Error Correction Techniques for Bioimpedance Measurement

Abstract

Determining the bioimpedance of a subject's body or a portion thereof has been used to determine health characteristics of the subject (e.g., heart condition). The systems and methods described herein can provide correction and / or compensation for electrode contact impedance and for accurately determining bioimpedance. The system can take into account impedance sensitivity and / or frequency sensitivity when performing a bioimpedance determination to improve the bioimpedance determination.

Description

[0001] Related Applications

[0002] The present disclosure claims priority to U.S. Provisional Application No. 62 / 790,619, filed on January 10, 2019, entitled “Error Correction Techniques for Bioimpedance Measurements,” the disclosure of which is incorporated by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to the field of impedance measurement and, more particularly, but not exclusively, to systems and methods for compensating for errors due to electrode contact impedance. Background Art

[0004] Impedance measurements of the body, referred to herein as bioimpedance, have many applications in healthcare and consumer applications. Impedance measurements can be made through electrodes provided in a body-worn system or wearable device, such as a watch, chest strap, headband, patch, etc. A circuit coupled to the electrodes can derive the unknown impedance of the body where the electrodes are located. Impedance measurements are particularly useful for vital sign monitoring, detecting tissue and fluid levels in the body to detect signs of congestive heart failure, electrical impedance tomography systems, electrical impedance spectroscopy, etc. Summary of the invention

[0005] The systems and methods described herein can provide a corrected and / or compensated voltage measurement of the bioimpedance of a subject's body. For example, a system for measuring bioimpedance (e.g., a four-wire system described herein) can have error sources when measuring bioimpedance, which can result in inaccurate measurements of bioimpedance. Techniques related to impedance sensitivity and frequency sensitivity disclosed herein can be implemented to correct and / or compensate voltage measurements of bioimpedance, which can improve the determination of bioimpedance values.

[0006] Some embodiments may include a circuit for determining a bio-impedance amount of a portion of a subject's body. The circuit may include a first impedance circuit coupled to a first pin of the circuit, the first pin coupled to a first side of the body portion, wherein the first impedance circuit selectively couples a first impedance to the first pin. The circuit may also include a second impedance circuit coupled to a second pin of the circuit, the second pin coupled to a second side of the body portion, wherein the second impedance circuit selectively couples a second impedance to the second pin. The circuit may also include a voltage measurement circuit coupled to the first pin and the second pin, the voltage measurement circuit used to determine a first voltage difference between the first pin and the second pin when the first impedance is coupled to the first pin and the second impedance is decoupled from the second pin, and to determine a second voltage difference between the first pin and the second pin when the first impedance is decoupled from the first pin and the second impedance is coupled to the second pin, the first voltage difference and the second voltage difference used to compensate to determine the bio-impedance amount.

[0007] Some embodiments may include a system for determining a bioimpedance value of a portion of a subject's body. The system may include a first electrode positioned at a first end of the portion of the body and a second electrode positioned at a second end of the portion of the body. The system may also include a circuit coupled to the first electrode and the second electrode, the circuit determining a voltage difference between the first electrode and the second electrode. The circuit may include a first impedance circuit coupled to the first electrode, the first impedance circuit selectively coupling a first impedance between the first electrode and a ground of the circuit. The circuit may also include a second impedance circuit coupled to the second electrode, the second impedance circuit selectively coupling a second impedance between the second electrode and a ground of the circuit. The circuit may also include a voltage measurement circuit coupled to the first electrode and the second electrode, the voltage measurement circuit being used to determine a voltage difference between the first electrode and the second electrode when the first impedance is selectively coupled between the first electrode and the ground of the circuit and the second impedance is selectively coupled between the second electrode and the ground of the circuit.

[0008] Some embodiments may include a method for determining a bioimpedance value of a portion of a subject's body. The method may include determining, by circuitry, a first voltage difference between a first electrode located on a first side of the body portion and a second electrode located on a second side of the body portion, wherein the circuitry has a first configuration, by the circuitry changing from the first configuration to the second configuration after determining the first voltage difference, and determining, by the circuitry, a second voltage difference between the first electrode and the second electrode, wherein the circuitry has a second configuration, the first voltage difference and the second voltage difference being used to compensate to determine the bioimpedance value. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure may be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with standard industry practice, various features are not necessarily drawn to scale and are only used for illustration purposes. Where scale is explicitly or implicitly shown, it is merely provided as an illustrative example. In other embodiments, the sizes of various features may be arbitrarily increased or decreased for clarity of discussion.

[0010] Figure 1 An example system with electrodes and circuitry for performing four-way impedance measurement of bioimpedance according to some embodiments of the present disclosure is illustrated.

[0011] Figure 2 Illustrated are example input capacitances that may be present in a circuit that may perform four-way impedance measurement of bioimpedance according to some embodiments of the present disclosure.

[0012] Figure 3 An example current leakage present in a circuit performing four-way impedance measurement of bio-impedance according to some embodiments of the present disclosure is illustrated.

[0013] Figure 4 Circuits are illustrated that can perform measurements that are less sensitive to errors caused by impedances on the S+ and S- branches according to some embodiments of the present disclosure.

