Abstract:
A biological information sensing device has a sensor portion formed in an elongate strap that can be attached to a living organism such that the sensor portion is maintained in intimate contact with a measurement area of the living organism. A plurality of signal processing portions are also formed in the elongate strip for processing biological information, such as pulse rate, blood pressure or serum concentrations, sensed by the sensor portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a biological information sensing device for sensing biological information such as arterial pulses or the like, and more particularly, to a biological information sensing device of a type like an arterial pulse wave detector which is wrapped around the wrist or the like.  
           [0002]    A portable arterial pulse wave detector has been proposed which is provided with a pressure forming elastic piece at an intermediate portion of a strap such that the elastic piece may press a sensor portion against an area of the wrist surface near the radial artery of the wrist for holding the sensor portion in intimate contact with the wrist surface area (JP-A-8-52118).  
           [0003]    However, the proposed portable arterial pulse wave detector has a drawback that precise measurements of arterial pulses cannot be obtained. This is because when its main body (head portion) unifying a display panel and processing circuit of great masses is subjected to a relatively great accelerative motion associated with the motion of the wrist during exercise or the like, for example, an inadvertent inertia force apt to rotate/displace the head portion about the wrist is applied to the head portion, thus varying the pressure on the sensor portion connected with the head portion for pressing the sensor portion against the wrist surface or causing the rotation/displacement of the sensor portion.  
           [0004]    In view of the foregoing, it is an object of the invention to provide a biological information sensing device which is capable of minimizing the effect of the inertia force on the device thereby minimizing the displacement thereof, irrespective of exposure to the accelerative motion during training or other exercises.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with the invention for achieving the above object, a biological information sensing device applied to a neck-like portion, inclusive of a predetermined measurement area, of a living organism as holding a sensor portion thereof in intimate contact with the measurement area for sensing biological information, the sensing device is characterized in that a variety of signal processing portions for handling the biological information sensed by the sensor portion take a form of an elongate strap as a whole in order to be wrapped around an outer periphery of the neck-like portion along with the sensor portion. The elongate strap is defined as follows. Assuming that, for example, a section of the wrist is an oval shape consisting of two opposite curved lines having small curvatures and two opposite curved lines having great curvatures, the strap has such a length as to cover at least two apexes of the curved lines.  
           [0006]    In the biological information sensing device according to the invention, the variety of signal processing portions for handling the biological information sensed by the sensor portion take the form of an elongate strap as a whole such that the signal processing portions along with the sensor portion may be wrapped around the neck-like portion thereby uniformly distributing the masses along an extension direction of the strap. Therefore, the inertia force applied to the strap in conjunction with a sudden accelerative or decelerative motion can be uniformly distributed and hence, there occurs little force acting to rotate the strap. As a result, the displacement of the sensor is minimized.  
           [0007]    The signal processing portions and the sensor portion constituting the main body of the sensing device are formed on a flexible substrate, for example, in a continuous fashion. However, at least one of the signal processing portions or the processing portions may be formed on a rigid substrate or on individual rigid substrates while the rigid substrate(s) may be connected via a flexible cable or the like. In either cases, it is preferred that the signal processing portions constituting the elongate strap-like main body of the sensing device present a uniform mass distribution along the longitudinal direction of the strap, with the proviso that the respective functions of the signal processing portions are not decreased. In other words, for the purpose of uniformly distributing the masses, the location of the circuit components may be properly changed as required, or otherwise, a kind of weights or masses having no effect on the functions of the main body of the sensing device may be attached to desired places along the longitudinal direction of the strap-like main body so long as such weights or masses do not results in an excessive increase of the mass of the main body of the sensing device.  
           [0008]    It is noted here that the strap-shaped main body of the biological information sensing device, which includes the sensor portion and the variety of signal processing portions, may be provided with a strap fastening hardware at an end thereof with respect to the longitudinal direction thereof. Furthermore, the biological information sensing device may further comprise, in addition to the strap-shaped main body of the sensing device including the sensor portion and the signal processing portions, strap-like fastening means for wrapping and fastening the main body of the sensing device around the neck-like portion.  
           [0009]    In the former case, the sensing device features an easy handling because the main body thereof is integrated with the strap fastening hardware. In the latter case, the main body of the sensing device is adapted for positional adjustment (positional change) relative to the strap-like fastening means and hence, the main body of the sensing device with the sensor portion precisely positioned at the measurement area can be stably secured to place by means of the strap-like fastening means, irrespective of the size or the like of the neck-like portion.  
