RU2522949C1 - Device for measuring electric parameters of individual's body area - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: device for measuring electric parameters of an individual's body area (3) comprises two conducting electrodes (5, 6) placed on the individual's body, an operating amplifier (2) and a microcontroller (1). The microcontroller (1) is configured to operate in the mode of the individual's body area impedance measurement, in the mode of the individual's skin resistance measurement and in the mode of the individual's body area potential measurement. The electrodes (5, 6) are connected to a negative feedback circuit of the operating amplifier (2), a non-inverting terminal of which is connected to the zero potential, and an output is connected to an input of an analogue-to-digital converter of the microcontroller (1), while an inverting terminal is connected through a resistor (4) to an in/out port (L) of the microcontroller (1). In the mode of the individual's body area impedance measurement, the microcontroller (1) provides forming a signal of a pre-set frequency whereat the impedance is measured, on the output of the in/out port (L). In the mode of the individual's skin resistance measurement, the microcontroller (1) provides forming a DC voltage signal on the output of the in/out port (L). In the mode of the individual's body area potential measurement, the microcontroller (1) provides switching off the in/out port (L).

EFFECT: more accurate measurement of the electric parameters of the individual's body areas by switching the microcontroller modes without change of the electrodes and their body position.

9 cl, 12 dwg

Description

FIELD OF TECHNOLOGY

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 A61B 5/0424) describes a system for measuring the impedance of a portion of the human body. 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 designed to measure only the impedance of a part of the body, 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.

CN 102579033 (publication July 18, 2012, IPC A43B 5/0402, A61B 5/053) describes a system for measuring the electrical resistance of a portion of a 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 A61B 5/053). The device contains electrodes placed on the human body, a DC amplifier and a microprocessor. The electrodes are 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 at 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 operational amplifiers the currents in these circuits, determined by the value of the output voltage of the operational amplifier supplied to the input of the analog-to-digital converter (ADC) of the microcontroller, s impedance, resistance body region between the electrodes or the difference in potential between the skin portions to which the electrodes are attached. 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 the electrodes with human skin, as well as an increase in the area of the electrodes and the optimization of the path of the current 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.

Figure 1 shows a circuit diagram of a device for measuring electrical parameters of a portion of a human body in accordance with the present invention.

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

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

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

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

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.

7 schematically shows the fastening of the device to the wrist.

On Fig 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 indicated in Fig.8 section AA of the holder in the region of one of the sections of the electrode.

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

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.

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

DETAILED DESCRIPTION OF THE INVENTION

A device for measuring the electrical parameters of a portion of the human body (Figure 1) includes two - first and second - conductive electrodes 5 and 6, respectively, placed on the human body, an operational amplifier 2 and a microcontroller 1. Electrodes 5 and 6 can be fixed in various places of the body person using a holder, for example, made in the form of a tape with a fastener fixed to the wrist, as shown in Fig.7.

The electrodes 5 and 6 (Figure 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 (Figure 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 extreme left position corresponds to the mode of measuring the impedance of a portion of the human body, the second central is the mode of measuring the active resistance of the skin, and the third is the extreme right corresponds to the mode of measuring the potential difference between the skin.

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 extreme left position of the switch 14. The 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:

_Rin U / R = U _{O 4} / Z ₃

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

R ₄ is the resistance of the resistor 4;

U _o - 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 and ₄ are known, then by measuring the voltage U _O the output of the operational amplifier 2, it is possible to determine the value of the impedance portion 3 of the body:

Z ₃ = R ₄ (U _o / U _o ).

In the second mode - measuring the active resistance of human skin - port L of the microcontroller 1 is switched to the input and is connected to the power supply with voltage E. Through the resistor 13 (usually called the "pull-up" resistor and present in the microcontroller 1). In Fig. 5, this corresponds to the central position of the switch 14. The equivalent circuit of the portion 3 of the human body in the measurement mode of the active resistance of the skin is shown in Figure 3 and includes a resistance of 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 ₁₃ ) = U _o

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

R ₄ is the resistance of the resistor 4;

R ₁₃ is the resistance of the resistor 13;

U _o - voltage at the output of the operational amplifier 2, supplied to the input of the ADC of the microcontroller 1;

R ₃ - the active resistance of the skin of the body portion of 3 people.

Since E, R ₄ 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 section 3 of the human body.

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 a resistance 11 and a 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.

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. 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 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, etc. In 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 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 and 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. 11, forming an electrode 5, in the same way as all sections 19 are electrically interconnected, forming an 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. 11. For example, a 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 electrode 6 (other switches 27 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 the 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 (9)

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 signal maskers, and a potential difference measurement mode between portions of human body skin microcontroller provides disabling input-output port. 2. The device according to claim 1, characterized in that the frequency of the signal generated by the microcontroller in the measurement mode of the impedance of a portion of the human body is from 1 kHz to 4 MHz. 3. The device according to claim 1, characterized in that it has a holder in which are placed the components of the electrical circuit of the device, including the aforementioned first and second conductive electrodes, an operational amplifier and a microcontroller, while the holder is made with the possibility of fixing around the 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 ited holder. 4. The device according to claim 3, characterized in that the number of sections of each electrode is at least three. 5. Apparatus according to claim 3, characterized in that each section of both electrodes has a contact area of at least 1 cm ^2. 6. The device according to claim 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 claim 3, characterized in that the holder is made in the form of a bracelet having sections pivotally connected to each other. 8. The device according to claim 3, characterized in that the holder is made in the form of a tight 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.

Images