Surgery – Truss – Pad
Patent
1995-04-14
1997-03-18
Manuel, George
Surgery
Truss
Pad
128903, A61B 504, A61B 50402
Patent
active
056113463
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of interference-tolerant heartbeat measurement, in which method a person's heartbeat signal is measured at a suitable part of the body and transmitted by telemetric transmission from a transmitter to a receiver as pulse data formed by successive measuring pulses, in which data a transmission interval of at least some pulse signals is proportional to the person's measured heartbeat rate.
Known telemetric transmitters of heartbeat measuring devices typically transmit a burst of about 5 kHz each time they detect an ECG signal. A transmitter circuit is constituted by a simple resonance circuit activated by transistor control. At heartbeat measurement, a transmitter unit sends a signal each time the heart beats. A receiver calculates the heartbeat rate on the basis of the difference of time between the successive signals transmitted, which means that the method in principle consists of time interval coding, i.e. that the data to be transmitted is included in the transmission and coded into the time between the pulses.
The known method described above is simple and reliable in conditions free of interference. Single interferences can be filtered off by comparing the obtained pulse value with preceding results: if a new measurement result differs too much from the preceding ones, it is obviously caused by some outer interference coupled to the transmission-reception channel and may thus be eliminated from the measurement results.
However, if wireless transmission of pulse data is performed in an interfered environment, the situation changes essentially. A continuous irregular pulse train may then arrive at the receiver, from which train to pick up the correct pulse signal is a difficult task, often even impossible. Such a situation arises easily when two or several users of pulsimeters are too close to each other.
SUMMARY OF THE INVENTION
The object of this invention is to provide methods by means of which the above-mentioned drawbacks are avoided and a coding of a pulse signal is effected in such a way that it is possible to pick up the correct signals from an incoming interfered signal flow reliably and accurately without deteriorating the original accuracy of the moment of timing the signal.
To achieve this, the method according to the invention is characterized in that each transmission of pulse data comprises at least two identification pulses, whereby the time interval between the identification pulses corresponds to a specific time interval determined for each transmitter-receiver pair, on the basis of which specific interval the receiver identifies the measuring pulses intended for itself.
By means of the method of the invention, it is possible to pick up the correct pulse data from the incoming interfered signal flow reliably and accurately without deteriorating the original accuracy of the moment of timing the signal carrying the pulse measuring information.
Preferred embodiments of the invention are characterized in what is disclosed below in the attached claims.
In the following the invention will be described in greater detail by means of embodiments with reference to the attached drawings, in which
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of a known telemetric heartbeat measuring device, to which the method according to the invention can be applied,
FIG. 2 illustrates schematically a burst signal applied to magnetic coils of a transmitter according to FIG. 1,
FIG. 3 illustrates an embodiment of the method of coding pulse data according to the invention,
FIG. 4 illustrates another embodiment of the method of coding pulse data according to the invention,
FIG. 5 illustrates a third embodiment of the method of coding pulse data according to the invention,
FIG. 6 illustrates the principle of a fourth embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Electrodes (not shown) of a telemetric heartbeat measuring device shown in FIG. 1 are connected to differential input terminals of an ECG preamplif
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Heikkila Ilkka
Pietila Arto
Layno Carl H.
Manuel George
Polar Electro OY
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