TW200803789A - Pulse measuring device - Google Patents

Abstract

A pulse measuring device is disclosed for measuring the blood pressure waveform in the artery by contacting the device on the surface of the living body. The pulse measuring device comprises of: the pressure detecting condenser (CX) having the static capacity varied according to the blood pressure in the artery; the charging unit (51) for applying the first charging voltage to the pressure detecting condenser (CX) in order to storing the first charge, and applying the second charging voltage which different from the first charging voltage, to the pressure detecting condenser (CX) in order to storing the second charge; the voltage changing unit (52) for producing the first changing voltage according to the first charge, and producing the second changing voltage according to the second charge; and the operation unit (54) for outputting the voltage denoting the static capacity of the pressure detecting condenser (CX), according to the first changing voltage and the second changing voltage.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse wave measuring device, and more particularly to a pulse wave measuring device that uses an electrostatic capacity element to measure a pressure waveform in an artery. [Prior Art] A pressure pulse measurement method for easily obtaining a pressure waveform in an artery using a non-blood observation type has a conventional pressure measurement (tonometry), which is described in GL Pressman, PM Newgard, " A Transducer for the Continuous External Measurement of Arterial Blood Pressure,,, IEEE TRANSACTIONS ON BIO-MEDICAL ELECTRONICS, 1 9 6 3, pp · 7 4 - 8 1 (Non-Patent Document 1). In the pressure measurement, the solid plate is crimped to the surface of the living body, and the surface of the living body is pressed to the extent that the solid plate forms a flat portion of the artery. Then, by maintaining the pressure balance state that excludes the influence of the tension generated on the surface of the artery, it is possible to accurately and stably measure only the pressure change in the artery. In recent years, a test in a living body has been carried out by calculating a feature amount from a pressure waveform in an artery measured by a pressure measurement technique. One of the tests was to make an effort to investigate the indicator AI (Augmentation Index) used to determine the degree of hardening of the arteries. The condition for measuring the pressure waveform in the artery using the pressure measurement method is that the surface of the pressing organism becomes a flat portion of the artery, and in addition, it is also required to be disposed directly on the flat portion of the artery. Sensor component. In addition, in order to accurately measure the pressure waveform in the artery, it is necessary to construct the width of the sensor element to be smaller than the width of the flat portion formed in the artery. Therefore, it is necessary to make the sensor element much smaller than the diameter of the artery. . In consideration of the above points, it is very difficult to position and arrange a single sensor element on the upper portion of the flat portion of the artery. Therefore, in reality, it is configured to be slightly processed. The pressure sensors of the sensor elements are configured to be substantially orthogonal to the direction of extension of the artery for measuring the pressure waveform. Generally, in the sensing method of measuring pressure, there are known sensing methods using a distorted resistance element and sensing methods using an electrostatic capacity element. In the sensing method using the electrostatic capacitance element, since the configuration of the sensor element is simpler than the distortion resistance element, there is an advantage that it can be inexpensively manufactured without using a semiconductor process requiring additional manufacturing. A pressure sensor in which an electrostatic capacitance element is arranged in an array on the measurement surface in order to obtain a pressure waveform in an artery is disclosed in Japanese Laid-Open Patent Publication No. 2005-5070-8 (Patent Document 1). A capacitive bridge type sensor device that constitutes a feedback loop, such as a capacitance element. However, in the sensor device described in Patent Document 1, when the accuracy is to be improved, the phase control and phase measurement of the signal in the feedback loop are required, which results in an increase in the circuit scale. . To solve this problem, Υ·Ε·Park and KD·Wise, “AN MOS SWITCHE D-CAPACITOR READOUT AMPLIFIER FOR CAPACITIVE PRESSURE SENSORS,,, Proc. IEEE Custom Circuit Conf·, May 1 9 8 3, pp.3 8 0-3 84 (Non-Patent Document 2) discloses a sensor device of a charge voltage conversion method 200803789 composed of an amplifier, a capacitor, a switch, etc. The charge voltage conversion method does not need to be necessary in the impedance bridge method. Phase control and phase measurement, so that the size of the sensor device can be reduced. Here, in the case of using a pressure sensor having a plurality of sensor elements as described above, it becomes necessary to select a multiplexer to come from The output of a plurality of sensor redundancy devices is generally required to be manufactured by a MOS (Metal Oxide Semiconductor) process. In the sensor device described in Non-Patent Document 2, since the MOS process is used, even In the case where a multiplexer is required, it is also possible to plan the process to be common, and the sensor device can be miniaturized. The sensor device described in Non-Patent Document 2 can be like this. Since it is miniaturized and uses a MO S process, it consumes a small amount of power, so it is used in MEMS (Micro Electro Mechanical Systems) pressure sensors and MEMS acceleration sensors. [Patent Document 1] Special Table 2005 -507083 [Non-Patent Document 1] GL Pressman, PM Newgard, "A Transducer for the Continuous External Measurement of Arterial Blood Pressure '1 ? IEEE TRANSACTIONS ON BIOMEDICAL ELECTRONICS, 1 9 6 3 5 pp. 74-81 [Non-patent Document 2] and·Ε· Park and KD Wise,"AN MOS SWITCHED-CAPACITOR READOUT AMPLIFIER FOR CAPACITIVE PRESSURE SENSORS”,Proc. IEEE Custom Circuit Conf.? May 1 9 8 3,ρρ·3 80-3 84 [Invention Contents] (The subject to be solved by the invention) 200803789 However, in the pressure wave used to measure the arteries, at least the frequency component of the pulse wave needs to be detected to a frequency component of about 30 Hz, and the pressure is to be carried out. The filtering process which affects the frequency from 0 Hz to about 30 Hz is not preferable, and the sensing described in Non-Patent Document 2 is generated by an amplifier. Frequency noise. In the non-patent detector device, since the MO S process is used, the power of the generated low-frequency noise becomes large. In the case of Ι/f noise and thermal noise generated by the amplifier, the device needs to detect a portion from 0 Hz to about 30 Hz. However, since the amplitude and phase of the frequency component of about 30 Hz are made as described above, it is not preferable. Therefore, in the non-patented device, it is not possible to remove the f/f noise and thermal noise of the analog filter or the digital device, and there is a problem that the deterioration can be caused. Accordingly, it is an object of the present invention to provide a pulse wave measuring device which can be prevented from being deteriorated and which can be miniaturized. (Means for Solving the Problem) A pulse wave measuring device according to an aspect of the present invention, the surface of the body is used to measure a pressure waveform in the artery, and the capacitor is changed according to the pressure in the artery. 1 The pulse waveform measuring device of the charging voltage form is reproduced from OHz (that is, DC is waveform-formed. Therefore, the error of the amplitude and phase of the component is due to the sense of the document 2, compared with the bipolar process, etc. In the case of the signal, the sensing filter used in the filtering process using the pulse wave measurement frequency component or the filtering process from 0 Hz to the large factor is amplified, so that the so-called detection pulse wave detection performance is amplified. The second charging voltage is stored in the charging unit to store the first electric charge, and the second charging voltage different from the first charging voltage is applied to the pressure detecting capacitor to store the second electric charge; The conversion unit generates a first converted voltage based on the first electric charge, and generates a second converted voltage based on the second electric charge; and the calculating unit according to the first converted voltage and the second converted voltage The voltage indicating the electrostatic capacitance of the pressure detecting capacitor is output. Preferably, the calculation unit outputs a voltage indicating the electrostatic capacitance of the pressure detecting capacitor based on the difference between the first converted voltage and the second converted voltage. Further, the measuring device further includes a voltage holding unit for holding the first converted voltage, and the charging unit stores the second electric charge in the voltage detecting capacitor based on the second charging voltage after the voltage holding unit holds the first converted voltage. After the voltage holding unit holds the first converted voltage, the voltage converting unit generates a second converted voltage based on the second electric charge stored in the pressure detecting capacitor, and the calculation unit converts the second converted voltage and the stored first transform. The voltage is a voltage indicating the electrostatic capacitance of the pressure detecting capacitor. The pulse wave measuring device according to another aspect of the present invention is configured to measure the pressure waveform in the artery by crimping the surface of the living body. : Capacitor for pressure detection, which changes the electrostatic capacity according to the pressure in the artery; the amplifier, whose inverting input terminal is combined with the pressure check One end of the capacitor is used instead of the inverting input terminal to be coupled to the first reference voltage; the charge transfer capacitor is coupled to the inverting input terminal of the operational amplifier, and the other is coupled to the output of the operational amplifier; the first switch, One end is coupled to the inverting input terminal of the operational amplifier, and the other end is coupled to the output of the operational amplifier; the charge holding capacitor is coupled at one end to the output of the computational amplification 200803789; the second switch is coupled to the charge retention at one end The other end of the capacitor is coupled to the second reference voltage. In addition, another aspect of the pulse wave measuring device of the present invention is configured to measure the pressure waveform in the artery via crimping on the surface of the living body. The capacitor for pressure detection has a capacitance that changes according to the pressure in the artery; the operational amplifier has an inverting input terminal coupled to one end of the pressure detecting capacitor, and the non-inverting input terminal is coupled to the first reference voltage; Capacitor with one end coupled to the inverting input terminal of the calculus and the other end The first switch has one end coupled to the inverting input terminal of the operational amplifier and the other end coupled to the output of the operational amplifier; the second switch, one end of which is coupled to the output of the operational amplifier: the first charge retention The capacitor has one end coupled to the other end of the second switch and the other end coupled to the second reference voltage; the differential amplifier having its first input terminal coupled to the other end of the second switch, and the second input terminal coupled to the calculation The output of the amplifier. Preferably, the pulse wave measuring device further includes: a third switch having one end coupled to the output of the operational amplifier; and a second charge holding capacitor having one end coupled to the other end of the third switch and the other end coupled to the first 3 reference voltage; the differential amplifier is coupled to the other end of the second switch by the first input terminal, and the second input terminal is coupled to the other end of the third switch.