           [0010]    In another aspect of the invention for achieving the above object, a biological information sensing device applied to a neck-like portion, inclusive of a predetermined measurement area, of a living organism as holding a sensor portion thereof in intimate contact with the measurement area for sensing biological information, the sensing device comprises a signal processing portion for processing the biological information sensed by the sensor portion, and a display/transmission portion for displaying/transmitting the processed signal, wherein the signal processing portion and the display/transmission portion take a form of an elongate strap as a whole in order to be wrapped around the neck-like portion along with the sensor portion.  
           [0011]    In this case, as well, the strap-shaped main body of the sensing device including the signal processing portion and the display/transmission portion may be provided with a strap fastening hardware at an end thereof with respect to the longitudinal direction thereof. Further, the biological information sensing device may further comprise, in addition to the strap-shaped main body of the sensing device including the sensor portion, the signal processing portion and the display/transmission portion, strap-like fastening means for wrapping and fastening the main body of the sensing device around the neck-like portion. Both of the cases have the same features as those described above.  
           [0012]    Although the neck-like portion is typically the wrist portion for example, other areas such as the cervical region with the carotid artery may be included.  
           [0013]    The biological information to be sensed typically includes for example information related to arterial pulses such as frequency of pulse and the like (accordingly, the biological information sensing device is a so-called arterial pulse wave detector). However, the biological information sensing device may also handle other biological information or signals indicative of blood pressure, serum concentrations of a particular component in blood and the like, or indicative of body fluids other than blood.  
           [0014]    The biological information sensing device according to the invention permits the sensor portion to be stably held against or secured to the measurement area of the living organism so that the biological information (frequency of pulse, variations of blood pressure, level of oxygen in blood and the like) during exercise can be sensed precisely.  
           [0015]    In a case where the biological information sensing device comprises an arterial pulse wave detector including an arterial pulse wave sensor based on supersonic wave, the biological information sensing device comprises, for example, an arterial pulse wave sensor portion including a supersonic transmitter and a supersonic receiver; and besides, a variety of signal processing portions which include an oscillating/actuating portion for the supersonic transmitter of the sensor portion, an arterial pulse wave receiver portion for extracting an analog arterial pulse signal from a supersonic signal received by the supersonic receiver of the sensor portion, a digital signal processing portion for converting the arterial pulse signal extracted by the arterial pulse wave receiver into a digital signal and processing the resultant digital signal, and a display portion for display of the results of the signal processing done by the digital signal processing portion. These signal processing portions are individually formed on separate rigid or flexible circuit boards to form separate blocks which are connected into a strap form by means of a flexible cable or the like. As mentioned supra, however, at least one of the signal processing portions may be divided into separate blocks or at least some of the signal processing portions may be combined into one block in order that the masses can be uniformly distributed. Incidentally, a power source such as a battery relatively prone to heavy weight may be located at a suitable place for accomplishing the uniform mass distribution of the strap. If required, the power source may consist of a plurality of batteries which may be distributed along the length of the strap-like main body of the sensing device.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 are a group of diagrams showing an arterial pulse wave detector according to one preferred embodiment of the invention, FIG. 1A representing a perspective view explanatory of a main body of the arterial pulse wave detector of one preferred embodiment, FIG. 1B representing a sectional view explanatory of a state where the arterial pulse wave detector of one preferred embodiment including the main body of FIG. 1A is worn on the wrist, FIG. 1C representing a sectional view resemblent to FIG. 1B and explanatory of an exemplary modification of FIG. 1B, and FIG. 1D representing a sectional view resemblent to FIG. 1B and explanatory of another exemplary modification of FIG. 1B;  
         [0017]    [0017]FIG. 2 are a group of block diagrams illustrating the functions of the arterial pulse wave detector shown in FIGS. 1A and 1B, FIG. 2A representing a functional block diagram showing an example of the arterial pulse wave detector shown in FIGS. 1A and 1B, and FIG. 2B representing a functional block diagram showing an exemplary modification of FIG. 2A;  
         [0018]    [0018]FIG. 3 are a group of schematic time charts of signals processed by the arterial pulse wave detector shown in FIGS. 1 and 2, FIG. 3A representing a transmitted supersonic signal, FIG. 3B representing a received supersonic signal modulated in frequency by the Doppler effect, FIG. 3C representing an amplitude modulated signal obtained by differential amplification, and FIG. 3D representing a signal of an extracted amplitude component;  
         [0019]    [0019]FIG. 4 is a perspective view explanatory of a sensor portion employed by the arterial pulse wave detector shown in FIGS. 1 and 2; and  
         [0020]    [0020]FIG. 5 are a group of diagrams showing other preferred embodiments of the arterial pulse wave detector of the invention, FIG. 5A representing a sectional view explanatory of a state where one preferred embodiment of the arterial pulse wave detector including the main body of FIG. 1C is worn on the wrist, FIG. 5B representing a sectional view resemblent to FIG. 5A and explanatory of a state where an arterial pulse wave detector including the main body of FIG. 1D is worn on the wrist, and FIG. 5C representing a sectional view resemblent to FIG. 5A and explanatory of a state where an arterial pulse wave detector including a modification of the main body is worn on the wrist. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Next, some of the preferred modes of the invention will be described with reference to the preferred embodiments thereof shown in the accompanying drawings.  
