JP5189158B2 - Body fat scale - Google Patents

Description

  The present invention relates to a body fat meter that determines body fat mass and body fat percentage by measuring impedance in the body.

  Conventionally, as a body fat meter of this type, for example, as disclosed in Patent Document 1, a plurality of electrodes are provided on a measurement plate, and the body fat mass is measured by placing both feet of the measurement subject on the electrodes. This is known. In such a body fat scale, electrical insulation between the electrodes is a condition for correct measurement. This is because the conventionally used in-body impedance measurement method can avoid only the contact impedance between the measurement electrode and the subject and can measure only the in-body impedance as the measurement target ( Kelvin double bridge method).

Japanese Patent Publication No. 5-49050

  Next, a measurement method using the conventional apparatus will be described with reference to FIG. As shown in the figure, in the four-terminal method, for example, electrodes E11 and E12 and electrodes E21 and E22 that are in contact with two skins on the soles of both feet are provided, respectively, and the constant current I is set using the electrodes E12 and E22 as power supply electrodes. And a voltage signal generated between the electrodes E11 and E21 is measured by a voltage measuring circuit composed of the AMP11 using the electrodes E11 and E21 as voltage measuring electrodes.

  Here, the contact impedances between the electrodes E11, E12, E21, and E22 and the skin are r11, r12, r21, and r22, respectively, and the input impedance of the voltage measurement circuit is set to a sufficiently large value as compared with these contact impedances. Thus, when a constant current is passed between the power application electrodes E12 and E22, the contact impedances r11 and r21 are prevented from substantially flowing a current that affects the measurement accuracy. Instead of diverting to the impedances r11 and r21, the current flows in a loop including the in-body impedance r0. In this way, since the potential drop in the contact impedances r11 and r21 can be ignored, the voltage generated between the points PQ in the body of the subject is measured by measuring the voltage between the electrodes E11 and E21. It will be possible.

  Thus, since the voltage (potential drop) between the points P and Q is the voltage V11 across the body impedance r0, the voltage V11 is measured to obtain the body impedance r0 by the equation V11 / I = r0. Can do. That is, the electrodes E11 and E21 function as electrodes that can measure only the in-body impedance r0 without being affected by the contact impedance.

  By the way, in the measurement method as described above, as shown in FIG. 16 (a), it is assumed that the resistance between the electrodes E11 and E12 and between the electrodes E21 and E22 is a value that cannot be ignored compared to the magnitude of the contact impedances r11 and r21. If the components R1 and R2 are present, current flows through a loop composed of r11, r12, R1 and r21, r22, R2, and a potential drop occurs in the contact impedances r11, r21.

  Then, the voltage measurement circuit cannot measure the voltage generated by the body impedance r0, which is the voltage between the points P and Q, and the voltage between the points R and S to which the voltage drops of the contact impedances r11 and r21 are added is measured. As a result, an accurate value of the in-body impedance r0 cannot be obtained.

  Also, as shown in FIG. 16B, if there is a resistance component R3 having a value that cannot be ignored compared to the in-body impedance r0 between the electrodes E12 and E22, a current that cannot be ignored compared to the current I. Since i flows toward the resistor R3, a large measurement error occurs when the in-body impedance r0 is obtained by the equation r0 = V1 · I.

  For this reason, in the conventional method, the action of the electrode is divided into an electrode for applying power and a measurement electrode for measuring voltage, and a constant current (or constant voltage) is applied to the power application electrode. By maintaining the insulation between the electrodes as much as possible between the electrodes and the measurement electrodes, only the accurate in-body voltage or in-body impedance is detected and measured from the voltage measurement electrodes.

  However, in the conventional measurement method, particularly when body fat is measured with the foot placed on the electrode, moisture or dirt often adheres to the foot. There is a problem in that the insulation state decreases, the electrical conductivity increases, and the above-described measurement error occurs. Note that this type of measuring instrument (especially a measuring instrument that combines a weight scale and a body fat scale) is often placed in a humid environment such as a bathroom, and it can be said that there is a high probability that such a measurement error will occur. .

  By the way, in the body fat measuring device using the conventional measuring method, the measurement surface error caused by the current flowing on the skin surface is avoided by the skin surface impedance being lowered due to the wet hands and feet of the measurer. In fact, the function of enabling correct measurement is not considered, and the function of issuing an alarm when such a measurement error occurs is not considered.

  In FIG. 15, especially when the contact state of the measurer with the electrodes E12 and E22 is inappropriate, the load of the constant current circuit becomes large, the output voltage is saturated, and the constant current characteristic cannot be maintained. A device that measures the output voltage of the constant current circuit and issues an alarm when the voltage exceeds a certain value before reaching such a situation. Has already been proposed. However, in the case of such a device, as the contact state becomes inappropriate, the measurement signal source impedance viewed from the input terminal of the voltage measurement circuit becomes extremely high, so that it is affected by the noise signal from the induction noise source. Thus, an unpredictable output appears in the output of the voltage measurement circuit. As a result, the measurer may not only mistake the output for the measured value, but may not be able to correctly determine the measurement failure. Moreover, in this conventional apparatus, no consideration is given to the function of warning which contact portion has a contact failure.

The present invention has been made in view of the above-described problems, and enables measurement of an in-body impedance and a contact impedance between an electrode and a body skin surface at the same time. An object of the present invention is to provide a body fat scale that can accurately measure the in-body impedance while accurately determining the measurement state of the person.
It is another object of the present invention to provide a body fat scale that allows a measurer to easily determine the location and extent of a problem in the measurement state from various viewpoints.

In order to achieve the above object, a body fat scale according to the present invention comprises:
A plurality of contact portions to be brought into contact with the body skin surface and a portion between the plurality of contact portions are formed of a conductive material, and the plurality of contact portions and the plurality of contact portions are always kept at a measurable electrical conductivity, The calculation for obtaining the in-body impedance is performed by eliminating the potential difference generated in the plurality of contact portions by the current flowing through the plurality of contact portions to be brought into contact with the body skin surface (first invention).

  In the first invention, the measurement operation of the impedance between the contact portions is performed before the measurement of the in-body impedance by the measurer, and the calculation of the in-body impedance is performed using the impedance measured by the measurement operation. It is preferable that this is done (second invention).

