WO2015133921A1 - Device for measuring electrical parameters of portion of human body - Google Patents

Abstract

The device allows for measuring the impedance of a portion of the body, and for measuring the active resistance and the potential difference between areas of skin. The device includes two electrodes positioned on a human body, an operational amplifier and a microcontroller. The conductive electrodes are connected to a negative feedback circuit of the operational amplifier, a non-inverting input of which is connected to a zero potential, an output is connected to an analogue-to-digital converter of the microcontroller, and an inverting input is connected by means of a resistor to an input-output port of the microcontroller. In a mode for measuring the impedance of a portion of the human body, the microcontroller forms a signal of a given frequency at the output of the input-output port; in a mode for measuring the active resistance of human skin, the microcontroller forms a DC voltage signal at the output of the input-output port; and in a mode for measuring the potential difference between areas of skin on the human body, the microcontroller provides for the disabling of the input-output port. The device is characterized in having a simple design and in being easy to control when measuring various electrical parameters of a portion of the human body.

Description

 DEVICE FOR MEASURING ELECTRICAL

 PARAMETERS HUMAN BODY AREA TECHNOLOGY AREA

 The invention relates to the field of measurements for diagnostic purposes, in particular to measuring devices using electric current, and can be used in human life monitoring systems.

BACKGROUND

 Various devices are known for measuring the electrical parameters of a portion of the human body.

 So, in the patent KR 2008028651 (publication 01.04.2008, IPC A61B5 / 0424) a system for measuring the impedance of a portion of a human body is described. The system includes two main electrodes that are connected to the differential inputs of a DC amplifier. Filters are connected to the input of the amplifier. From the output of the amplifier, the signal is supplied to the processing device. This system is intended to measure only the impedance of a body part, and is not intended to measure other electrical parameters of a part of the human body, for example, the active resistance of human skin or the potential difference between parts of the human body skin.

 The patent CN 102579033 (publication July 18, 2012, IPC A43B5 / 0402, A61B5 / 053) describes a system for measuring the electrical resistance of a part of the human body, containing electrodes, amplifiers and a microprocessor. The electrodes are connected to the input of the DC amplifier, the output of the amplifier through a parallel RC filter is connected to the input of the analog-to-digital converter of the microprocessor. This system is designed to measure only one parameter - the electrical resistance of a portion of the human body - and is not suitable for measuring other electrical parameters of a portion of the human body.

The closest analogue is the device and method for measuring the impedance of a portion of the human body, described in patent US 8089283 (publication 03.01.2012, IPC A61B5 / 053). The device contains electrodes placed on the human body, a DC amplifier and a microprocessor. Electrodes connected to the input of the amplifier, from the output of which signals with impedance characteristics are recorded. A number of filters are also connected to the amplifier inputs, switching of which is carried out by a microprocessor. This system is designed to measure only one parameter - impedance - and is not suitable for measuring other electrical parameters of a portion of the human body.

 The technical problem to which the claimed invention is directed is to create a simple device with which it is possible to measure various electrical parameters of a part of the human body, in particular, the impedance of a part of the human body, the active resistance of human skin and the potential difference between the parts of the human body skin.

SUMMARY OF THE INVENTION

 In accordance with the present invention, a device for measuring electrical parameters of a portion of a human body includes two conductive electrodes placed on the human body, an operational amplifier and a microcontroller. The microcontroller is configured to operate in three modes - in the mode of measuring the impedance of a portion of the human body, in the mode of measuring the active resistance of the human skin and in the mode of measuring the potential difference between the sections of the skin of the human body. Conducting electrodes are included in the negative feedback circuit of the operational amplifier, the non-inverting input of the operational amplifier is connected to zero potential, and the output of the operational amplifier is connected to the input of the analog-to-digital converter of the microcontroller. The inverting input of the operational amplifier through a resistor is connected to the input / output port of the microcontroller. In the mode of measuring the impedance of a portion of the human body, the microcontroller at the output of the input-output port provides a signal of a given frequency at which the impedance of the portion of the human body is measured. In the mode of measuring the active resistance of human skin, the microcontroller at the output of the input-output port provides the formation of a constant voltage signal. In the mode of measuring the potential difference between the parts of the skin of the human body, the microcontroller provides the disconnection of the input-output port.