Preferably, the pulse wave measuring device further includes: a charging unit for applying a charging voltage to the other end of the pressure detecting capacitor; and a control unit that controls the charging unit, the first switch, and the second switch; The first charging voltage is applied to the other end of the detecting capacitor to turn the first switch ON - -10-200803789 state, and then the first switch is turned off, then the second switch is turned ON, and the first charging voltage is turned on. After the application is stopped, the second switch is turned to the OFF state, and then the second charging voltage is applied to the other end of the pressure detecting capacitor, the first switch is turned on, and then the first switch is turned off. Then, the application of the second charging voltage is stopped. Preferably, the control unit applies a first reference voltage to the other end of the pressure detecting capacitor when the application of the first charging voltage is stopped and when the application of the second charging voltage is stopped. Preferably, the absolute value of the first charging voltage and the second charging voltage are equal and the application direction is reversed. Preferably, the pulse wave measuring device further includes: a charging unit for applying a charging voltage to the other end of the pressure detecting capacitor; and a control unit that controls the charging unit, the first switch and the second switch; and the pressure The other reference voltage is applied to the other end of the detecting capacitor, and the first switch is turned on. Then, the first switch is turned off, then the second switch is turned on, and then the second switch is turned off. Then, a charging voltage different from the first reference voltage is applied to the other end of the pressure detecting capacitor, and the first switch is turned on, and then the first switch is turned OFF. Then, the application of the charging voltage is stopped. Preferably, the pulse wave measuring device further includes: a charging unit for applying a charging voltage to the other end of the pressure detecting capacitor; and a control unit that controls the charging unit, the first switch, and the second switch; The other end of the pressure detection electric power is applied with a charging voltage different from the first reference voltage, -11-200803789 turns the first switch to the ON state, and then turns the first switch to the OFF state, and then turns the second switch ON. The state and the application of the charging voltage are stopped, and then the second switch is turned off. Then, the first reference voltage is applied to the other end of the pressure detecting capacitor, the first switch is turned on, and then the first switch is turned on. It is in the OFF state. (Effects of the Invention) According to the present invention, deterioration of the pulse wave detecting performance can be prevented, and the size can be reduced. [Embodiment] Hereinafter, embodiments of the present invention will be described using the drawings. In the drawings, the same or equivalent parts will be denoted by the same reference numerals and the description will not be repeated. <First Embodiment> [Structure and Basic Operation of Pulse Wave Measuring Apparatus] Fig. 1 is an external view of a pulse wave measuring apparatus according to a first embodiment of the present invention. In addition, Fig. 1 shows the measurement state in which the sensor array is pressed against the wrist. Fig. 2 is a schematic cross-sectional view showing the wrist and pulse wave measuring device in the measurement state shown in Fig. 1. Referring to Figs. 1 and 2, the pulse wave measuring device 100 is used to measure the pressure waveform in the artery of the wrist of the subject. The pulse wave measuring device 1 具备 is provided with a mounting table 110, a sensor unit 1, and a tightening belt 130. The sensor unit 1 includes a housing 1 22, a pressing curve portion 18, and a sensor array 19°. The mounting table 110 includes a mounting portion 112 for placing a wrist of one of the wrists 200 of the subject and Front wrist. The tightening belt 130 is used to fix the wrist portion of the wrist portion 200 of the mounting table 110 that is placed -12-200803789. The sensor unit 1 is mounted on a tightening belt 130, and has a built-in sensor array 19. Referring to Fig. 1, in a state where the wrist is fixed to the mounting table 1 1 , the artery 210 is located in a direction parallel to the extending direction of the wrist 200, and the inside of the sensor unit 1 is built by referring to Fig. 2 The pressing curve portion 18 in the body 1 22 expands, causing the sensor array 19 to descend, causing the sensor face of the sensor array 19 to be crimped toward the surface of the wrist. The pressing curve portion 18 adjusts the internal pressure by a pressurizing pump 15 and a negative pressure pump 16 which will be described later. The sensor array 19 is configured such that the electrode 3 1 disposed at the lower surface of the sensor surface, which will be described later, extends in a direction substantially orthogonal to the direction in which the artery 210 extends. At the time of pressing, the artery 2 10 becomes a state in which the sensor surface of the tibia 220 and the sensor array 19 is sandwiched from the up and down direction, and a flat portion is formed in the artery 2 10 . Then, at least one sensor element 28 is present on the front of the flat portion formed on the artery 2 10 . Fig. 3 shows the configuration of the sensor array 19, the multiplexer 20, and the C-V conversion unit 21 of the pulse wave measuring device according to the first embodiment of the present invention. Fig. 4 is a perspective view showing the appearance of the sensor array 19. Referring to Fig. 3, the sensor array 19 is used in combination with the multiplexer 20 and the C-V conversion unit 21. The C-V conversion unit 21 includes a charging unit 51. Referring to Fig. 4, the sensor array 19 includes a lower electrode 31, an upper electrode 32, and a spacer member 30. The lower electrode 31 is composed of a plurality of strip-shaped copper foil electrodes which are arranged in a line in parallel with each other and extend substantially linearly. The upper electrode 32 is composed of a plurality of strip-shaped copper foil electrodes which are arranged in a line in the direction orthogonal to the lower electrodes 31 and which are substantially parallel to each other and are linearly extended. Between the lower electrode 3 1 and the upper electrode 3 2 , a spacer 30 made of ruthenium rubber is disposed at an intersection of the lower electrode 3 1 and the upper electrode 3 2 , and the lower electrode 3 1 and The upper electrodes 3 2 are disposed to face each other and are separated from each other by a specified distance by the spacer members 30. In this manner, the sensor element 28 is formed at the intersection of the lower electrode 31 and the upper electrode 32. That is, the sensor array 19 includes a plurality of sensor elements 28 that are arranged in rows and columns. The sensor elements 28 are distorted in a direction approaching each other in accordance with the pressure applied to the upper electrode 3 2 or the lower electrode to vary the electrostatic capacity. Referring to Fig. 3, the C-V conversion unit 21 is connected to the electrodes of one of the lower electrode 31 and the upper electrode 32 via the multiplexer 20. The multiplex 20 selects the specific lower electrode 3 1 and the upper electrode 3 2 . With this configuration, it is possible to obtain as the output voltage of the C-V conversion unit 21 of any one of the plurality of sensor elements 28 arranged in a matrix. For example, when the multiplexer 20 selects the lower electrode 31 of the second column from the top and the upper electrode 3 2 of the third row from the left, the sensor element 28 A is connected to the CV conversion unit 2 1. Therefore, the pressure waveform at any position of the sensor array 19 can be measured. In addition, in FIG. 3, the upper electrode 3 2 is connected to the charging portion 5 1 via the workpiece 20, but the connection relationship between the lower electrode 31 and the upper electrode may be reversed, and the lower electrode 3 1 may be constructed. The device 20 is connected to the charging portion 51. Fig. 5 is a block diagram showing the operation and the shape of the pulse wave measuring device according to the first embodiment of the present invention. Referring to Fig. 5, the pulse wave measuring device 100 includes a sensor unit 1, a display unit 3, and a mounting table 110. The display unit 3 includes an operation unit 24 and a display unit 25. The sensor unit 1 includes a pressing curve portion 18 and a sensor array [J 19 . The mounting table 110 includes a R〇M (Read Only Memory) 12, a RAM (Random Access Memory) 13, a CPU (Central Processing Unit) (control unit) 11, a drive circuit 14, a pressurizing pump 15, and a negative pressure pump 16. The change valve 17, the multiplexer 20, the CV conversion unit 21, the low pass filter 22, and the A/D conversion unit 23. The operation unit 24 detects an operation from the outside, and outputs the detection result as an operation signal to the CPU 1 1 or the like. The user operates the operation unit 24 to input various information about the pulse wave measurement to the pulse wave measuring device 100. The display portion 2 5 includes LEDs (Light Emitting Diode) and LCD (Liquid Crystal Display) 0 ROM 1 2 and RAM 1 3 for outputting various information such as an arterial position detection result and a pulse wave measurement result to the outside, for example, It is the data and program used by the memory control pulse wave measuring device. The drive circuit 14 drives the pressurizing pump 15, the negative pressure pump 16, and the shift valve 17 in accordance with a control signal from C P U 1 1 . The CPU 11 accesses the ROM 12 and reads the program, and expands the read program on the R Α Μ 1 3 and executes the program to perform control and calculation processing of each block of the pulse wave measuring device 100. . Further, C P U 1 1 performs control processing of each block of the pulse wave measuring device 1 根据 based on an operation signal from a user who has received the operation unit 24. That is, the CPU 11 