  In addition, it is preferable that the in-body impedance and the contact impedances of the body skin surface and a plurality of contact portions to be brought into contact with the body skin surface are obtained independently (third invention).

  In the third aspect of the invention, it is preferable that display means for displaying the determination result of the contact impedance for each region and the determination result for each region of the equivalent impedance between the contact portions is provided (fourth invention). ).

  Here, the determination result of the contact impedance means that the contact impedance is measured, and the measurement value is too larger than a preset reference value, so that the measurement is inappropriate, and the part and the degree are determined. The result should be displayed with letters, numbers, voice, etc. (Fifth Invention).

  The determination result of the contact impedance is a determination result indicating that the contact impedance is measured and the measurement value is too smaller than a preset reference value, and that the measurement is inappropriate, and its part and degree. May be displayed by letters, numbers, voice, etc. (sixth invention).

  Further, the determination result of the equivalent impedance means that the impedance between each contact portion is measured, and that the measurement value is too small than a preset reference value, and that the measurement is inappropriate, and its part and degree. The determination result to be displayed is preferably displayed by letters, numbers, voices, etc. (seventh invention).

  In the fourth aspect of the invention, it is preferable that the impedance measurement operation between the contact portions and the zero point adjustment operation in a state where there is no weight load are performed by the same command operation (eighth aspect).

  In the fourth aspect of the present invention, at least five contact portions between the body skin surface and the conductive measurement plate are provided, and the mental sweating amount of the measurer is measured from the amount of change in the contact impedance of these contact portions. Preferred (9th invention).

  According to the present invention, since a plurality of contact portions that are brought into contact with the body skin surface and a portion between the plurality of contact portions are made of the conductive material, measurement is always possible between the contact portions that are brought into contact with the body skin surface and the contact portions. Therefore, a current having an appropriate magnitude flows. Therefore, although a voltage drop also occurs at the contact portion, current flows between all the contact portions and between the contact portions, so that the in-body impedance and the contact impedance can be accurately measured. In addition, it is possible to accurately warn of a measurement plate having the contact portion and a measurement person's measurement failure status. Furthermore, even if there is moisture adhesion between the contact parts and the electrical conductivity between the contact parts increases to the extent that an error occurs in the conventional measurement method, the measurement takes into account the equivalent resistance value between the contact parts. By performing the calculation, an accurate in-body impedance can be measured without degrading accuracy. In addition, the measurement plate does not need to be specially provided with metal electrodes, and can be integrally formed of the same material, so that the structure of the measurement plate can be simplified as compared with the conventional one, and manufacturing is easy. There is also an advantage of being.

  Further, according to the configuration of the fifth aspect of the present invention, even when the measurer takes any contact state with the contact portion, the body impedance and the contact impedance are measured without being affected by the induction noise, and the contact impedance is large. An accurate measurement failure alarm can be issued by judging the part and degree. Furthermore, according to the configuration of the sixth invention, when the measurer affects the measurement accuracy due to the wet skin surface, the portion and degree of contact impedance including the skin internal tissue near the contact portion are reduced. Judgment can be made and an accurate measurement failure alarm can be issued.

  In addition, according to the configuration of the seventh invention, it is possible to determine whether the measuring table is in a poor condition, such as when the contact portions are abnormally wet with moisture, and to alert the measurer including its location and degree. Can be issued. Moreover, according to the structure of the said 8th invention, measurement operation can be simplified and a tester's burden can be reduced. Furthermore, according to the configuration of the ninth aspect of the invention, since the impedance of many contact portions can be measured at a time, for example, a minute sweating phenomenon of a fingertip can be accurately captured.

Equivalent resistance circuit diagram of body fat scale according to one embodiment of the present invention (a), side view of conductive plate (b) The figure which shows the mode of the electric current which flows between each contact part terminal at the time of a measurement (1) The figure which shows the mode of the electric current which flows between each contact part terminal when a constant current circuit is connected to the terminal p1 and the terminal p2 when a measurement person is not on the measuring stand. The figure which shows the mode of the electric current which flows between each contact part terminal when a constant current circuit is connected to the terminal p1 and the terminal p3 when a measurer is not on the measuring stand. The figure which shows the mode of the electric current which flows between each contact part terminal at the time of a measurement, and in a body (2) The top view (a) and its AA sectional view (b) of the body weight and body fat scale concerning one example of the present invention Block diagram of weight and body fat scale of this example Detailed block diagram of the measurement arithmetic circuit in FIG. The figure which shows the other Example of a measurement board A plan view (a) and an equivalent circuit diagram (b) showing still another embodiment of the measurement plate The figure which shows the other Example of a measuring device The figure which shows further another Example of a measuring device. The figure (a) which shows further another Example of a measuring device, and its equivalent circuit schematic (b) The figure (a) which shows further another Example of a measuring device, and its equivalent circuit schematic (b) Conventional measurement method explanatory diagram (1) Conventional measurement method (2)

  Next, specific embodiments of the body fat scale according to the present invention will be described with reference to the drawings.

  FIG. 1 is an equivalent resistance circuit diagram (a) of a body fat scale according to an embodiment of the present invention, and a side view (b) of a conductive plate, and FIG. 2 shows a state of current flowing between contact portions during measurement. FIG.

  This embodiment relates to a measuring instrument that can measure body weight as well as body fat mass and rate by measuring impedance between both feet. In the present embodiment, a thin conductive resin plate 1 is used for a measurement table on which both feet are placed. In this conductive resin plate 1, the position of the foot on the surface is indicated by a pattern, and the back side of the resin plate 1 where the back of the foot is in contact with the resin plate 1 is electrically connected to the measurement circuit. Terminals E1, E2, E3, and E4 for exchanging signals are mounted at a total of four locations, two on each leg. Moreover, these terminals E1-E4 and the measurement circuit are connected by an electric wire.