The inclusion of electrodes in the negative feedback circuit (OOS) of the operational amplifier allows for given electrical parameters to the output of the input / output port of the microcontroller, to which the inverting input of the operational amplifier is connected through a resistor, as well as the ratios of the resistances in the input circuit, the OOS circuit and the currents in these circuits, known for operational amplifiers, to determine by the value of the output voltage of the operational amplifier supplied to the input of the analog the digital converter (ADC) of the microcontroller, the impedance value, the active resistance of the body area between the electrodes or the potential difference between the skin areas to which are applied electrodes. The use of a microcontroller ensures the formation of the required electrical parameters at the output of the I / O port that specify the measurement mode.

 Thus, the device in accordance with the present invention allows you to measure various electrical parameters of a portion of the human body, such as impedance, resistance, and even the potential difference between the skin areas. In this case, all parameters are measured using the same electrodes placed on the human body, and one simple non-tunable electrical circuit, the control of which is also simple and is carried out through a microcontroller.

 In particular, the frequency of the signal generated by the microcontroller in the mode of measuring the impedance of a portion of the human body for measurements for diagnostic purposes can be from 1 kHz to 4 MHz.

 In addition, the device may have a holder in which are placed the components of the electrical circuit of the device, including conductive electrodes, an operational amplifier and a microcontroller. Moreover, the holder is made with the possibility of fixing around the wrist of a person so that the electrodes are adjacent to the wrist. Each of the electrodes is made sectional with the possibility of separately connecting sections, and sections of the first and second electrodes are alternately arranged in the same row on the inner surface of the holder.

This embodiment of the device allows you to use it to measure the indicated electrical parameters of the human body in the wrist. The execution of the electrodes sectional and their location alternately in the same row can improve the stability of the recorded signal and the sensitivity of the device. This is due to an increase in the reliability of the contact of electrodes with human skin, as well as an increase in the area of electrodes and optimization of the current path through the body section between the electrode sections. Due to the fact that each of the sections is made with the possibility of separate connection (that is, inclusion in the composition of the corresponding electrode), the potential difference between the individual points of the wrist and the average potential difference can be measured.

In addition, the number of sections of each electrode may be at least three, and each section of both electrodes may have a contact area of at least 1 cm ² .

 In the particular case, the holder can be made in the form of a flexible tape fixed to the wrist with a fastener, such as Velcro.

 In another particular case, the holder may be made in the form of a bracelet having sections pivotally connected to each other.

 In another particular case, the holder can be made in the form of a tight wrist cuff.

 The device can be additionally equipped with a transceiver for controlling the microcontroller and transmitting the measured electrical parameters of a portion of the human body, while the transceiver is placed in a holder.

BRIEF DESCRIPTION OF THE DRAWINGS

 The invention is illustrated by the following graphic materials.

 In FIG. 1 is a circuit diagram of an apparatus for measuring electrical parameters of a portion of a human body in accordance with the present invention.

 In FIG. Figure 2 shows an equivalent diagram of a portion of the human body in the impedance measurement mode.

 In FIG. Figure 3 shows an equivalent diagram of a human skin site in the mode of measuring active resistance.

 In FIG. Figure 4 shows an equivalent diagram of a portion of the human body in the mode of measuring the potential difference between parts of the skin of the human body.

 In FIG. Figure 5 shows the equivalent wiring of the microcontroller I / O port in three measurement modes.

In FIG. 6 shows a perspective view of an example embodiment of a device for measuring electrical parameters of a portion of a human body in accordance with the present invention with a holder in the form of a flexible tape with a fastener. In FIG. 7 schematically shows the fastening of the device to the wrist.

 In FIG. 8 shows the location of the sections of the conductive electrodes on the holder and the electrical connection of the sections of the first and second electrodes of the device shown in FIG. 6.

 In FIG. 9 shows a view of FIG. 8 is a section AA of the holder in the region of one of the electrode sections.