[0014] Figure 5 is a flow chart illustrating a method for performing measurements that are less sensitive to errors caused by impedances on the S+ and S- branches according to some embodiments of the present disclosure.

[0015] Figure 6 is a flow chart illustrating a method for performing measurements that are less sensitive to errors associated with frequency according to some embodiments of the present disclosure.

[0016] Figure 7 An example measurement arrangement is illustrated in which the techniques described herein may be implemented according to some embodiments of the present disclosure.

[0017] Figure 8 An example system arrangement is illustrated that may implement the techniques described herein in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION

[0018] The following disclosure provides many different embodiments or examples for realizing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not restrictive. In addition, the present disclosure may repeat reference numerals and / or letters in various examples or across different drawings in some cases. This repetition is for the purpose of simplicity and clarity and does not itself specify the specific relationship between the various embodiments and / or configurations discussed. Different embodiments may have different advantages, and any embodiment does not necessarily require a specific advantage.

[0019] Bioimpedance measurements of a subject's body or a portion thereof may be used to determine health characteristics of the subject (e.g., heart condition). However, performing bioimpedance measurements may present sources of error that may result in inaccurate bioimpedance measurements. For four-way or four-wire impedance measurement methods for measuring bioimpedance, the measurement system may have parasitic capacitance that may result in inaccurate measured bioimpedance.

[0020] The systems and programs described herein may take into account impedance sensitivity and / or frequency sensitivity that may be used to correct and / or compensate for bioimpedance measurements. For example, the systems and programs may include performing multiple measurements using signals of different frequencies applied to the bioimpedance and / or different impedances coupled to electrodes of the system for measuring bioimpedance to determine impedance sensitivity and / or frequency sensitivity of the bioimpedance measurements. The systems and programs may correct and / or compensate for the determined impedance sensitivity and / or frequency sensitivity.

[0021] It should be noted that throughout the figures, certain reference numerals may be repeated to indicate that a particular device or block is completely or substantially identical in the figures. However, this is not intended to imply any particular relationship between the various embodiments disclosed. In some examples, the genus of an element may be referred to by a specific reference numeral ("widget 10"), while examples of individual species or genera may be represented by hyphenated numerals ("first specific widget 10-1" and "second specific widget 10-2").

[0022] Four-way or four-wire impedance measurement

[0023] Techniques for impedance measurement of bioimpedance may include a four-terminal sensing scheme, which may also be referred to as a four-way impedance measurement scheme, four-wire sensing, or Kelvin sensing. Bioimpedance may be generated by a subject's body or a portion thereof. In particular, bioimpedance may include an impedance presented by a subject's body or a portion thereof, which impedance may be applied to the flow of current through the body. The technique may involve placing a plurality of electrodes on the subject's body. For example, the technique may involve placing four electrodes on the subject's body, and these electrodes may be used to sense or derive an unknown bioimpedance of a portion of the subject's body corresponding to the placement of the electrodes. In some cases, the bioimpedance of the measurable body portion is approximately 100 ohms.

[0024] Figure 1 An example system 100 having electrodes and circuitry for performing four-way impedance measurement of bioimpedance according to some embodiments of the present disclosure is shown. In the illustrated embodiment, the unknown bioimpedance 102 is shown as Z BODY . Bioimpedance 102 may represent a bioimpedance generated by a subject's body or a portion thereof. As used throughout this disclosure, a relationship of an element to bioimpedance 102 may refer to a relationship of the element to the subject's body. For example, a reference to a voltage applied across bioimpedance 102 may refer to a voltage applied to the body or a portion thereof that generates bioimpedance 102. Additionally, reference to an electrode coupled to a first end of bioimpedance 102 and a second end of bioimpedance 102 may refer to an electrode coupled to a first end of the body or a portion thereof that generates bioimpedance 102 and a second end of the body or a portion thereof.

[0025] System 100 may include multiple electrodes. In the illustrated embodiment, system 100 includes four electrodes: electrode 104, electrode 106, electrode 108, and electrode 110. The electrodes may contact the subject's body. For example, the electrodes may be located on the subject's body, wherein the electrodes may be located at different locations on the subject's body.

[0026] Based on the contact of the electrode with the subject's body, each electrode may present a corresponding impedance. The amount of impedance presented by each electrode may depend on the quality of the contact with the subject's body. Electrode 104 presents a corresponding contact impedance Z E1 , the electrode 106 presents a corresponding contact impedance Z E2 , the electrode 108 presents a corresponding contact impedance Z E3 , and the electrode 110 presents a corresponding contact impedance Z E4 .

[0027] The system may also include a circuit 150 coupled to the electrode. In some embodiments, the circuit 150 may be packaged as an integrated circuit or chip. The circuit 150 may include pins (or connectors) to which the electrodes may be coupled. For example, the circuit 150 may have a pin CE0 electrically coupled to the electrode 104. The circuit 150 may also include a pin AIN2 electrically coupled to the electrode 106. The circuit 150 may also include a pin AIN3 electrically coupled to the electrode 108. The circuit 150 may also include a pin AIN1 electrically coupled to the electrode 110.

