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Claims  |
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What is claimed is:
1. Process for the measuring of the heart pulse frequency, particularly for
the measuring of the heart pulse frequency of a moving test person for the
purpose of a performance test, comprising the steps of detecting heart
pulse signals at the body of the test person, counting the heart pulses,
eliminating from said counted heart pulse periods the interval of time of
which deviates from the preceding heart pulse by more than 20% in either
direction from the magnitude resulting from the period duration of said
heart pulse, producing a constant frequency pulse, determining the mean
value of the heart pulse frequency from the number of counted pulses of
constant frequency which fall into a period of time defined by a
predetermined number n of heart pulse periods E not so eliminated by
forming a first term corresponding to the sum of the counted pulses within
the period of time of -1 to n-1, forming a second term corresponding to
the negative value of the first term divided by the predetermined number n
of heart pulse periods E not so eliminated, forming a third term
corresponding to the number of counted pulses not eliminated within the
period of time n-1 to n and forming the sum of said first, second and
third terms.
2. Process in accordance with claim 1, including the step of eliminating
changes of the mean value of the heart pulse frequency within a heart
period of more than a single unit.
3. Process in accordance with claim 1, including the step of amplifying the
signals detected at the body of the test person as a function of the peak
value of the preceding signal, subsequently, storing said amplified
signals as constant values until the next successive signal is detected
and triggering, by means of the amplified signals, a threshold value
switch for indicating amplified signals of a predetermined magnitude for
use in said determining step.
4. A heart pulse frequency meter comprising a receiver for receiving heart
pulses, an amplifier connected to the receiver for amplifying the signals
produced by the receiver, means connected to said amplifier for forming
the mean value of the heart-pulse frequency, said mean value forming means
determining the mean value of the pulse frequency over a period of time of
n heart pulse periods in view of the number of counted pulses falling
within said period of time, said mean value forming means including
counter means for determining the counted pulses falling into periods of
time -1 to n-1 and n-1 to n, means for eliminating from said mean value
forming means heart pulse periods the interval of time of which deviates
from the preceding heart pulse by more than 20% in either direction from
the magnitude resulting from the period duration of said preceding heart
pulse, computing means for computing the mean value based on the counted
pulses in the counter means, means connecting said counter means to said
computing means and means for displaying the mean value.
5. A heart pulse meter in accordance with claim 4, including means for
varying the amplification of said amplifier, short-time constant value
storage means connected to said amplifier and to said amplification
varying means, a threshold value switch connected to the output of said
amplifier and a monostable multivibrator connected to the output of said
threshold value switch, the output of said monostable multivibrator being
connected to said mean value forming means.
6. A heart pulse meter in accordance with claim 5, wherein the monostable
multivibrator has an unstable state, the period of time of which is a
value which permits the measuring of the pulse frequency up to a limit
value.
7. A heart pulse meter in accordance with claim 6, wherein said limit value
is 220 heart beats per minute.
8. A heart pulse meter in accordance with claim 5, including at least one
filter comprising a band pass amplifier connected in circuit between the
receiver and the threshold value switch.
9. A heart pulse meter in accordance with claim 5, wherein said
amplification varying means includes a field effect transistor for varying
the feedback to said amplifier, said transistor having a gate, source and
drain, a further amplifier having an input and an output, said gate being
connected with the output of said further amplifier, said source being
connected to the output of said amplifier, said drain being connected to
ground, the input of said further amplifier being connected to said
short-time constant value storage means for receiving the peak value of
the signal stored therein.
10. A heart pulse meter in accordance with claim 5, wherein the receiver
comprises at least two body electrodes, each electrode being connected to
an impedance transformer, the outputs of said transformers being connected
to the inputs of a sum-and-difference amplifier.
11. A heart pulse meter in accordance with claim 5, wherein the receiver
comprises an optoelectrical pulse receiver.
12. A heart pulse meter in accordance with claim 5, wherein said
amplification varying means includes a field effect transistor for varying
the feedback to said amplifier, said transistor having a gate, source and
drain, a further amplifier having an input and an output, said gate being
connected with the output of said further amplifier, said source being
connected to the output of said amplifier, said drain being connected to
an input of said amplifier, the input of said further amplifier being
connected to said short-time constant value storage means for receiving
the peak value of the signal stored therein.
