CN114431863A

CN114431863A - System for measuring electrode contact impedance and impedance measuring method

Info

Publication number: CN114431863A
Application number: CN202011215043.3A
Authority: CN
Inventors: 任健; 刘启翎; 杨龙
Original assignee: Shenzhen Mindray Bio Medical Electronics Co Ltd
Current assignee: Shenzhen Mindray Bio Medical Electronics Co Ltd
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2022-05-06

Abstract

The application discloses a system and an impedance measurement method for measuring electrode contact impedance. The at least two measuring electrodes are used for being connected to the skin of a person to be measured to measure physiological parameters, and at least two measuring electrode groups are formed. At least two alternating current excitation sources are respectively and correspondingly connected with the at least two measuring electrodes, wherein the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different. The driving electrode is connected to the skin of the person to be measured and provides a common mode potential for the measuring electrode. The controller is used for acquiring the voltage and the current at the measuring electrodes and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the acquired voltage and current. The contact impedance of the measuring electrode can be obtained when the physiological parameter is measured, and an indication is provided for the physiological signal quality.

Description

System for measuring electrode contact impedance and impedance measuring method

Technical Field

The present disclosure relates to the field of medical measurement, and more particularly, to a system and method for measuring contact impedance between a human skin and an electrode attached to the human skin.

Background

The measurement of human electrophysiological signals is widely applied in clinical practice, and the measured signals include Electrocardiogram (ECG), electroencephalogram (EEG), Electromyogram (EMG), etc., and the measured electrophysiological signals are mainly used for disease diagnosis or daily monitoring of patients. Electrophysiological signals generated by the human body are usually weak, e.g. the amplitude of ECG and EMG signals is of the order of mV, whereas EEG signals have an amplitude of the order of uV. The weak electrophysiological signals are susceptible to interference from the measurement system and the external environment. For a measurement system to obtain good physiological signal quality, it is necessary to monitor the state of the measurement system to prevent variations in the measurement system from affecting accurate measurement of the physiological signal.

Typically, measurement of electrophysiological signals of the human body is achieved by non-invasive or invasive connection of measuring electrodes to the human body. The noninvasive mode is that an electrode plate or conductive paste is pasted on the skin surface of a human body, and then the human body is connected with a measuring system through a measuring electrode; the invasive method is to use a needle electrode to puncture the skin of a human body and then connect the needle electrode to the skin of the human body through an electric cable. Since the needle electrode is invasive, more noninvasive electrode pads, such as self-adhesive electrode pads or electrode pads fixed to the body surface by conductive paste, are clinically used for measurement. The contact impedance exists between the measuring electrode and the skin of the human body, and the size of the contact impedance reflects the quality of the connection between the physiological signal measuring system and the human body through the electrode, so that the measuring quality of the current physiological signal is directly influenced, and further the analysis and judgment of medical staff on the measured physiological signal can be influenced.

Therefore, there is a need to provide a method for accurately and synchronously monitoring the contact impedance of the electrode, which can prompt medical staff to intervene in the treatment in time when the contact impedance of the electrode is too large to affect the quality of the measured physiological signal.

Disclosure of Invention

The application provides a system and an impedance measuring method for measuring electrode contact impedance, which can accurately and synchronously monitor the contact impedance of an electrode when measuring human body electrophysiological signals, thereby providing reference for the signal quality of the human body electrophysiological signals.

In one aspect, embodiments of the present application provide a system for measuring electrode contact impedance, the system including at least two measurement electrodes, at least two ac excitation sources, a drive electrode, and a controller. The at least two measuring electrodes are used for being connected to the skin of a person to be measured to measure physiological parameters, wherein the at least two measuring electrodes form at least two measuring electrode groups. The current output ends of the at least two alternating current excitation sources are respectively and correspondingly connected with the at least two measuring electrodes, wherein the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other. The driving electrode is used for being connected to the skin of a person to be measured so as to provide common-mode potential for the at least two measuring electrodes. The controller is coupled with each measuring electrode and used for acquiring the voltage and the current at each measuring electrode and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

In another aspect, an embodiment of the present application provides an impedance measurement method, where the method includes: respectively connecting at least two measuring electrodes to the skin of a person to be measured, wherein the at least two measuring electrodes form at least two measuring electrode groups; providing currents for the at least two measuring electrodes through at least two alternating current excitation sources respectively, wherein current output ends of the at least two alternating current excitation sources are respectively and correspondingly connected with the two measuring electrodes, and working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other; and acquiring the voltage and the current at each measuring electrode, and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

In yet another aspect, a system for measuring electrode contact impedance is also provided, the system comprising at least one measurement electrode, at least one alternating current excitation source, a drive electrode, and a controller. The at least one measuring electrode is used for being connected to the skin of a person to be measured to measure physiological parameters, wherein the at least one measuring electrode forms at least one measuring electrode group. And the current output ends of the at least one alternating current excitation source are respectively and correspondingly connected with the at least one measuring electrode, wherein the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other. The driving electrode is used for being connected to the skin of a person to be measured and providing a common-mode potential for the plurality of measuring electrodes. The controller is coupled with the current output end of each alternating current excitation source and each measuring electrode and is used for acquiring the voltage and the current at each measuring electrode and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

In another aspect, an impedance measuring method is provided, which is applied in a system for measuring contact impedance of an electrode, and the method includes: connecting at least one measuring electrode to the skin of a person to be measured, wherein the at least one measuring electrode forms at least one measuring electrode group; respectively providing current for the at least one measuring electrode through at least one alternating current excitation source, wherein the current output end of the at least one alternating current excitation source is respectively connected to the at least one measuring electrode, and the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other; and acquiring the voltage and the current at each measuring electrode, and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

In the application, alternating current is provided for the measuring electrodes through the alternating current excitation source, the alternating current does not interfere with physiological signals, the contact impedance between each measuring electrode and the skin of a person to be measured can be obtained while the measuring electrodes measure/monitor physiological sign parameters, and an indication is provided for the quality of the physiological signals measured by the measuring electrodes. In addition, the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other, so that each measuring electrode group does not influence the measurement of the contact impedance of the measuring electrodes of other measuring electrode groups, and the accuracy and the synchronism are improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a system for measuring contact impedance of an electrode according to an embodiment of the present application.

Fig. 2 is a block diagram of an internal module of a controller according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a monitoring device to which a system for measuring contact impedance of an electrode according to an embodiment of the present application is applied.

Fig. 4 is a schematic diagram of a display of a waveform of a measurement signal and an indication of contact impedance in an embodiment of the present application.

Fig. 5 is a schematic diagram showing a waveform of a measurement signal and an indication of contact impedance in another embodiment of the present application.

Fig. 6 is a schematic diagram of a system for measuring contact impedance of an electrode according to another embodiment of the present application.

Fig. 7 is a flowchart of an impedance measuring method according to an embodiment of the present application.

Fig. 8 is a flowchart of an impedance measuring method according to another embodiment of the present application.

Fig. 9 is a flowchart of an impedance measurement method in other embodiments of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In this application, "connected" or "coupled" includes both direct and indirect connections.

Fig. 1 is a schematic structural diagram of a system 100 for measuring contact impedance of an electrode according to an embodiment of the present application. The system 100 includes at least two measurement electrodes 1, at least two ac excitation sources 2, a drive electrode 3, and a controller 4.

The at least two measuring electrodes 1 are used for connecting to the skin 101 of the person to be measured for physiological parameter measurement, wherein the at least two measuring electrodes 1 form at least two measuring electrode groups 10. Each ac excitation source 2 includes an ac output terminal 21, and the at least two ac excitation sources 2 are respectively and correspondingly connected to the at least two measuring electrodes 1, that is, the current output terminals 21 of the at least two ac excitation sources are respectively connected to each measuring electrode of the at least two measuring electrode groups 10, wherein the operating frequencies of the ac excitation sources 2 connected to the measuring electrodes 1 of different measuring electrode groups 10 are different from each other. The driving electrode 3 is used for connecting to the skin 101 of the person to be measured and providing a common-mode potential for the at least two measuring electrodes 1. The controller 4 is coupled to the current output end 21 of each ac excitation source 2 and each measurement electrode 1, and is configured to obtain the voltage and the current at each measurement electrode 1, and calculate the contact impedance between each measurement electrode 1 and the skin 101 of the person to be measured according to the voltage and the current at each measurement electrode 1.

Therefore, in the present application, the alternating current excitation source 2 provides the measuring electrode 1 with the alternating current, which does not interfere with the physiological signal, and can obtain the contact impedance between each measuring electrode 1 and the skin 101 of the person to be measured while the measuring electrode 1 performs measurement/monitoring of the physiological sign parameters, so as to provide an indication for the quality of the physiological signal measured by the measuring electrode 1. In addition, the working frequencies of the alternating current excitation sources 2 connected with the measuring electrodes 1 of different measuring electrode groups 10 are different from each other, so that each measuring electrode group does not influence the measurement of the contact impedance of the measuring electrodes 1 of other measuring electrode groups 10, the accuracy is improved, and the synchronism is realized.

The contact impedance between each measuring electrode 1 and the skin 101 of the person to be measured is the electrode contact impedance between the person to be measured and the electrode attached to the person to be measured. The working frequency of the ac excitation source 2 is the frequency of the current provided by the ac excitation source 2.

It should be understood that, as described above, in some embodiments, when a certain measurement electrode group 10 includes a number of measurement electrodes 1 equal to 2, the ac excitation sources 2 connected to the measurement electrodes 1 of the measurement electrode group 10 have the same operating frequency and amplitude, and are opposite in phase; in other embodiments, when a certain measurement electrode group 10 includes a number of measurement electrodes 1 equal to 2, the operating frequency and amplitude of the ac excitation source 2 connected to the measurement electrodes 1 of the measurement electrode group 10 may not be the same. That is, the operating frequencies of the ac excitation sources 2 connected to the measurement electrodes 1 of different measurement electrode groups 10 are different from each other, and the operating frequencies and amplitudes of the ac excitation sources connected to the measurement electrodes 1 of the same measurement electrode group 10 may be the same or different.