  Since terminals E1 to E4 of each contact portion are mutually conductive, terminals E1 to E2, terminals E2 to E3, terminals E3 to E4, terminals E1 to E3, terminals E2 to E4, terminals E1 The equivalent resistance values between .about.E4 are r1, r2, r3, r4, r5, r6. Further, M represents the in-body impedance of the measurer, X and Y represent the two contact impedances of the portion where the left foot is in contact with the resin plate 1, and similarly the two contact impedances of the portion where the right foot is in contact with the resin plate 1 Assuming Z and U, respectively, the state of the current flowing between the terminals through the conductor inside and outside the measurement person's body at the time of measurement in a state where a constant current circuit for supplying a constant current I is connected to the terminals p1 and p4 is shown in FIG. 2 as shown. Here, since the thickness of the conductive resin plate 1 is thin, the impedance value in the thickness direction is small, but the impedance in the thickness direction between the surface of the resin plate 1 and the terminals is defined as the contact impedance X, Y, Z, U. To be included. These impedances include the impedance of the body tissue around the contact portion.

  As described above, in this embodiment, electric current is applied to all the contact portions by providing conductivity between the contact portions at the time of measurement. Therefore, as in the conventional measurement method, the functions performed by the respective electrodes are essentially different from each other, such as a current application electrode for passing a current and a voltage measurement electrode for not passing a current.

  By the way, the conductivity between the terminals does not always take a constant value, and depending on the measurement environment, for example, if moisture adheres, the conductivity of the resin plate 1 changes. The equivalent resistance value of will change. Therefore, in the present embodiment, it is assumed that the measurer has a function of measuring and storing the inter-terminal resistance values r1 to r6 in advance before the measurer is placed on the measurement table. When the measuring device also serves for weight measurement as in the present embodiment, the inter-terminal resistance values r1 to r6 can be obtained by the same command at the same timing as the zero point measurement of the scale for accurately measuring the weight. Efficient and convenient.

  FIG. 3 shows the state of current flowing between the terminals when a constant current circuit having a current value I is connected to the terminals p1 and p2 when the measurer is not on the measuring table. In FIG. 3, the power supply application circuit and the voltage measurement circuit are omitted.

As is clear from FIG. 3, first, when a constant current I is passed between the terminals p1 and p2, the following equation is used between the voltage between the terminals and the current flowing through the equivalent resistance between the terminals. A relationship is established.
Between p1 and p2: r1 · i1 = V11 (1)
Between p3 and p2: r2 · (i2 + i3) = V12 (2)
Between p4 and p3: r3 · i3 = V13 (3)
Between p1 and p3: r4 · i2 = V11−V12 (4)
Between p4 and p2: r5 · {I− (i1 + i2 + i3)} = V12 + V13
...... (5)
Between p1 and p4: r6 · {I− (i1 + i2)} = V11−V12−V13
...... (6)

Next, as shown in FIG. 4, when the connection point of the constant current circuit is changed to the terminal p1 and the terminal p3, and the constant current I flows between the terminals p1 and p3, the connection between the terminals is made. The relationship of the following equation holds between the voltage and the current flowing through the equivalent resistance between terminals.
Between p1 and p2: r1 · j1 = V21 (7)
Between p2 and p3: r2 · (j1−j3) = V22 (8)
Between p4 and p3: r3 · {I− (j1 + j2) + j3} = V23
...... (9)
Between p1 and p3: r4 · j2 = V21 + V22 (10)
Between p2 and p4: r5 · j3 = V22−V23 (11)
Between p1 and p4: r6 · {I− (j1 + j2)} = V21 + V22−V23
(12)

  As described above, when the measurer gives an adjustment instruction from the outside in a state where the measurer is not placed on the resin plate 1 of the measurement table prior to the measurement, the two terminals (p1-p2, p1-p3) are constant current circuits. Voltage measurement is performed, and the values of voltages V11, V12, V13, V21, V22, and V23 shown in equations (1) to (12) are obtained.

In these formulas (1) to (12),
From (1) / (7) i1 / j1 = V11 / V21 = a (13)
From (2) / (8) (i2 + i3) / (j1-j3) = V12 / V22 = b (14)
From (3) / (9) i3 / {I− (j1 + j2) + j3} = V13 / V23 = c (15)
From (4) / (10) i2 / j2 = (V11−V12) / (V21 + V22) = d (16)
From (5) / (11) {I− (i1 + i2 + i3)} / j3 = (V12 + V13) / (V22−V23) = e
...... (17)
From (6) / (12) {I− (i1 + i2)} / {I− (j1 + j2)} = (V11−V12−V13) / (V21 + V22−V23) = f (18)
Here, a, b, c, d, e, and f are known numerical values because they are the division results of the measured voltage values.

From equation (13): i1 = a · j1 (19)
From equation (14): i2 + i3 = b · (j1-j3) (20)
From equation (15): i3 = c · {I− (j1 + j2) + j3} (21)
From equation (16): i2 = d · j2 (22)
From Expression (17) I− (i1 + i2 + i3) = e · j3 (23)
From Expression (18) I− (i1 + i2) = f · {I− (j1 + j2)} (24)

Substituting Equations (22) and (21) into Equation (20),
i2 + i3 = d.j2 + c. {I- (j1 + j2) + j3} = b.j1-b.j3
Therefore,
(B + c) * j1 + (cd) * j2- (b + c) * j3 = c * I
...... (25)
Substituting equations (19) and (20) into equation (23),
I- (i1 + i2 + i3) = I-a.j1-b. (J1-j3) = e.j3
Therefore,
(A + b) · j1 + (eb) · j3 = I (26)
Substituting equations (19) and (22) into equation (24),
I- (i1 + i2) = I-a.j1-d.j2 = f.If-j1-f.j2
Therefore,
(Af) .j1 + (df) .j2 = (1-f) .I (27)
Thus, from the equations (25), (26), and (27), j1, j2, and j3 can be expressed by the product of the known numerical values a to f and the known constant current value I.
Here, the obtained j1, j2, and j3 are
j1 = k1 · I
j2 = k2 · I
j3 = k3 · I
By substituting these values into the equations (7) to (12), the values of the equivalent resistance values r1 to r6 can be obtained.