13. Process for the measuring of heart pulse frequency, particularly for
the measuring of the heart pulse frequency of a moving test person for the
purpose of a perforance test, comprising the steps of detecting a signal
at the body of the test person, amplifying the detected signal as a
function of the peak value of the preceding detected signal, subsequently
storing as a constant value the signal detected at the body of the test
person until the next successive signal is detected, triggering, by means
of the amplified signal, a threshold value switch for indicating amplified
signals having a predetermined magnitude, determing the mean value of
heart pulse frequency from the amplified signals indicated by the
threshold value switch and displaying the heart pulse frequency.
14. A heart pulse frequency meter comprising receiver for receiving
detected heart pulses, an amplifier connected to said receiver for
amplifying the signals received by the receiver, means for varying the
amplification of said amplifier, short-time storage means connected to
said amplifier and to said amplification varying means for storing said
signals as constant values, a threshold value switch connected to the
output of said amplifier, a monostable multivibrator connected to the
output of said threshold value switch, means connected to the output of
said monostable multivibrator for determining the mean value of the
frequency of said signals, said mean value corresponding to heart pulse
frequency and means connected to said determining means for displaying the
heart pulse frequency. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The invention concerns a process for the measuring of the heart pulse
frequency, particularly for the measuring of the heart pulse frequency of
a moving test person for the purpose of a performance test as well as a
heart pulse frequency meter.
The measuring of the heart pulse frequency with the known processes and
units is generally unsatisfactory, at least when the test person moves
during the measuring process as is the case during a performance test. In
particular, the accuracy is unsatisfactory, but, in addition, interfering
influences are not eliminated to a sufficient degree.
SUMMARY AND OBJECTS OF THE INVENTION
An object of the invention is to provide a process and apparatus for the
measuring of the heart pulse frequency wherein interfering influences are
eliminated, for example, interference pulses, for supplying accurate
values and which requires an easily effected, simple adjustment to the
test person. This object is performed according to the invention by the
fact that the mean value of the heart pulse frequency is determined from
that number of counted pulses of constant frequency which falls into a
period of time defined by a predetermined number n of heart pulse periods
E whereby the sum of the counted pulses is formed of three terms of a sum,
the first term of which corresponds to the sum of the counted pulses
within the period of time -1 to n-1, the second term to the negative value
of the first term divided by the predetermined number n of heart pulse
periods and the third term to the number of counted pulses within the
period of time n-1 to n. The sliding mean value determined in this manner,
which is always determined from the number of counted pulses which has
fallen into the period of time of the n+1 heart pulse periods terminated
at the moment of the measuring, is very accurate. Another considerable
advantage of the process according to the invention consists of the fact
that the computation of this sliding mean value with the aid of an
arithmetic computer with program storage requires a relatively low
expenditure since only two storage spaces are necessary.
In order to eliminate interfering influences, it is advantageous to
eliminate changes of the mean value of the heart pulse frequency within a
heart pulse period of more than a single unit.
In order to reliably pick up each signal produced by a pulse beat, in the
case of a preferred embodiment, the signals taken from the body of the
test person are amplified as a function of the peak value of the preceding
signal and subsequently stored until the next signal occurs. Furthermore,
a threshold value switch is triggered by means of the amplified signals.
Owing to the amplification of the signals as a function of the peak value
of the preceding signal, fluctuations of the signal volume, which are due
to interferences when picking up the signals by means of the receiver, can
be eliminated to a sufficient degree. The peak value of the amplified
signal is, therefore, in a predetermined range and is thus in a position
to trigger a subsequent threshold value switch. The triggering of this
threshold value switch due to the peak value of the amplified signal
leads, furthermore, to the elimination of interference signals. In this
way it is thus insured that, with each pulse beat, the threshold value
switch and a pulse shaper circuit, which is preferably arranged subsequent
to it, are triggered which results in a sequence of pulses corresponding
to the pulse beats in a selective form and magnitude.
For reasons of expediency, the signals are additionally filtered. For this
purpose, it is advantageous to eliminate pulse signals the period of which
is smaller than 80% and larger than 120% of the period of the preceding
pulse signal, i.e., which do not meet the condition 0.8 E.sub.n-1 <E.sub.n
<1.2 E.sub.n-1 and to not take into account when forming the mean value,
those pulse signals whose period duration is outside the predetermined
limits, preferably below 0.2 second and above 2 seconds.