outputs the control 丨g number to each block based on the ί as is number received from the operation unit 24 -15 - 200803789. Further, C P U 1 1 displays the pulse wave measurement result and the like on the display unit 25. The pressure pump 15 is a pump for pressurizing the internal pressure of the pressing curve portion 18. Further, the negative pressure pump 16 is a pump for decompressing the internal pressure of the pressing curve portion 18. The shift valve 17 is such that either one of the pressurizing pump 15 and the negative pressure pump 16 is selectively connected to the air tube 6. The pressing curve portion 18 includes an air pocket that is pressure-adjusted to press the sensor array 19 against the wrist. The sensor array 191 is pressed against the measurement site of the wrist or the like of the subject by the pressure of the pressing curve portion 18. The sensor array 19 is in a state of being pressed, and detects a pulse wave of the subject, that is, a pressure waveform in the artery, through the radial artery. The multiplexer 20 selects any one of the plurality of sensor elements 28 in the sensor array 19 in accordance with a control signal received from the CPU 11. The CV conversion unit 2 1 converts the electrostatic capacitance 値 of the sensor element 28 selected by the multiplexer 20 into a voltage, that is, a pressure vibration transmitted from the artery to the surface of the living body for indicating the pressure waveform in the artery. The wave is output as a voltage signal (hereinafter also referred to as a pressure signal). The low pass filter 22 attenuates the specified frequency component among the pressure signals received from the C-V conversion unit 21. The A/D conversion unit 23 converts the pressure signal of the analogy signal passing through the low-pass filter 22 into a digital signal and outputs it to the CPU 11.

Further, the mounting table 110 may be configured to include the display unit 3°. The mounting table 110 may be configured to include the CPU 11, the ROM 12, and the RAM-16-200803789 13', but may be configured to be included in the display. Unit 3. In addition, it is also possible to construct a CPU and a PC (Personal Computer) for various control. [Operation of Pulse Wave Measuring Apparatus] Fig. 6 is a flowchart for determining an operation procedure of the pulse wave measuring apparatus according to the first embodiment of the present invention when performing pulse wave measurement. The flow shown in Fig. 6 is realized by the CPU 11 accessing the ROM 12 and reading the program, and expanding the read program on the RAM 13 and executing the program. Referring to Fig. 6, first, when power is supplied to the pulse wave measuring device 1 ,, the CPU 11 instructs the drive circuit 14 to drive the negative pressure pump 16. The drive circuit 14 converts the change valve 17 to the negative pressure pump 16 side in accordance with an instruction from the CPU to drive the negative pressure pump 16 (S101). The driven negative pressure pump 16 depressurizes the internal pressure of the pressing curve portion 18 to be much lower than atmospheric pressure via the shift valve 17. With this configuration, it is possible to prevent the sensor array 19 from accidentally protruding to cause malfunction and malfunction. The CPU 1 1 starts the pulse wave measurement when it detects that the sensor array 19 has moved to the measurement site (S 1 0 2). Here, the sensor unit 1 is provided with a micro switch or the like not shown in the figure, which is used to detect the movement of the sensor array 19, and the CPU 1 1 recognizes the sensor array 19 according to the detection signal of the micro switch. The location. Further, it is also possible to construct the pulse wave measurement when the CPU 1 1 detects that the measurement start switch (not shown) included in the operation unit 24 is pressed. The CPU 1 1 instructs the drive circuit 14 to drive the pressurizing pump 15 when the sensor array 19 moves to the measurement site (YES in S 1 02). The drive circuit 14 shifts the shift valve 17 to the side of the pressurizing pump 15 in accordance with an instruction from the CPU 1 to drive the 200803789 pressure pump 1 5 (S 1 0 3 ). The driven pressurizing pump 15 pressurizes the internal pressure of the pressing curve portion 18 via the shift valve 17 to press the sensor array 19 against the surface of the measurement portion of the subject. When the sensor array 19 is pressed against the measurement portion, the multiplexer 20 causes the sensor element 28 connected to the C-V conversion portion 21 to be time-divisionally changed in accordance with the control of the CPU 11. The C-V conversion unit 21 converts the capacitance □ of the sensor element 28 selected by the multiplexer 20 into a voltage. The low pass filter 22 attenuates the specified frequency component among the pressure signals received from the C-V conversion unit 21. The A/D conversion unit 23 converts the pressure signal passed through the low pass filter 22 into digital information and outputs it to the CPU 11. The CPU 1 1 creates a tension map indicating the relationship between the position of the sensor element 28 and the pressure signal based on the digital information received from the A/D conversion unit 23, and displays it on the display unit 25 (S104). The CPU 1 1 detects and selects the sensor element 28 located on the artery based on the resulting tension map (S 105). In addition, as for the processing of the sensor element 28, the technique described in Japanese Laid-Open Patent Publication No. 2004-222847, which is hereby incorporated by reference. Further, the CPU 1 1 extracts the DC component of the pressure signal output from the C-V conversion unit 21 based on the digital information received from the A/D conversion unit 23 (S106). The DC component of the pressure signal is a pressure signal that utilizes the average 値 of the pressure signal during the specified period, removes the component below the specified frequency in the pressure signal (ie, the pulse component), and the pulse rising point (ie, the pulse component is mixed) The pressure signal level of the former) is expressed. More specifically, the output change of the pressure signal can be divided into windows (intervals) of a specified period every -18-200803789', and the average of each window is calculated, and the DC component is extracted. Alternatively, it is possible to calculate the maximum 値 and the minimum 値 in each window, and similarly, the DC component can be extracted. Further, the predetermined period of time described above is set in advance in the pulse wave measuring device 100 regardless of the pulse of the subject, and is preferably equal to or longer than the normal pulse interval (1.5 seconds or so). Next, the CPU 1 1 controls the drive circuit 14 to perform optimum pressure adjustment, i.e., adjusts the internal pressure of the pressing curve portion 18 to stabilize the DC component of the pressure signal (S107). Next, the CPU 1 1 acquires waveform data based on the pressure signal from the currently selected CV conversion unit 21 indicated by the digital information received from the A/D conversion unit 23, and measures the pulse wave based on the acquired waveform data (S 1 08). Then, when the end condition of the pulse wave measurement is established (YES in S1 09), the CPU 11 controls the drive circuit 14 to drive the negative pressure pump 16 to release the pressing state of the sensor array 19 to the measurement site ( S 1 1 0). Here, the end condition of the pulse wave measurement may be a predetermined time (for example, 30 seconds) set in advance, or may be an instruction from the end of the measurement by the user and an indication of the measurement interruption. On the other hand, when the specified condition is not satisfied (NO in S 10 9), the CPU 11 repeats the transfer processing of the waveform data to continue the pulse wave measurement (S 108). [Structure and basic operation of the C-V conversion unit and the sensor element] Fig. 7 is a functional block diagram showing the configuration of the C-V conversion unit 21 and the capacitor CX of the pulse wave measuring device according to the first embodiment of the present invention. Referring to Fig. 7, the C-V conversion unit 21 includes a charging unit 51, a voltage change -19-200803789 change unit 52, a voltage holding unit 53, and an arithmetic unit 54. Capacitor CX sensor element 2 8. In addition, in FIG. 7, in order to simplify the description, the multiplexer 20 is not shown, and only the capacitance selected by the multiplexer 20 is displayed as the capacitor CX in the sensor array of the pulse wave measuring device 1 in the living body. The surface state is the capacitance according to the arterial pressure of the living body. The charging unit 51 applies a first charging voltage to the capacitor CX for one charge. The voltage conversion unit 52 generates a first converted voltage based on the charge stored in the capacitor CX and outputs it to the voltage holding unit 53. The electric unit 53 holds the first converted voltage received from the voltage converting unit 52. Then, the charging unit 51 applies a second charging electric charge to the capacitor CX to store the second electric charge. The voltage conversion unit 52 generates a second converted voltage based on the second electric charge stored in the capacitor, and outputs it to the calculation unit 54. The calculation unit 54 outputs a voltage for the capacitance of the container CX based on the first change held by the voltage holding unit 53 and the second converted voltage received from the voltage conversion unit 52. Further, the C-V conversion unit 21 may be constructed to include the electric portion 53. For example, the first converted voltage (not shown) outside the pulse wave measuring device 100 is held in the RAM or the like. Then, the charging unit 51 applies a second charging voltage to CX for storing the second electric charge, and the voltage 52 generates a second electric pressure based on the second electric charge stored in the capacitor CX, and outputs it to the calculating unit 54. Further, the calculation unit 54 may be configured to generate a second converted voltage from the first conversion electric power obtained from the RAM via a CPU (not shown), and output the electric power.