The system 100 further includes an inverting amplifier 5, an input end 51 of the inverting amplifier 5 is coupled to the at least two measuring electrodes 1, and an output end 52 of the inverting amplifier 5 is connected to the driving electrode 3, and is configured to apply the voltages of the at least two measuring electrodes 1 to the skin 101 of the person to be measured through the driving electrode 3 after inverting, so as to provide a common mode potential for the plurality of measuring electrodes 1.

Since the skin 101 of the subject, i.e. the skin of the human body, generally has bioelectricity, but is not at the same system potential as the potential of the system 100, the potentials of the system 100 and the skin 101 of the subject can be driven to the same system potential, i.e. the common mode potential, by the driving electrode 3 after the measuring electrode 1 and the driving electrode 3 contact the skin 101 of the subject.

As shown in fig. 1, a resistor R is further connected between the output end 52 of the inverting amplifier 5 and the driving electrode 3, and the output end 52 of the inverting amplifier 5 is connected to the driving electrode 3 through the resistor R.

As shown in fig. 1, the system 100 further includes an operational circuit 6, where the operational circuit 6 is connected between the at least two measurement electrodes 1 and the input end 51 of the inverting amplifier 5, and is configured to operate the voltages of all the measurement electrodes 1 to obtain an operational voltage, and output the operational voltage to the input end 51 of the inverting amplifier 5, and the inverting amplifier 5 is specifically configured to invert the operational voltage, apply the inverted operational voltage to the skin 101 of the person to be measured through the driving electrode 3, and provide a common mode potential for the plurality of measurement electrodes 1.

That is, in some embodiments, the inverting amplifier 5 inverting the voltages of the at least two measurement electrodes 1 comprises: the voltages of all the measuring electrodes 1 are firstly operated by the operation circuit 6 to obtain an operation voltage, and then the operation voltage is inverted by the inverting amplifier 5.

The operation circuit 6 performs an average operation on the voltages of all the measurement electrodes 1 to obtain the operation voltage. Wherein the averaging operation may include, but is not limited to, a geometric averaging operation, an arithmetic averaging operation, and the like.

In this embodiment, the number of the at least two ac excitation sources 2 is equal to the number of the at least two measuring electrodes 1, and the current output ends 21 of the at least two ac excitation sources 2 are connected to the at least two measuring electrodes 1 in a one-to-one correspondence manner.

After the measuring electrode 1 in each measuring electrode group 10 receives the current with the corresponding frequency from the current output end of the correspondingly connected ac excitation source, the current with the corresponding frequency is at least partially shunted to the other measuring electrode groups 10, during the measurement of the contact impedance of a certain measuring electrode, the controller 4 may obtain a first target voltage with the corresponding frequency in the certain measuring electrode group 10 and obtain a second target voltage with the same frequency as the other measuring electrodes 1 which are not in the same measuring electrode group 10 as the certain measuring electrode, and then obtain the contact impedance of the corresponding measuring electrode 1 according to the first target voltage, the second target voltage and the current with the corresponding frequency.

Specifically, the controller 4 may calculate a difference between the first target voltage and the second target voltage, and then divide the difference by the current of the corresponding frequency to obtain the contact impedance of the corresponding measurement electrode 1.

As shown in fig. 1, in an embodiment, each two measurement electrodes form one measurement electrode group 10, the magnitude and frequency of the current generated by the two ac excitation sources 2 connected to the two measurement electrodes 1 in the measurement electrode group 10 are the same, and the phases are opposite, so that, for each measurement electrode group 10 including the measurement electrode 1, the current of the corresponding frequency generated by the corresponding ac excitation source 2 flows in from one measurement electrode 1 in the measurement electrode group 10, the current of the corresponding frequency generated by the corresponding ac excitation source 2 flows out from the other measurement electrode 1 in the measurement electrode group 10 after passing through the skin 101 of the subject mostly, and flows at least partially to the measurement electrodes in the other measurement electrode groups 10, and generally, the current of the corresponding frequency is extremely small when flowing into the other measurement electrode groups 10, such as the current 1/100 generated by the ac excitation source 2, and so on. It should be understood that each two measuring electrodes 1 selected to be used as the same measuring electrode group 10 in the embodiments of the present application may be two measuring electrodes adjacent to each other, or may be any two measuring electrodes that are not adjacent to each other, and are not particularly limited herein.

In other embodiments, the number of measuring electrodes 1 included in each measuring electrode group 10 may also be one, three, etc.

In some embodiments, the controller 4 includes at least two signal inputs 41, each signal input 41 is coupled to a current output of a corresponding ac excitation source 2 and connected to a corresponding measurement electrode 1, wherein the signal input 41 of the controller 4 is electrically coupled to the measurement electrode 1, the voltage received by the signal input 41 is equal to the voltage of the measurement electrode 1, the current flowing through the measurement electrode 1 is the current provided by the ac excitation source 2 connected to the measurement electrode 1, and the controller 4 thus receives the voltage of the measurement electrode 1 from the signal input 41 and can also obtain the current provided by the ac excitation source 2 connected to the measurement electrode 1.

In some embodiments, the current provided by each ac excitation source 2 has a corresponding relationship with the signal input terminal 41 of the controller 4, and the controller 4 determines the current provided by the ac excitation source 2 connected to each signal input terminal 41 according to the corresponding relationship.

That is, in the present application, the current output end 21 of the corresponding ac excitation source 2 coupled to each signal input end 41 of the controller 4 may be determined in advance according to a hardware connection relationship, and then the current provided by the ac excitation source 2 and the signal input end 41 are associated to obtain the corresponding relationship. Each signal input end 41 of the controller 4 has a unique port number, and the current provided by each ac excitation source 2 and the port number of the corresponding signal input end 41 can be associated and bound to obtain the corresponding relationship between the current provided by each ac excitation source 2 and the signal input end 41 of the controller 4.

In other embodiments, the system 100 may include a current detection circuit (not shown), and the controller 4 may detect the current obtained from each measuring electrode 1 through the current detection circuit.

That is, in other embodiments, the current of each measuring electrode 1 is directly detected by the current detecting circuit.

In some embodiments, when the at least two measuring electrodes 1 are attached to the skin 101 of the person to be measured to measure the physiological signals, the at least two ac excitation sources 2 simultaneously generate currents to the corresponding measuring electrodes 1, so as to measure the contact impedance between each measuring electrode 1 and the skin 101 of the person to be measured.

However, also because at least two ac excitation sources 2 are used to generate current to the corresponding measuring electrodes 1 simultaneously, although, as mentioned above, for example, two measuring electrodes 1 in the same measuring electrode group 10 form a current loop, the current mainly flows in from one measuring electrode 1 in the measuring electrode group and flows out from the other measuring electrode 1 in the measuring electrode group 10 after passing through the skin 101 of the person to be measured, in practice, more or less current generated by each ac excitation source 2 flows to the other measuring electrodes 1 and the driving motor 3. Therefore, the voltage received by each signal input 41 of the controller 4 actually includes a plurality of voltages generated by the plurality of alternating current excitation sources 2 through which the current flows to the measuring electrode 1, and the plurality of voltages respectively have the same frequency as the operating frequency of the corresponding alternating current excitation source 2.

Therefore, in some embodiments, the controller 4 further filters the voltage collected by each signal input terminal 41 to extract a target voltage with a corresponding frequency.

Specifically, for the voltage collected by any signal input terminal 41, the controller 4 filters the voltage collected by the signal input terminal 41 according to the operating frequency of the ac excitation source 2 connected to the signal input terminal 41, and extracts a first target voltage having the operating frequency of the ac excitation source 2 connected to the signal input terminal 41. Then, the contact impedance between the corresponding measuring electrode 1 and the skin 101 of the person to be measured is calculated based on the extracted first target voltage and the current flowing through the corresponding measuring electrode 1.

Wherein, the first target voltage with the working frequency of the ac excitation source 2 connected to the signal input terminal 41 is a voltage generated by the ac excitation source 2 connected to the signal input terminal 41 flowing through the corresponding measuring electrode, and for each measuring electrode connected to the signal input terminal 41, the controller 4 calculates the contact impedance of the measuring electrode connected to the signal input terminal 41 mainly according to the voltage generated by the ac excitation source 2 connected to the signal input terminal 41 flowing through the corresponding measuring electrode and the current provided by the ac excitation source 2 connected to the signal input terminal 41.

Further, during the measurement of the contact impedance of a certain measuring electrode 1 connected to a certain signal input end 41, the controller obtains a second target voltage which is obtained by filtering the voltage of the signal input end 41 connected to the other measuring electrode 1 which is not in the same measuring electrode group 10 as the certain measuring electrode 1 and has the same frequency as the current provided by the alternating current excitation source 2 connected to the certain measuring electrode 1.

In this application, for the voltage collected by any signal input terminal 41, the controller 4 is further configured to perform filtering again on the voltage collected by the signal input terminal 41, and extract a second target voltage with other frequencies, which is different from the operating frequency of the ac excitation source 2 connected to the signal input terminal 41, where the voltage collected by each signal input terminal 41 is filtered again to obtain a plurality of second target voltages, and the plurality of second target voltages are voltages generated by other ac excitation sources 2 with other operating frequencies flowing through the measurement electrode 1 connected to the signal input terminal 41.

Thus, during the measurement of the contact impedance of a certain measuring electrode 1 connected to a certain signal input terminal 41, the controller may obtain a second target voltage having the same frequency as the current supplied by the ac excitation source 2 connected to the certain measuring electrode 1, which is obtained by filtering in the signal input terminal 41 connected to the other measuring electrode 1 which is not in the same measuring electrode group 10 as the certain measuring electrode 1.

The calculating of the contact impedance between the corresponding measuring electrode 1 and the skin 101 of the person to be measured based on the extracted first target voltage and the current flowing through the corresponding measuring electrode 1 specifically includes: and calculating the contact impedance between the corresponding measuring electrode 1 and the skin 101 of the person to be measured according to the extracted first target voltage, the extracted second target voltage and the current flowing through the corresponding measuring electrode 1.