 In FIG. 10 shows another example of a holder design with a cavity for accommodating components of an electrical circuit of a device in accordance with the present invention.

 In FIG. 11 shows a diagram of the electrical connection of the sections of the first and second electrodes with the formation of the first and second electrodes of the device.

 In FIG. 12 illustrates the direction of electric currents between the electrode sections of a device in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

 Device for measuring electrical parameters of a human body

(Fig. 1) includes two - the first and second - conductive electrodes 5 and 6, respectively, placed on the human body, an operational amplifier 2 and a microcontroller 1. The electrodes 5 and 6 can be fixed in different places of the human body using a holder, for example, made in the form of a tape with a fastener fastened to the wrist, as shown in FIG. 7.

 The electrodes 5 and 6 (Fig. 1) are included in the OOS circuit of the operational amplifier 2 between its inverting input and output. Accordingly, when the electrodes are mounted on the human body and have electrical contact with the body, a portion 3 of the human body (or skin surface) is turned on in the OOS circuit of the operational amplifier between the electrodes 5 and 6. The non-inverting input of the operational amplifier 2 is connected to zero potential. The output of the operational amplifier 2 is connected to the port of the analog-to-digital converter (ADC) of the microcontroller 1, and the inverting input of the operational amplifier 2 through a resistor 4 is connected to the input-output port L of the microcontroller 1.

The microcontroller 1 can switch on the input-output port L in one of three modes, as shown in the equivalent circuit (Fig. 5). Here, the connection of the input-output port L of the microcontroller 1 is conditionally represented by a switch 14 having three positions: the first is the leftmost position - corresponds to the mode of measuring the impedance of a part of the human body, the second - central - corresponds to the mode of measuring the active resistance of the skin, and the third - rightmost - corresponds to the mode of measuring the potential difference between the skin areas.

 In the first mode — measuring the impedance of a portion of the human body — port L of microprocessor 1 switches to the output, and a probe signal of frequency F is applied from the output of port L in the range from 1 kHz to 4 MHz. In FIG. 5, this corresponds to the leftmost position of the switch 14. An equivalent circuit of the portion 3 of the human body in this mode is shown in FIG. 2. It includes an active resistance 7 and a parallel-connected circuit including a capacitance 9 and a resistance 8.

 Considering the known properties of operational amplifiers (infinitely large input impedance and, accordingly, zero input current and zero potential difference at the inputs) and taking into account that the non-inverting input of operational amplifier 2 is connected to zero potential, in this inclusion an alternating current flowing through resistor 4, equal to the current flowing through section 3 of the human body between the electrodes 5 and 6. This equality can be written as:

where: U _ex is the voltage of the sounding signal with a frequency of F from the output L of the microcontroller 1;

 R4 is the resistance of the resistor 4;

U _{ebix is the} voltage at the output of the operational amplifier 2, supplied to the input of the ADC of the microcontroller 1;

Z ₃ - the impedance of section 3 of the human body.

Since U _I and R4 are known, then, by measuring the voltage U _eblx at the output of the operational amplifier 2, we can determine the impedance value of the portion 3 of the human body:

Z ₃ = R ^ U ^ x / U ^).

In the second mode - measuring the active resistance of human skin - the port L of the microcontroller 1 is switched to the input and connected through the resistor 13 (usually called the "pull-up" resistor and available in the microcontroller 1) to a voltage source of voltage E. In FIG. 5, this corresponds to the central position of the switch 14. An equivalent circuit of the human body portion 3 in the mode of measuring skin resistance is shown in FIG. 3 and includes resistance 10.

 As in the case of measuring impedance, in this inclusion, the direct current flowing through resistor 4 and resistor 13 is equal to the current flowing through section 3 of the human body between electrodes 5 and 6. This equality can be written as:

E / (R ₄ + R _l3 ) = U _eblx / R ₃ ,

where: E is the supply voltage of the microcontroller 1;

 R4 is the resistance of the resistor 4;

R ₁₃ is the resistance of the resistor 13;

U _O -voltage on the output of the operational amplifier 2 supplied to the ADC input of microcontroller 1;

 R3 - the active resistance of the skin of a portion of the body of 3 people

Since E, R4 and R _{13 are} known, then, by measuring the voltage U _o at the output of the operational amplifier 2, it is possible to determine the value of the active resistance of the skin of section 3 of the human body:

R ₃ = (R ₄ + R _i3 ) - (u _eblx / u.