[0028] System 100 may include multiple branches, each of which may include an electrode and a pin. For example, system 100 has four branches in the illustrated embodiment: an F+ branch including electrode 104 and pin CE0, an S+ branch including electrode 106 and pin AIN2, an S- branch including electrode 108 and pin AIN3, and an F- branch including electrode 110 and pin AIN1. The F+ branch including electrode 104 may be coupled to a first end of a part of the body of an object generating unknown bioimpedance 102. The S+ branch including electrode 106 may be coupled to a first end of a part of the body of an object generating unknown bioimpedance 102. The S branch including electrode 108 may be coupled to a second end of a part of the body of an object generating unknown bioimpedance 102. The F branch including electrode 110 may be coupled to a second end of a part of the body of an object generating unknown bioimpedance 102. The four branches are connected to corresponding pins of circuit 150. The F+ branch and the F- branch may be referred to as force lines. The S+ branch and the S- branch may be referred to as sensing lines. The portion of each branch shown outside the circuit 150 can represent a cable extending from the circuit 150 and an electrode at an opposite end of the cable from the circuit 150, where the electrode can be mounted in the patch at the other end of the cable. In other embodiments, the portion of each branch shown outside the circuit 150 can represent a conductor or wire having an electrode at the end of the conductor or wire. In some embodiments, the conductor and electrodes can be mounted in a wearable device. Optionally, an isolation circuit can be included between the electrodes and the pins to provide isolation and protection between the subject's body and the circuit 150. The isolation circuit can include and / or generate a capacitor C located between the corresponding electrode and the pin. ISO1 , C ISO2 , C ISO3 , C ISO4 , to provide isolation and protection between the human user's body and the circuit 150. For example, the capacitor C ISO1 , capacitor C ISO2 , capacitor C ISO3 and capacitor C ISO4Can be included between the corresponding electrode pairs and pins to provide isolation and protection (e.g., to block DC signals) between the human user's body and the circuits within circuit 150. In the case where the isolation circuit includes the isolation circuit, the capacitor C ISO1 , C ISO2 , C ISO3 , C ISO4 Can be included in the corresponding branch.

[0029] The circuit 150 may include a signal generator 116 (eg, a sinusoidal signal generator). The signal generator 116 may generate a signal with a peak voltage V PEAK The signal generator 116 can generate a variety of signals. For example, the signal generator 116 can generate signals of different frequencies. To measure bioimpedance, signals with different frequencies from 0 Hz to hundreds / thousands / millions of Hz can be used. Applications such as impedance tomography and impedance spectroscopy often benefit from using signals with a wide frequency range. The signal generator 116 can apply a signal that generates a bioimpedance 102 to the body or a portion thereof, which can cause a current to flow through the bioimpedance 102 and produce a voltage drop across the unknown bioimpedance 102. In some embodiments, the signal generator 116 can force a current to flow through the unknown bioimpedance 102.

[0030] Circuit 150 may include voltage measurement circuit 118 to measure a voltage between a positive input and a negative input of voltage measurement circuit 118. In the example shown, the positive input is coupled to the S+ branch and the negative input is coupled to the S- branch to measure V IN1 and V IN2 The voltage difference between IN1 –V IN2 . For example, the positive input of the voltage measurement circuit 118 can be coupled to pin AIN2 and the negative input of the voltage measurement circuit 118 can be coupled to pin AIN3. In some embodiments, the voltage measurement circuit 118 can include an instrumentation amplifier (inAmp) 120 having a positive terminal and a negative terminal to sense a voltage difference between the positive terminal and the negative terminal, and output a voltage output representing the voltage difference. In some embodiments, the positive terminal of inAmp 120 can be coupled to pin AIN2 and the negative terminal of inAmp 120 can be coupled to pin AIN3. The voltage measurement circuit 118 can include a discrete Fourier transform (DFT) block 122 and a summation block 124 to generate a voltage measurement based on the voltage output from inAmp 120.

[0031] The circuit 150 may also include a current measurement circuit 126 to measure the current at the input of the current measurement circuit 126. In the example shown, the input is coupled to the F-branch to measure the current flowing through the F-branch. In some embodiments, the current measurement circuit 126 may include a transimpedance amplifier (TIA) 128 to convert the current at the input terminal of the TIA 128 to a voltage output representing the current. The current measurement circuit 126 may include a DFT block 130 and a summation block 132 to generate a current measurement based on the voltage output from the TIA 128.