       EXAMPLES  
       [0022]    Out of FIGS.  1  to  4  for illustrating an arterial pulse wave detector  1  as a biological information sensing device according to one preferred embodiment of the invention, FIG. 1 are a general view showing the arterial pulse wave detector  1 .  
         [0023]    As shown in FIG. 1A for example, the arterial pulse wave detector  1  includes a strap-like main body  2  of the detector, and a strap-like support portion  3  for supporting the main body  2  of the detector.  
         [0024]    The main body  2  of the detector includes an arterial pulse wave sensor portion  10  including a supersonic signal transmitter/receiver portion or sensor body  14  comprising a supersonic transmitter  11  and a supersonic receiver  12 ; and besides, a variety of signal processing portions  20 ,  30 ,  40  and  50  which include an oscillating/actuating portion  20  for the supersonic transmitter  11  of the sensor portion  10 , an arterial pulse wave receiving portion  30  for extracting an analog arterial pulse signal P 4  from a supersonic signal P 2  (FIG. 3) received by the supersonic receiver  12  of the sensor portion  10 , a digital signal processing portion  40  for converting the arterial pulse signal P 4  extracted by the arterial pulse wave receiving portion  30  into a digital signal and processing the resultant digital signal, and a display portion  50  for displaying the results of the signal processing done by the digital signal processing portion  40 .  
         [0025]    The circuit components  10 ,  20 ,  30 ,  40  and  50  constituting the main body  2  of the detector each comprise, for example, a circuit board and a circuit device incorporated in the circuit board. The circuit components  20 ,  10 ,  30 ,  40  are each connected with the respective adjoining circuit components  10 ,  30 ,  40  and  50  via respective flexible cables  61 ,  62 ,  63  and  64 . It is noted here that each of the circuit boards may be a printed wiring board such as formed of a resin or ceramic, or a circuit board perse forming an integrated circuit board. In the example shown in FIG. 1A, the circuit board itself typically has rigidity but may have flexibility. Additionally, the circuit components  20 ,  30 ,  40 ,  50  may be accommodated in a case such as a plastic case, respectively.  
         [0026]    The strap-like support portion  3  is formed of a flexible strap material such as a urethane resin, and includes, for example, circuit components  20 ,  10 ,  30 ,  40  and  50 ,individually serving to support their respective strap forming bases  71 ,  72 ,  73 ,  74  and  75  and interconnection portions  76  for interconnecting the forming bases  71  to  75 . The strap forming bases  71 ,  72 ,  73 ,  74  and  75  of the strap-like support portion  3  have the corresponding circuit components  10 ,  20 ,  30 ,  40  and  50  laid thereon or embedded therein. In this connection, the strap forming bases  71 ,  72 ,  73 ,  74  and  75  are previously formed with recesses or openings on either one surface or both surfaces thereof for receiving therein the corresponding circuit components  20 ,  10 ,  30 ,  40  and  50 . The circuit components  20 ,  10 ,  30 ,  40  and  50  are fixed in the recessesor openings by disposing, engagement or bonding. In this case, the circuit components  20 ,  10 ,  30 ,  40  and  50  may be individually disposed in the corresponding recesses while adjoining circuit components may be interconnected by means of the respective flexible cables  61 ,  62 ,  63  and  64 . If desired, of course, at least some or all of the strap forming bases  71 ,  72 ,  73 ,  74  and  75  may be formed integrally with the corresponding circuit components  20 ,  10 ,  30 ,  40  and  50  so as to at the forming of the strap forming bases  71 ,  72 ,  73 ,  74  and  75  be embedded in the corresponding strap forming bases  71 ,  72 ,  73 ,  74  and  75  of the strap-like support portion  3 .  