  The measurement operation described above is appropriate to be performed immediately before the measurer measures his / her body fat and body weight. Therefore, a measurement preparation button is provided and commanded separately from the measurement button for measuring body fat. Or, if the measurement person presses the zero adjustment button together with the zero adjustment button usually attached to the scale, the above-mentioned equivalent resistance measurement between terminals is performed simultaneously with the zero adjustment. This is advantageous for the measurement work because it saves the operation.

  By the way, in order to carry out the measurement method as described above, it is necessary that there is always a certain electric conductivity or more between the contact portions. For example, if the terminals E1 to E4 are basically kept in an insulated state as in the prior art, the values of j1, j2, and j3 are extremely small under environmental conditions where the measurement surface is normally dry. Measurement cannot be performed with high accuracy. Therefore, in the measurement method of this embodiment, even if there is an environmental change from the dry state to the wet state of the measurement surface, the electrical contact between the contact portions is always kept at an appropriate electrical conductivity, and the terminals, that is, the contacts It is a necessary and sufficient condition for measuring the in-body impedance without degrading accuracy so that the equivalent resistance value between the parts changes within a measurable range.

  When the obtained equivalent resistance value between the terminals is abnormally low, it is considered that the contact portions, that is, between the body contact portions on the conductive plate of the measurement table, are abnormally wet with moisture. Thus, if the measurement surface is abnormally wet, the body skin also gets wet, and the current flowing through the body surface increases, so that accurate in-body impedance cannot be measured. Therefore, if the equivalent resistance values r1 to r6 are set to a certain lower limit value, and any of these equivalent resistance values falls below the set lower limit value, each value is regarded as a bad state of the measuring table. It is preferable to give a warning to the measurer with a display or voice including the corresponding part and the degree of the state failure.

  Next, as described above, the electrical conductivity between the contact portions is obtained in the form of an equivalent resistance value, and those values are stored in a memory. Thereafter, the measurer puts his feet on the electrode and puts the body fat The measurement operation of the in-body impedance when instructing to start measuring the amount will be described. Here, the measurement start may be instructed by the measurer himself / herself with a key switch, or when the measuring device is also used for weight measurement, it is automatically started upon detection of a certain weight value or more. You may do it.

  As shown in FIG. 2, first, a constant current circuit (not shown) that supplies a current value I is connected between terminals p1 and p4. As a result, the current is given to all terminals through the equivalent resistance of the resin plate 1, in other words, the current is given to the body impedance and all the contact impedances existing for each terminal, and the potential drops at each part. Arise. On the other hand, the voltage between all terminals is measured by a voltage measurement circuit (not shown).

The circuit equation shown by the following equation is established in the body, the contact portion, and the resin plate (conductive plate) portion.
Between p1 and p2: X · {I− (i1 + i2 + i3)} + Y · {I− (i1 + i2 + i3 + i4)} = V1 (28)
Between p3 and p4: -Z. {I- (i1 + i2 + i4 + i6)} + U. (i4-i5) = V3- (V1 + V2) (29)
Between p1 and p4: X. {I- (i1 + i2 + i3)} + M.i4 + U. (i4-i5) = V3 (30)

Further, a relational expression represented by the following expression is established between each equivalent resistance and current.
Between p1 and p2: r1 · i3 = V1 (31)
Between p1 and p4: r6 · i1 = V3 (32)
Between p1 and p3: r4 · i2 = V1 + V2 (33)
Between p2 and p4: r5 · i6 = V3−V1 (34)
Between p2 and p3: r2 · {I− (i1 + i2 + i4 + i6)} = V2 (35)
Between p3 and p4: r3 · {I− (i1 + i4 + i6) + i5} = V3− (V1 + V2)
...... (36)
Here, I is a known constant current value, and r1 to r6 are all known by prior measurement, so that all current values i1 to i6 can be obtained from the equations (31) to (36). .

Next, as shown in FIG. 5, a constant current circuit for supplying a current value I is connected between the terminals p2 and p4. At this time, a circuit equation represented by the following equation is established in the contact portion.
Between p1 and p2: X.j4-Y.j2 = -V4 (37)
Between p3 and p4: -Z.j6 + U. (j2 + j4-j6) = V6-V5
...... (38)

Further, a relational expression represented by the following expression is established between each equivalent resistance and current.
Between p2 and p3: r2 · j3 = V5 (39)
Between p3 and p4: r3 · (j3 + j5 + j6) = V6-V5 (40)
Between p1 and p3: r4 · j5 = V5−V4 (41)
Between p2 and p4: r5 · j1 = V6 (42)
Between p1 and p2: r1 · {I− (j1 + j2 + j3)} = V4 (43)
Between p1 and p4: r6 · {I− (j1 + j2 + j3 + j4 + j5)} = V6-V4
(44)
Thus, all the current values of j1 to j6 can be obtained from the equations (39) to (44).

  By solving the circuit equations (28), (29), (30), (37), and (38), the contact impedances X, Y, Z, U and the in-body impedance M are represented by values of i1 to i6 and j1 to j6. It is. Here, i1-i6 can be represented by r1-r6 and V1, V2, V3, j1-j6 can be represented by r1-r6 and V4, V5, V6, and r1-r6 are known in the measurement preparation mode. And stored in the memory, the values of the impedances X, Y, Z, U, and M are obtained when the measurement voltages V1 to V6 are obtained. Further, the body fat mass and the body fat percentage can be obtained using the value of the in-body impedance M in the same manner as a conventional body fat meter.

  Even if moisture adheres to the resin plate (conductive plate) 1 and the conductivity between the contact portions changes, the resistance value measurement step between the terminals of the contact portion is performed each time, so that the time between the terminals is changed. Resistance values r1 to r6 can be obtained. Therefore, if the body fat measurement step is performed after measuring the resistance values r1 to r6 between the terminals in advance according to the measurement preparation command, it is possible to avoid occurrence of an error in the process of calculating the in-body impedance M.