Specifically, if the first target voltage obtained by extracting the voltage of a certain signal input end is V1, the second target voltage is V2, and the current flowing through the corresponding measuring electrode 1 is I, the contact impedance between the corresponding measuring electrode 1 and the skin 101 of the person to be measured can be calculated according to the formula (V1-V2)/I.

Specifically, the voltage difference between the first target voltage and the second target voltage is calculated, and then the ratio of the voltage difference to the current flowing through the corresponding measuring electrode 1 is calculated to obtain the contact impedance between the corresponding measuring electrode 1 and the skin 101 of the person to be measured.

For example, as shown in fig. 1, there are 4

measurement electrodes

1, and 4 measurement electrodes 1 are respectively set as measurement electrodes 1a, 1b, 1c and 1d, wherein the measurement electrodes 1a and 1b constitute a measurement electrode group 10, and the measurement electrodes 1c and 1d constitute another measurement electrode group 10; the contact points of the four measuring electrodes 1a, 1b, 1c and 1d with the skin 101 of the person to be measured are a, b, c and d, respectively, the signal input terminals 41 connected with the four measuring electrodes 1a, 1b, 1c and 1d by the controller 4 are

signal input terminals

41a, 41b, 41c and 41d, respectively, and the voltages received by the four

signal input terminals

41a, 41b, 41c and 41d are Va, Vb, Vc and Vd, respectively.

Let I be the current supplied by an AC excitation source 2 connected to four measuring electrodes 1a, 1b, 1c and 1d_ω1、-I_ω1、I_ω2and-I_ω2The operating frequencies are ω 1, ω 2, and ω 2, respectively. That is, the measuring electrodes 1a and 1b constitute a measuring electrode group 10, and the frequencies of the currents supplied from the two ac excitation sources 2 connected thereto are equal and the phases thereof are opposite, and the measuring electrodes 1c and 1d also constitute a measuring electrode group 10, and the frequencies of the currents supplied from the two ac excitation sources 2 connected thereto are equal and the phases thereof are opposite.

Therefore, for the measurement of the contact impedance between the measuring electrode 1a and the skin 101 of the person to be measured, since the working frequency of the alternating current excitation source 2 connected to the measuring electrode 1a is ω 1, the supplied current is I_ω1Therefore, the controller 4 filters the voltage Va received by the signal input terminal 4a connected to the measuring electrode 1a to extract the voltage Va (ω 1) with the frequency ω 1 as the first target voltage, in this case, for the measuring electrode 1a, the measuring electrodes 1c and 1d are the measuring electrodes in the other measuring electrode group 10, and in this case, the controller 4 may further obtain the voltage Vc (ω 1) or Vd (ω 1) with the same frequency as the current provided by the ac excitation source 2 connected to the measuring electrode 1a, which is filtered by the signal input terminal 41c or 41d connected to the measuring electrode 1c or 1d, as the second target voltage.

Therefore, the contact of the measuring electrode 1a with the skin 101 of the subjectThe contact impedance Z1 can be determined according to the voltage Va (ω 1), Vc (ω 1) and the current I_ω1Calculated or calculated according to the voltages Va (omega 1), Vd (omega 1) and the current I_ω1And (5) calculating.

That is, the contact impedance Z1 between the measurement electrode 1a and the skin 101 of the subject is (Va (ω 1) -Vc (ω 1))/I_ω1＝(Va(ω1)-Vd(ω1))/I_ω1。

Wherein, as shown in fig. 1, the contact impedance Z1 between the measuring electrode 1a and the skin 101 of the person to be measured is equivalent to a resistance, and I provided by the ac excitation source 2 connected to the measuring electrode 1a_ω1After flowing in from the measuring electrode 1a, it flows out mainly from the measuring electrode 1b, or from the driving electrode 3, but a small amount flows out from the measuring electrodes 1c, 1d and is received by the signal input terminal 41c or 41 d. At this time, I provided by the AC excitation source 2_ω1The voltage generated at the end of the contact impedance Z1 connected to the signal input 4a is the voltage Va (ω 1), whereas I received by the signal input 41c or 41d due to the small amount of current flowing from the measuring electrodes 1c, 1d is received by the signal input 41c or 41d_ω1The current component is small, and therefore, the differential pressure formed by the contact impedance between the measurement electrodes 1c and 1d and the skin 101 of the subject is small. Therefore, I provided by the AC excitation source 2_ω1The voltage generated at the other end of the contact impedance Z1 can be considered to be equal to the voltage Vc (ω 1) or Vd (ω 1) filtered in the signal input terminal 41c or 41d connected to the measuring electrode 1c or 1 d. Therefore, the voltage difference between the voltage Va (ω 1) and the voltage Vc (ω 1), or the voltage difference between the voltage Va (ω 1) and the voltage Vd (ω 1) can be regarded as the voltage difference between the two ends of the contact impedance Z1 between the measuring electrode 1a and the skin 101 of the person to be measured, and the voltage difference and the current I are calculated by the above calculation formula_ω1The contact impedance Z1 can be obtained from the ratio of the two.

For another example, for the measurement of the contact impedance between the measuring electrode 1c and the skin 101 of the person to be measured, the working frequency of the ac excitation source 2 connected to the measuring electrode 1c is ω 2, and the supplied current is I_ω,2Therefore, the controller 4 filters the voltage Vc received by the signal input terminal 4c connected to the measuring electrode 1c, and extracts the voltage Vc (ω 2) with the frequency ω 2 as the first target voltage, and at this time, for the measuring electrode 1c,the measuring electrodes 1a, 1b are measuring electrodes in another measuring electrode group 10, and the controller 4 may obtain the voltage Va (ω 2) or Vb (ω 2) filtered in the

signal input terminal

41a or 41b connected to the measuring electrode 1a or 1b and having the same frequency as the current supplied by the ac excitation source 2 connected to the measuring electrode 1c as the second target voltage.

Therefore, the contact impedance Z3 between the measuring electrode 1c and the skin 101 of the person to be measured can be determined according to the voltages Vc (ω 2), Va (ω 2) and the current I_ω2Calculated or calculated from the voltages Vc (ω 2), Vb (ω 2) and the current I_ω2And (6) calculating.

That is, the contact impedance Z3 between the measurement electrode 1c and the skin 101 of the subject is (Vc (ω 2) -Va (ω 2))/I_ω2＝(Vc(ω2)-Vb(ω2))/I_ω2。

For the same reason as described above, the voltage difference between the voltage Vc (ω 2) and the voltage Va (ω 2), or the voltage difference between the voltage Vc (ω 2) and the voltage Vb (ω 2) can be regarded as the voltage difference between both ends of the contact impedance Z3 between the measurement electrode 1c and the skin 101 of the subject, and the voltage difference and the current I are calculated by the above-described formula_ω2The contact impedance Z3 can be obtained from the ratio of the two.

The contact impedance Z2 between the measuring electrode 1b and the skin 101 of the person to be measured and the contact impedance Z4 between the measuring electrode 1d and the skin 101 of the person to be measured can be obtained in the same manner as the measurement of the contact impedance between the measuring electrodes 1a and 1c and the skin 101 of the person to be measured, and are not described here.

The controller 4 may include a plurality of filters 44 (as shown in fig. 2), and the filters 44 are used for filtering to obtain voltages with different frequencies. For example, the plurality of filters may be a plurality of band pass filters, and each band pass filter has a frequency range corresponding to a current frequency including only one ac excitation source 2, so that voltages of other frequencies can be filtered by the band pass filter to a voltage having the same frequency as the current frequency of the corresponding ac excitation source 2.

As shown in fig. 2, the controller 4 further includes an analog-to-digital converter 42 and a processing unit 43, the analog-to-digital converter 42 is connected to each of the at least two signal input terminals 41, and is configured to convert the analog voltage received by the signal input terminal 41 into a digital voltage, and the processing unit 43 calculates the contact impedance between the measuring electrode 1 and the skin 101 of the person to be measured according to the digital voltage and the current flowing through the measuring electrode 1. Specifically, the analog-to-digital converter 42 of the controller 4 performs an analog-to-digital conversion function to obtain a voltage in a digital form, and the processing unit 43 performs the functions of calculating the contact impedance of the controller 4.

That is, after the

signal input terminals

41a, 41b, 41c, 41d receive the voltages Va, Vb, Vc, Vd in analog form, the analog-to-digital converter 42 performs analog-to-digital conversion to obtain the voltages Va, Vb, Vc, Vd in digital form, and then the processing unit 43 obtains the contact impedance between each measuring electrode 1 and the skin 101 of the person to be measured through the above calculation method.

The analog-to-digital converter 42 may be one, and includes a plurality of inputs and a plurality of outputs corresponding to the plurality of inputs, each of the inputs is connected to the corresponding signal input terminal 41, and each of the outputs is connected to a corresponding pin of the processing unit 43. The pins of the processing unit 43 correspond to the signal input terminals 41 one by one through the input and output of the analog-to-digital converter 42, so that when the pins of the processing unit 43 receive the voltage, it can know which signal input terminal the voltage is collected, and thus the current provided by the ac excitation source 2, that is, the current flowing through the corresponding measuring electrode 1, can be obtained according to the correspondence between the current provided by the ac excitation source 2 and the signal input terminal 41.

In other embodiments, the analog-to-digital converter 42 may be a component independent from the controller 4, for example, the analog-to-digital converter 42 may be connected between each of the measuring electrodes 1, the driving electrodes 3 and the signal input 41 of the controller 4, and the signal input 41 of the controller 4 receives the voltage in digital form obtained by analog-to-digital conversion by the analog-to-digital converter 42.

When the analog-to-digital converter 42 is a component independent from the controller 4, similarly, the analog-to-digital converter 42 may be one, and include a plurality of inputs and a plurality of outputs corresponding to the plurality of inputs one to one, each input is connected to one measuring electrode 1 or driving electrode 3, and each output is connected to the signal input 41 of the controller 4. The signal input 41 can thus be in one-to-one correspondence with the measuring electrodes 1 and the ac excitation sources 2 connected thereto, or with the drive electrodes 3, via the input and output of the analog-to-digital converter 42. Thus, there is still a one-to-one correspondence between the signal input terminal 41 and the ac excitation source 2, and the aforementioned correspondence between the current supplied by the ac excitation source 2 and the signal input terminal 41 is formed.

