
into the last period counter register 157, itself controlled by the logic
circuit 156. The count in register 157 is introduced into a divider 159
immediately before reloading. In the divider 159, the count present in the
register 157 is divided into the constant 60.times.2.sup.9 from counter
168. The output of the divider 159 is the rate in pulses per minute. It is
introduced into counter register 160 and in turn introduced into last
pulse rate register 161 where the last pulse rate in pulse per minute is
temporarily stored. Output lead 171 from the register 161 is used to
convey that last pulse rate signal to multiplexer 112 where it is in turn
applied to the instantaneous pulse display. In addition to the register
161, there are four storage registers 163 through 166, each of which store
the last four sequential pulse rates with the transfer of pulse rates
between the stages 161 through 166 under the control of shift logic
circuit 162. The total number of pulses in the registers 163 through 166
is obtained in adder 167. By dividing by 2.sup.2 in divider 168, the
number of storage registers 163 through 167, the average pulse rate for
the last four pulses is obtained and introduced via lead 172 after passing
through an average count register 169. The running average on lead 172 is
also introduced into the multiplexer 112 for display in the average pulse
position digits of display 14 of FIG. 1.
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