[0032] In order to make an impedance measurement, a voltage drop may be generated across the unknown bioimpedance 102. The voltage drop across the unknown bioimpedance 102 may be considered as V1-V2. The voltage drop across the unknown bioimpedance 102 may be generated or applied by a signal generator 116. For example, the signal generator 116 may apply a signal to the subject's body through the electrode 104, wherein the signal causes a voltage drop across the bioimpedance 102 based on the current flowing through the bioimpedance and the value of the bioimpedance 102. At the same time, the voltage drop across the unknown bioimpedance 102 may be measured by the voltage measurement circuit 118, and the current through the unknown bioimpedance 102 may also be measured by the current measurement circuit 126. The measured voltage drop and the measured current may be used to derive an impedance value of the unknown bioimpedance 102. The circuit 150 may include circuitry and / or one or more processors (not shown) to derive an impedance value of the unknown bioimpedance 102 based on the measured voltage from the voltage measurement circuit 118 and the measured current from the current measurement circuit 126. In other embodiments, the circuit 150 may include a communication circuit to transmit the measured voltage and / or the measured current to a remote device (e.g., a server, computer, or other computing device located away from the circuit 150) in a wired or wireless manner, wherein the remote device may derive an impedance value of the bio-impedance 102 based on the measured voltage and / or the measured current.

[0033] The measurement scheme assumes that inAmp 120 has an infinite input impedance and no current flows through the S+ and S- branches under ideal conditions. In this ideal condition, all current I flowing through the unknown bioimpedance 102 is BODY will flow through the F-branch, that is, I BODY =I ZF- When there is no current flowing through the impedance Z E2 and impedance Z E3 When absorbing, V IN1 = V1, and V IN2 = V2, therefore, the voltage difference measured by the voltage measurement circuit 118 represents the voltage across the unknown bioimpedance 102, i.e., V IN1 -V IN2 =V1-V2.

[0034] In conventional bidirectional impedance measurements, measurement problems may arise from the cable impedance (including the contact impedance of the electrodes) being added to the unknown bio-impedance 102, thereby corrupting the impedance measurement. For simplicity, the impedances present are lumped together as the contact impedance shown in each branch. In theory, a four-way impedance measurement can avoid such problems. Furthermore, the measurement can be sufficiently accurate when the unknown bio-impedance 102 is much higher than the impedance of the cable. However, Figure 1 The setup seen in Figure 1 may have some other limitations or be undesirable in practice. For example, these limitations may be important when making impedance measurements at low frequencies, high frequencies, certain frequencies, or a variety of frequencies. In some cases, the contact impedance Z E1 , contact impedance Z E2 , contact impedance Z E3 and contact impedance Z E4 One or more of the impedances may be greater than the unknown bioimpedance 102. For example, mechanical and / or environmental reasons (e.g., humidity, movement, etc.) may cause poor contact and may significantly increase one or more contact impedances. For example, the contact impedance may be greater than 2 kΩ. In some cases, the optional capacitor C used for isolation ISO1 , optional capacitor C ISO2 , optional capacitor C ISO3 and optional capacitor C ISO4 It can also significantly increase or affect the impedance of the cable. In some cases, the contact impedance Z E1 , contact impedance Z E2 , contact impedance Z E3 and contact impedance Z E4 There may be an imbalance between the two paths (for example, the imbalance may be greater than 1 kΩ). These limitations have been found to reduce the accuracy of the four-way impedance measurement.

[0035] One aspect that may cause these limitations to reduce the accuracy of the bioimpedance measurement is that there may be large input capacitance (eg, approximately 40 picofarads (pF)) at Pins AIN2 and AIN3. Figure 2 204 and 205. The diagram illustrates example input capacitances (e.g., parasitic capacitances in a printed circuit board, printed circuit board trace capacitances, and / or wiring / conductor capacitances) that may be present in a circuit that may perform four-way impedance measurements of bioimpedance according to some embodiments of the present disclosure. A grounded input capacitor C1202 may be present at pin AIN2, and a grounded input capacitor C2204 may also be present at pin AIN3. The grounded input capacitor C1202 and the capacitor C ISO2 A filter can be formed. The grounded input capacitor C2204 and the capacitor C ISO3 It can also form a filter. Ideally, the voltage V1 should be equal to the voltage V IN1 The voltage V2 should be the same as the voltage V IN2Due to the grounded input capacitor C1202 and the grounded input capacitor C2204, at certain frequencies, the voltage V1 may be different from the voltage V IN1 Different, voltage V2 may be different from voltage V IN2 The voltage across voltage V1 and voltage V2 may be different from V IN1 and V IN2 The voltage across the two ends is different. For example, in the case of bioimpedance measurements at 100kHz or higher, the input (parasitic) capacitance of the instrumentation amplifier 120 significantly reduces the input impedance of the instrumentation amplifier 120. At 200kHz, an input (parasitic) capacitance of 10pF is equivalent to a resistance of 80kOhm. The voltage drop across the contact impedance is no longer negligible, and the voltage measurement may be severely affected. The negative effects of the grounded input capacitance C1202 and the grounded input capacitance C2204 can be observed at various frequencies and when the contact impedance is high, such as in the range of hundreds or thousands of ohms. In addition, the grounded input capacitance C1202 and the grounded input capacitance C2204 can be attributed to the imbalance of the contact impedance. The imbalance of the branch contact impedance produces different cutoff frequencies, resulting in different attenuation of each branch.