Obviously, in other embodiments, there may be more than one analog-to-digital converter 42, and each signal input 41 may be connected to one analog-to-digital converter 42 for performing analog-to-digital conversion independently, regardless of whether the analog-to-digital converter 42 is integrated in the controller 4.

Fig. 2 is a block diagram of the controller 4 according to an embodiment. Wherein, when the controller 4 comprises a plurality of filters 44, the plurality of filters 44 may be located between the analog-to-digital converter 42 and the processing unit 43.

The number of the analog-to-digital converters 42 is one, and the analog-to-digital converters 42 include a plurality of inputs 421 and outputs 422 corresponding to the plurality of inputs 421, the analog-to-digital converters 42 are configured to perform analog-to-digital conversion on the voltage at the corresponding one of the measurement electrodes 1 received by each input to obtain a digital voltage, and then send the digital voltage to the processing unit 43 for calculation, and the plurality of filters may be included between each output 422 of the analog-to-digital converter 42 and the processing unit 43, so as to extract voltages with a plurality of frequencies.

In some embodiments, a plurality of filters 44 are connected in parallel between an output 422 of the analog-to-digital converter 42 and the processing unit 43, and each filter 44 is further connected in series with a switch 45, the plurality of parallel filters 44 and the switch 45 connected in series with the filters 44 form a filter bank 440, and the filter bank 440 is disposed between each output 422 of the analog-to-digital converter 42 and the processing unit 43. The processing unit 43 is connected to the switch 45 of each filter bank 440, and by controlling the corresponding switch 45 to be turned on, the corresponding filter 44 is enabled for filtering, so as to extract the voltage of the corresponding frequency.

For example, when the voltage received at the signal input terminal 41a needs to be filtered to obtain the voltage with the frequency of ω 1, the switch 45 connected to the filter 44 for filtering the voltage except for the frequency of ω 1 in the plurality of filters 44 in the filter bank 440 coupled to the signal input terminal 41a may be controlled to be turned on, and the switch 45 connected to the other filter 44 coupled to the signal input terminal 41a may be controlled to be turned off, so that the voltage received at the signal input terminal 41a is filtered by the filter 44 for filtering the voltage except for the frequency of ω 1, and the voltages of other frequencies are filtered, leaving only the voltage with the frequency of ω 1, and thus the voltage V (ω 1) with the frequency of ω 1 is extracted.

Wherein the filter bank 440 coupled to the signal input 41a refers to: the output 422 of the analog-to-digital converter 42 to which the filter bank 440 is connected corresponds to the input to which the signal input 41a is connected. It should be understood that the hardware implemented filter bank 440 is shown in the figure, and in other embodiments, the hardware implemented filter bank may be omitted and the filtering function implemented in software, i.e., in other embodiments, a software filter may be integrated in the controller 4 to implement the filtering function.

The switch 45 may be a MOSFET, a BJT, an IGBT, or other switching transistor.

As shown in fig. 1, the system 100 further includes at least two signal buffers 7, each signal buffer 7 is connected between a signal input 41 of the controller 4 and the corresponding ac excitation source 2/measuring electrode 1. The signal buffer 7 is used for buffering the voltage at the measuring electrode 1, and as mentioned above, the signal input terminal 41 of the controller 4 obtains the voltage at the measuring electrode 1 by means of electric coupling.

In some embodiments, a signal buffer 7 is also connected between the driving electrode 3 and the corresponding signal input 41 of the controller 4, and the signal buffer 7 connected between the driving electrode 3 and the corresponding signal input 41 is used for isolating the voltage at the driving electrode 3. The signal input 41 of the controller 4 obtains the voltage at the driving electrode 3 by means of electrical coupling.

Wherein, when the analog-to-digital converter 42 is a component independent from the controller 4, each signal buffer 7 can be located between each measuring electrode 1 or driving electrode 3 and the analog-to-digital converter 42.

In some embodiments, the controller 4 is further configured to control to output an alarm signal to alarm when the calculated contact impedance between any one of the measuring electrodes 1 and the skin 101 of the person to be measured exceeds a preset threshold.

Namely, the controller 4 further compares the calculated contact impedance between any one of the measuring electrodes 1 and the skin 101 of the person to be measured with the preset threshold, and controls to output an alarm signal to give an alarm when the contact impedance exceeds the preset threshold.

Wherein the preset threshold is a threshold at which the quality of the physiological signal exceeds an allowable value when the contact impedance exceeds the value.

In some embodiments, the alarm signal includes at least one of a text, a pattern, and a video, the controller 4 is further connected to a display 200, and the controller 4 controls the display 200 to display the alarm signal when the calculated contact impedance between any one of the measuring electrodes and the skin 101 of the person to be measured exceeds a preset threshold.

Wherein the alarm signal may specifically indicate which of the abnormal measuring electrodes is. For example, the alarm signal may be a text message containing "XX measuring electrodes are abnormal in contact impedance, please check" or a pattern including a plurality of measuring electrodes 1, and the measuring electrodes with the release resistance exceeding a preset threshold are highlighted, for example, highlighted, marked with a highlight color, such as red, yellow, etc. When the alarm signal is a video, the position of the measuring electrode exceeding the preset threshold value in the plurality of measuring electrodes 1 can be displayed in a video mode, and voice broadcasting is performed at the same time, for example, the voice content is "XX measuring electrode contact impedance is abnormal, please check".

The display 200 may be an independent display, or an electronic device with a display screen, such as a mobile phone, a tablet computer, or a notebook computer. The display 200 and the controller 4 can receive the alarm signal sent by the controller 4 for displaying through a wired or wireless connection.

The display 200 may be a separate component from the system 100, for example, the display 200 may be temporarily accessible to a user. Obviously, the display 200 may also be a component included in the system 100, for example, at least two ac excitation sources 2, driving electrodes 3, controller 4, inverting amplifier 5, and operational circuit 6 of the system 100 may be integrated into a device, and the display 200 may serve as a display screen of the device.

In some embodiments, the system 100 further comprises an alarm circuit 8, the alarm circuit 8 is configured to output an audible and visual alarm signal, and the controller 4 controls the alarm circuit 8 to output the audible and visual alarm signal when the calculated contact impedance between any one of the measuring electrodes and the skin 101 of the person to be measured exceeds a preset threshold.

Wherein, the audible and visual alarm signal at least comprises one of an optical signal and a sound signal, and the alarm circuit 8 can comprise at least one of an LED lamp, a loudspeaker and the like, and can output the audible and visual alarm signal. The audible and visual alarm signal may be at least one of a flashing light signal, a normally bright light signal with a specific color, a continuously emitted droplet sound, and a sound signal having a voice content such as "XX measuring electrode is abnormal in contact impedance, please check".

Therefore, the alarm signal is output, so that a user can be reminded in time, for example, medical staff can check whether the contact of the measuring electrode 1 is intact or not, and the measuring electrode 1 with poor contact can be attached again in time, so that the influence on the measurement of the physiological parameters is avoided.

Obviously, in some embodiments, the controller 4 may also not need to compare the contact impedance with the preset threshold, and may also not need to use the alarm circuit, and the controller 4 may control to directly output the contact impedance, so as to allow the medical staff to determine whether there is an abnormality according to the contact impedance.

In some embodiments, the system 100 may further include a memory 9, and the correspondence between the current provided by each ac excitation source 2 and the signal input 41 of the controller 4, and the like, may be stored in the memory 9. Wherein, the memory 9 can be an SD card, a solid-state memory, and the like.

The controller 4 can be a central processing unit, a singlechip, a digital signal processor and the like. When the controller 4 includes the digital-to-analog converter 42 and the processing unit 43, the controller 4 may be a central processing unit, a single chip, a digital signal processor, etc. integrated with an analog-to-digital conversion circuit; the processing unit 43 is part of the processing circuitry in the controller 4. When the digital-to-analog converter 42 is located outside the processing unit 43, the processing unit 43 may be a central processing unit, a single chip, a digital signal processor, etc.

Please refer to fig. 4-5, which are schematic diagrams illustrating waveforms of measurement signals and indications of contact impedance according to an embodiment of the present application. The controller 4 is connected to the aforementioned display 200, and the controller 4 is further configured to control the display 200 to display a waveform of the physiological signal measured by the measuring electrode and an indication of contact impedance of the measuring electrode, where the indication of contact impedance is used to indicate a magnitude of contact impedance of the corresponding measuring electrode. In the system 100 of the embodiment shown in fig. 1, having 4 measuring electrodes 1a-1b, generally, a physiological signal waveform can be measured by any two or more electrodes. For example, the measurement electrodes 1a and 1b measure a first physiological signal waveform, denoted by S1-2, and the measurement electrodes 1c and 1d measure a second physiological signal waveform, denoted by S3-4. In other embodiments, the measuring electrode 1d may be used as a common terminal, and three physiological signal waveforms (not shown) are measured by the measuring electrodes 1a, 1b and 1c and the measuring electrode 1d as the common terminal.

In the vicinity of each physiological signal waveform, the contact impedance between each measuring electrode and the skin of the human body can be correspondingly and respectively displayed, as shown in fig. 4; the common contact impedance between two or more electrodes used for measuring the physiological waveform signal of the channel and the skin of the human body can also be correspondingly displayed, as shown in fig. 5. Specifically, as shown in FIG. 4, below the physiological signal waveform S1-2 measured by the measurement electrodes 1a and 1b in common, indications J1 and J2 of the contact impedance of the measurement electrodes 1a and 1b, respectively, with the human skin corresponding to the physiological signal waveform S1-2 are displayed. The measurement electrodes 1c and 1d measure a physiological signal waveform S3-4, and the contact impedance indications J3 and J4 of the measurement electrodes 1c and 1d corresponding to the physiological signal and the human skin are correspondingly displayed below the physiological signal waveform. The physiological signal waveform S1-2, the corresponding contact impedance indications J1 and J2, the physiological signal waveform S3-4, and the corresponding contact impedance indications J3 and J4 are arranged in sequence. Wherein the contact impedance indications J1 and J2 are spaced from the physiological signal waveform S1-2 less than the contact impedance indications J1 and J2 are spaced from the physiological signal waveform S3-4. That is, in some embodiments, the contact impedance indications J1 and J2 are spaced less from the corresponding physiological signal waveform S1-2 than other physiological signal waveforms S3-4 measured from other measurement electrodes. Obviously, the controller 4 can control the display 200 to display the waveforms of the physiological signals measured by all the measuring electrodes and the corresponding indications of the contact impedance.