Corresponding to , I CX in the figure. 19 Crimp connection Change static storage No. 1 voltage hold Press: CX voltage change Indicates voltage hold The CPU converts the capacitor change unit to form the voltage and the voltage of the electrostatic capacitance of the connector CX -20- 200803789. Fig. 8 is a circuit diagram for showing the configuration of the C-V converting portion 21 and the capacitor CX of the pulse wave measuring device of the third embodiment of the present invention. Referring to Fig. 8, the C-V conversion unit 21 is used in combination with a capacitor (pressure detecting capacitor) CX corresponding to the sensor element 28. The CV conversion unit 2 1 includes a capacitor CC, a charge transfer capacitor CF, a capacitor (charge holding capacitor) CN, a capacitor CH1, a switch (first switch) SW1, a switch (second switch) SW2, a switch SW3, and an operational amplifier G1. ~G3, and charging unit 51. The charging unit 51 includes switches SW51 to SW54 and power supplies VI and V2. The switches SW1 to SW3 are, for example, analog switches. Further, in Fig. 8, for simplification of the explanation, the multiplexer 20 is not shown in the figure, and only the capacitor CX selected by the multiplexer 20 is displayed. Here, the operational amplifier G1, the switch SW1, and the capacitor CF correspond to the voltage conversion unit 52 shown in Fig. 7. Further, the switch SW2 and the capacitor CN correspond to the voltage holding portion 53 shown in Fig. 7. In addition, the switch SW2, the capacitor CN, and the operational amplifier G1 correspond to the calculation unit 54 shown in Fig. 7. The operational amplifier G1 has its inverting input terminal connected to one end of the capacitor CX and one end of the capacitor CC, instead of the inverting input terminal. Connect to the ground voltage (first reference voltage). The capacitor CF has one end connected to the inverting input terminal of the operational amplifier G1 and the other end connected to the output of the operational amplifier G1. The switch SW1 has one end connected to the inverting input terminal of the operational amplifier G1 and the other end connected to the output of the operational amplifier G1. The capacitor CN has one end connected to the output of the operational amplifier G1. The switch SW2 has one end -21 - 200803789 connected to the other end of the capacitor CN and the other end connected to the ground voltage (second reference voltage). The non-inverting input terminal of the operational amplifier G2 is connected to one end of the switch SW2, and the inverting input terminal is connected to the output of the operational amplifier G2. The switch SW3 has one end connected to the output of the operational amplifier G2 and the other end connected to one end of the capacitor CH1 and the non-inverting input terminal of the operational amplifier G3. The other end of capacitor CH 1 is connected to a ground voltage. The inverting input terminal of the calculus G3 is connected to the output of the operational amplifier G3. In the charging portion 51, one end of the switch SW51 is connected to the positive electrode of the power source VI, and the other end is connected to one end of the switch SW5 2 and the other end of the capacitor CX. One end of the switch SW54 is connected to the negative electrode of the power source V2, and the other end is connected to one end of the switch SW53 and the other end of the capacitor CC. The other end of the switch SW52, the other end of the switch SW53, the negative electrode of the power supply VI, and the positive electrode of the power supply V2 are connected to the ground voltage. In addition, the output voltage 电源 of the power supply VI and the power supply V2 is VCC. The capacitor CC is referred to as a counting capacitor and is disposed for the purpose of adjusting the capacitance of the capacitor CX.

The switches SW to SW3 change the ON state and the OFF state based on the control signals SCI to SC3 received from the CPU. The switches SW51 to SW54 are switched between the ON state and the OFF state based on a control signal not shown in the figure received from the CPU 11. [Operation of C-V conversion unit] Fig. 9 is a timing chart showing the operation of the C-V conversion unit 21 when the pulse wave measuring device according to the first embodiment of the present invention performs pulse wave measurement. -22- 200803789 VP is the voltage applied to the other end of the capacitor CX, VN is the voltage applied to the other end of the capacitor CC, VG1 is the output voltage of the operational amplifier G1, VG2 is the output voltage of the operational amplifier G2, and VOUT is The output voltage of the amplifier G3. When the control signals SCI to SC3 are at the high level, the respective switches SW1 to SW3 are in the ON state, and in the low state, the OFF state is in the OFF state. Fig. 10 is a flowchart for determining the operational sequence of the C-V conversion unit when the pulse wave measuring device according to the first embodiment of the present invention performs pulse wave measurement. The processing shown in the flowchart of Fig. 1 is realized by the CPU accessing the ROM 12, reading the program, expanding the read program on the RAM 13 and executing the program. Referring to Fig. 9 and Fig. 10, first, the CPU 1 1 turns the switch SW1 into an ON state, and causes the switches SW2 and SW3 to be in an OFF state. Further, the CPU 1 1 turns the switches SW52 and SW53 into an ON state, and turns off the switches SW51 and SW54, thereby applying a ground voltage (first charging voltage) to the other end of the capacitor CX and the other end of the capacitor CC. Here, it is desirable that the ground voltage applied to the non-inverting input terminal of the operational amplifier G1 is fed back from the output of the operational amplifier G1 to the inverting input terminal of the operational amplifier G1. However, there is a case where the potential of the inverting input terminal of the operational amplifier G1 caused by the thermal noise generated by the operational amplifier G and the charge injection of the 1/f noise and the analog switch cannot be the ground potential. In this case, a potential difference is generated across the capacitor CX and the capacitor CC, and a charge corresponding to the noise component is stored in the capacitor CX and the capacitor CC (step S1). Next, the CPU 1 1 turns the switch SW1 to the OFF state. As a result, -23-200803789, the charge stored in capacitor CX and capacitor cc moves to capacitor CF. Then, a voltage (first converted voltage) corresponding to the charge stored in the capacitor CF is output from the operational amplifier G1 as the output voltage VG1, that is, the charge corresponding to the noise component described above is converted into a voltage (step S2). Next, the CPU 1 1 turns the switch SW2 into an ON state. In this manner, the capacitor CN is charged based on the first converted voltage output from the operational amplifier G1 (step S3). In addition, the switch SW2 may also be in an ON state in steps si and S2. Next, the CPU 1 1 turns the switch SW2 to the OFF state (step S4). Next, the CPU 1 1 turns the switch SW1 into an ON state. Further, the CPU 1 1 is configured to apply the charging voltage VCC (second charging voltage) to the other end of the capacitor Cx by turning the switches SW52 and SW53 to the OFF state and the switch SW51 and the switch SW54 to the ON state, and to the capacitor Cc. On the other end, a charging voltage -VCC is applied, that is, a voltage equal to the charging voltage VCC and equal to the applied direction is applied. Here, the ground voltage applied to the non-inverting input terminal of the operational amplifier G, that is, the ground voltage, is fed back from the output of the operational amplifier G1 to the inverting input terminal of the arithmetic amplifier G1. Therefore, the electric charge corresponding to the charging voltage VCC is stored in the capacitor CX, and the electric charge corresponding to the charging voltage -VCC is stored in the capacitor CC (step S5). Next, the CPU 1 1 turns the switch SW1 to the OFF state (step S6). Next, the CPU 1 1 stops the application of the charging voltages VCC and -VCC, and applies a ground voltage (first reference voltage) to the other end of the capacitor CX and the other end of the capacitor CC. As a result, the charge corresponding to the difference between the amount of charge stored in the capacitor CX -24 - 200803789 and the amount of charge stored in the capacitor CC is moved to the capacitor CF. Then, a voltage (second converted voltage) corresponding to the electric charge stored in the capacitor CF is output from the operational amplifier G1 as the output voltage G1 (step S7). More specifically, when the capacitance of the capacitor CX is CX, the capacitance of the capacitor CC becomes CC, and the voltage 充电 of the charging voltage VCC becomes VCC, the charge transferred to the capacitor CF is expressed by (CX-CC) x VCC. On the other hand, when the capacitance of the capacitor CF is set to CF, the electric potential of the capacitor CF is converted into a voltage (second conversion voltage) represented by (CX - CC) / CF) x VCC by the operational amplifier G1. Here, the charge stored in the capacitor CF includes, in addition to the charge corresponding to the electrostatic capacity of the capacitor CX, the thermal noise and 1 /f noise generated by the operational amplifier G 1 and the analog switch in the above manner. A charge corresponding to low frequency noise such as charge injection. Therefore, the second converted voltage includes a noise voltage corresponding to