[0036] Another aspect that can cause these limitations to reduce the accuracy of bioimpedance measurements is current leakage. Figure 3 The diagram illustrates an example current leakage present in a circuit for performing four-way impedance measurement of bioimpedance according to some embodiments of the present disclosure. S- The impedance Z of the F-branch with the electrode 110 driving the TIA 128 may be similar to F- , so current leakage will occur. This causes the current I flowing through the unknown bioimpedance 102 BODY A portion of the current I flows through the S-branch having electrode 108, and not all of the current I BODY will flow through the F-branch with electrode 110. In other words, the current I ZS- Ideally, it is zero, and the current I through the F-branch having electrode 110 ZF- Ideally equal to the current I BODY In fact, the current I ZS- As a result, the current I through the branch having electrode 110 ZF- Not equal to current I BODY , and the current I BODY A portion of the current I is not measured by the current measurement circuit 126. BODY If a portion of the current is not measured by the current measurement circuit 126, the current measurement will be corrupted, and therefore the impedance measurement will also be corrupted. This problem can be exacerbated by high contact impedance and / or impedance imbalance in the branch.

[0037] As mentioned before, in practice, some current will leak / draw through the S+ and S- legs, since the input impedance of the inAmp 120 is finite. Current leakage through the S+ and S- legs will also corrupt the voltage measurement, since the impedance Z E2 Unknown voltage drop and / or impedance Z across the E3 The unknown voltage drop across the terminals means that the voltage difference 118 measured by the voltage measurement circuit no longer accurately represents the voltage across the unknown bioimpedance 102, i.e., V IN1 -V IN2 ≠ V1 - V2. The measurement may be further degraded due to the presence of large contact impedances and / or impedance imbalances in the branches.

[0038] Ways to address the source of the error

[0039] While the four-way impedance measurement scheme can effectively measure bioimpedance, techniques can be applied to correct or compensate for certain error sources to make the four-way impedance measurement scheme less susceptible to error sources. In addition, some reasonable assumptions can be made to allow these techniques to extend the tolerable contact impedance while still being able to measure bioimpedance over a frequency range.

[0040] Specifically, two techniques (which may be used together or separately) are described herein for making impedance measurements (more specifically, voltage measurements performed by instrumentation amplifier 120) less susceptible to possible error sources. One technique may expose the sensitivity of the measurement to the impedance on the S+ and S- branches, and may be used to correct or compensate the measurement based on the impedance sensitivity. Another technique may expose the sensitivity of the measurement to the frequency, and may be used to correct or compensate the measurement based on the frequency sensitivity.

[0041] Both techniques may involve taking multiple measurements under different conditions and performing a linear combination of the measurements to be corrected or compensated and the differences between the measurements to perform error correction or compensation. The resulting measurement combination may advantageously take sensitivity into account and perform appropriate correction or compensation on the measurements.

[0042] Impedance sensitivity based correction

[0043] A first technique for making the impedance less susceptible to error sources may include correction based on impedance sensitivity. As previously described, the impedance Z is 100 Ω due to non-idealities such as input (parasitic) capacitance and / or the finite input impedance of inAmp 120. E2 The unknown voltage drop and impedance Z across the two ends E3The unknown voltage drop across the terminals corrupts the four-way impedance measurement. Considering the case of input (parasitic) capacitance at inAmp 120, the error introduced by the input capacitance can be determined by calculating the voltage difference measured by inAmp 120 from the unknown bioimpedance 102 (e.g., V1-V2) impedance on the S+ and S- branches and the voltage across the input capacitance of inAmp 120. In the presence of input (parasitic) capacitances C1 and C2, the voltage V at the input of inAmp 120 is IN1 and voltage V IN2 It can be defined as follows:

[0044]

[0045]

[0046] Voltage V IN1 is the voltage at the positive input terminal of inAmp 120. The voltage V IN2 is the voltage at the negative input terminal of inAmp 120. Impedance Z1 may include the contact impedance Z of the S+ branch. E2 , or more broadly, the impedance on the S+ branch includes the impedance generated from electrode 106 to the positive input terminal of inAmp 120. Impedance Z2 may include the contact impedance Z of the S- branch. E2 , or more generally the impedance on the S+ branch includes the impedance from electrode 108 to the negative input of inAmp 120. Capacitor C1 (e.g., C1202) represents the input (parasitic) capacitance at the positive input of inAmp 120. Capacitor C2 (e.g., C2204) is the input (parasitic) capacitance at the negative input of inAmp 120. inAmp 120 measures the voltage V IN1 and voltage V IN2 The difference between IN1 -V IN2 ). The measured voltage difference that may be generated by the instrumentation amplifier 120 may be defined as follows:

[0047]

[0048]

[0049] In Equation 3, V1-V2 represents the desired voltage across the unknown bioimpedance 102, represents the error term due to the input (parasitic) capacitance. For example, V1-V2 may represent the voltage drop caused by the bioimpedance 102 of the subject's body. The voltage drop caused by the impedance of the S+ branch, the impedance of the S- branch, the capacitance of the positive input of the inAmp 120, and the capacitance of the negative input of the inAmp 120 may be represented. The technical task is to correct the measurement in a way that minimizes the error term, thereby making the measurement less sensitive to errors caused by the impedance on the S+ and S- branches (including parasitic capacitance at the input of inAmp 120). For example, the measurement of the bioimpedance 102 performed by inAmp 120 may be improved by minimizing and / or compensating for the voltage drop caused by the impedance of the S+ branch, the impedance of the S- branch, the capacitance of the positive input of inAmp 120, and the capacitance of the negative input of inAmp 120.