Wherein the contact impedance indications J1 and J2 are displayable below the corresponding physiological signal waveform S1-2.

Wherein the contact impedance indicates J1 and J2 and continues to indicate the magnitude of the contact impedance of the corresponding measurement electrode 1a and 1b for the duration of the physiological signal waveform S1-2. Specifically, the contact impedance indication J1 is used to correspondingly indicate the contact impedance of the measurement electrodes 1a and 1b used to measure the physiological signal waveform S1-2 at various times, thereby further indicating the signal quality of the physiological signal waveform S1-2 at the corresponding time.

When the contact impedance is too large, it indicates that the measuring electrode 1a and/or 1b has poor contact or falls off, so the signal quality at this time is not good, that is, the collected physiological signal may have too much noise interference, and the reliability is not high. And when the contact impedance is smaller, the contact of the measuring electrodes 1a and/or 1b is good, so that the signal quality is better, namely, the acquired physiological signals are not doped with other interference signals due to poor contact, and the reliability is high. Therefore, the contact impedance at each time is indicated by the contact impedance indications J1 and J2, which can reflect the signal quality of the physiological signal waveform S1-2 at the corresponding time.

The impedance display of the measuring electrodes 1c and 1d is the same as that of the measuring electrodes 1a and 1b, and will not be described herein again.

Because at least two measuring electrodes measure a physiological signal, the quality of the physiological signal is determined by the two measuring electrodes. Therefore, in other embodiments, it is not necessary to display the respective contact impedance of each measuring electrode and the human skin separately, but rather, the "combined impedance" of the two measuring electrodes and the human skin, that is, the common contact impedance value of the equivalent rear measuring electrodes 1a and 1b and the human skin, can be displayed. For example, in the illustrated embodiment of FIG. 5, the common contact impedance value J1-2 of the measurement electrodes 1a and 1b measuring the physiological signal with the skin is displayed below the physiological signal waveform S1-2; the common contact impedance value J3-4 of the measuring electrodes 1c and 1d measuring the physiological signal is displayed below the physiological signal waveform S3-4.

Wherein the physiological signal measured by the measuring electrode comprises at least one of an Electrocardiogram (ECG) signal, an electroencephalogram (EEG) signal and an Electromyogram (EMG) signal.

That is, the measuring electrode may be an electrode pad for being attached to the skin of the chest of a human body to obtain an electrocardiographic signal through measurement, or an electrode pad for being attached to the head to obtain an electroencephalogram signal through measurement, or an electrode pad for being attached to the skin of a muscle part to be detected to obtain an electromyographic signal through measurement.

In some embodiments, the contact impedance indication includes at least one of a color and a pattern, and the contact impedance indication is different according to a difference of an impedance section in which a magnitude of the contact impedance is located.

That is, in some embodiments, the contact impedance indication may be a color indication, indicating different magnitudes of contact impedance by different colors, or the contact impedance indication may be a pattern, indicating different magnitudes of contact impedance by different patterns, wherein the different patterns may include patterns of different content, patterns of different shapes, and so forth. In some embodiments, the contact impedance indication may be a combination of patterns and colors, with different sizes of contact impedance being indicated by the differences in patterns and colors.

In some embodiments, the impedance intervals include a first impedance interval, a second impedance interval, and a third impedance interval. The first impedance interval, the second impedance interval and the third impedance interval can be set according to the corresponding contact impedance range when the measuring electrode is in good contact, poor contact and completely falls off respectively, the first impedance interval is smaller than the second impedance interval, and the second impedance interval is smaller than the third impedance interval.

That is, the first impedance interval is a range in which the contact impedance of the measurement electrode is located when the measurement electrode is in good contact, the second impedance interval is a range in which the contact impedance of the measurement electrode is located when the measurement electrode is in contact but the contact is not good, and the third impedance interval is a range in which the contact impedance of the measurement electrode is located when the measurement electrode is completely detached.

The controller 4 may calculate the contact impedance between the one or more measurement electrodes and the skin 101 of the person to be measured at each time, determine a corresponding contact impedance indication according to an impedance interval in which the calculated contact impedance is located at each time, and then control the display 200 to display the physiological signal waveform measured by the measurement electrodes and the determined corresponding contact impedance indication.

For example, as shown in FIG. 4, the contact impedance indication J1 may be a color indication in the present application. The controller 4 controls the contact impedance indication J1 to present a first color Y1 when determining that the contact impedance of the measuring electrode 1a at a certain moment or within a certain period of time is in a first impedance interval, the controller 4 controls the contact impedance indication J1 to present a second color Y2 when determining that the contact impedance of the measuring electrode 1a at a certain moment or within a certain period of time is in a second impedance interval, and controls the contact impedance indication J1 to present a third color Y3 when determining that the contact impedance of the measuring electrode 1a at a certain moment or within a certain period of time is in a third impedance interval.

Wherein the first color Y1 may be green, the second color Y2 may be yellow, and the third color Y3 may be red. Obviously, in other embodiments, the first color Y1, the second color Y2, and the third color Y3 may be other colors.

Obviously, in other embodiments, the contact impedance indication J1 may be a pattern indication, for example, a pattern indication that may be of a different shape. Specifically, the controller 4 controls the contact impedance indication J1 to assume a straight line shape when determining that the contact impedance of the measuring electrode 1a at a certain time or within a certain period of time is in a first impedance interval, the controller 4 controls the contact impedance indication J1 to assume a wave shape when determining that the contact impedance of the measuring electrode 1a at a certain time or within a certain period of time is in a second impedance interval, and controls the contact impedance indication J1 to assume a sawtooth wave shape when determining that the contact impedance of the measuring electrode 1a at a certain time or within a certain period of time is in a third impedance interval, and so on.

Therefore, in the present application, the controller 4 may control the display 200 to display the physiological signal waveform measured by each measuring electrode, and may also synchronously display the contact impedance indication corresponding to the measuring electrode to correspondingly indicate the magnitude of the contact impedance of each measuring electrode at each time, so as to reflect the signal quality of the corresponding physiological signal waveform at each time. Thus, a reference is provided for the subsequent analysis of the physiological signal, for example, when the contact impedance is large and the signal quality is poor, the waveform of the physiological signal should be discarded and not analyzed. Alternatively, the contact impedance indication can prompt the medical staff to check the contact condition of the corresponding measuring electrode 1, and the measuring electrode with the falling or poor contact is reattached.

Fig. 6 is a schematic structural diagram of a system for measuring contact impedance of an electrode according to another embodiment of the present application. In other embodiments, the system 100 may also include at least one measurement electrode 1, at least one AC excitation source 2, a drive electrode 3, and a controller 4. The at least one measuring electrode 1 is used for connecting to the skin 101 of a person to be measured for physiological parameter measurement, wherein the at least one measuring electrode 1 forms at least one measuring electrode group 10. Each ac excitation source 2 includes an ac output 21, and the at least one ac excitation source 2 is correspondingly connected to the at least one measuring electrode 1, that is, the current output 21 of the at least one ac excitation source is connected to each measuring electrode in the at least one measuring electrode group 10, wherein the operating frequencies of the ac excitation sources 2 connected to the measuring electrodes 1 of different measuring electrode groups 10 are different from each other. The driving electrode 3 is used for connecting to the skin 101 of the person to be measured and providing a common-mode potential for the plurality of measuring electrodes 1. The controller 4 is coupled to the current output end 21 of each ac excitation source 2 and each measurement electrode 1, and is configured to obtain the voltage and the current at each measurement electrode 1, and calculate the contact impedance between each measurement electrode 1 and the skin 101 of the person to be measured according to the voltage and the current at each measurement electrode 1.

That is, in other embodiments, the system 100 may include only one measurement electrode set 10, and when the measurement of the physiological signal is performed by one measurement electrode set 1, the contact impedance of each measurement electrode 1 is also measured.

The number of the at least one measuring electrode 1 can be odd or even, and every two measuring electrodes 1 form a pair to form a measuring electrode group 10.

When the number of the at least one measuring electrode 1 is even, every two measuring electrodes 1 form a pair to form a measuring electrode group 10, so that the at least one measuring electrode 1 can be paired in pairs to form a plurality of measuring electrode groups, and the same measuring electrode group 10 can independently form a current loop for measuring contact impedance.

Wherein, as shown in fig. 6, the number of the at least one measuring electrode 1 may be an odd number. When the number of the at least one measuring electrode 1 is odd, every two measuring electrodes 1 form a pair to form a measuring electrode group 10, and the same measuring electrode group 10 can separately form a current loop L1, and the remaining independent measuring electrode 1 separately forms a measuring electrode group 10 and forms a loop L2 with the driving electrode 3. For a measuring electrode group 10 including two measuring electrodes 1, a current flows in from one measuring electrode 1 of the measuring electrode group 10 and flows out from the other measuring electrode 1 of the measuring electrode group 10 after passing through the skin 101 of the subject, while for the remaining individual measuring electrodes 1, a current flows in from the individual measuring electrode 1 and flows out from the drive electrode 3 after passing through the skin 101 of the subject.

That is, in another embodiment, when the number of the at least one measuring electrode 1 is odd, after every two measuring electrodes 1 form a pair to form one measuring electrode group 10, one more measuring electrode 1 will be added, and the added measuring electrode 1 and the driving electrode 3 can form a current loop L2, so as to realize the measurement of the contact impedance at the measuring electrode 1. Therefore, when the number of the at least one measuring electrode 1 is odd, the driving electrode 3 is used for forming a current loop with the more measuring electrode 1 besides providing the common-mode potential, so as to realize the measurement of the contact impedance at the measuring electrode 1.