  According to the measurement method of the present embodiment, the measurement input terminal of the voltage measurement circuit does not become high resistance regardless of the contact state of the measurer with the contact portion. For example, in the circuit of FIG. 2, since a constant current circuit is connected between the terminals p1 and p4, when the voltage measurement circuit is connected at the same time, the impedance between the input terminal and the terminal of this voltage measurement circuit is Even in the maximum case (when the measurer is separated from the contact portion), the combined resistance value determined by the inter-terminal resistance values r1 to r6, and the impedance viewed from the input end of the voltage measurement circuit is always low. Become. Therefore, unlike the conventional measurement method, the contact state is deteriorated, the signal source impedance at the input end becomes extremely high, and a situation in which erroneous measurement is caused by adding inductive noise does not occur. Thus, since the voltage between the terminals p1 to p4 can always be accurately measured, the contact impedances X, Y, Z, U and the in-body impedance M can be accurately obtained without being affected by noise.

  However, if the voltage between the terminals p1 and p2, between the terminals p2 and p3, and between the terminals p3 and p4 is close to the same value as when the measurer is not in contact with the contact portion, naturally, the above circuit equation is used. Therefore, a large value is obtained as the value of the contact impedance X, Y, Z, U. In such a state, since the inflow current into the body is insufficient and an accurate in-body impedance M cannot be obtained, the values of the contact impedances X, Y, Z, and U are larger than a certain value. In this case, it is preferable to output a warning together with a position corresponding to the contact impedance as a contact failure.

  When the values of the contact impedances X, Y, Z, and U are large and small, even if the value of the in-body impedance M changes by the same amount, the amount of change in the current flowing through the inter-terminal resistance values r1 to r6 differs. If the amount of change in current is small, the amount of change in voltage between terminals p1 and p2, between terminals p2 and p3, and between terminals p3 and p4 is also small. If the voltage change amount is too small, there is an upper limit on the sensitivity of the measurement circuit (A / D converter resolution), and accurate measurement cannot be performed. As described above, since the measurement limit capable of measuring the in-body impedance M with a predetermined accuracy can be determined in view of the resolution of the A / D converter, the contact impedances X, Y, Z, U can be determined accordingly. The limit of the value of can also be determined by design. Thus, the measurement limit alarm can be accurately transmitted based on the limit determined from the design viewpoint, regardless of the contact state of the measurer.

  On the other hand, it is possible to warn of a malfunction of the body fat scale by using the fact that the values of the contact impedances X, Y, Z, and U are too small. For example, in a finger measurement type body fat scale that measures the impedance in the body using two fingers of both hands, the values of contact impedance X, Y, Z, U are the contact impedances of the fingertip skin surface and the electrode or conductive plate. In addition, the impedance from the skin surface to the root of each finger is also included, but the fingertip has a joint and exhibits an impedance of several hundred ohms when the finger is dry. However, when the measurement is performed in the wet state of the hand, the current flowing on the skin surface of the fingertip increases, and the values of the contact impedances X, Y, Z, and U become extremely small. In this case, not only the impedance of the contact portion between the skin surface and the electrode portion is reduced, but also the branch points P and Q in the measurement of the tissue of the two left and right fingers in FIG. 2 move toward the fingertip. As a result, the in-body impedance M increases, and there is a problem that the measured value of the in-body impedance is different even in the same individual.

  Therefore, in the case of such a finger measurement type body fat scale, for each individual, a lower limit value considering the fingertip impedance value in a standard dry state is set for each type of finger if necessary, When the values of contact impedance X, Y, Z, U are compared with the respective lower limit values at the time of measurement, and any of these X, Y, Z, U values is less than the lower limit value, the measurement that maintains the accuracy is performed. If it is not possible, a warning is given to the measurer along with words / characters indicating the unsuitable part. Here, the standard value may be obtained by, for example, averaging a plurality of measured values at normal times for each individual.

Thus, for each contact portion, the upper limit values Xu, Yu, Zu, Uu and the lower limit values Xl, Yl, Zl, Ul for maintaining accurate measurement are set in advance in the measuring instrument, and the contact impedance is set. When the measurement results of X, Y, Z, and U satisfy the following expression, it is assumed that the measurement is normal, and when any one of the expressions is not satisfied, an alarm is issued as an abnormal measurement together with a word / character indicating the part.
Xl <X <Xu
Yl <Y <Yu
Zl <Z <Zu
Ul <U <Uu

  If the equivalent resistance values r1 to r6 are too small, a current sufficient to maintain the measurement accuracy does not flow toward the in-body impedance. In this case, however, the measurement preparation command is used as described above. Judged by the measurement result. That is, a minimum reference value rl suitable for measurement is set, and if r1 to r6> rl, it is suitable for measurement, and if any one of the equivalent resistance values does not satisfy this inequality, an alarm is given as inappropriate for measurement. To emit.

  In addition, since the equivalent resistance value on the measurement surface and the impedance value in the vicinity of the contact portion of the measurer can be quantified in this way, the measurer is shown how inappropriate it is for each inappropriate or abnormal value. At the same time, the improvement state of the measurement conditions can be easily shown to the measurer.

  For example, when the current value of the measurement surface equivalent resistance r1 is r1p, if r1> r1p, the measurement is inappropriate. However, the deviation r1e = r1p−r1 is further compared with a set value rd prepared in advance, and r1e <rd If rd <r1e <rl, the measurer displays the contents of the meaning representing the unsuitable stage corresponding to the display together with the words / characters representing the parts of r1, r2,. It can be a convenient index for managing the surface.

  The same is true for the display of the wet state of the fingertip described above. In other words, if the magnitude of the difference between the current measured value and the lower limit is evaluated, a display with stepped meanings such as slightly inappropriate, very inappropriate, etc. will be displayed together with words / characters etc. representing the part. It is convenient for the measurer to manage and judge his / her skin condition when using the measuring instrument.

  Next, specific examples of the body fat scale according to the present invention will be described.

  FIG. 6 shows a plan view (a) of a body weight / body fat scale according to one embodiment of the present invention and a cross-sectional view (b) taken along the line AA.

  In the weight / body fat scale 2 of the present embodiment, as shown in FIG. 6 (a), a display 3 is arranged at the front, and a measuring plate 4 on which a measurer puts his / her foot on the rear is provided. It is arranged. Here, the display device 3 includes measurement values such as body weight, body fat mass and body fat percentage, and set values such as age and sex, and key switches for inputting setting data and instructing various operations. ing. On the measurement plate 4, a pattern 5 is drawn that indicates the positions where the front and rear portions of the backs of both feet are brought into contact with each other. Further, as shown in FIG. 6B, a measuring instrument cover 7 is provided on the lower surface of the measuring plate 4 via an insulating sheet 6 and terminals 8 are arranged, and each terminal 8 reaches a measuring circuit. Lead wire 9 is connected.