 In the third mode - measuring the potential difference between areas of the human skin - the input / output port L of the microcontroller 1 switches to input and a high resistance is provided at its output. In FIG. 5, this corresponds to the extreme right position of the switch 14. The equivalent circuit of the human body portion 3 for this case is shown in FIG. 4 and includes resistance 1 1 and voltage source 12.

Since with this inclusion, the current flowing through the resistor 4 and, accordingly, the current flowing through the portion 3 of the human body are equal to zero (the voltage at the inverting input of the operational amplifier 2 is also equal to zero), then the voltage U _o at the output of the operational amplifier 2 will be equal to potential differences between electrodes 5 and 6, that is, the measured potential difference between areas of human skin. Thus, due to the simple switching of the microcontroller modes, without changing the electrodes and their position on the human body, the device is transferred to any of the three described modes of measuring the electrical parameters of a portion of the human body.

 The described device without any changes is suitable for measuring both the impedance in a wide range of frequencies, and for measuring both types of human skin-galvanic reaction.

 In FIG. 6 is a perspective view showing an example embodiment of a device for measuring electrical parameters of a portion of a human body in accordance with the present invention. The device 16 includes a holder 17 with a first electrode 5 and a second electrode 6 mounted on it (Fig. 8), which are made in the form of separate sections 18 and 19, respectively. In this example, the holder 17 of the electrodes 5 and 6 is made in the form of a flexible tape with a fastener 20 such as Velcro, which allows you to fix it tightly around the wrist 22, as shown in FIG. 7. The holder 17 of the electrodes can be made of plastic and other materials that ensure the holder is wrapped around the wrist 22. It is understood by a person skilled in the art that the holder of the electrodes can have a different design, for example, can be made in the form of a bracelet having sections pivotally connected to each other, or in the form of a cuff tightly worn on the wrist (these options are not shown in the drawings).

 The electrodes 5 and 6, made in the form of separate sections 18 and 19, respectively, are placed on the inside of the holder 17, so that when putting the device 16 on the wrist 22 sections 18 and 19 of the electrodes 5 and 6 are adjacent to the wrist 22. Sections 18 and 19 of both electrodes 5 and 6 are arranged alternately on the holder 17 in a row. That is, section 18 of electrode 5 is followed by section 19 of electrode 6, then again section 18 of electrode 5, followed by section 19 of electrode 6, and so on. FIG. 6, FIG. 8, FIG. 10 - FIG. 12 sections 18 of the electrode 5 are marked with the letter "a", and sections 19 of the electrode 6 are marked with the letter "b".

It has been experimentally established that a close to optimal embodiment of the device 16 contains four sections of each electrode 5 and 6. The contact area of each section 18, 19 is at least 1 cm ² . The shape of the sections 18 and 19 of the electrodes 5 and 6 can be varied, for example, rectangular, as shown in FIG. 6, or round, as shown in FIG. 10. All sections 18 are interconnected, as shown in FIG. 8 and FIG. 1 1 forming electrode 5, as well as all sections 19 are electrically connected to each other, forming electrode 6.

 In the mode of measuring the potential difference between sections of the skin of the human body, sections 18, 19 of the electrodes 5, 6 can be switched using switches 26 and 27, as shown in FIG. I. For example, the potential difference can be measured between two sections 18 and 19, for this, using one switch 26, the corresponding section 18 is included in the electrode 5 (the remaining switches 26 are open), and with one switch 27 the corresponding section 19 is included in the composition electrode 6 (the remaining switches 27 are open). As switches 26, 27, jumpers or various electronic circuits, for example, field-effect transistors, can be used. The average potential difference can also be measured when all switches 26 and 27 connect sections 18 and 19 to the respective electrodes 5 and 6.