When the number of the at least one measuring electrode 1 is one, the one measuring electrode 1 and the driving electrode 3 may form a current loop L2, so as to realize the measurement of the contact impedance at the measuring electrode 1. Therefore, even with only one measuring electrode 1, measurement of the contact impedance at that measuring electrode 1 can be achieved.

Thus, regardless of whether the number of the measuring electrodes 1 is an odd number or an even number, accurate measurement of the contact impedance between each measuring electrode 1 and the skin 101 of the subject can be achieved.

In some embodiments, when one measuring electrode 1 in one measuring electrode group 10 is in poor contact with the skin 101 of the person to be measured, another measuring electrode 1 in the measuring electrode group 10 and the driving electrode 3 form a loop, and current flows in from the another measuring electrode 1 and flows out from the driving electrode 3 after passing through the skin 101 of the person to be measured.

That is, in some embodiments, when two measuring electrodes 1 form one measuring electrode group 10, and one measuring electrode 1 has an abnormality such as poor contact, which may result in that it may not be able to form a current loop with the other measuring electrode 1 in the measuring electrode group 10, the other measuring electrode 1 having a good contact and the driving electrode 3 may form a loop, and a current flows in from the other measuring electrode 1, passes through the skin 101 of the subject, and then flows out from the driving electrode 3. At this time, the measurement of the contact impedance between the measurement electrode 1 and the skin 101 of the subject can still be achieved.

In some embodiments, when there is a measurement electrode 1 with abnormality in the plurality of measurement electrode groups 10 and cannot form a current loop with another measurement electrode 1 in the same measurement electrode group 10, another measurement electrode 1 in each of the plurality of measurement electrode groups 10 can form a loop with the driving electrode 3, and it is still possible to ensure the measurement of the contact impedance between the skin 101 of the subject with the measurement electrode 1 without abnormality.

As described above, since the operating frequencies of the ac excitation sources 2 connected to the measuring electrodes 1 of different measuring electrode groups 10 are different from each other, even if the other measuring electrode 1 of the plurality of measuring electrode groups 10 forms a loop with the driving electrode 3, and a current flows from each other measuring electrode 1 into the skin 101 of the subject and then flows from the driving electrode 3, the frequencies of the currents flowing through each measuring electrode 1 and the driving electrode 3 are different from each other, and thus the measurement electrodes can be distinguished from each other without mutual interference.

As shown in fig. 6, the driving electrode 3 is also coupled to a signal input 41 of the controller 4. As shown in fig. 6, assuming that the contact position of the driving electrode 3 and the skin 101 of the person to be measured is e, and the signal input terminal 41 coupled to the driving electrode 3 by the controller 4 is a signal input terminal 41e, wherein the current provided by each ac excitation source 2 also flows to the driving electrode 3 by a small amount, and passes through the contact impedance Z5 between the driving electrode 3 and the skin 101 of the person to be measured, so as to form a voltage Ve, which is received by the signal input terminal 41e coupled to the driving electrode 3.

The second target voltage may be a voltage filtered from the voltage at the signal input 41 connected to the driving electrode 3 and having the same frequency as the current supplied by the ac excitation source 2 connected to the certain measuring electrode 1.

Specifically, in the process of measuring the contact impedance of a certain measuring electrode 1 connected to a certain signal input terminal 41, the controller 4 may further obtain a second target voltage having the same frequency as the frequency of the current supplied by the ac excitation source 2 connected to the certain measuring electrode 1, which is obtained by filtering the voltage of the signal input terminal 41 connected to another measuring electrode 1 or the drive electrode 3 that is not in the same measuring electrode group 10 as the certain measuring electrode 1.

For example, for the measurement of the contact impedance of the measuring electrode 1a and the skin 101 of the person to be measured, the controller 4 may further obtain, as the second target voltage, the voltage Ve (ω 1) filtered in the signal input terminal 412 connected to the driving electrode 3 and having the same frequency as the current supplied by the ac excitation source 2 connected to the measuring electrode 1 a.

Therefore, the contact impedance Z1 of the measuring electrode 1a and the skin 101 of the person to be measured can be further determined according to the voltages Va (ω 1), Ve (ω 1) and the current I_ω1And (6) calculating.

That is, the contact impedance Z1 between the measurement electrode 1a and the skin 101 of the subject is (Va (ω 1) -Vc (ω 1))/I_ω1＝(Va(ω1)-Vd(ω1))/I_ω1＝(Va(ω1)-Ve(ω1))/I_ω1。

For the measurement of the contact impedance of the measuring electrode 1c and the skin 101 of the person to be measured, the controller 4 may further obtain, as the second target voltage, the voltage Ve (ω 2) filtered in the signal input terminal 412 connected to the driving electrode 3 and having the same frequency as the current supplied by the ac excitation source 2 connected to the measuring electrode 1 a.

Therefore, the contact impedance Z3 between the measuring electrode 1c and the skin 101 of the person to be measured can also be measured according to the voltages Vc (ω 2), Ve (ω 2) and the current I_ω2And (6) calculating.

That is, the contact impedance Z3 between the measuring electrode 1c and the skin 101 of the person to be measured may be equal to (Vc (ω 2) -Ve (ω 2))/I_ω2。

Accordingly, the drive electrode 3 may be an auxiliary electrode for measuring the contact impedance between each measurement electrode 1 and the skin 101 of the subject, and the measurement of the contact impedance between each measurement electrode 1 and the skin 101 of the subject may be realized.

The system 100 shown in fig. 6 is different from the system 100 shown in fig. 1 mainly in that the driving electrode 3 can also be used as an auxiliary electrode for measuring the contact impedance between each measuring electrode 1 and the skin 101 of the person to be measured, so that the contact impedance can be measured when the measuring electrodes 1 are in poor contact or fall off in only one measuring electrode group 10 or in one measuring electrode group 10.

For example, as shown in fig. 2, the controller 4 may include a plurality of filters 44, and the filters 44 are configured to respectively filter voltages with different frequencies. For example, the plurality of filters may be a plurality of band pass filters, and each band pass filter has a frequency range corresponding to a current frequency including only one ac excitation source 2, so that voltages of other frequencies can be filtered by the band pass filter to a voltage having the same frequency as the current frequency of the corresponding ac excitation source 2. For another example, the controller 4 further includes an analog-to-digital converter 42 and a processing unit 43, the analog-to-digital converter 42 is connected to the at least one signal input terminal 41, and is configured to convert the voltage in the analog form received by the signal input terminal 41 into a voltage in the digital form, and the processing unit 43 calculates the contact impedance between the measuring electrode 1 and the skin 101 of the person to be measured according to the voltage in the digital form and the current flowing through the measuring electrode 1.

For a more detailed description, reference is made to the foregoing description, which is not repeated herein.

Referring to fig. 3, a schematic block diagram of a monitoring device 300 is shown, in some embodiments, the aforementioned system 100 can be disposed in the monitoring device 300, so that the monitoring device 300 can simultaneously measure physiological signals of a human body and monitor contact impedances of various measuring electrodes and skin of the human body to be measured, thereby providing an effective reference for quality of the physiological signals.

In other embodiments, the various components of the system 100 may be located partially within the monitoring device 300 and partially outside of the monitoring device 300. For example, the controller 4, etc. may be located in the monitoring device 300, and the measuring electrode 1, the alternating current excitation source 2, etc. may be located outside the monitoring device 300.

The monitoring device 300 can be a bedside monitor, a wearable monitor, a handheld monitor, or the like.

The monitoring device 300 further comprises a monitoring component 301, wherein the monitoring component 301 is connected to the plurality of measuring electrodes 1 and is configured to acquire physiological signals through the measuring electrodes 1 for monitoring physiological signs. When the monitoring component 301 obtains the physiological signal through the measuring electrode 1 to monitor the physiological signs, the system 100 can simultaneously perform the signed measurement of the contact impedance between the measuring electrode 1 and the skin 101 of the person to be measured, so as to provide a reference for the quality of the physiological signal.

Referring to fig. 7, a flowchart of an impedance measurement method according to an embodiment of the present application is shown, where the method is applicable to the system 100, and the method includes:

at least two measuring electrodes are respectively connected to the skin of the person to be measured, wherein the measuring electrodes form at least two measuring electrode groups (S601).

The at least two measuring electrodes are respectively supplied with current by at least two alternating current excitation sources, wherein current output ends of the at least two alternating current excitation sources are respectively connected to each measuring electrode in the measuring electrode groups, and the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other (S603).

The voltage and current at each measurement electrode are acquired, and the contact impedance between each measurement electrode and the skin of the person to be measured is calculated from the voltage and current at each measurement electrode (S605).

In some embodiments, the number of the at least two ac excitation sources is equal to the number of the at least two measurement electrodes, and the current output terminals of the at least two ac excitation sources are connected to the at least two measurement electrodes in a one-to-one correspondence. In some embodiments, the obtaining the voltage and the current at each measuring electrode and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode may include: in the process of measuring the contact impedance of a certain measuring electrode, acquiring a first target voltage with corresponding frequency in a certain measuring electrode group and acquiring a second target voltage with the same frequency of other measuring electrodes which are not in the same measuring electrode group with the certain measuring electrode, and then obtaining the contact impedance of the corresponding measuring electrode according to the first target voltage, the second target voltage and the current with corresponding frequency.

In some embodiments, each measuring electrode is connected to a signal input terminal of the controller and coupled to a current output terminal of a corresponding ac excitation source, the signal input terminal of the controller is electrically coupled to the measuring electrode, the voltage collected/received by the signal input terminal is equal to the voltage of the measuring electrode, and the current provided by the ac excitation source to the corresponding measuring electrode is the current flowing through the corresponding measuring electrode, i.e. the current at the measuring electrode; the obtaining the voltage and current at each measurement electrode may comprise:

and acquiring the voltage at the corresponding measuring electrode by acquiring the voltage from the signal input end of the controller, and acquiring the current provided by the alternating current excitation source connected with the corresponding measuring electrode to acquire the current at the measuring electrode.

Further, the obtaining the current provided by the ac excitation source connected to the corresponding measuring electrode to obtain the current at the measuring electrode may include: and determining the current provided by the alternating current excitation source connected with each signal input end according to the corresponding relation between the current provided by each alternating current excitation source and the signal input end of the controller.