the above-described noise and a sensor voltage corresponding to the electrostatic capacitance of the capacitor CX. However, the capacitor CN stores a charge corresponding to the first converted voltage, and the charge stored in the capacitor CN and the charge stored in the capacitor CF are opposite in polarity when viewed from the non-inverting input terminal of the operational amplifier G2. Therefore, when the voltage 値 of the first converted voltage is VN1, the voltage of the noise voltage in the second converted voltage is VN2, and the voltage corresponding to the electrostatic capacitance of the capacitor CX among the second converted voltage is set to VS. When the input voltage of the non-inverting input terminal of the operational amplifier G2 becomes (VS + VN2) - VN1. -25 - 200803789 Here, when the time interval between the operations of steps S1 to S4 and the operations of steps S5 to S7 is such that the rate of change of the above-described noise component is a short interval, VN1 and VN2 become substantially equal, and the calculation is performed. The input voltage of the non-inverting input terminal of amplifier G2 becomes (VS + VN2) - VN1 and VS. Therefore, at the non-inverting input terminal of the operational amplifier G2, the voltage corresponding to the electrostatic capacitance of the capacitor CX (i.e., the pressure in the artery of the living body) from which the noise component is removed is input. Then, a voltage corresponding to the pressure in the artery is output from the operational amplifier G2 as the output voltage VG2. Next, the CPU 1 1 turns the switch SW3 into an ON state. In this manner, the capacitor CH1 is charged in accordance with the output voltage of the operational amplifier G2 (step S8). Next, the CPU 1 1 turns the switch SW3 to the OFF state. In this manner, the voltage input to the non-inverting input terminal of the control unit 3 is fixed. Then, from the operational amplifier G3, a voltage corresponding to the electric charge stored in the capacitor CH1 (that is, a voltage corresponding to the pressure in the artery of the living body) is output to the low-pass filter 22 as the output voltage VOUT (step S9). . The CPU 11 repeats the processing of steps S1 to S9 for updating the pressure signal output from the C-V conversion unit 21. In this way, the pressure waveform in the artery is measured. However, in the sensor device described in Patent Document 1, in order to improve the accuracy, it is necessary to perform phase control and phase measurement of the signal of the feedback loop, and there is a problem that the circuit scale is increased. However, in the pulse wave measuring device according to the first embodiment of the present invention, a charge voltage conversion method is employed. In other words, the voltage converting unit 52 generates a converted voltage based on the electric charge stored in the capacitor CX which changes the electrostatic capacitance according to the pressure in the artery of the biological body -26 - 200803789. With this configuration, the phase control and phase measurement necessary for the impedance bridge method can be eliminated, and the miniaturization of the pulse wave measuring device can be attempted. Further, in the sensor device described in Non-Patent Document 2, the analog filter, the digital filter, or the like cannot be used to remove the 1/f noise and thermal noise of the amplifier, and the detection performance is deteriorated. problem. However, in the pulse wave measuring apparatus according to the first embodiment of the present invention, the charging unit 51 applies a first charging voltage to the capacitor CX to store the first electric charge, and applies a second charging voltage to the capacitor CX to store the second electric charge. . The voltage converting unit 5 2 generates a first converted voltage based on the first electric charge stored in the capacitor CX, and generates a second converted voltage based on the second electric charge stored in the capacitor CX. Then, the calculation unit 54 outputs a voltage indicating the electrostatic capacitance of the capacitor CX based on the first converted voltage and the second converted voltage. With this configuration, the voltage corresponding to the low frequency noise such as the thermal noise 'and the 1 / f noise generated by the operational amplifier G1 can be excluded from the pressure signal. Therefore, in the pulse wave measuring device according to the first embodiment of the present invention, deterioration of the pulse wave detecting performance can be prevented, and the size can be reduced. Further, in the pulse wave measuring apparatus according to the first embodiment of the present invention, when the application of the second charging voltage is stopped, the first reference voltage is applied to the other end of the capacitor CX. More specifically, when the CPU 1 1 stops applying the charging voltage VCC to the other end of the capacitor CX, the other end of the capacitor CX is applied with a voltage (ground voltage) applied to the non-inverting input terminal of the operational amplifier G1. With this configuration, it is possible to make the operating range of the operational amplifier G 1 -27 - 200803789 larger. Further, in the pulse wave measuring device according to the first embodiment of the present invention, a ground voltage (first charging voltage) is applied to the other end of the capacitor CX to generate a first converted voltage, and a capacitor CX is passed. The charging voltage VCC (second charging voltage) is applied to one end to generate a second converted voltage. However, the present invention is not limited to this. If the first charging voltage and the second charging voltage are different voltages, the voltage corresponding to the low frequency noise such as the thermal noise generated by the operational amplifier G1 and the Ι/f noise can be removed from the pressure signal. For example, similarly to the pulse wave measuring device according to the second embodiment to be described later, the first charging voltage and the second charging voltage can be made equal to each other and the applied direction is the opposite voltage. Further, in the pulse wave measuring apparatus according to the first embodiment of the present invention, the first converted voltage is generated by applying a ground voltage to the other end of the capacitor CX, and then the charging voltage VCC is applied to the other end of the capacitor CX. The second converted voltage is generated, but is not limited to such a method. It is also conceivable to apply a charging voltage VCC to the other end of the capacitor CX to generate a first converted voltage, and then apply a ground voltage to the other end of the capacitor CX to generate a second converted voltage. Second, the drawings are used to illustrate another embodiment of the present invention. In addition, the same or equivalent parts will be denoted by the same reference numerals, and the description will not be repeated. <Second Embodiment> The present embodiment relates to a pulse wave measuring device that changes the configuration of the C-V converting unit 21. -28 - 200803789 [Configuration of c-V conversion unit and sensor element] Fig. 1 is a circuit diagram showing a CV conversion unit 21 and a capacitor CX in the pulse wave measuring device according to the second embodiment of the present invention. Composition. Referring to Fig. 1, the C-V conversion unit 2 1 is used in combination with a capacitor (pressure detecting capacitor) cx corresponding to the sensor element 28. The CV conversion unit 21 includes a capacitor CC, a charge transfer capacitor CF, a capacitor (first charge holding capacitor) CH11, a capacitor (second charge holding capacitor) CH12, a capacitor CH13, resistors R1 and R9, and a switch (first switch). SW1, switch (second switch) SW12, switch (third switch) SW13, switch SW14, operational amplifiers G1 and G5, charging unit 51, and differential amplifier 55. The differential amplifier 55 includes operational amplifiers G2 to G14 and resistors R2 to R8. The charging unit 51 includes switches SW51 to SW54, and power sources VI and V2. The switch SW1 and the switches SW12 to SW14 use, for example, an analog switch. Here, the operational amplifier G1, the switch S W1, and the capacitor CF correspond to the voltage conversion unit 52 shown in Fig. 7. Further, the switch SW12 and the capacitor CHI 1 correspond to the voltage holding portion 53 shown in Fig. 7. Further, the switch SW13 and the capacitor CH12 correspond to the voltage holding portion 53 shown in Fig. 7. Further, the differential amplifier 55 corresponds to the arithmetic unit 54 shown in Fig. 7. The resistor R1 has one end connected to the output of the operational amplifier G1. The switch SW12 has one end connected to the other end of the resistor R1 and the other end connected to one end of the capacitor CH11 and the non-inverting input terminal of the operational amplifier G12. The switch SW1 3 has one end connected to the other end of the resistor R1, and the other end -29-200803789 is connected to one end of the capacitor CH 1 2 and the non-inverting input terminal of the operational amplifier G 1 3 . The other end of the capacitors CH 1 1 to CH 1 2 is connected to the ground voltage (second reference voltage). The output of the operational amplifier G12 is connected to one end of the resistor R2 and one end of the resistor R5, and the inverting input terminal is connected to the other end of the resistor R2 and one end of the resistor R3. The output of the operational amplifier G 1 3 is connected to one end of the resistor R4 and one end