  In this embodiment, the measurement plate 4 is a conductor and is made of a conductive resin or the like. If the measuring instrument cover 7 is made of resin, the insulating sheet 6 can be omitted, and in this case, the measurement surface can be easily constituted by a single conductive resin plate. There is also a method of sticking a thin insulating sheet having a hole in a portion corresponding to the picture 5 on the conductive measurement plate. In addition, as a method of attaching a terminal for electrically connecting the measurement plate 4 and the measurement circuit, a method of directly screwing the measurement plate 4 to the back surface, a method using a screw or a conductive adhesive, a standard foot There are a method of using a terminal based on a thin metal plate as large as the contact area, a method of providing a terminal together with a metal film which is directly sputtered or vapor-deposited on a resin. In addition, since this metal film is formed on the back surface of the resin plate and does not directly touch the measurer, even a thin film is not worn out.

  FIG. 7 shows a block diagram of the weight / body fat scale 2 of this embodiment, and FIG. 8 shows a detailed block diagram of the measurement arithmetic circuit in FIG.

  As shown in FIG. 7, a weight sensor (LC) 11 is supported on the measurement plate 4 via a support fitting 10. The terminals E1, E2, E3, E4, the weight sensor 11 and the display 3 of the measurement plate 4 are configured to exchange signals with the measurement arithmetic circuit 12, respectively. Here, the weight sensor 11 is assumed to be equipped with a strain gauge type load cell in this embodiment.

  As shown in FIG. 8, in the measurement arithmetic circuit 12, the contact impedances between the measurement plate 4 and the front and rear skin surfaces of the soles are X, Y, Z, and U, respectively. The impedance is M. R1 to r6 are equivalent resistance values between the four terminals attached to the back of the measurement plate 4. The equivalent resistance value varies depending on the surface state of the measurement plate 4.

  The terminals E1 to E4 are respectively connected to the circuit terminals p1, p2, p3 and p4, and these terminals p1 to p4 are connected to the output terminal o1 and the input terminal of the constant current circuit 13 via the analog switches AS3 and AS4 of the internal circuit board. The voltage measurement circuit 14 can be connected to the terminals s1 and s2 through the analog switches AS1 and AS2. Here, the constant current circuit 13 is a circuit in which the voltage signal V0 (known) is inputted from the non-inverting input terminal and outputs the constant current I, and the constant current I is outputted from the operational amplifier AMP1. The reference resistance Rs (known) for controlling the current is controlled, and a constant current of I = V0 / Rs is flown into the body and the attached resistance. The voltage measurement circuit 14 includes an operational amplifier AMP2 that outputs a voltage generated between the terminals s1 and s2, and input resistors R1 and R2 of the operational amplifier AMP2. The input resistors R1 and R2 are selected to be large values that do not hinder measurement accuracy compared to the signal source impedance of the measurement signal.

  In the measurement arithmetic circuit 12, a power source (POW) 15 for exciting the gauge bridge of the load cell LC (gravity sensor 11) and an arithmetic circuit 16 composed of AMP3 as an amplifier circuit for the load cell signal are provided. ing.

  An output signal (AC) from the operational amplifier AMP2 of the voltage measurement circuit 14 is converted into a DC signal by a rectifier circuit (REC) 17 and smoothed by a filter (FIL1) 18. On the other hand, the weight signal output from the AMP 3 of the arithmetic circuit 16 is smoothed by the weight signal filter (FIL 2) 19. An output of each of the filters 18 and 19 is connected to an A / D converter 20 via an analog switch AS5, and the analog signal is digitized by the A / D converter 20. Further, output data from the A / D converter 20 is read by the I / O circuit 21, and various calculations are executed by the CPU 22 based on the data from the I / O circuit 21. Further, the CPU 22 is connected to a memory 23 composed of a ROM / RAM or the like for storing the calculation results of the CPU 22, various calculation programs, numerical value settings, calculation operations, and the like. A display 3 (DIS) 3 for operating data and an operation switch (KEY) 24 for inputting data are connected.

  The CPU 22 outputs ON / OFF control signals of the analog switches AS1 to AS5 through the I / O circuit 21. Here, the analog switch AS5 is switched to the filter 18 side in the impedance measurement, and is switched to the filter 19 side in the weight value measurement.

  Next, the measurement procedure will be described. First, prior to the measurement of body weight and body fat, when the measurer presses the measurement preparation button on the measuring instrument, the analog switch AS5 selects the filter 19, and the weight in the unloaded state on the measurement plate 4 is A. The digital value of the weight is obtained by inputting to the / D converter 20. Then, the obtained value is inputted to the zero point weight memory, and the zero point adjustment is completed. Thereafter, the analog switch AS5 is connected to the filter 18 side, and the current interelectrode impedance of the measurement plate 4 is measured. This procedure is as described with reference to FIGS. 3 and 4. Thus, the measured values r1 to r6 of the equivalent resistance value between the terminals are stored in the memory 23.

  In this embodiment, since the measuring plate 4 is made of a conductive material such as a conductive resin, the current between the terminals always has a certain resistance value or less regardless of the surface state of the measuring plate 4. Flow and potential drop occur. As a result, the equivalent resistance value between terminals can always be measured regardless of the state on the measurement plate 4. If the impedance between the terminals further changes due to moisture adhering or the like, the resistance component due to the moisture enters the resistors r1 to r6 in parallel, and the change in the value can be measured.

  Next, when the above-described zero adjustment and the state storage on the measurement plate are completed, the measurer places the pattern 5 on the measurement plate 4 on the measurement table so that the front part and the rear part of both feet are in contact with each other. Appear. At this time, the weight level is detected and automatically (or when the measurer presses the measurement button), the analog switch AS5 is switched to the filter 19 side again. Thereafter, when the vibration waveform of the weight signal is stabilized, the weight value of the measurer is measured and stored, and at the same time, the analog switch AS5 is switched again to the filter 18 side to shift to the in-body impedance measurement mode. In this case, it is preferable to give a “measurable” signal (display or sound) to the measurer when the zero point adjustment and the state storage on the measurement plate are completed.