[0050] The first technique can reveal how sensitive the measurement is to impedance changes on each of the S+ branch and the S- branch, and can correct the measurement based on the impedance sensitivity. The impedance on each of the S+ branch and the S- branch can be resistive and / or capacitive. Therefore, this technique can expose the resistive and / or capacitive sensitivity on the S+ branch and the S- branch, and apply corrections accordingly. When the corrections are applied appropriately, the error terms included in Equation 3 can be reduced.

[0051] Figure 4 Circuits are shown that can perform measurements that are less sensitive to errors caused by impedances (e.g., capacitance and resistance) on the S+ branch and the S- branch in accordance with some embodiments of the present disclosure. To expose impedance sensitivity, circuit 402 on the S+ branch can be implemented to add a predetermined amount of impedance to the S+ branch, and circuit 404 on the S- branch can be implemented to add a predetermined amount of impedance on the S- branch. Circuit 402 can be controlled to add a predetermined amount of impedance (e.g., resistance or capacitance) to the S+ branch, such as at the positive input of inAmp 120. Circuit 404 can be controlled to add a predetermined amount of impedance (e.g., resistance or capacitance) to the S- branch, such as at the negative input of inAmp 120. For example, circuit 402 can be controlled to add a parallel capacitor C P coupled to the S+ branch, and the circuit 404 can be controlled to connect the parallel capacitor C P Coupled to the S-branch. Parallel capacitor C P The capacitance value can be in the tens or hundreds of pF.

[0052] By taking some measurements while appropriately controlling circuit 402 and circuit 404, impedance sensitivity can be exposed by observing the measurements taken under different conditions. Specifically, three measurements can be taken under three different conditions (in any suitable order):

[0053] 1. Circuit 402 and circuit 404 do not add their respective predetermined impedances. This measurement made by instrumentation amplifier 120 is called V D1 .

[0054] 2. Circuit 402 can be controlled to add a predetermined amount of impedance to the S+ branch. This measurement made by instrumentation amplifier 120 is called V D2 As an example, circuit 402 adds a small capacitor C P As the predetermined impedance of the S+ branch.

[0055] 3. Circuit 404 can be controlled to add a predetermined amount of impedance to the S-branch. This measurement made by instrumentation amplifier 120 is called V D3 As an example, circuit 404 adds a small capacitor C P As the predetermined impedance of the S-branch.

[0056] The three measurements can be expressed as follows:

[0057]

[0058]

[0059]

[0060] The derived impedance sensitivity, by adding predetermined impedances to the S+ and S- branches and performing various measurements under different conditions, can be used to correct the impedance measurement, assuming that the error caused by the impedance sensitivity is proportional to the impedance, for example, in a linear manner. Figure 4 The correction circuit 410 can process the measurements and perform corrections accordingly. The correction performed by the correction circuit 410 can involve finding the difference in the measurements and scaling the difference appropriately. The scaling can be performed based on the impedance ratio on the branches. The scaled difference can be used to correct the measurement V D1 In some cases, the difference can be compared with the measured V based on a predetermined scaling or weighting factor (e.g., determined based on a known model of how sensitivity affects the measurement). D1 By measuring V D1 Combined with the weighting / scaling differences in the measurement caused by adding a predetermined amount of impedance to the branch, sensitivity can be taken into account.

[0061] Calculate the difference between the two values, V D2 -V D1 and V D3 -V D1 These differences may expose the sensitivity of the measurement to the small amount of predetermined impedance added to the S+ and S- legs.

[0062] V D2 Subtract V D1 , which gives the measured difference caused by adding a predetermined amount of impedance on the S+ branch:

[0063]

[0064] V D3 Subtract V D1 , which gives the measured difference caused by adding a predetermined amount of impedance on the S-branch:

[0065]

[0066] The result of equation 6 can be expressed as scaling, which is the ratio of the input (parasitic) capacitance at the positive input of the inAmp 120 to the amount of predetermined impedance added to the S+ branch (e.g., C P ) between them.

[0067] The result of equation 7 can be expressed as scaling, which is the input (parasitic) capacitance at the negative input of the inAmp 120 and the amount of predetermined impedance added to the S- branch (e.g., C P ) between them.

[0068] The input (parasitic) capacitance C1 on the S+ branch and the input (parasitic) capacitance C2 on the S- branch can be measured. For example, the input (parasitic) capacitance can be measured directly as a capacitance measurement. In another example, the input (parasitic) capacitance can be measured indirectly using a known resistor (e.g., a calibration resistor) instead of an unknown bioimpedance. A predetermined amount of impedance, such as C1, is added to the S+ branch and the S- branch. P , is also known.

