DE3028120A1 - Body function frequency measuring appts. esp. for breathing rate - determines quotient of measured to reference count values using programmable memory and binary counters - Google Patents

Abstract

The circuit is for measuring the frequency of a periodic signal and is esp. applicable to bodily functions such as breathing. The conventional method of counting breaths over a period of half to one minute is automated simply. The number of pulses derived from a signal corresp. to the function is fed to a programmable memory with a number of reference pulses. The quotient of the measured reference pulse counts is digitally determined. The derived and reference pulses are fed to binary counters whose output values are fed as addresses to the programmable memory or memories at defined times. The transfer times are determined by a decoder. At these times the count values are first input to intermediate memories and converted into addresses before transfer to the programmable memories.

Description

Method and circuit arrangement for determining the frequency of a periodic signal

The invention relates to a method for frequency tuning a periodic signal, in particular a body function such as breathing. Furthermore concerns the Invention a circuit arrangement for performing this method.

It is, for example, when taking an exercise ECG necessary, in addition to the cardiac activity, the breathing frequency to hold on. The cardiac activity is automatically recorded by means of a recorder; the breathing frequency, on the other hand, is still calculated by counting the breaths over half a minute to a minute, after which the result is written by hand next to the heart curves.

The present invention is based on the object of 20. automating the method mentioned at the beginning in a simple manner. This object is achieved according to the invention in that electrical pulses are derived from the signal, the number of which, together with the number of reference pulses, are fed to at least one programmable memory for a digital determination of the quotient from the numbers of derived and reference pulses.

Should z. If, for example, the breathing frequency is determined, one pulse per breath can advantageously be generated for this purpose. This can be done by pressing a button, by measuring the air flow or the temperature of the breathing air, but also

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by changing the resistance across the chest or by determining the mechanical expansion of the chest. It is also possible to generate several impulses per breath. At the same time, reference pulses are used as a time scale, so to speak generated, for example, one pulse per second. The quotient of the number of those produced by breathing Pulses to the reference pulses generated during this period directly sets the breathing frequency This quotient is according to the invention in a programmable Memory formed. The number of respiratory and reference pulses make up the addresses at which the corresponding frequency values are stored.

In an advantageous development of the invention it is provided that the derived as well as the reference pulses are given to a binary counter, the output values of which are used as addresses at certain times programmable memory are supplied. The specific times can be particularly easily set by a Decoder are specified, for example after every second Breath releases the values of the two binary counters for forwarding.

In an advantageous further development of the method, it is provided that these values are initially stored in buffers arrive, from where they are fed as addresses to the programmable memory. Thereby x-; earth the current numerical values are requested at certain times, placed in the buffer and held there until the next query, while the Change the values of the binary counters continuously.

The memory value belonging to a certain address represents a unit of time (usually when breathing one minute) related quotients and thus the

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desired frequency. This memory value is advantageous either for driving a recorder or used on a numeric display.

If it is again a question of the registration of an exercise ECG, In addition to the cardiac activity, the respiratory rate can be written down directly on an additional writing channel will.

For each decimal place of the .possible frequency spectrum a separate programmable memory can be provided.

Another object of the present invention is to provide a method for carrying out the method described indicate suitable circuit arrangement, which consists of as few digital modules as possible in a space-saving manner.

According to the invention, this object is achieved by the characteristics of claim 7 specified features solved. Further details and advantages of this circuit arrangement result from the exemplary embodiment which is described and explained in more detail below with reference to a figure will. The only figure shows a block diagram for the automatic digital frequency determination breathing.

A respiratory pulse generator 1 generates z. B. one pulse per breath. A clock generator 2 generates a time base Reference pulse per second. The output of the clock

2 is with the count input of a first binary counter

3 connected. The output of the respiratory pulse generator 1

is correspondingly with the counting input of a second binary counter 4 connected. The most significant output of counter 3 is connected to the reset input of counter 4 ^

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the other outputs are led to a first buffer store 5. Likewise, except for the lowest value, all outputs of the counter 4 are routed to a further buffer store 6. All outputs of the counter h are also connected to a NOR gate 7, the output of which is led to the reset input of the counter 3.