The invention is also based on an object to provide a heart pulse frequency
meter to perform the process according to the invention which is of as
simple a design as possible but is, nevertheless, operationally reliable.
This object is accomplished according to the invention by a receiver which
produces a sequence of electrical signals due to the pulse beats with
amplification by a subsequent amplifier, a counting pulse generator with
constant pulse frequency, a device for the formation of the mean value
which determines the mean value of the pulse frequency over a period of
time of n heart pulse periods owing to the number of counted pulses
falling into this period of time, counters which determine the counted
impulses falling into the period of time -1 to n-1 and n-1 to n as well as
a calculator circuit which deducts from the sum of the number of pulses
counted by the two counters with the nth part of the number of counted
pulses within the period of time -1 to n-1.
In the case of a preferred embodiment, the amplifier subsequent to the
receiver is designed as an amplifier with variable amplification
subsequent to which a threshold value switch as well as a short-time
storage are installed to which a control circuit for the control of the
amplification is connected. Preferably, a monostable multivibrator is
connected to the output of the threshold value switch, the unstable state
of which is, in the case of a preferred embodiment, adjusted at a period
of time which permits the measuring of the pulse frequency up to 220 heart
beats per minute. Interferences which occur within the unstable state are
eliminated by the monostable multivibrator.
Preferably, there is at least one filter, designed as band pass amplifier,
installed between the receiver and the threshold value switch. In this
way, a great part of the interference signals can be filtered out before
the signals reach the monostable multivibrator.
The amplification of the amplifier, installed in front of the short-time
storage, can be controlled in a manner corresponding to the peak value of
the signal stored in the short-time storage at particularly low expense if
a field effect transistor is provided in the return circuit of the
amplifier. The gate of the field effect transistor is connected with the
output of an amplifier at the input of which the peak value of the signals
stored in the short-time storage is located. The input of the last
mentioned amplifier can be selected at such a high impedance (Z) that it
does not affect the stored peak value and, by means of the field effect
transistor, the amplification can be changed within a large range and very
rapidly.
In order to adapt the device as effectively as possible to the different
conditions in the case of different persons, the amplifier controlling the
field effect transistor has an adjustable and variable amplification.
The receiver can consist of two or three body electrodes. When using two
body electrodes, an impedance transformer is installed subsequent to each
of them and when using three body electrodes, only two of them have each
installed such an impedance transformer. The third body electrode serves
as mass supplier. The outputs of the impedance transformers are connected
to a sum-and-difference amplifier. However, the receiver can also comprise
an optoelectrical pulse receiver to be preferably placed at the ear.
Below, the invention is explained in detail by means of two exemplified
embodiments shown in the drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a wiring diagram of the first exemplified embodiment;
FIG. 2 is a wiring diagram of the second exemplified embodiment; and
FIG. 3 is a wiring diagram of the device for the formation of the mean
value.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
A device for the production of a sequence of square wave pulses
corresponding to the pulse beats of a human being has, as is shown in FIG.
1, four inputs 1, 2, 3 and 4. The input 2 is on ground connection.
Either two or three body electrodes 28 or an optoelectrical pulse receiver
29 can be utilized as receivers. The body electrodes are connected to the
inputs 1, 2 and 3, the optoelectrical pulse receiver to the inputs 2 and
4. The inputs 1 and 3 are connected to the two inputs of a
sum-and-difference amplifier 7, each through an impedance transformer 5
and 6 each of which comprises one amplifier. The input 4 is connected to
the output of the sum-and-difference amplifier 7 subsequent to which a
filter constructed as a band pass amplifier 8 is installed.
The signals filtered by the band pass amplifier 8 are supplied, over a
coupling resistor 9, to the inverting input of an operational amplifier
10, the non-inverting input of which is connected, via a resistor 11, with
ground. The operational amplifier 10 has a return line connecting its
output with the inverting input which is formed by the series connection
of a field effect transistor 12 and a resistor 13. It is the purpose of
the field effect transistor 12 to control changes in the amplification of
the operational amplifier 10.
