JPH07294564A - Waveform detection apparatus - Google Patents

Abstract

PURPOSE:To obtain a waveform detection apparatus which is low in cost and whose measuring precision is high by amplifying an analog signal which is output periodically and converting it into a digital signal. CONSTITUTION:A photodiode 2 receives reflected light radiated from an LED 1. A light-emission control part 3 supplies a driving current which makes the LED 1 emit light. A light-reception control part 5 drives the photodiode 2, and it takes out a change in the reflected light as a change in a current. In addition, an amplifier circuit 6 converts an infinitestimal current signal from the control part 5 into a voltage signal, it controls an amplification factor according to an amplification-factor control signal (a) from a control part 4, and it outputs the voltage signal to a 4-bit A/D converter 7 and a 5-bit A/D converter 8. The converter 7 converts the output voltage of the circuit 6 into 4-bit digital data so as to be outputted to the control part 4, and the converter 8 converts the output voltage of the circuit 6 into 5-bit digital data so as to be outputted to the control part 4. Then, the control part 4 computes or the like a pulse on the basis of the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform detecting device for detecting a signal waveform of an analog signal which changes periodically.

[0002]

2. Description of the Related Art A waveform detecting apparatus for detecting a periodically changing waveform of an analog signal usually has an analog / digital (A / D) converter for converting the analog signal into a digital signal. The frequency, period, amplitude, etc. are obtained from the digital signal converted by the converter, and the measurement accuracy of the frequency, period, etc. is determined by the number of bits of the A / D converter.

For example, in a pulse measuring apparatus for calculating and displaying a pulse per minute from a pulse wave signal detected by a pulse sensor, an analog pulse wave signal detected by the pulse sensor is amplified by an amplifier and the amplified pulse is detected. The wave signal is converted into a digital signal by an A / D converter, and one cycle time is calculated from the digital signal. In that case, the larger the number of bits of the A / D converter, the shorter the sampling interval of the pulse wave signal can be, so that the time of one cycle can be measured with higher accuracy.

[0004]

As described above, in the conventional waveform detecting apparatus, it is necessary to use an A / D converter having a large number of bits in order to improve the waveform detecting accuracy. There is a problem that the cost becomes high.

An object of the present invention is to provide a waveform detecting device that is low in cost and has high measurement accuracy.

[0006]

A waveform detecting apparatus according to a first aspect of the present invention includes an amplifying means for amplifying an analog signal periodically output, and an analog signal amplified by the amplifying means is sampled into a digital signal. A / D conversion means for conversion, time data storage means for storing time data of sampling timing of the A / D conversion means, and A / D conversion means
Start point processing means for processing one of the time data stored in the time data storage means as the start point of the cycle of the analog signal when the digital signal converted by the D conversion means falls within a predetermined range. Equipped with.

In the waveform detecting apparatus of the second invention, the amplifying means for amplifying the analog signal periodically output, and the analog signal amplified by this amplifying means are sampled to obtain N (where N is 2 or more). (Integer) bits and at least N + 1 bit digital signals converted into digital signals, and the digital signal converted by the N + 1 bit A / D conversion means of the A / D conversion means is within a predetermined range. At this time, there is provided a start point processing means for processing one of the sampling timings of the N-bit A / D conversion means as the start point of the cycle of the analog signal.

The above-mentioned A / D conversion means is, for example, first A / D conversion means for sampling an analog signal and converting it into a digital signal of at least N + 1 bits, and a part of the analog signal waveform for the first A / D conversion means. The second A / D conversion means performs sampling at a time interval shorter than that of the / D conversion means and converts it into an N-bit digital signal. The start point processing means is one of sampling timings of the second A / D conversion means when the digital signal converted by the first A / D conversion means falls within a predetermined range, for example. Is calculated as the start point of the cycle of the analog signal, and the cycle of the analog signal is calculated from the time data between the start points.

A waveform detecting apparatus according to a third aspect of the invention samples at least an analog signal that is periodically output and at least N
The first A / D conversion means for converting a + k (N is an integer of 2 or more, k is an integer) bit digital signal, and a part of one cycle of the analog signal from the first A / D conversion means When the second A / D converting means for sampling at a short time interval and converting into an N-bit digital signal and the digital signal converted by the first A / D converting means fall within a predetermined range. , Peak value detecting means for obtaining the peak value of the analog signal based on the N-bit digital signal converted by the second A / D converting means.

[0010]

In the first aspect of the invention, the time data of the sampling timing of the A / D conversion means is stored, and when the A / D converted digital signal is within a predetermined range, the stored time data is set to 1 Since one of them is processed as the starting point of the cycle of the analog signal, the cycle of the analog signal can be calculated with high accuracy.