of the resistor R6, and the inverting input terminal is connected to the other end of the resistor R4 and the other end of the resistor R3. The inverting input terminal of the operational amplifier G14 is connected to the other end of the resistor R5 and one end of the resistor R7, and the non-inverting input terminal is connected to the other end of the resistor R6 and one end of the resistor R8, and the output is connected to the other end of the resistor R7 and One end of resistor R9. The switch S W 1 4 has one end connected to the other end of the resistor R9 and the other end connected to one end of the capacitor CH 1 3 and the non-inverting input terminal of the operational amplifier G 1 5 . The output of the operational amplifier G 1 5 is connected to the inverting input terminal. The other end of the capacitor CH 1 3 and the other end of the resistor R8 are connected to the ground voltage. One end of the charging portion 51 and the switch SW55 is connected to the positive electrode of the power source VI, and the other end is connected to the other end of the capacitor CC. One end of the switch SW5 6 is connected to the negative electrode of the power source V2, and the other end is connected to the other end of the capacitor CX. The switches S W 1 2 to S W 1 4 are switched between the ON state and the OFF state in accordance with the control signals SCI 2 to SC14 received from C P U 1 1 . [Operation of CV Conversion Unit] -30- 200803789 Fig. 12 is a timing chart for showing the C-V conversion unit 2 of the pulse wave measuring device according to the second embodiment of the present invention when performing pulse wave measurement action. VP is the voltage applied to the other end of the capacitor CX, and VN is the voltage applied to the other end of the capacitor CC. When the control signals SCI and SC12 to SC 14 are at a high level, the switches SW 1 and SW respectively corresponding to each other are made. 1 2 to SW14 are in the ON state, and are turned OFF in the case of the low level. Fig. 1 is a flowchart for determining the operation procedure of the C-V conversion unit 21 when the pulse wave measuring device according to the second embodiment of the present invention performs pulse wave measurement. The processing shown in the flowchart of Fig. 13 is such that the CPU 11 accesses the ROM 12 to read the program, expands the read program on the RAM 13, and executes the program. Referring to Fig. 12 and Fig. 13, first, the CPU 11 turns on the switch SW1 and turns off the switches SW12 to SW14. Further, the CPU 1 1 is configured to apply a charging voltage VCC (first charging voltage) to the other end of the capacitor CX by turning on the switches SW51 and SW54 and turning off the switches SW52, SW53, SW55, and SW56. The other end of the capacitor CC is applied with a charging voltage -VCC. Here, from the output of the operational amplifier G1, the voltage (i.e., the ground voltage) applied to the non-inverting input terminal of the operational amplifier G1 is fed back to the non-inverting input terminal of the calculation amplifier G1. Therefore, the electric charge corresponding to the charging voltage VCC is stored in the capacitor CX, and the electric charge corresponding to the charging voltage -VCC is stored in the capacitor CC (step S11). Next, the CPU 11 turns off the switch SW1 (step S12). 200803789 Next, the CPU 11 turns the switches SW52 and WS53 into an ON state, and turns off the switches SW51 and SW54 to SW56 to make the charging voltages VCC and -VCC. The application is stopped, and a ground voltage (first reference voltage) is applied to the other end of the capacitor CX and the other end of the capacitor CC. As a result, the charge corresponding to the difference between the amount of charge stored in the capacitor CX and the amount of charge stored in the capacitor CC is moved to the capacitor CF. Then, the voltage (first converted voltage) corresponding to the charge stored in the capacitor CF is output from the operational amplifier G1 as the output voltage G1 (step S13). More specifically, when the capacitance of the capacitor CX is CX and the capacitance of the capacitor CC is CC, the charge which is moved to the capacitor CF is expressed by (CX-CC) x VCC. The charge transferred to the capacitor CF is converted into a voltage (first converted voltage) represented by ((CX - CC) / CF) x VCC by the operational amplifier G1 when the capacitance of the capacitor CF is CF. Then, the CPU 11 turns the switch SW12 into an ON state. In this manner, the capacitor CH11 is charged based on the first converted voltage output from the operational amplifier G1 (step S13). At this time, a voltage corresponding to the charge stored in the capacitor CH 11 is input to the non-inverting input terminal of the operational amplifier G12. The operational amplifier G12 outputs a voltage corresponding to the voltage input to the non-inverting input terminal to the inverting input terminal of the operational amplifier G 1 4 . Next, the CPU 1 1 turns the switch SW12 to the OFF state (step S14). In this way, the voltage input to the non-inverting input terminal of the operational amplifier G 1 2 is fixed. Next, the CPU 1 1 turns the switch SW1 into an ON state. Further, the CPU 1 1 turns the switches SW55 and SW56 into an ON state, and turns off the switches SW51 to -32-200803789 SW54 to apply a charging voltage - VCC (second charging voltage) to the other end of the capacitor CX, and The other end of the capacitor CC is applied with a charging voltage VCC. Here, the voltage applied to the non-inverting input terminal of the operational amplifier G1 (i.e., the ground voltage) is fed back from the output of the operational amplifier G1 to the inverting input terminal of the arithmetic amplifier G1. Therefore, the electric charge corresponding to the charging voltage -VCC is stored in the capacitor CX, and the electric charge corresponding to the charging voltage VCC is stored in the capacitor CC (step S15). Next, the CPU 11 turns off the switch SW1 (step S16). Next, the CPU 1 turns the switches SW52 and SW53 into an ON state, and turns off the switches SW51 and SW54 to SW56 to make the charging voltages VCC and -VCC. The application is stopped, and a ground voltage (first reference voltage) is applied to the other end of the capacitor CX and the other end of the capacitor CC. As a result, the charge corresponding to the difference between the amount of charge stored in CX and the amount of charge stored in the capacitor CC is moved to the capacitor CF. Then, a voltage (second converted voltage) corresponding to the electric charge stored in the capacitor CF is output from the operational amplifier G1 as the output voltage G1 (step S17). More specifically, when the capacitance of the capacitor CX is CX and the capacitance of the capacitor CC is CC, the charge that moves to the capacitor CF is represented by -(CX_CC) X VCC . On the other hand, when the capacitance of the capacitor CF is set to CF, the amplifier G1 is converted to a voltage represented by ((CC-CX)/CF)xVCC (second conversion voltage). Then, the CPU 1 1 Turns the switch SW13 into an ON state. As a result, -33 - 200803789 'charges the capacitor CH12 based on the second converted voltage output from the operational amplifier G 1 (step S17). At this time, a voltage corresponding to the charge stored in the capacitor CH12 is input to the non-inverting input terminal ' of the operational amplifier G13. The operational amplifier G 1 3 inputs a voltage 'corresponding to the voltage input to the non-inverting input terminal' to the non-inverting input terminal of the operational amplifier G 1 4 . Next, the CPU 11 turns off the switch SW13 (step S1 8). In this way, the voltage input to the non-inverting input terminal of the operational amplifier G 1 3 is fixed. Here, the charge stored in the capacitor CF includes, in addition to the charge corresponding to the electrostatic capacity of the capacitor CX, thermal noise and 1 /f noise generated by the operational amplifier G 1 in the above manner, and an analog switch. The voltage corresponding to low frequency noise such as charge injection. Therefore, the first converted voltage and the second converted voltage include a noise voltage corresponding to the above-described noise component and a sensor voltage corresponding to the electrostatic capacitance of the capacitor CX. Here, the voltage 値 of the noise voltage in the first converted voltage is VN1, and the voltage corresponding to the electrostatic capacitance of the capacitor CX among the first converted voltages is VS1 and the noise voltage in the second converted voltage. When the voltage 値 is VN2 and the voltage 对应2 corresponding to the capacitance of the capacitor CX in the second converted voltage is VS2 and the gain of the entire differential amplifier 55 is K, the output voltage VDIFF of the differential amplifier 55 becomes K> ((VN1+VS1)-(VN2 + VS2)). In addition, VS1 is a voltage 对应 corresponding to the charging voltage VCC, and VS2 is a voltage 对应 corresponding to -VCC, so VS1 and VS2 become absolute 値 equal -34 - 200803789 and the voltages of different signs are 値. Further, when the time interval between the operations of steps S11 to S14 and the operations of steps S1 5 to S1 8 is such that the rate of change of the above-described noise component is a short interval, VN 1 and VN2 become substantially equal. Therefore, the output voltage VDIFF of the differential amplifier 55 becomes Kx ((VNl + VSl) - (VN2 + VS2)) and 2xKxVNl. That is, the output voltage VD IFF of the differential amplifier 55 is a voltage corresponding to the electrostatic capacitance of the capacitor Cx (i.e., the pressure in the artery of the living body) from which the noise component is removed. Next, the CPU 1 1 turns the switch SW14 into an ON state. In this manner, the capacitor CH13 is charged in accordance with the output voltage VDIFF (step S1 9). Next, the CPU turns the switch SW14 to the OFF state (step s20). In this way, the voltage input to the non-inverting input terminal of the operational amplifier G12 is fixed. Then, a voltage corresponding to the voltage corresponding to the electric charge stored in the capacitor CH13 (i.e., the pressure in the artery of the living body) is output from the operational amplifier G15 to the low-pass filter 22 as the output voltage V OUT . The CPU 11 repeats the processing of steps S11 to S20 to update the pressure signal output from the C-V conversion unit 2 1 . In this way, the pressure waveform in the artery is measured. Other configurations and operations are the same as those of the pulse wave measuring device of the first embodiment, and thus detailed description thereof will not be repeated here. Therefore, in the pulse wave measuring device according to the second embodiment of the present invention, similarly to the pulse wave measuring device of the first embodiment, deterioration of the pulse wave measuring device can be prevented, and the size can be reduced. Further, in the pulse wave measuring device according to the second embodiment of the present invention, the configuration of the CPU 1 1 is applied to the other end of the capacitor CX by applying a charging voltage VCC (first charging voltage). The first converted voltage is generated, and the second converted voltage can be generated by applying a charging voltage -VCC (second converted voltage) to the other end of the capacitor CX. However, the present invention is not limited to this. If the first charging voltage and the second charging voltage are different voltages, the voltage corresponding to the thermal noise and 1 /f noise generated by the operational amplifier can be excluded from the pressure signal. For example, similarly to the pulse wave measuring device of the first embodiment, the first converted voltage is generated by applying a ground voltage to the other end of the capacitor CX, and the charging voltage VCC is applied to the other end of the capacitor CX. A second converted voltage is generated. Further, in the pulse wave measuring device according to the second embodiment of the present invention, the CV converting unit 21 may include the switch SW12 and the capacitor CH11 as the voltage holding unit 53, and the switch SW13 and the capacitor CH12, but not only the switch Limited to this method. The voltage holding unit 53 can be configured to hold at least the first converted voltage. Therefore, the C-V converting unit 2 1 can be configured not to include the switch SW12 and the capacitor CH11, or to include the switch SW13 and the capacitor C Η 1 2 . Further, in the pulse wave measuring apparatus according to the first embodiment and the second embodiment of the present invention, both the first reference voltage and the second reference voltage are formed to have a ground voltage, but the present invention is not limited to this. Even when the first reference voltage and the second reference voltage are different voltages and are different from the ground voltage, low frequencies such as thermal noise and 1 /f noise generated in the operational amplifier can be excluded from the pressure signal. The voltage corresponding to the noise. All parts of the embodiments disclosed herein are used by way of example only and are not intended to limit the invention to -36 - 200803789. The scope of the present invention is defined by the scope of the claims and the claims BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an external view of a pulse wave measuring device according to a first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing the wrist and pulse wave measuring device in the measurement state shown in Fig. 1. Fig. 3 shows the configuration of the sensor array 19, the multiplexer 20, and the C-V conversion unit 21 of the pulse wave measuring device according to the first embodiment of the present invention. Fig. 4 is a perspective view showing the appearance of the sensor array 19. Fig. 5 is a functional block diagram of a pulse wave measuring device according to a first embodiment of the present invention. Fig. 6 is a flow chart for determining the operational steps of the pulse wave measuring device according to the first embodiment of the present invention for performing pulse wave measurement. Figure 7 is a functional block diagram showing the configuration of the C-V conversion unit 21 and the capacitor CX of the pulse wave measuring device according to the first embodiment of the present invention. Fig. 8 is a circuit diagram showing the configuration of the C-V conversion unit 21 and the capacitor CX of the pulse wave measuring device according to the first embodiment of the present invention. Fig. 9 is a timing chart showing the operation of the C-V conversion unit 21 when the pulse wave measuring device according to the first embodiment of the present invention performs pulse wave measurement. The first diagram is a flowchart showing the operation procedure of the C-V conversion unit 21 when the pulse wave measuring device according to the first embodiment of the present invention performs pulse wave measurement. Fig. 11 is a circuit diagram showing the configuration of the C-V conversion unit 21 and the capacitor c X of the pulse measuring device of the pulse-37 - 200803789 according to the second embodiment of the present invention. Fig. 12 is a timing chart showing the operation of the C-V conversion unit 21 when the pulse wave measuring device according to the second embodiment of the present invention performs pulse wave measurement. Fig. 1 is a flowchart for determining the operation procedure of the C-V conversion unit 21 when the pulse wave measuring device according to the second embodiment of the present invention performs pulse wave measurement. [Main component symbol description]

1 Sensor unit 3 Display unit 11 CPU (control unit) 12 ROM 13 RAM 14 Drive circuit 15 Pressurizing pump 16 Negative pressure pump 17 Shift valve 18 Pressing curve portion 19 Sensor array 20 multiplexer 21 CV converting portion 22 Low-pass filter 23 A/D conversion unit 24 Operation unit 25 Display unit 26 PCB - 38 - 200803789 27 Flexible wiring 28, 28 A Sensor element 30 Spacer member 3 1 Lower electrode 32 Upper electrode 5 1 Charging portion 52 Voltage Conversion unit 53 voltage holding unit 54 calculation unit 55 differential amplifier 100 pulse wave measuring device 110 mounting table 122 housing 130 tightening belt 200 wrist portion 2 10 artery 220 tibia cx capacitor (capacitor for pressure detection) cc capacitor CF charge transfer Capacitor CN capacitor (charge holding capacitor) CHI 1 capacitor (first charge holding capacitor) CH12 capacitor (second charge holding) Capacitor) S W1 Switch (1st Switch) -39 - 200803789 SW2 Switch (2nd Switch) SW13, S W14 Switch S W5 1 to S W54 Switch G1 to G3 Logic Amplifier G12~G15 Logic Amplifier VI, V2 Power Supply R1 to R9 Resistance-40 -

Claims (1)

200803789 X. Patent application scope: 1 · A * @ pulse wave measuring device is used to measure the pressure waveform in the artery by crimping on the surface of the living body, which is characterized by: S-capacitor detecting capacitor (cx) The electrostatic capacitance is changed according to the pressure in the artery; the charging unit (51) applies the ith charging voltage to the pressure detecting capacitor (CX) to store the first electric charge, and applies the pressure detecting capacitor (CX). a second charging voltage different from the ith charging voltage to store the second electric charge; the voltage converting unit (52) generating the first converted voltage 'based on the first electric charge and generating the second converted voltage based on the second electric charge; The calculation unit (54) outputs a voltage indicating the electrostatic capacitance of the pressure detecting capacitor (CX) based on the first converted voltage and the second converted voltage. 2. The pulse wave measuring device according to the first aspect of the invention, wherein the calculating unit (54) outputs static electricity indicating the pressure detecting capacitor (CX) based on a difference between the first converted voltage and the second converted voltage. The voltage of the capacity. 3. The pulse wave measuring device according to claim 1, wherein the pulse wave measuring device further includes a voltage holding portion (53) for holding the first converted voltage; the charging portion (51) After the voltage holding unit (53) holds the first converted voltage, the second charge is stored in the pressure detecting capacitor (CX) based on the second charging voltage; the voltage converting unit (52) After the voltage holding unit (53) holds the first converted voltage, the second converted voltage is generated based on the second electric charge stored in the pressure detecting capacitor 200803789 (CX); the calculating unit (54) A voltage indicating the electrostatic capacitance of the pressure detecting capacitor (CX) is output based on the second converted voltage and the stored first converted voltage. 