The output of the respiratory pulse generator 1 and the lowest value output of the counter 4 are on another NOR gate 8 switched, the output of which is connected to the set inputs of the two buffers 5 and 6 is. These caches can be, for. B. to be D-registers that their output signals accordingly change the applied input signal only with a positive edge triggering at the set input. All exits the two buffers 5 and 6 are used as addresses in parallel on two programmable memories 9 or 10 given, in which the corresponding breathing frequency is stored for every possible combination of time and number of breaths. Memory 9 represents the first and memory 10 the second decimal place.

The frequency values can be available in BCD code and are saved via the outputs of the programmable memory 9 and 10 are fed to a numeric display 11. Instead of This numeric display can also send the output values to a writer, e.g. B. a channel of a multi-channel recorder, for direct recording of the respiratory rate over time. The frequency values can also available in a 7-segment code for direct control of a corresponding display =

The mode of operation of the present circuit is as follows:

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The clock generator 2 sends reference pulses to the binary counter 3. As long as the binary counter k is "zero", ie has not yet received any breathing impulses, the binary counter 3 is set to zero.

At the first breathing pulse, the counter k jumps to one, and the lock for the counter 3 disappears, so that this also begins to count. After every second breathing pulse, the two buffers 5 and are triggered via the NOR gate 8 in such a way that they take over the counter values. The two NOR gates 7 and 8 can, for. B. be formed by a commercially available decoder.

The buffer values form the address for the two programmable memories 9 and 10, in which for every possible combination of time and number of breathing impulses the corresponding quotient and thus the breathing frequency is programmed. In the present case, these values are already in the BCD code for the first : Decimal place from memory 9 and for the second from Memory 10 passed on to a numeric display 11.

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The counting range is in this exemplary embodiment 16 breaths and 64 seconds. After every second breath, the new counter reading is returned to the memory transferred from where he took two breaths serves as an address and determines the respiratory rate.

If the work area is in one of the two counters 3 or 4 is exceeded, both counters are reset to zero and the frequency determination begins again.

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Since the quotient is formed completely digitally, for the circuit arrangement according to the invention only a few integrated modules are required. In addition, there is no need for tuning, which is necessary for analog circuits.

The circuit arrangement is not limited to the frequency determination of body functions. By increasing the number of bits in the counters and the other components, the frequency range can be easily expanded. By connecting the NOR gate 8 to a more significant bit of the counter k , the time span between the transfers to the buffer can also be increased.

8 claims
1 figure

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Claims (8)

- JT - VPA 80 P 5957 DE patent claims - * \ 1./Method for determining the frequency of a periodic ■■■ - Signal, in particular a body function such as breathing, characterized in that electrical pulses are derived from the signal, the number of which together with the number of reference pulses at least one programmable memory (9, 10) are supplied for the digital determination of the quotient from the number of derived reference pulses. 2. The method according to claim 1, characterized that the derived as well as the reference pulses are sent to a binary counter (3, 4) are given whose output values at certain times as addresses to the programmable memory (s) (9-i .10). 3. The method according to claim 2, characterized that the specific times are predetermined by a decoder (8) and the counter values first get to the buffer (5, 6), from v / o they are used as addresses for the programmable one or more Memory (s) (9, 10) are supplied. 4. The method according to any one of claims 1 to 3, d a through characterized in that the output signal of the programmable memory (s) (9, 10) is used to control a recorder. 5. The method according to any one of claims 1 to 3, d a through characterized in that the output signal of the programmable memory (s) (9, 10) used to control a numeric display will. 1300B7 / 028Ö -JS- VPA 80 P 5957 DE 6. The method according to any one of claims 1 to 5, d a through marked that for each decimal place of the frequency value to be determined one programmable memory (9, 10) is provided. 7. The method according to any one of claims 1 to 5, d a characterized in that for each two decimal places of the frequency value to be determined a programmable memory (9, 10) is provided. 8. Circuit arrangement for performing the method according to one of claims 1 to 7, characterized that a first binary counter (3) is provided, at whose input the reference pulses are applied, that a second binary counter (4) is provided is, at the input of which the derived pulses are placed, that the outputs of the first counter (3) with the parallel inputs of the first buffer (5) and the outputs of the second counter (A) with the parallel The inputs of the second buffer (6) are connected to the input and the outputs of the second counter (4) are also connected to such a decoder (7, 8) that the transfer of the counter output values takes place after a certain number of derived pulses and that the outputs of the two Intermediate memory (5, 6) are connected to the address inputs of at least one programmable memory (9, 10). 130067/0280