In the second invention, for example, N-bit A /
The sampling interval of the D conversion means is N + 1 bit A /
By making the sampling interval shorter than the D conversion means and processing one of the sampling timings of the N-bit A / D conversion means as the start point of the cycle of the analog signal, the A / D conversion means with a small number of bits can be used. The period can be measured with higher accuracy.

According to a third aspect of the invention, the first A / D converting means samples the entire waveform of one cycle of the analog signal, and the second A / D converting means having a smaller number of bits than that samples the first A / D converting means. By sampling a part of the waveform including the peak value of the analog signal at a time interval shorter than that of the D conversion means, the waveform near the peak value of the analog signal can be sampled at a fine sampling interval.

Therefore, without using a multi-bit number A / D conversion means capable of sampling the entire waveform at short time intervals,
The peak value of the waveform can be measured with high accuracy by using the A / D conversion means having a small number of bits.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of a wrist watch type pulse measuring device of an embodiment for detecting an analog pulse wave signal output from a pulse sensor to measure a pulse rate.

In FIG. 1, LED 1 is an infrared light emitting diode which emits infrared light, and photodiode 2
Is a light receiving element that receives the reflected light emitted from the LED 1 and reflected by the fingertip. Since the amount of light reflected by a human fingertip changes according to the blood flow, the photodiode 2
The pulse wave signal corresponding to the blood flow can be measured by detecting the change in the reflected light.

The light emission control section 3 is a circuit for supplying a drive current for causing the LED 1 to emit light according to an instruction from the control section 4.
The light-reception control unit 5 is a circuit that similarly drives the photodiode 2 and extracts a change in reflected light as a current change.

The amplifier circuit 6 converts the minute current signal output from the light emission control section 5 into a voltage signal and also controls the control section 4
The amplification factor is controlled in accordance with the amplification factor control signal a from, and the converted voltage signal is amplified based on the amplification factor and output to the 4-bit A / D converter 7 and the 5-bit A / D converter 8. The amplification factor of the amplifier circuit 6 is controlled by the control unit 4 so that the maximum value of the output voltage of the amplifier circuit 6 is 1.5 V or more and the output voltage is within the range of 0V to 2V.

The 4-bit A / D converter 7 is, for example, a successive approximation type A / D converter, and outputs the output voltage of the amplifier circuit 6 to 4 bits.
It is converted to bit digital data and output to the control unit 4. Similarly, the 5-bit A / D converter 8 also converts the output voltage of the amplifier circuit 6 into 5-bit digital data and outputs it to the control unit 4.

The control unit 4 is an LED for the light emission control unit 3.
1 drive instruction, light receiving instruction to the light receiving control unit 5, output of amplification factor control signal a to the amplifier circuit 4, 4 bit A / D
Central processing for storing the peak value of the output voltage of the converter 7 and the 5-bit A / D converter 8 in the RAM 9, storing the time data at each sampling timing in the RAM 9, and calculating the pulse based on the data. And executes these processes according to a control program stored in the ROM 10. Further, the control unit 4 outputs the calculated pulse data to the display drive unit 11 and causes the display unit 12 including a liquid crystal display or the like to display the pulse data.

The key input unit 13 is used to start pulse measurement,
It is composed of an S1 key for instructing stop and outputs operation signals of those keys to the control unit 4. Where the RA
The configuration of M9 will be described with reference to FIG. The display register 21 of the RAM 9 stores display data to be displayed on the display unit 12, and the time measurement register 22 stores time data updated at regular time intervals.
The time data of 2 is stored as time data at the sampling timing of the 4-bit A / D converter 7 and the 5-bit A / D converter 8 described later.

The 4-bit maximum value register 23 has
The maximum value of the digital data A / D converted by the 4-bit A / D converter 7 is stored and stored in the 5-bit maximum value register 2
In 4, the maximum value of the digital data A / D converted by the 5-bit A / D converter 8 is stored. Furthermore, the previous time data register 25 stores the time data of the start point of the cycle of the pulse wave signal at the time of the previous measurement calculated by the measurement process (described later), and the current time data register 26 measures this time. The time data at the start point of the cycle is stored, and the time data memory 27 sequentially stores the time data at each sampling timing of the 4-bit A / D converter 7 and the 5-bit A / D converter 8.

The flag M is a flag indicating whether or not the output data of the 5-bit A / D converter 8 has become larger than a predetermined value A. When the output data becomes larger than "A", 1 ”is set. Further, the flag F is
This is a flag indicating whether or not the pulse is being measured, and is "1" when the pulse is being measured and "0" when the pulse is not being measured.
Is set.