4. A pulse wave measuring device for measuring a pressure waveform in an artery by crimping on a surface of a living body, characterized in that: a pressure detecting capacitor (CX) is used to change static electricity according to pressure in the artery. Capacity; the operational amplifier (G 1 ), whose inverting input terminal is coupled to one end of the pressure detecting capacitor (CX), and the non-inverting input terminal is coupled to the first reference voltage; the charge transfer capacitor (CF) has one end Combined with the inverting input terminal of the operational amplifier (G 1 ), and the other end is coupled to the output of the operational amplifier (G 1 ); the first switch (SW1) has one end coupled to the inverse of the operational amplifier (G1) Input terminal, the other end is coupled to the output of the operational amplifier (G 1); the charge holding capacitor (CN) has one end coupled to the output of the operational amplifier (G1); and the second switch (SW2), one end of which is coupled The other end of the charge holding capacitor (CN) is connected to the second reference voltage. 5. The pulse wave measuring device according to claim 4, wherein the pulse wave measuring device further includes a charging portion (51) for applying a charging voltage to the other end of the pressure detecting capacitor (CX), And control-42-200803789 (1 1); the control unit (11) controls the charging unit (51), the first switch (SW1), and the second switch (SW2); and the pressure detecting capacitor (CX) The other end is applied with the first charging voltage, the first switch (SW 1 ) is turned on, and then the first switch (SW 1) is set to the 〇FF state, and then the second switch (SW2) is turned on. In the ON state, the application of the first charging voltage is stopped, and then the second switch (SW2) is turned off, and then the second charging voltage is applied to the other end of the pressure detecting capacitor (CX). The first switch (SW1) is turned on, and then the first switch (SW1) is turned off, and then the application of the second charging voltage is stopped. 6. The pulse wave measuring device according to claim 5, wherein the control unit (11) is when the application of the first charging voltage is stopped, and when the application of the second charging voltage is stopped, The other reference voltage is applied to the other end of the pressure detecting capacitor (CX). 7. The pulse wave measuring device according to claim 5, wherein the first charging voltage and the second charging voltage are equal to each other, and the application direction is opposite. 8 • The pulse wave according to item 4 of the patent application scope The measuring device, wherein the pulse wave measuring device further comprises: a charging portion (51) for applying a charging voltage to the other ~* end of the pressure detecting capacitor (CX); and -43 - 200803789 control portion (1) 1); the control unit (11) controls the charging unit (51), the first switch (SW1), and the second switch (SW2); and applies the first reference to the other end of the pressure detecting capacitor (CX) The voltage causes the first switch (SW1) to be in an ON state, and then the first switch (SW1) is turned off, and then the second switch (SW2) is turned on, and then the second switch is turned on ( SW2) is in an OFF state, and then a charging voltage different from the first reference voltage is applied to the other end of the pressure detecting capacitor (CX), and the first switch (SW1) is turned on, and then the first switch is turned on. The switch (SW1) is turned OFF, and then, the charging voltage is made Plus stops. 9. The pulse wave measuring device of claim 4, wherein the pulse wave measuring device further comprises: a charging portion (51) for applying a charging voltage to the other end of the pressure detecting capacitor (CX) And a control unit (11); the control unit (11) controls the charging unit (51), the first switch (SW1), and the second switch (SW2); and the capacitor for detecting the pressure (CX) On the other end, a charging voltage different from the first reference voltage is applied to turn the first switch (SW1) to the ON state, and then the first switch (SW1) is turned off, and then -44 - 200803789 makes the second When the switch (SW2) is in the ON state and the application of the charging voltage is stopped, the second switch (SW2) is turned off, and then the first reference is applied to the other end of the pressure detecting capacitor (CX). The voltage causes the first switch (SW1) to be in an ON state, and then the first switch (SW1) is turned off. 1 〇. A pulse wave measuring device for measuring a pressure waveform in an artery by crimping on a surface of a living body, characterized in that: a pressure detecting capacitor (CX) is used according to the pressure in the artery The electrostatic capacitance is changed; the operational amplifier (G 1 ) has an inverting input terminal coupled to one end of the pressure detecting capacitor (CX), and the non-inverting input terminal is coupled to the first reference voltage; a charge transfer capacitor (CF) One end is coupled to the inverting input terminal of the operational amplifier (G1), and the other end is coupled to the output of the operational amplifier (G1); the first switch (SW1) has one end coupled to the operational amplifier (G1) The other end is coupled to the output of the operational amplifier (G1); the second switch (SW2) has one end coupled to the output of the operational amplifier (G1); and a first charge holding capacitor (CN). One end is coupled to the other end of the second switch (SW2), and the other end is coupled to the second reference voltage; and -45 - 200803789 differential amplifier, the first input terminal is coupled to the second switch (SW2) The other end, and a second input terminal coupled to the output of the calculation amplifier (G1) of. 1 1 · The pulse wave measuring device of claim 10, wherein the pulse wave measuring device further comprises: a third switch (SW3), one end of which is coupled to an output of the operational amplifier (G1); The second charge holding capacitor (CN) has one end coupled to the other end of the third switch (SW3) and the other end coupled to the third reference voltage. The differential amplifier is coupled to the second input terminal by the first input terminal. The other end of the switch (SW2) is coupled to the other end of the third switch (SW3). 1 2 . The pulse wave measuring device of claim 10, wherein the pulse wave measuring device further comprises: a charging portion (51) for applying the other end of the pressure detecting capacitor (CX) a charging voltage; and a control unit (1 1), the control unit (1 1) controls the charging unit (51), the first switch (SW1), and the second switch (SW2); and the pressure detecting capacitor The other charging terminal (CX) applies a first charging voltage to turn the first switch (SW1) to the ON state, and then turns the first switch (SW1) to the 0FF state, and then turns the second switch (SW2) ON. The state, and the application of the voltage of the first charging -46 - 200803789 is stopped, and then the second switch (SW2) is turned off, and the first electric voltage of the pressure detecting capacitor (CX) is made first. When the switch (SW1) is turned on, the first switch (SW1) is turned off, and the application of the second charging voltage is stopped. 1 3 The pulse wave measuring device (11) of the first application of the patent application is the first application of the first charging voltage. When the application of the electric voltage is stopped, the first end of the pressure detecting end is applied. The reference voltage. 14. The pulse wave measuring device of claim 12 is equivalent to the absolute voltage of the second charging voltage. 1 5 · The pulse wave measuring device of the 10th item of the patent application scope is further provided with: a charging unit (5 1 ) for applying a charging voltage to one end of the pressure detecting power; and a control unit (1 1); the control unit (1 1) controls the charging unit (51) and the second switch (SW2); and the first reference voltage of the pressure detecting capacitor (CX), the first switch ( SW1) is turned ON, the first switch (SW 1) is in the 〇FF state, the second switch (SW2) is turned on, and then the second state is applied to the − terminal, and then, the control unit and the control unit The second charging container (CX), wherein the first charging is performed, and a direction phase is applied, wherein the container (CX) is additionally: the first switch (SW 1) is applied to the first state at one end, then, then, then -47-200803789 The second switch (SW2) is turned off, and then a charging voltage different from the first reference voltage is applied to the other end of the pressure detecting capacitor (CX), so that the first switch (SW1) becomes In the ON state, then the first switch (SW1) is turned off, and then, The application of the charging voltage is stopped. The pulse wave measuring device of the first aspect of the invention, wherein the pulse wave measuring device further comprises: a charging portion (51) for applying the other end of the pressure detecting capacitor (CX) a charging voltage; and a control unit (1 1); the control unit (11) controls the charging unit (51), the first switch (SW1), and the second switch (S W2); and the pressure detecting capacitor (CX) The other end is applied with a charging voltage different from the first reference voltage, the first switch (SW1) is turned on, and then the first switch (SW1) is turned off, and then the second switch is turned on ( SW2) is turned on, and the application of the charging voltage is stopped. Then, the second switch (SW2) is turned off, and then the first reference voltage is applied to the other end of the pressure detecting capacitor (CX). The first switch (SW1) is turned on, and then the first switch (SW1) is turned off. -48-