In some embodiments, the method may further comprise: in the process of measuring the contact impedance of a certain measuring electrode connected with a certain signal input end, the controller filters the voltage collected by the signal input end according to the working frequency of an alternating current excitation source connected with the signal input end, and extracts a first target voltage with the working frequency of the alternating current excitation source connected with the signal input end; and the controller also acquires a second target voltage which is obtained by filtering the voltages of the signal input ends connected with other measuring electrodes or driving electrodes which are not in the same measuring electrode group with the certain measuring electrode and has the same frequency as the current provided by the alternating current excitation source connected with the certain measuring electrode.

The obtaining of the contact impedance of the corresponding measuring electrode according to the first target voltage, the second target voltage and the current of the corresponding frequency may specifically include: and calculating the contact impedance between the corresponding measuring electrode and the skin of the person to be measured according to the extracted first target voltage, the extracted second target voltage and the current flowing through the corresponding measuring electrode.

Specifically, the calculating the contact impedance between the corresponding measuring electrode and the skin of the person to be measured according to the extracted first target voltage, the extracted second target voltage, and the current flowing through the corresponding measuring electrode may further include: firstly, calculating to obtain the voltage difference between the first target voltage and the second target voltage, and then calculating the ratio of the voltage difference to the current flowing through the corresponding measuring electrode to obtain the contact impedance between the corresponding measuring electrode and the skin of the person to be measured.

In some embodiments, the method may further comprise: and controlling a display to display the physiological signal waveform measured by the measuring electrodes and the contact impedance indication of each measuring electrode, wherein the contact impedance indication is used for indicating the contact impedance of the corresponding measuring electrode in real time.

Wherein the contact impedance indication comprises at least one of color and pattern, and the contact impedance indication is different according to different impedance intervals in which the contact impedance is located.

Wherein each physiological signal waveform is displayed adjacent to a corresponding contact impedance indication. Wherein the contact impedance indication is displayable below a corresponding physiological signal waveform. The display of the contact impedance indication is described in detail above and will not be described in detail here.

Referring to fig. 8, a flowchart of an impedance measurement method according to an embodiment of the present application is shown, where the method is applicable to the system 100, and the method includes:

at least two measuring electrodes are respectively connected to the skin of a person to be measured, wherein the plurality of measuring electrodes form at least two measuring electrode groups (S701).

And respectively providing currents for the at least two measuring electrodes through at least two alternating current excitation sources, wherein the current output ends of the at least two alternating current excitation sources are respectively connected to each measuring electrode in the measuring electrode groups, and the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other (S703).

The voltage and current at each measurement electrode are acquired, and the contact impedance between each measurement electrode and the skin of the person to be measured is calculated from the voltage and current at each measurement electrode (S705).

And when the calculated contact impedance between any one measuring electrode and the skin of the person to be measured exceeds a preset threshold value, controlling to output an alarm signal to alarm (S707).

Wherein, the alarm signal may include at least one of text, pattern, and video, and the step S705 may include: and when the calculated contact impedance between any one measuring electrode and the skin of the person to be measured exceeds a preset threshold value, controlling a display to display the alarm signal.

In another embodiment, the alarm signal may be an audible and visual alarm signal, and at least one of an optical signal and an audio signal, and the step S705 may include: and when the calculated contact impedance between any measuring electrode and the skin of the person to be measured exceeds a preset threshold value, controlling an alarm circuit to output an audible and visual alarm signal, wherein the alarm circuit can comprise at least one of structures such as an LED lamp and a loudspeaker.

Steps S701 to S705 correspond to steps S601 to 605 in the method shown in fig. 7, and more detailed description can refer to related descriptions of steps S601 to 605 in fig. 7, which are not repeated herein.

In addition, the impedance measurement method in another embodiment of the present application shown in fig. 8 may also include the aforementioned additional method steps or more specific steps. For example, the method may further comprise: and controlling a display to display the physiological signal waveform measured by each measuring electrode and the contact impedance indication of each measuring electrode, wherein the contact impedance indication is used for indicating the magnitude of the contact impedance of the corresponding measuring electrode in real time. Wherein the contact impedance indication comprises at least one of color and pattern, and the contact impedance indication is different according to the difference of the impedance interval in which the contact impedance is positioned.

Referring to fig. 9, a flow chart of an impedance measurement method in another embodiment of the present application is shown, the method can be applied to the system 100, such as the system 100 shown in fig. 3, and the method includes:

at least one measuring electrode is connected to the skin of a person to be measured, respectively, wherein the at least one measuring electrode forms at least one measuring electrode group (S801).

The at least one measuring electrode is supplied with current by at least one alternating current excitation source, wherein a current output end of the at least one alternating current excitation source is connected to each measuring electrode in the measuring electrode groups, and the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other (S803).

In some embodiments, the number of the at least one AC excitation sources is equal to the number of the at least one measurement electrode, and the current output end of the at least one alternating current excitation source is correspondingly connected with the at least one measuring electrode one by one, when the number of the at least one measuring electrode 1 is more than or equal to two, every two measuring electrodes 1 form a pair to form a measuring electrode group, the current generated by the two alternating current excitation sources connected with the two measuring electrodes 1 in the measuring electrode group has the same magnitude and frequency and opposite phases, thus, when the current is respectively provided for the at least one measuring electrode by at least one AC excitation source, for the same measuring electrode group, current flows in from one measuring electrode in the measuring electrode group, and flows out from the other measuring electrode in the measuring electrode group after passing through the skin of the person to be measured.

When the number of the at least one measuring electrode is odd, the remaining independent measuring electrode forms a measuring electrode group separately and forms a loop with the driving electrode, except that every two measuring electrodes 1 form a pair to form a measuring electrode group, for the same measuring electrode group, the current flows in from one measuring electrode in the measuring electrode group and flows out from the other measuring electrode in the measuring electrode group after passing through the skin of the person to be measured, and for the remaining independent measuring electrode, the current flows in from the independent measuring electrode and flows out from the driving electrode 3 after passing through the skin of the person to be measured.

The voltage and current at each measurement electrode are acquired, and the contact impedance between each measurement electrode and the skin of the person to be measured is calculated from the voltage and current at each measurement electrode (S805).

Therefore, in other embodiments, the number of the measurement electrode groups may be at least one, and the driving electrode may also be used as an auxiliary electrode for measuring the contact impedance between each measurement electrode and the skin of the subject, so as to measure the contact impedance between each measurement electrode and the skin of the subject, and thus, when there is only one measurement electrode group or there is a measurement electrode in a certain measurement electrode group that has a poor contact or falls off, the measurement of the contact impedance may still be achieved.

The steps S801 to S805 correspond to the steps S601 to S605 in fig. 7, and more specific descriptions can refer to more specific descriptions of the steps S601 to S605 in fig. 7.

The impedance measuring methods shown in fig. 7, 8 and 9 of the present application correspond to the functions of the system 100, and the related descriptions may be referred to each other.

In some embodiments, the present application also provides a computer-readable storage medium. The computer readable storage medium may be the aforementioned memory 4, and a plurality of program instructions are stored in the computer readable storage medium for being invoked by the controller 4 to execute.

Wherein, after the program instructions stored in the computer readable storage medium are called and executed by the controller 4, some or all of the steps of the method shown in any one of fig. 7-9 or any combination of the steps thereof may be executed.

Therefore, according to the measurement electrode 1, the alternating current is provided for the measurement electrode 1 through the alternating current excitation source 2, interference to physiological signals is avoided, the contact impedance between each measurement electrode 1 and the skin of a person to be measured can be obtained while the measurement electrode 1 carries out physiological parameter measurement, and an indication is provided for the quality of the physiological signals measured by the measurement electrode 1. In addition, the working frequencies of the alternating current excitation sources 2 connected with the measuring electrodes 1 of different measuring electrode groups 10 are different from each other, so that each measuring electrode group does not influence the measurement of the contact impedance of the measuring electrodes 1 of other measuring electrode groups 10, the accuracy is improved, and the synchronism is realized.

Reference is made herein to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope hereof. For example, the various operational steps, as well as the components used to perform the operational steps, may be implemented in differing ways depending upon the particular application or consideration of any number of cost functions associated with operation of the system (e.g., one or more steps may be deleted, modified or incorporated into other steps).

Additionally, as will be appreciated by one skilled in the art, the principles herein may be reflected in a computer program product on a computer readable storage medium, which is pre-loaded with computer readable program code. Any tangible, non-transitory computer-readable storage medium may be used, including magnetic storage devices (hard disks, floppy disks, etc.), optical storage devices (CD-ROMs, DVDs, Blu Ray disks, etc.), flash memory, and/or the like. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including means for implementing the function specified. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified.

While the principles herein have been illustrated in various embodiments, many modifications of structure, arrangement, proportions, elements, materials, and components particularly adapted to specific environments and operative requirements may be employed without departing from the principles and scope of the present disclosure. The above modifications and other changes or modifications are intended to be included within the scope of this document.

The foregoing detailed description has been described with reference to various embodiments. However, one of ordinary skill in the art would recognize that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, the disclosure is to be considered in an illustrative and not a restrictive sense, and all such modifications are intended to be included within the scope thereof. Also, advantages, other advantages, and solutions to problems have been described above with regard to various embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any element(s) to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, system, article, or apparatus. Furthermore, the term "coupled," and any other variation thereof, as used herein, refers to a physical connection, an electrical connection, a magnetic connection, an optical connection, a communicative connection, a functional connection, and/or any other connection.

Those having ordinary skill in the art will recognize that many changes can be made to the details of the above-described embodiments without departing from the underlying principles of the application. Accordingly, the scope of the present application should be determined only by the following claims.