         [0027]    More specifically, the strap-like support portion  3  is provided with a strap fastening structure  80  on opposite ends thereof, as shown in FIG. 1B or  1 C, the strap fastening structure  80  comprising a strap engaging hardware  81  as a strap fastening portion, and a fastening strap piece  82 . The strap fastening structure  80  may be formed in a desired fashion according to a material used or fastening strength.  
         [0028]    [0028]FIG. 1B shows an arterial pulse wave detector  1   a  wherein the elements  71 - 75  of the strap-like support portion  3  are formed of a material having a relatively high rigidity and the interconnection portions  76  are flexible, whereas FIG. 1C shows an arterial pulse wave detector  1   b  wherein the elements  71 - 75  of the strap-like support portion  3  are formed of a soft material having a relatively high flexibility so that the interconnection portions  76  as well as the elements  71 - 75  are flexible and round. On the other hand, FIG. 1D shows an arterial pulse wave detector  1   c  wherein the circuit boards themselves are also flexible and incorporated into the strap-like support portion  3  for distributing the masses as uniformly as possible. Thus, the elements  20 ,  30 ,  40  and  50  of the main body  2  of the detector, but for the sensor portion  10  including the transmitter/receiver portion  14 , practically belong to the flexible strap-like support portion  3 .  
         [0029]    As shown in FIG. 4 for example, the sensor portion  10  comprises a common substrate  13  incorporating therein the supersonic transmitter/receiver or the sensor body  14  which includes the supersonic transmitter  11  and the supersonic receiver  12  individually including a piezoelectric device. As seen in FIGS.  1 B- 1 D, the supersonic transmitter  11  and receiver  12  of the sensor portion  10  are placed in a manner to be properly pressed into intimate contact with a wrist surface area A 1  where the radial artery B through the human wrist A is closest to the wrist surface. More specifically, in order to accomplish an effective fastening/fixing of the strap-like support portion  3  when the supersonic transmitter/receiver portion  14  of the sensor portion  10  is placed on the wrist surface area A 1  close to the radial artery B, the strap-like support portion  3  is adjusted lengthwise so as to position the strap fastening structure  80  at a bumped side A 2  of the wrist A near the cubitus D. In order to permit such a positional adjustment, a strap portion  83  supporting the hardware  81  may be adapted for lengthwise adjustment.  
         [0030]    In the arterial pulse wave detector  1 , as shown in FIG. 2A, the supersonic transmitter  11  of the sensor portion  10  is actuated to transmit a supersonic signal P 1  under the control of the oscillating/actuating circuit portion  20  including a high-frequency oscillator circuit  21  and a sensor actuating circuit  22  while the signal P 1  is reflected as impinging upon blood components, such as blood cells or the like, in blood flowing through the radial artery B. The supersonic signal emitted from the supersonic transmitter  11  is typically the signal P 1  practically having a constant frequency and amplitude, as shown in FIG. 3A for example.  
         [0031]    A supersonic signal P 2  reflected by the blood components in blood as a pulsing stream through the radial artery B and received by the supersonic receiver  12  is modulated in frequency due to the Doppler effect associated with the pulse of the blood components as the reflector of the transmitted supersonic signal P 1 . Thus, the signal P 2  assumes a form as shown in FIG. 3B, for example.  