[0069] To perform the calibration and obtain the corrected measurement value V DCorr , measured value V D1 Subtract the value in formula 6. The result of scaling is also subtracted from the value in formula 7. The result of scaling:

[0070]

[0071]

[0072] In Equation 9, which is an expanded version of Equation 8, V1-V2 represents the desired voltage across the unknown bioimpedance 102, represents the error term.

[0073] Comparing the error terms in Equation 3 and Equation 9, we can see that the error terms are different. Note that if And similarly, Rules and will be close to zero. and When it is close to zero, it means that the error term in Formula 9 will also be close to zero. Therefore, the error caused by impedance sensitivity is effectively reduced or corrected by the correction shown in Equation 8.

[0074] The correction scheme of equations 8 and 9 has the unexpected technical advantage that the measured phase is minimally affected. and similarly The error term of Equation 9 produces a purely real number. In the absence of the imaginary error term, the desired voltage in Equation 9 remains unchanged and the phase is minimally affected by the correction scheme.

[0075] Figure 5 is a flowchart illustrating a method 500 for performing a measurement that is less sensitive to errors caused by impedances (e.g., capacitance and resistance) on the S+ and S- branches according to some embodiments of the present disclosure. In 502, a first measurement, such as V_D1, is performed without any predetermined amount of impedance added to the S+ and S- branches. In 504, a second measurement, such as V_D2, is performed using a predetermined amount of impedance added to the S+ branch. In 506, a third measurement, such as V_D2, is performed using a predetermined amount of impedance added to the S- branch. The measurements in 502, 504, and 506 can be performed in any suitable order. Although voltage measurements are performed in 502, 504, and 506, current measurements can also be performed on the F- branch. In 508, a correction measurement V_DCorr can be calculated by combining the first, second, and third measurements. For example, the difference between the measurement value to be corrected and the measurement value can be linearly combined. An example of a linear combination is shown by equation 8 (e.g., by correction circuit 410). In some cases, the corrected measurement V_DCorr can be used as part of the calculations in a four-way impedance measurement scheme to derive the unknown bioimpedance 102. The resulting impedance measurement is less affected by errors due to input (parasitic) capacitances on the S+ and S- branches because the sensitivity of the measurement to changes in branch impedance is taken into account.

[0076] Correction based on frequency sensitivity

[0077] The second technique can reveal how sensitive the measurement is to frequency changes, and the measurement can be corrected or compensated based on the frequency sensitivity. Similar to the impedance sensitivity technique, multiple measurements can be made under different conditions, i.e. two different frequencies, and these measurements can be combined to form a corrected measurement. For example, the difference between the measurement to be corrected and the measurements made at two different frequencies can be combined linearly.

[0078] The bioimpedance may be primarily resistive and should not vary with frequency. A second technique may assume that the error due to frequency sensitivity scales linearly with frequency. The frequency sensitivity may be exposed by measuring using at least a first frequency and a second frequency near the first frequency (the second frequency is equal to the first frequency minus / plus the delta frequency), and the exposed frequency sensitivity (i.e., the measured difference of the first and second frequencies) may be applied in a correction scheme. When the correction is applied correctly, the error term in Equation 9 may be eliminated or reduced.

[0079] Go back to formula 9 and replace k1 with and replace it with k2 The error term in Equation 9 can be rewritten as:

[0080]

[0081] The second technique can be applied to the corrected measurement of Equation 8. Based on the reformulation of the error term shown in Equation 10, the corrected measurement of Equation 8 measured at the first frequency ω can be given by:

[0082] V DCor (ω)=V1-V2+V1Z1 2 ω 2 (C1+C P ) 2 -V2Z2 2 ω 2 (C2+C P ) 2 (Equation 11)

[0083] The corrected measurement value ω+Δω of Equation 8 measured at a second frequency close to the first frequency may be given by:

[0084] V DCorr (ω+Δω)=V1-V2+V1Z1 2 (ω+Δω) 2 (C1+C P ) 2

[0085] -V2Z2 2 (ω+Δω) 2 (C2+C P ) 2 (Equation 12)

[0086] Using formula 11, V DCorr Subtract V from Formula 12 from the result of (ω) DCorr As a result of (ω+Δω), the difference between two corrected measurements at two different frequencies can be given by:

[0087] ΔVDCorr =V1Z1 2 (C1+C P ) 2 2ωΔω-V2Z2 2 (C2+C P ) 2 2ωΔω (Equation 13)

[0088] The measured value V to be corrected DCorr (ω) and the difference between the two measurements ΔV DCorr can be linearly combined to form a corrected measurement that takes frequency sensitivity into account. For example, replacing ΔV in Equation 13 DCorr The result is multiplied by (e.g., the ratio of the first frequency to twice the frequency increment) and subtract V from Equation 11 DCorr (ω) we get:

[0089]

[0090] The error terms seen previously in Equation 11 can be eliminated or reduced. Note that correction techniques based on frequency sensitivity can be effective as long as the measurements are made at a first frequency and a second frequency near the first frequency. The errors caused by frequency sensitivity can be eliminated using the measurements obtained at the first frequency and the second frequency. In other words, the second technique can be a point frequency correction for a given measurement made at a specific frequency point of interest, where the correction can be frequency specific. The incremental frequency Δω can be selected according to the application.