  In this in-body impedance measurement mode, measurement is performed as described with reference to FIGS. In this way, since the in-body impedance M is obtained using the equivalent resistance value between terminals according to the state at that time, the in-body impedance value is not influenced by external factors as in the prior art.

  In the present embodiment, the measurement plate is formed of a conductive plate so that a measurable current always flows between the terminals. However, as shown in FIG. The contact portion may be constituted by electrodes (metal plates) 8 and 8 which are fitted into the measurement plate (conductive plate) 4 and attached. Further, as shown in FIG. 9B, the electrodes (metal plates) 8 and 8 are fitted into the insulator plate 6 and the electrodes 8 and 8 are connected by a resistor rn having an appropriate value. You may make it give the electrical conductivity of the appropriate value always with respect to an electrode.

  In the present embodiment, the measurement plate has been described as having a substantially rectangular shape so as to give appropriate electrical conductivity between all the contact portions. However, as shown in FIG. The measurement plate 4 ′ made of resin is formed in a substantially U shape in a plan view, and is configured such that only the terminals E1-E2, the terminals E2-E4, and the terminals E3-E4 have equivalent resistance values r1, r5, r3, respectively. You can also An equivalent resistance circuit in this case is shown in FIG.

  Furthermore, as shown in FIGS. 11 (a) and 11 (b), two sets of metal electrodes are arranged on two separated sets of conductors, and only between electrodes E1-E2 and between electrodes E3-E4 are equivalent. It can also be configured to have resistance values r1, r3. As an application example of a measuring instrument having such a circuit configuration, there is a body fat scale having a configuration in which one finger is brought into contact with each electrode as shown in FIG. In the case of such a body fat scale, a sufficient distance is maintained between the pair of electrodes E1 and E2 and the pair of electrodes E3 and E4 because of the electrode arrangement, and the electrical conductivity is extremely small. Changes in electrical conductivity do not affect measurement accuracy. However, the distance between the electrodes E1 and E2 that are adjacent to each other and the distance between the electrodes E3 and E4 are extremely short, so even if they are made of an insulating material, the electrical conductivity easily changes due to environmental changes. Resulting in. On the other hand, according to the measurement method as in the present embodiment, an appropriate electrical conductivity is maintained between the electrodes E1 and E2 and between the electrodes E3 and E4, and a current flows between the contact portion and the electrodes. Therefore, it can be said that the body fat scale of such a form is effective for application to the measurement method of this embodiment.

  In the measurement plate of this example, all of the contact portions have both current application and voltage measurement functions at the same time. When the terminals of each contact portion are attached to the back surface of the measurement plate, or the contact portion is a metal electrode. Various forms such as arranging the electrodes in proximity to each other on the insulating plate are possible. In this case, according to the present embodiment, even when the material between the contact portions or between the electrodes is made of a conductor or an insulator, even when the conductivity between adjacent contact portions is changed due to an environmental change, compensation is made. There is a feature in what can be done.

  Further, according to the measurement method of the present embodiment, the contact impedance of the conductor contact portion or the metal electrode can be obtained independently simultaneously with the in-body impedance.

  If the contact impedance is too large, the output of the constant current circuit operational amplifier APM1 in FIG. 8 is saturated and correct measurement cannot be performed. Even if it does not reach that point, if the contact impedance becomes too large, the current applied to the body becomes too small, causing an error. Therefore, as described above, if any of the contact impedance values becomes too large, an alarm is issued. More specifically, for example, numbers 1 to 4 are respectively displayed corresponding to the contact portions of the measurement surface shown in FIG. 6A, and the impedance of the contact portions corresponding to the numbers is a predetermined value or more. When it becomes a large value, the measurer is warned by means of a display or voice. The measurer can easily know which part is in contact with this alarm. If the contact impedance value or the stepwise level of the impedance value is displayed, the degree of contact failure can be easily known. In this way, a highly accurate and reproducible measurement operation can be performed.

  On the contrary, for example, when the impedance of the fingertip tissue is taken into account, it is a problem if the contact impedance is too small than a predetermined value. In this case, there is a possibility that the range of the tissue to be measured as in-body impedance changes. Therefore, in this embodiment, the measurer is also warned by a display or voice of the degree and part of the contact impedance that is too small.

  In the above description, it has been described that the equivalent resistance value between the terminals or electrodes of the contact portion is obtained during the measurement preparation operation, but the state of the surface of the measurement table can be known from this measurement value. Even if measurement is performed without error in consideration of the conductive state on the surface of the measurement plate, there is still a limit. If there is too much moisture, the skin itself gets wet and causes an error. Therefore, similarly to the contact impedance, a boundary value is provided for the equivalent impedance value between the contact portions, and if any one of the equivalent impedance values r1 to r6 is smaller than the predetermined value, the portion and the degree are numerically expressed. It is preferable to display a warning by text or voice display.

  As described above, according to the present embodiment, the measurement person can be surely notified of the measurement state of the measurement person, the quality of the measurement table and the location thereof, so that the measurement person can review the contact state, This makes it possible to grasp the state of the measurement table and to maintain and manage the surface of the measuring table in a normal state.

  According to the measurement method of this embodiment, since the contact impedance of each finger can be measured simultaneously, the portable (card type) body fat scale as shown in FIG. It is preferable to apply to a body fat scale in which the pairs E1, E2 and E3, E4 are arranged.

  The contact impedance varies depending on the sweating action of the skin. However, in the case of the body fat meter shown in FIG. 12, the sweating of the skin surface at four locations is simultaneously separated by the impedance of only the contact portion separated from the body impedance. Therefore, it is convenient for detecting a sweating phenomenon that is essentially a minute change. In addition, since such a measuring instrument is required to be entertaining and easy to measure, it is an important condition that it is portable and has a finger measurement type, and such a configuration is extremely useful.