         [0032]    As shown in FIG. 2A for example, the arterial pulse wave receiving portion  30  for extracting the analog arterial pulse signal P 4  from the supersonic signal P 2  received by the supersonic receiver  12  of the sensor portion  10  includes a doppler signal detector circuit  31 , a filter/amplifier circuit  32  and an arterial pulse signal detector circuit  33 . An output from the doppler signal detector circuit  31  is, for example, an electrical signal of a wave form P 2  similar to that of the received supersonic signal P 2 . The filter/amplifier circuit  32  amplifies an amount of variation of the doppler signal P 2 ˜sin{(ω+Δω)t} using the original transmission signal P 1 ˜sin(ω·t) as a reference or a reference signal, so as to extract a differential amplification signal P 3 ˜{sin(Δω/2)t}·sin{ω−(Δω/2)}t as shown in FIG. 3C. It is noted here that ω denotes an angular frequency of the supersonic signal P 1 , and that Δω=Δω(t) denotes a modulated angular frequency dependent upon time t due to the Doppler effect. In the arterial pulse wave receiving portion  30 , the arterial pulse signal detector circuit  33  extracts, as the arterial pulse signal P 4 , an amplitude modulated component sin(Δω/2)t from the differential amplification signal P 3 . In the case of a square law detection, the arterial pulse component can be extracted as sin(Δω)t.  
         [0033]    Although FIG. 3 show the arterial pulse wave P 4  quite in a simple wave form, the arterial pulse wave P 4  actually presents much more complicated time-dependent wave form than that of FIG. 3D. Particularly in a state where the cardio pulmonary circulatory system is over taxed during or after exercise, the arterial pulse wave P 4  assumes a much more complicated and irregular wave form containing a wide range of high frequency components.  
         [0034]    In the case of an arterial pulse wave detector  1  shown in FIG. 2A, the digital signal processing portion  40  includes an analog/digital (A/D) converter circuit  41  for converting the analog signal P 4  indicative of the arterial pulse wave into a digital signal P 5  indicative of the arterial pulse wave; a central processing unit (CPU)  45  for receiving the digital arterial pulse signal P 5 ; and a low-frequency oscillator circuit  46  for supplying the CPU  45  with a reference signal for processing. In this case, the CPU  45  includes a memory for storing a frequency-of-pulse operation program and a microprocessor for executing the program, thus forming a frequency-of-pulse operating portion  43  for operating the frequency of pulse based on the digital arterial pulse signal P 5  with reference to the low-frequency signal from the low-frequency oscillator circuit  46 . Typically, the CPU forms a digital signal processor (DSP) wherein a part of the frequency-of-pulse operation program including a fast Fourier transformation (FFT) process is incorporated in a digital signal processor circuit. It is noted that the CPU  45  further includes a device operation portion  44  for receiving an operation command from an operation command input portion  47  such as a push-button switch.  
         [0035]    According to FIG. 2A, the display portion  50  comprises a display unit such as a liquid crystal panel for displaying the operation result or frequency of pulse Q determined by the frequency-of-pulse operating portion  43  of the CPU  45 .  
         [0036]    According to the foregoing description, the A/D converter circuit  41 , the operation command input portion  47  and the like belong to the digital signal processing portion  40 . However, the A/D converter circuit  41  may belong to, for example, an output circuit portion of the arterial pulse wave receiving portion  30  for processing the analog signal. Further, the operation command input portion  47  like a push-button switch may be integrally formed with the display unit  50  as an article. Similarly, the other components may be freely combined into blocks, as desired, so long as such combinations contribute to the mass distribution as a whole.  
         [0037]    Needless to say, the CPU  45  may perform other operations during spare-time when the frequency of pulse Q is not operated or at an interval between the operations of the frequency of pulse Q. One example of the other operations include a time counting operation as a clock. Specifically, the CPU  45  is, for example, capable of performing the time counting operation as a timer and hence, the display portion  50  is also capable of functioning as a display of a digital clock.  
         [0038]    The arterial pulse wave detector  1  (more specifically, the detector  1   a ,  1   b  and  1   c  which are represented by the reference numeral  1  in the this paragraph) of the above construction may be worn on the wrist A as follows. The arterial pulse wave detector  1  is placed around the wrist A in a manner to bring the sensor body  14  of the sensor portion  10  into abutment against the wrist surface area A 1  near the radial artery B of the wrist A. With the hardware  81  positioned at the wrist bump area A 2  near the cubitus D, the strap piece  82  is threaded through the hardware  81  and then fixed by means of engagement portions  84 ,  84  such as hook and loop fasteners.  