Subsequent to the amplifier with variable amplification formed by the
operational amplifier 10 and the variable resistance feed-back, a
short-time storage is installed which is designated generally by 14. The
short-time storage 14 consists of a diode 15, a resistor 16 and a
condenser 17 which are installed in this sequence, whereby the diode is
connected to the output of the operational amplifier 10, with its
conduction direction as shown in the drawing and the condenser is
connected with ground.
The short-time storage 14 is followed by a threshold value switch 18 which,
in the exemplified embodiment, is designed as a Schmitt trigger comprising
an operational amplifier. Since the threshold value switch 18 should then
emit a signal at its output when the peak value of the signal stored in
the short-time storage 14 exceeds the threshold value, the one input of
the operational amplifier contained in the threshold value switch 18 is
connected with the connection between the resistor 16 and the condenser
17. The other input is connected to the output of the operational
amplifier 10.
Since the amplification of the operational amplifier 10 is to be controlled
as a function of the peak value of the signal stored in the short-time
storage, the value of the peak value signal so stored remains constant for
the duration it is stored in the short-time storage. A voltage divider
comprising the resistors 19 and 20, and which is of a high-impedance
character, is connected in parallel to the input of the threshold value
switch 18. This voltage divider is also in parallel to the connection in
series formed by the diode 15 and the resistor 16. The center pick-up of
the voltage divider formed by the resistors 19 and 20 is connected with
the non-inverting input of an operational amplifier 21, the inverting
input of which is, via a resistor 22, connected at the pickup of a voltage
divider 23 and is, via a resistor 24, connected with the output of
operational amplifier 21. By means of the voltage divider 23 and a voltage
source, which is not shown, the amplification of the operational amplifier
21 can be adjusted and changed. The output of the operational amplifier 21
is connected with the gate of the field effect transistor 12.
Subsequent to the threshold value switch 18, there is a monostable
multivibrator 25 at the output of which a sequence of square wave pulses
occurs which corresponds to the sequence of pulse beats which are picked
up by means of the receiver. The time of the unstable state of the
monostable multivibrator 25 has been chosen such that pulse frequencies up
to 220 heart beats per minute can be measured. Interferences which occur
within the unstable state are eliminated.
Owing to the fact that the amplification of the operational amplifier 10 is
controlled as a function of the peak value of the preceding signal stored
by means of the short-time storage 14, the peak value of the signals
occurring at the output of the operational amplifier is, independently of
interfering influences, within a range which makes an additional
evaluation possible. Since the amplitude of the signal can be very
different in case of different persons, the device can be adjusted to
these differences by setting a suitable amplification by the use of the
voltage divider 23.
In the case of the exemplified embodiment shown in FIG. 2, the output of
the sum-and-difference amplifier 107, the two inputs of which are
connected with the impedance transformers 105 and 106, is connected with
the inverting input of the operational amplifier 110 over a coupling
resistor 109. Also the input 104 of the receiver 29 is connected to this
input via a coupling resistor 127. The non-inverting input of the
operational amplifier 110 is connected with the ground through resistor
111.
The operational amplifier 110 has, just as the operational amplifier 10 of
FIG. 1, a return line connecting its output with the inverting input. This
is formed by a resistor 113 which, on the one hand, is connected to the
inverting input and, on the other hand, to the pick-up of a voltage
divider which is formed by a fixed resistor 126 and a field effect
transistor 112. The voltage divider is installed between the output of the
operational amplifier 110 and the ground and this in such a manner that
the resistor 126 is connected with the output of the operational amplifier
110 and the field effect transistor 112 with ground.
The output of the operational amplifier 110 is connected with the input of
the threshold value switch 118 over a band pass amplifier 108. But also
the operational amplifier 110 has the effect of a band pass amplifier.
A peak value short-time storage is connected to the input of the threshold
value switch 118 being in contact with the band pass amplifier 108; this
peak value short-time storage is formed by a connection in series
consisting of the diode 115, the resistor 116 and the condenser 114. The
condenser 114 is, on the one hand, connected with ground and, on the other
hand, with one input of a sum-and-difference amplifier 121 at the other
input of which there is a reference voltage U.sub.ref.sbsb.1. The output
of the sum-and-difference amplifier 121 is connected with the gate of the
field effect transistor 112. The condenser 114 is, over the diode 115 and
the resistor 116, charged to the peak value of the signal occurring at the
output of the band pass amplifier 108 and modulates the field effect
transistor 112 as a function of the difference between this peak value and
the reference voltage at the other input whereby the potential at the
pick-up of the voltage divider for the return of the operational amplifier
110 and thus the amplification degree of this operational amplifier is
adjusted to the value obtained by the desired signal amplitude at the
output of the operational amplifier 110.