Next, the operation of the embodiment having the above configuration will be described with reference to the flow charts of FIGS. FIG. 3 is a flowchart of the key processing. In step S1, it is determined whether or not the S1 key is operated, and when it is determined that the S1 key is operated, step S2
Then, it is determined whether the flag F is "0". When it is determined that the flag F = 0 in this determination, "1" is set to the flag F in step S3, and L is set in the next step S4.
The ED1 is caused to emit light to start measuring the pulse.

On the other hand, when F ≠ 0 is determined in the determination of step S2, it means that the S1 key is operated during the pulse measurement of F = 1, so that the process proceeds to step S5 and "0" is set to the flag F. Then, the pulse measurement is ended, and the light emission of the LED 1 is stopped in the next step S6. When it is determined in step S1 that the operated key is not the S1 key, another key process of step S7 is executed.

Next, the operation when the S1 key is operated and the pulse measurement is started will be described with reference to FIG. LED
When 1 emits light and pulse measurement is started, first, in step S11, the maximum value of the output voltage of the amplifier circuit 6 is 1.5 to 2V.
It is determined whether it is within the range of. When the maximum value of the output voltage is less than 1.5 V or greater than 2 V, the amplification factor of the amplifier circuit 6 is adjusted in step S12 so that the maximum value of the output voltage falls within the range of 1.5 to 2 V.

On the other hand, in the determination of step S1, the amplifier circuit 6
When it is determined that the maximum value of the output voltage of is within the range of 1.5 to 2 V, the measurement process of step S13 is executed.

The contents of this measurement process will be described below with reference to the flowchart of FIG. First, step S in FIG.
At 21, the analog input signal of the 4-bit A / D converter 7 is converted into digital data, and the time data at the time of sampling is sequentially stored in the time data memory 27 of the RAM 9. Then, in the next step S22, 4-bit A
It is determined whether or not the output data of the / D converter 7 has reached the maximum value "1111" (binary number).

In step S22, the output data has the maximum value "1".
When it is determined that the value has reached “111”, step S2
Proceeding to step 3, the 5-bit waveform measurement process by the 5-bit A / D converter 8 is executed. In this waveform measurement process, 5 bits A
The analog pulse wave signal input to the / D converter 8 is converted into digital data, and the time data at the time of sampling is sequentially stored in the time data memory 27 of the RAM 9. Then, in step S24, the 5-bit A / D converter 8
It is determined whether or not the digital data converted in step 1 is larger than a predetermined first value "A" [for example, hexadecimal "18" (1,1,0,0,0)].

Based on this determination, the 5-bit A / D converter 8 outputs A /
When it is determined that the D-converted digital data is larger than "A" (S24, YES), step S25.
After setting the flag M to "1", the process returns to step S23.

On the other hand, 5 bits A are determined in step S24.
When it is determined that the digital data A / D converted by the / D converter 8 is equal to or less than "A" (S24, N
O), the process proceeds to step S26, and it is determined whether or not the digital data is smaller than a predetermined second value "B" (maximum value-2 of the output data of the 5-bit A / D converter 8).

When it is determined in this determination that the output data of the 5-bit A / D converter 8 is "B" or more (S2
6, NO), and returns to step S23 to continue the 5-bit waveform measurement process. At this time, when it is determined that the output data of the 5-bit A / D converter 8 is smaller than "B" (S26, YES), the process proceeds to step S27 and the flag M is set.
It is determined whether the value of is "1".

The output data of the 5-bit A / D converter 8 is
When the value is equal to or less than the first value "A" described above, the value of the flag M remains "0", and in that case, step S
The determination result in 27 is NO, the process returns to step S23, and the 5-bit waveform measurement process is continuously executed.

On the other hand, when the output data of the 5-bit A / D converter 8 becomes larger than the above-mentioned first value "A" and then becomes smaller than the second value "B", the value of the flag M becomes Since it is "1", in this case, the determination in step S27 is YES and the process proceeds to the pulse wave start time calculation process in step S28.

In the processing of steps S23 to S27, the digital data A / D converted by the 5-bit A / D converter 8 becomes larger than the first value "A" (for example, 18 (H)). After that, when it becomes smaller than the second value B (for example, the maximum value −2), that is, the waveform measurement processing is performed up to a point where the amplitude of the pulse wave signal exceeds “A” and further decreases from the maximum value by “2”. When the process is completed, the process proceeds to the next step S28, and the pulse wave start time calculation process is executed.