         [0039]    When the arterial pulse wave detector  1  is wrapped around the wrist A in this manner, the main body  2  and strap-like support portion  3  of the arterial pulse wave detector  1  have substantially uniform mass distribution along the longitudinal direction thereof. Therefore, even when the wrist A is subjected to the accelerative motion due to exercise or the like, such a great inertia force as to bring the arterial pulse wave detector  1  into mono-directional rotation about the wrist A will not actually occur. Accordingly, the sensor body  14  of the sensor portion  10  of the arterial pulse wave detector  1  is maintained in intimate contact with the measurement area A 1 , thus achieving the precise measurement of the arterial pulses.  
         [0040]    Another approach may replace the direct display of the frequency of pulse Q on the display portion  50  shown in FIG. 2A. As shown in FIG. 2B, a transmitter portion  50  including an antenna or coil is adapted to transmit the data on the frequency of pulse Q, obtained by the frequency-of-pulse operating portion  40 , in the form of an electromagnetic signal R such as of an electromagnetic wave or variable magnetic field, whereas a separate receiver portion  55  receives the electromagnetic signal R, from which the frequency of pulse Q is extracted to be displayed on a display unit  56 . In this case, an arterial pulse wave detector  1 B worn on the wrist of one arm may take the form of a headless strap as shown in FIGS.  1 B- 1 D or a strap free from mass concentration thus presenting wide mass distribution whereas the frequency of pulse Q may be displayed on the display unit  56  with a clock function which is worn on the other arm, for example. This permits the whole body of the display unit  56  prone to heavy weight to be mechanically separated from the arterial pulse wave detector  1 B, contributing to the weight reduction and mass distribution of the arterial pulse wave detector  1 B. As a result, the arterial pulse wave detector  1 B is less susceptible to such a force as to move the sensor body  14  of the arterial pulse wave detector  1 B relative to the wrist A or such a force as to cause the variations of the pressure for pressing the sensor body  14  against the wrist A. Thus, the arterial pulse wave detector  1 B can more precisely or more reliably take measurements.  
         [0041]    The arterial pulse wave detector wherein the strap fastening structure  80  is directly attached to an end of the strap-like support portion  3  with the main body  2  of the detector incorporated therein may have an alternative mode of an arterial pulse wave detector  1 D. As shown in FIG. 5A, the arterial pulse wave detector  1 D has an arrangement wherein a strap-like measuring unit  5  formed by incorporating the strap-like main body  2  of detector in the strap-like support portion  3  is adapted to be fastened to a predetermined position of the wrist A by means of a measuring-unit fastening strap  90  provided with a strap fastening structure  80   a  resemblent to the strap fastening structure  80  at an end thereof. In the arterial pulse wave detector  1 D, the strap-like measuring unit  5  and the fastening strap  90  are formed as independent articles. The strap-like measuring unit  5  is adapted for positional adjustment relative to the fastening strap  90 . Accordingly, in a state where the sensor body  14  of the sensor portion  10  of the detector body  2  of the strap-like measuring unit  5  is exactly positioned at the optimum place A 1  corresponding to the radial artery B, a strap fastening hardware  91  of the fastening structure  80   a  of the fastening strap  90  can be positioned at the bump place A 2  near the cubitus D where the fastening structure is optimally secured to the wrist A. If desired in this case, the unit  5  may be locked to the fastening strap  90  by means of engaging or locking means such as hook and loop fasteners in a manner to be adapted for positional adjustment.  
         [0042]    It is noted that FIG. 5A illustrates the arterial pulse wave detector  1 D wherein the flexible strap-like portion  3  resemblent to that of FIG. 1C is adapted for application using the separate fastening strap  90 , whereas FIG. 5B illustrates an arterial pulse wave detector  1 E wherein the unit  5  comprising the flexible strap-like portion  3  and detector body  2  resemblent to those of FIG. 1D is adapted for application using the separate fastening strap  90 . In a case where the unit  5  comprising the main body  2  of detector and the strap-like portion  3  is adapted for application using the separate fastening strap  90 , an arterial pulse wave detector  1 F may also be employed wherein, for example, shown in FIG. 5C, the unit  5  comprising the strap-like portion  3  and the main body  2  of detector extends along a part of an outside circumference of the wrist A (say, about a half or less of the outside circumference) rather than the substantially overall length of the outside circumference of the wrist.  
         [0043]    In a case where the fastening strap  90  independent from the main body  2  of detector is used, the arterial pulse wave detector may dispense with the strap-like support portion  3  and have an arrangement wherein the main body  2  of detector extended in a strap form is directly fastened to the wrist by means of the fastening strap  90 .