  By the way, in the case of the measuring instrument shown in FIG. 12, since the electrodes are installed on the front and back sides of the measuring instrument main body, it is unlikely that the electrical conductivity between the two electrodes changes due to environmental changes. However, at least as shown in FIG. 11A, a resistance is connected between the electrodes, or the electrodes are made of a material having an appropriate electrical conductivity. In this case, if the value of the inter-electrode resistance component is known from the design time, the prior electrical conductivity measurement can be omitted, and this known value can be used as a constant coefficient for impedance calculation.

  Further, as described above, the contact impedance changes due to the sweating action of the skin, but since the amount of change is small, the more measurement points, in other words, the more measurement data, the easier detection and the more accurate measurement becomes possible. That is, according to the measurement method of the present embodiment, for example, the values of the contact impedances X, Y, Z, and U can be collected simultaneously from four contact portions, so that each change Δx, Δy, Δz, Δu is a small value. Even if each of them varies in size, it can be used in the form of an added value such as Δx + Δy + Δz + Δu, so that a minute impedance change amount can be easily captured and accurate measurement can be expected.

  FIG. 13 (a) shows a body fat / mental dynamometer with the number of electrodes increased to five. In this example, the electrodes E1 and E2 are pressed with two fingers of the right hand during measurement, and the electrodes E3, E4, and E5 are pressed with the three fingers of the left hand. FIG. 13 (b) is an equivalent circuit diagram of this body fat / mental dynamometer. In the figure, the power supply circuit and the measurement circuit are omitted. In FIG. 13 (b), M represents the impedance in the body, X and Y represent the combined impedance of the contact portion between each electrode and each finger and the finger joint portion regarding the two fingers of the right hand, and Z, U and K represent the left hand. The combined impedance of the contact part of each electrode and each finger | toe and finger joint part regarding three fingers is represented.

  In this circuit, the same analysis as in the case of four electrodes is possible. For example, a constant current is applied between the terminals p1 and p5 and between the terminals p2 and p3, and the measured voltage at each terminal and the distance between the electrodes. Six independent circuit equations are established from the values of the equivalent resistance values r1, r2, and r3, and the impedances X, Y, Z, U, K, and M can be expressed by the measured voltage and the interelectrode equivalent resistance value. Therefore, in this case, the impedance change of the five contact portions can be captured.

  Similarly, if each finger is provided with at least one contact part between the electrodes, a body fat / mental sway meter that can detect the impedance value and the amount of change of at least 10 contact parts is constructed. can do. In addition, even when a plurality of electrodes are arranged at one contact portion per finger, more accurate sweat measurement can be expected by detection from many contact portions.

  Of course, the measurement signal detector of this measuring instrument is not of a type that is sandwiched between fingers, but a system in which grips 25 and 25 for both hands attached to the portable measuring instrument as shown in FIG. You can also An equivalent circuit diagram in this case is shown in FIG.

  In these methods, in the case of a method in which an electrode is brought into contact with a plurality of locations on the palm or a method in which a plurality of contact electrodes are provided for the same finger (see FIG. 11), the contact impedance between the electrodes is extremely small. The equivalent resistance value r1 is selected to be small, or a resistor having an appropriate resistance value is inserted between the measurement terminal and the electrode in series with the contact impedance so that the apparent contact impedance is set to an appropriate value. It is necessary to increase and select a larger r1 to balance the current distribution.

DESCRIPTION OF SYMBOLS 1 Conductive resin board 2 Body weight and body fat meter 3 Indicator 4 Measuring board 5 Picture 6 Insulation sheet 7 Measuring instrument cover 8 Electrode 9 Lead wire 10 Support metal fitting 11 Weight sensor 12 Measurement arithmetic circuit 13 Constant current circuit 14 Voltage measurement circuit 15 Power supply 16 Arithmetic circuit 17 Rectifier circuit 18, 19 Filter 20 A / D converter 21 I / O circuit 22 CPU
23 Memory 24 Operation switch AS1 to AS5 Analog switch E1 to E6 Electrode or terminal

Claims (9)

  A plurality of contact portions to be brought into contact with the body skin surface and a portion between the plurality of contact portions are formed of a conductive material, and the plurality of contact portions and the plurality of contact portions are always kept at a measurable electrical conductivity, A body fat scale, wherein a calculation for obtaining an in-body impedance is performed by excluding potential differences generated in the plurality of contact portions due to currents flowing in the plurality of contact portions brought into contact with the body skin surface.   The impedance measurement operation between the contact portions is performed before the measurement of the in-body impedance by the measurer, and the calculation of the in-body impedance is performed using the impedance measured by the measurement operation. Body fat scale according to.   2. The body fat scale according to claim 1, wherein the body impedance and the contact impedances of the body skin surface and a plurality of contact portions that contact the body skin surface are independently determined.   The body fat scale according to claim 3, further comprising a display unit configured to display a determination result of the contact impedance by region and a determination result of the equivalent impedance between the contact portions by region.   The determination result of the contact impedance is a measurement result indicating that the contact impedance is measured and the measurement value is too large than a preset reference value, and the measurement result is unsuitable, and the determination result indicating the part and the degree. 5. The body fat scale according to claim 4, wherein the body fat scale is displayed by numbers, sounds, and the like.   The determination result of the contact impedance is a measurement result indicating that the contact impedance is measured and the measurement value is too small than a preset reference value, and that the measurement result is inappropriate, and the determination result means the part and the degree. 5. The body fat scale according to claim 4, wherein the body fat scale is displayed by numbers, sounds, and the like.   The determination result of the equivalent impedance is a determination that means that the impedance between the respective contact portions is measured, and that the measurement value is too small than a preset reference value, that the measurement is inappropriate, and its part and degree. The body fat scale according to claim 4, wherein the result is displayed by letters, numbers, voice and the like.   The body fat scale according to claim 4, wherein the impedance measurement operation between the contact portions and the zero point adjustment operation in a state where there is no weight load are performed by the same command operation.   The body fat meter according to claim 4, wherein at least five contact portions between the body skin surface and the conductive measurement plate are provided, and the mental sweating amount of the measurer is measured from the amount of change in contact impedance of these contact portions.

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