In this pulse start time calculation process, the maximum value of the output data of the 5-bit A / D converter 8 is changed to "100".
4-bit A / D stored in the time data memory 27 of the RAM 9 corresponding to the value obtained by subtracting "00" (binary number)
The time data of the converter 7 is obtained as a start time (start point of the cycle) or a stop time. At this time, R
If the time data is not stored in the current time data register 26 of AM9, the measured time data is stored in the current time data register 26, while if the time data is already stored in the current time data register 26,
The time data stored in the previous time data register 2
After transferring to 5, the time data measured this time is stored in the current time data register 26.

Then, in the next step S29, the time of one cycle of the pulse wave is calculated from the start time stored in the previous time data register 25 of the RAM 9 and the stop time stored in the current time data register 26. Then, the pulse rate per minute is obtained, and the pulse rate is displayed on the display unit 12.

As described above, in this embodiment, N + k (N is 2
The whole pulse wave signal waveform is A / D converted by the above-mentioned integer, k is an integer) bit A / D converter (5-bit A / D converter 8 in the embodiment), and an N-bit A / D converter. (In the embodiment, a part of the waveform of the pulse wave signal by the 4-bit A / D converter 7 is A / D converted, and the resolution of the two A / D converters is set to 2k times. , A value corresponding to the difference in bit number between the two (for example, "10000")
The start point for calculating the period of the pulse wave signal can be specified by a simple bit operation of subtracting from the maximum value of the output data of the converter. Thereby, the process for calculating the cycle of the analog signal can be simplified.

When the calculation of the pulse rate is completed as described above, the process proceeds to step S30 to clear each memory of the RAM 9 and then, at the next step S31, it is determined whether or not the flag F is "1". When it is determined that the flag F = 1 in this determination, the process returns to step S21 and the above-described measurement process is repeated.

The operation for calculating the pulse wave period will now be described with reference to FIG. In the 5-bit A / D converter 8, the A / D of the entire signal waveform is A / D at a predetermined sampling interval determined by the amplitude of the input pulse wave signal and the resolution of the A / D converter.
D conversion is performed, and the 4-bit A / D converter 7 A / D converts a part of the waveform of the pulse wave signal at a sampling interval smaller than that of the 5-bit A / D converter 8. And each A
The time data of the sampling timings of the / D converters 8 and 7 are sequentially stored in the time data memory 27 of the RAM 9.

Now, the maximum value of one waveform of the pulse wave signal A / D converted by the 5-bit A / D converter 8 is "1E (H)",
It is assumed that the D-converted value becomes smaller than "maximum value -2, [for example, 1C (H)]". In that case, the time data t ₁ (sampling timing of the 4-bit A / D converter 7) corresponding to the value obtained by subtracting “10 (H)” from the maximum value “1E” (point A in FIG. 6, E (H)) (Time data determined by) is RA
The time data t ₁ read from the time data memory 27 of M9 is stored in the current time data register 26.

Next, similarly, the A / D for one waveform of the pulse wave signal is obtained.
The time data t ₂ (4 bit A / D converter) corresponding to the value (point B in FIG. 6) obtained by subtracting “10 (H)” from the maximum value of the pulse wave signal that has been converted is converted. The time data determined by the sampling timing of 8) is read from the time data memory 27 of the RAM 9. Then, the time data t ₁ stored in the time data register 26 this time.
Is transferred to the previous time data register 25, and the time data t ₂ measured this time is stored in the current time data register 26. Then, the cycle of the pulse wave signal is calculated from the difference data between the time data t ₂ stored in the current time data register 26 and the time data t ₁ stored in the previous time data register 25, and the cycle is further calculated. From this, the pulse rate per minute is obtained.

Although the above-described embodiments have been described with respect to the case where the present invention is applied to the pulse measuring device, the present invention is not limited to this, and the present invention can be applied to a waveform detecting device for detecting an analog signal waveform. Further, although the above-described embodiment has been described with respect to the case of measuring the period of the signal, the present invention is not limited to the period and can be applied to the case of detecting the peak value of the analog signal. For example, the entire analog signal waveform is sampled by the first A / D converter, and the waveforms before and after the peak value of the analog signal are
A second A / D having a smaller number of bits than the first A / D converter
The converter samples at a sampling interval shorter than the sampling interval of the first A / D converter, and the second A
The digital data converted by the / D conversion can be stored, and the maximum value of those digital data can be obtained as the peak value of the analog signal. In this case, since the peaks are detected at short sampling intervals, the peak value can be measured with high accuracy by using the A / D converter having a small number of bits.