As is shown in FIG. 2, there exists also a reference voltage
U.sub.ref.sbsb.2 at the second input of the threshold value switch 118.
The threshold value switch 118 is triggered when the signal occurring at
the output of the band pass amplifier 108 reaches the necessary amplitude.
The threshold value switch 118 triggers the monostable multivibrator 125.
Each time the monostable multivibrator 125 is triggered, a square wave
pulse develops at its output. The time of the unstable state of the
multivibrator 125 is determined in such a way that pulse frequencies up to
220 heart beats per minute can still be processed. Interferences which
occur as long as the monostable multivibrator 125 is in its unstable
stage, are eliminated.
As in the case of the exemplified embodiment according to FIG. 1, the
device has four inputs 101 to 104 to which two or three body electrodes 28
or an optoelectrical pulse receiver 29 are connected.
As in the case of the exemplified embodiment according to FIG. 1, there is
also in the case of that according to FIG. 2, a device for the formation
of the mean value, designated by reference numeral 30, and installed
subsequent to the monostable multivibrator 125. This device, as shown in
FIG. 3, consists of a pulse generator 31, two pulse counters 32 and 33, a
summing connection 34 as well as two dividing connections 35 and 36.
The output signals of the monostable multivibrator, the intervals of which
in time correspond to the coordinated heart pulse period, are used for the
control of the two pulse counters 32 and 33 to which counted pulses i are
supplied which are produced by the pulse generator 31 and have a frequency
of 50 Hz in the exemplified embodiment.
Since the frequency meter according to the invention indicates the heart
pulse frequency in the form of a sliding mean value from 25 heart pulse
periods, the counter 32 always counts the number of the counted pulses i
which fall into the period of time between the -1st and the 24th heart
pulse period. On the other hand, the counter 33 forms continuously the sum
of the counted pulses in the period of time between the 24th and 25th
heart pulse period. The two sums determined by the counters 32 and 33 are
supplied to the summing connection 34 to which is also supplied the
negative value of the initial value of the dividing connection 35 which
divides the sum formed by the counter 32 by the value 25. Therefore, the
following equation is applicable for the initial dimension of the summing
connection:
##EQU1##
By means of components in the circuit not shown in detail, all those
initial pulses of the monostable multivibrator, the period duration of
which is under 0.2 second and above 2 seconds, are eliminated.
The summing connection 34 is followed by the dividing connection 36 which,
in the exemplified embodiment, determines the magnitude:
##EQU2##
The magnitude F represents the sliding mean value of 25 heart pulse
periods E measured in pulse beats per minute. From this dimension as well
as the frequency of the counted pulses and the number of the heart pulse
periods used for the formation of the mean value results the value given
in the counter.
The dividing connection is designed in such a manner that, per heart pulse
period, the value F can only change by one unit up or down. Since the
heart pulse frequency also changes correspondingly slowly, additional
interfering influences are eliminated in this way.
For the elimination of interfering influences, an additional filter can be
provided which forms a time window with the conditions:
0.8 E.sub.n -1<E.sub.n <1.2 E.sub.n-1
and eliminates all pulses which do not fall into this time window.
The task of the counters 32 and 33, of the summing connection 34 and of the
dividing connections 35 and 36 are advantageously performed by an
arithmetic computer with program storage which, for reasons of expediency,
consists of an input/output unit, a microprocessor and an ROM/RAM storage.
In this connection it is of particular advantage that only two storage
places are required for the computation of the sum of the counted pulses.
In the case of the exemplified embodiments, the sliding mean value F is
continuously displayed or displayed on call in digital form on a display
37.
Although only preferred embodiments are specifically illustrated and
described herein, it will be appreciated that many modifications and
variations of the present invention are possible in light of the above
teachings and within the purview of the appended claims without departing
from the spirit and intended scope of the invention.
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