Claims

1. A system for measuring electrode contact impedance, comprising:

the device comprises at least two measuring electrodes, a measuring unit and a control unit, wherein the at least two measuring electrodes are connected to the skin of a person to be measured to measure physiological parameters, and form at least two measuring electrode groups;

the current output ends of the at least two alternating current excitation sources are respectively and correspondingly connected with the at least two measuring electrodes, wherein the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other;

the driving electrode is used for being connected to the skin of a person to be measured and providing a common-mode potential for the at least two measuring electrodes;

and the controller is coupled with each measuring electrode and used for acquiring the voltage and the current at each measuring electrode and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

2. The system of claim 1, wherein after the measuring electrodes in each measuring electrode group receive the current with the corresponding frequency from the current output terminal of the corresponding connected ac excitation source, the current with the corresponding frequency is at least partially shunted to other measuring electrode groups, during the measurement of the contact impedance of a certain measuring electrode, the controller obtains a first target voltage with the corresponding frequency in the certain measuring electrode group and obtains a second target voltage with the same frequency of other measuring electrodes which are not in the same measuring electrode group as the certain measuring electrode, and then obtains the contact impedance of the corresponding measuring electrode according to the first target voltage, the second target voltage and the current with the corresponding frequency.

3. The system of claim 2, wherein the monitoring device further comprises an inverting amplifier, an input of the inverting amplifier is coupled to the at least two measuring electrodes, and an output of the inverting amplifier is connected to the driving electrode for providing a common mode potential to the at least two measuring electrodes by applying the driving electrode to the skin of the subject after inverting the voltages of the at least two measuring electrodes.

4. The system of claim 3, wherein the monitoring device further comprises an operational circuit, the operational circuit is connected between the at least two measuring electrodes and the input end of the inverting amplifier, and is configured to operate the voltages of all the measuring electrodes to obtain an operational voltage, and output the operational voltage to the input end of the inverting amplifier, and the inverting amplifier is configured to provide a common mode potential for the plurality of measuring electrodes by applying the operational voltage to the skin of the subject through the driving electrodes after inverting the operational voltage.

5. The system of claim 1, wherein the at least two ac excitation sources are equal in number to the at least two measurement electrodes, and the current outputs of the at least two ac excitation sources are connected in one-to-one correspondence with the at least two measurement electrodes.

6. The system according to any one of claims 2-5, wherein the controller comprises at least one signal input terminal, each signal input terminal is coupled to a current output terminal of a corresponding AC excitation source and connected to a corresponding measurement electrode, wherein the signal input terminal of the controller is electrically coupled to the measurement electrode, the voltage received at the signal input terminal is equal to the voltage of the measurement electrode, the current of the measurement electrode is the current provided by the AC excitation source connected to the measurement electrode, and the controller obtains the current provided by the AC excitation source connected to the measurement electrode and calculates the contact impedance between the measurement electrode and the skin of the person to be measured according to the obtained current provided by the AC excitation source connected to the measurement electrode and the voltage of the measurement electrode.

7. The system of claim 6, wherein the current provided by each ac excitation source corresponds to a signal input of the controller, and the controller determines the current provided by the ac excitation source connected to each signal input according to the correspondence.

8. The system of claim 6, wherein the monitoring device further comprises a current detection circuit, and the controller detects the current obtained from each measurement electrode through the current detection circuit.

9. A system as claimed in claim 6, characterized in that, during the measurement of the contact impedance of a measuring electrode connected to a signal input, the controller filters the voltage collected by the signal input end according to the working frequency of the alternating current excitation source connected with the signal input end, and a first target voltage having an operating frequency of an ac excitation source connected to the signal input is extracted, the controller also obtains a second target voltage which is obtained by filtering the voltages of the signal input ends connected with other measuring electrodes which are not in the same measuring electrode group with the certain measuring electrode and has the same frequency as the current provided by the alternating current excitation source connected with the certain measuring electrode, the controller calculates contact impedance between the corresponding measuring electrode and the skin of the person to be measured according to the extracted first target voltage, the extracted second target voltage and the current flowing through the corresponding measuring electrode.

10. The system of claim 9, wherein the controller calculates a voltage difference between the first target voltage and the second target voltage, and then calculates a ratio of the voltage difference to the current flowing through the corresponding measuring electrode to obtain the contact impedance between the corresponding measuring electrode and the skin of the subject.

11. The system of claim 6, wherein the monitoring device further comprises at least one signal buffer, each signal buffer being connected between a signal input of the controller and the corresponding AC excitation source.

12. The system according to any one of claims 1-11, wherein the controller is further configured to control an alarm signal to be generated for alarming when the calculated contact impedance between any one of the measurement electrodes and the skin of the subject exceeds a preset threshold.

13. The system of claim 12, wherein the alarm signal comprises at least one of text, pattern, and video, and the controller is further connected to a display, and the controller controls the display to display the alarm signal when the calculated contact impedance between any one of the measuring electrodes and the skin of the subject exceeds a predetermined threshold.

14. The system of claim 12, further comprising an alarm circuit for outputting an audible and visual alarm signal, wherein the controller controls the alarm circuit to output an audible and visual alarm signal when the calculated contact impedance between any one of the measuring electrodes and the skin of the subject exceeds a preset threshold.

15. The system of claim 1, wherein the controller is further connected to a display, and the controller is further configured to control the display to display the waveform of the physiological signal measured by the measuring electrode and an indication of contact impedance of the measuring electrode, the indication of contact impedance being indicative of a magnitude of contact impedance of the corresponding measuring electrode.

16. The system of claim 15, wherein the contact impedance indication includes at least one of a color, a pattern, and a difference in the contact impedance indication based on a difference in an impedance interval in which a magnitude of the contact impedance is located.

17. An impedance measuring method applied to a system for measuring contact impedance of an electrode, the method comprising:

respectively connecting at least two measuring electrodes to the skin of a person to be measured, wherein the at least two measuring electrodes form at least two measuring electrode groups;

providing currents for the at least two measuring electrodes through at least two alternating current excitation sources respectively, wherein current output ends of the at least two alternating current excitation sources are respectively and correspondingly connected with the at least two measuring electrodes, and working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other;

and acquiring the voltage and the current at each measuring electrode, and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

18. The method of claim 17, wherein after the measuring electrodes in each measuring electrode set receive the current of the corresponding frequency from the current output terminal of the corresponding connected ac excitation source, the current of the corresponding frequency will be at least partially shunted to the other measuring electrode sets; the calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode comprises the following steps:

in the process of measuring the contact impedance of a certain measuring electrode, acquiring a first target voltage with corresponding frequency in a certain measuring electrode group and acquiring a second target voltage with the same frequency of other measuring electrodes which are not in the same measuring electrode group with the certain measuring electrode, and then obtaining the contact impedance of the corresponding measuring electrode according to the first target voltage, the second target voltage and the current with corresponding frequency.

19. The method of claim 18, wherein each measuring electrode is connected to a signal input of a controller and coupled to a current output of a corresponding ac excitation source, the signal input of the controller is electrically coupled to the measuring electrode, the voltage collected at the signal input is equal to the voltage of the measuring electrode, and the ac excitation source provides the current flowing through the corresponding measuring electrode as the current at the measuring electrode; the obtaining the voltage and current at each measurement electrode may comprise:

20. The method of claim 19, wherein the method further comprises:

in the process of measuring the contact impedance of a certain measuring electrode connected with a certain signal input end, the controller filters the voltage collected by the signal input end according to the working frequency of an alternating current excitation source connected with the signal input end, and extracts a first target voltage with the working frequency of the alternating current excitation source connected with the signal input end;

acquiring a second target voltage which is obtained by filtering voltages of signal input ends connected with other measuring electrodes or driving electrodes which are not in the same measuring electrode group with the certain measuring electrode and has the same frequency as the current provided by the alternating current excitation source connected with the certain measuring electrode;

the obtaining of the contact impedance of the corresponding measuring electrode according to the first target voltage, the second target voltage and the current of the corresponding frequency includes:

and calculating the contact impedance between the corresponding measuring electrode and the skin of the person to be measured according to the extracted first target voltage, the extracted second target voltage and the current flowing through the corresponding measuring electrode.

21. The method of claim 20, wherein calculating the contact impedance between the corresponding measuring electrode and the skin of the subject based on the extracted first target voltage, second target voltage, and the current flowing through the corresponding measuring electrode comprises:

firstly, calculating to obtain the voltage difference between the first target voltage and the second target voltage, and then calculating the ratio of the voltage difference to the current flowing through the corresponding measuring electrode to obtain the contact impedance between the corresponding measuring electrode and the skin of the person to be measured.

22. The method of any one of claims 17-21, further comprising:

and when the calculated contact impedance between any one measuring electrode and the skin of the person to be measured exceeds a preset threshold value, controlling to output an alarm signal to give an alarm.

23. The method of claim 17, wherein the method further comprises:

and controlling a display to display the physiological signal waveform measured by the measuring electrode and the contact impedance indication of the measuring electrode, wherein the contact impedance indication is used for indicating the magnitude of the contact impedance of the corresponding measuring electrode in real time.

24. The system of claim 23, wherein the contact impedance indication includes at least one of a color, a pattern, and a difference in the contact impedance indication based on a difference in an impedance interval in which a magnitude of the contact impedance is located.

25. A system for measuring electrode contact impedance, comprising:

at least one measuring electrode, which is used for connecting to the skin of a person to be measured to measure physiological parameters, wherein the at least one measuring electrode forms at least one measuring electrode group;

the current output end of the at least one alternating current excitation source is respectively and correspondingly connected with the at least one measuring electrode, wherein the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other;

the driving electrode is connected to the skin of a person to be measured and provides common-mode potential for the plurality of measuring electrodes;

and the controller is coupled with the current output end of each alternating current excitation source and each measuring electrode and is used for acquiring the voltage and the current at each measuring electrode and calculating the contact impedance between each measuring electrode and the skin of the person to be measured according to the voltage and the current at each measuring electrode.

26. An impedance measuring method applied to a system for measuring contact impedance of an electrode, the method comprising:

connecting at least one measuring electrode to the skin of a person to be measured, wherein the at least one measuring electrode forms at least one measuring electrode group;

respectively providing current for the at least one measuring electrode through at least one alternating current excitation source, wherein the current output end of the at least one alternating current excitation source is respectively connected to the at least one measuring electrode, and the working frequencies of the alternating current excitation sources connected with the measuring electrodes of different measuring electrode groups are different from each other;