[0043]

According to the present invention, the first bit having a large number of bits is used.
The analog signal waveform is A / D converted by the second A / D converter, and a part of the signal waveform is converted by the second A / D converter having a smaller number of bits than the first A / D converter to A / D
By performing A / D conversion at a sampling interval shorter than that of the converter, the period of the analog signal and the like can be measured with high accuracy using the A / D converter having a small number of bits.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a RAM.

FIG. 3 is a flowchart of key processing.

FIG. 4 is a flowchart of gain adjustment.

FIG. 5 is a flowchart of measurement processing.

FIG. 6 is an explanatory diagram of cycle measurement of a pulse wave signal.

[Explanation of symbols]

 1 LED 2 Photodiode 4 Controller 7 4-bit A / D Converter 8 5-bit A / D Converter 9 RAM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H03M 1/12 C

Claims (11)

[Claims] 1. Amplifying means for amplifying a periodically output analog signal, A / D converting means for sampling the analog signal amplified by the amplifying means and converting it into a digital signal, and this A / D conversion. Time data storage means for storing time data of sampling timing of the means, and time stored in the time data storage means when the digital signal converted by the A / D conversion means falls within a predetermined range. A starting point processing means for processing one of the data as a starting point of the cycle of the analog signal, the waveform detecting apparatus. 2. The waveform detecting apparatus according to claim 1, wherein the amplifying unit has an amplification factor changing unit that changes the amplification factor so that the output voltage falls within a predetermined range. 3. The waveform detection device according to claim 1, wherein the analog signal periodically input to the amplification means is a signal output from a sensor. 4. The waveform detecting device according to claim 1, wherein the analog signal periodically input to the amplifying means is a pulse signal output from a pulse sensor. 5. The analog signal periodically input to the amplifying means is a pulse signal output from a pulse sensor, and the start point processing means uses time data from a start point to a next start point. The waveform detection device according to claim 1, wherein pulse data per minute is obtained. 6. An amplifying means for amplifying an analog signal which is periodically output, and an analog signal amplified by the amplifying means is sampled to obtain N (where N is an integer of 2 or more) bits and at least N + 1 bits. A / convert to digital signal
D conversion means and at least N + 1 bit A / D of this A / D conversion means
Start point processing means for processing one of the sampling timings of the N-bit A / D conversion means as the start point of the cycle of the analog signal when the digital signal converted by the conversion means falls within a predetermined range. A waveform detection device comprising: 7. The A / D conversion means samples the analog signal amplified by the amplification means and converts it into a digital signal of at least N + 1 bits, and 1 of the analog signal. A second signal for sampling a part of the cycle at a time interval shorter than that of the first A / D conversion means and converting it into an N-bit digital signal
The A / D conversion means of the second A / D conversion means is provided when the digital signal converted by the first A / D conversion means falls within a predetermined range. 7. The waveform detecting apparatus according to claim 6, wherein one of sampling timings of the converting means is processed as a start point of a cycle of the analog signal, and the cycle of the analog signal is calculated from time data between the start points. 8. An analog signal periodically output is sampled to sample at least N + k (N is an integer of 2 or more, k
Is an integer) first digital signal converted to a digital signal of A /
D conversion means, and a signal of a part of one cycle of the analog signal to the first A
A second A / D converting means for sampling at a time interval shorter than that of the / D converting means and converting into an N-bit digital signal, and the digital signal converted by the first A / D converting means are predetermined. When the range is reached, the second A / D
And a peak value detecting means for obtaining a peak value of the analog signal based on the N-bit digital signal converted by the converting means. 9. The peak value detecting means is configured to detect the first A-value.
When the digital signal converted by the A / D conversion unit falls within a predetermined range, one of the sampling timings of the second A / D conversion unit is processed as a start point of the cycle of the analog signal. 9. The waveform detecting apparatus according to claim 8, wherein the peak value of the analog signal is obtained based on the N-bit digital signal converted by the second A / D conversion means. 10. A pulse detecting means for detecting a pulse and outputting a periodic analog signal corresponding to the pulse, an amplifying means for amplifying the analog signal output from the pulse detecting means, and an amplification factor of the amplifying means. And an amplification factor control means for controlling the maximum value of the analog signal output from the amplification means to fall within a predetermined first range, and sampling the analog signal output from the amplification means. A / D conversion means for converting N (where N is an integer of 2 or more) bits and at least N + 1 bit digital signals, and at least N + 1 bit A / D of the A / D conversion means
When the digital signal converted by the converting means reaches the predetermined second range, processing is started by using one of the sampling timings of the N-bit A / D converting means as the starting point of the cycle of the analog signal. A waveform detecting apparatus comprising: point processing means. 11. The waveform detecting apparatus according to claim 10, wherein the starting point processing means obtains pulse data per minute from time data between the starting points.