 Inside the holder 17, the components of the electrical circuit of the device 16 are installed in the form of a flexible printed circuit board 21 (Fig. 9 and Fig. 10), or a printed circuit board in the form of separate sections (not shown) connected by flexible conductors. On the printed circuit board 21 can also be placed the power elements of the device.

 The device can be additionally equipped with a transceiver with an antenna for controlling the microcontroller and transmitting the measurement results to an external device, while the transceiver is also placed in a holder (not shown in the drawings).

Due to the implementation of the holder 17 in the form of a flexible tape and a fastener 20, the device 16 is fixed around the wrist 22, while the contact surfaces of the sections 18 and 19 of the electrodes 5 and 6 are tightly attached to the skin of the wrist 22. The implementation of the electrodes 5 and 6 section provides reliable contact with the skin at least at least two sections 18 and 19 of the electrodes 5 and 6 for any hand movements. Due to the fact that the electrodes are sectional and each section has an area of at least 1 cm ² , the total area of each electrode, for example, when it is made of four sections, is at least 4 cm ² , which increases the reliability of the contact of the electrodes 5 and 6 with skin and device sensitivity. The arrangement of sections 18 and 19 alternately (Fig. 12) ensures the passage of electric current 25 (shown by dashed arrows) through the soft tissue 23 of the wrist 22, while the currents from the individual sections 18 and 19 are summed. With this arrangement of sections 18 and 19, the current does not pass through the bones 24 of the arm, which have greater electrical resistance than blood-saturated soft tissues 23, which also affects the sensitivity of the device in the direction of its increase.

 Such a structural embodiment of the device provides improved measurement accuracy in the three described modes. This is due to increasing the reliability of the contact of the electrodes with human skin, increasing the contact area of the electrodes and optimizing the current path between the electrode sections. Based on this device, it is possible to create systems for continuous monitoring of various parameters of human life.

Claims

CLAIM 1. A device for measuring the electrical parameters of a portion of the human body, including two conductive electrodes placed on the human body, an operational amplifier and a microcontroller configured to measure the impedance of a portion of the human body, in the mode of measuring the active resistance of the human skin and in the mode of measuring the difference potentials between areas of the skin of the human body, while the above electrodes are included in the negative feedback circuit of the operational amplifier, the non-inverting input of which connected to the zero potential, the output is connected to the input of the analog-to-digital converter of the microcontroller, and the inverting input through the resistor is connected to the input-output port of the microcontroller, while in the mode of measuring the impedance of a portion of the human body, the microcontroller at the output of the input-output port provides a signal of a given frequency on which the impedance is measured, in the mode of measuring the active resistance of human skin, the microcontroller at the output of the input-output port provides a constant voltage, and in the mode of measuring the potential difference between areas of the skin of the human body, the microcontroller ensures the shutdown of the input-output port. 2. The device according to claim 1, characterized in that the frequency of the signal generated by the microcontroller in the mode of measuring the impedance of a portion of the human body is from 1 MHz to 4 MHz. 3. The device according to claim 1, characterized in that it has a holder in which the components of the device’s electrical circuitry are located, including the aforementioned first and second conductive electrodes, an operational amplifier and a microcontroller, the holder being adapted to be fastened around the human wrist so that the electrodes Adjacent to the wrist, each of the electrodes is made sectional with the possibility of separately connecting sections, and the sections of the first and second electrodes are alternately arranged in the same row on the inner surface the eternity of the holder. 4. The device according to p. 3, characterized in that the number of sections of each electrode is at least three. 5. The device according to p. 3, characterized in that each section of both electrodes has a contact area of at least 1 cm ² . 6. The device according to p. 3, characterized in that the holder is made in the form of a flexible tape fixed to the wrist with a fastener. 7. The device according to p. 3, characterized in that the holder is made in the form of a bracelet having sections pivotally connected to each other. 8. The sensor according to claim 3, characterized in that the holder is made in the form of a tightened wrist cuff. 9. The device according to claim 3, characterized in that it is additionally equipped with a transceiver for controlling the microcontroller and transmitting the measured electrical parameters of a portion of the human body, while the transceiver is located in the holder.