[0091] In some cases, the second technique can be applied to uncorrected measurements, such as V in Equation 3 D1 .

[0092] Figure 6 6 is a flow chart illustrating a method 600 for performing measurements that are less sensitive to errors associated with frequency according to some embodiments of the present disclosure. At 602, a measurement can be made at a first frequency, e.g., according to Equation 11. At 604, a measurement can be made at a second frequency near the first frequency, e.g., according to Equation 12. At 606, a correction can be applied to make the measurement less susceptible to non-idealities of a four-way measurement scheme, especially at high frequencies, e.g., according to Equation 14. The correction can be determined by Figure 4 The correction circuit 410 performs the correction of the measured V DCorr2 It can be calculated by combining the measurement to be corrected and the difference between the two measurements made at the first frequency and the second frequency. For example, the measurement to be corrected and the difference between the measurements can be combined linearly. In some cases, the corrected measurement V DCorr2Can be used as part of the calculations in a four-way impedance measurement scheme to derive unknown bioimpedance 102. The resulting impedance measurement may be less affected by frequency errors because the sensitivity of the measurement to branch frequency variations is accounted for.

[0093] In some embodiments, the measurements are made at frequencies within a frequency range. Figure 4 , the signal generator 116 can be configured to generate signals of different frequencies so that measurements can be made at different frequencies. At least two measurements are made, for example, once at a first frequency and once at a second frequency, to correct the frequency sensitivity of the measurement made at the first frequency. In some cases, multiple measurements can be made at frequencies across a frequency range, with frequency increments between frequencies. Preferably, for each measurement made at a first frequency, a measurement is also made at a second frequency so that a correction can be performed. The measurement results can then be used to correct the frequency sensitivity of the frequency range of interest. In other words, a scan over a frequency range can provide frequency sensitivity information that can be used to perform a correction.

[0094] Figure 7 An example measurement arrangement 700 is illustrated that can implement the techniques described herein according to some embodiments of the present disclosure. In particular, the measurement arrangement 700 can include circuitry 702 that can implement one or both of the techniques in the embodiments.

[0095] The measurement device 700 may include a bioimpedance 704. The bioimpedance 704 may represent a portion of a subject's body, where the portion of the body may present a certain impedance to an electric current flowing through the portion of the body. The amount of the bioimpedance 704 may be used to determine information about the subject, such as making a determination about the health of the subject.

[0096] Circuit 702 may determine one or more electrical characteristics related to bio-impedance 704 that may be used to determine the amount of bio-impedance 704. In particular, the electrical characteristics may be used to determine the amount of impedance presented by bio-impedance 704. For example, circuit 702 may apply a signal to bio-impedance 704 and determine a voltage drop produced by bio-impedance 704 due to the applied signal.

[0097] The circuit 702 may be coupled to the bioimpedance 704 via a plurality of electrodes. For example, the circuit 702 is coupled by a first electrode 706, a second electrode 708, a third electrode 710, and a fourth electrode 712. Each electrode may include one or more features of electrodes described throughout the present disclosure. For example, each of the first electrode 706, the second electrode 708, the third electrode 710, and the fourth electrode 712 may include the electrode 104 ( Figure 1 )、Electrode 106( Figure 1 )、Electrode 108( Figure 1 ) and electrode 110( Figure 1 ). The electrodes may be positioned on the subject's body or a portion thereof, corresponding to bio-impedance 704. Each electrode may present a contact impedance based on contact with the subject's body. In particular, the amount of the electrode's contact impedance may be based on the quality of contact between the electrode and the subject's body. The first electrode 706 may present a first contact impedance (e.g., contact impedance Z E1 ), the second electrode 708 may present a second contact impedance (eg, contact impedance Z E2 ), the third electrode 710 may present a third contact impedance (eg, contact impedance Z E3 ), the fourth electrode 712 may present a fourth contact impedance (eg, contact impedance Z E4 ).

[0098] Circuit 702 may include one or more pins that may be coupled to an electrode. In some embodiments, circuit 702 may be included in an integrated circuit or chip, wherein the pins of circuit 702 may include contacts with the integrated circuit or chip, or may include an electrical connector of a system in which circuit 702 is implemented. In the illustrated embodiment, circuit 702 includes a first pin 714, a second pin 716, a third pin 718, and a fourth pin 720. The first pin 714 may be coupled to the first electrode 706, the second pin 716 may be coupled to the second electrode 708, the third pin 718 may be coupled to the third electrode 710, and the fourth pin 720 may be coupled to the fourth electrode 712. Wires, cables, or other coupling devices may be located between each pin and the electrode to which the pin is coupled. In some embodiments, an isolation circuit may be implemented between each electrode and the corresponding pin. For example, a capacitor (e.g., capacitor C) may be implemented between each electrode and the corresponding pin. ISO1 , C ISO2 , C ISO3 and C ISO4 ). In other embodiments, the isolation circuit may be omitted. Each of the corresponding electrodes, pins, and (if included) capacitors may be referred to as branches. For example, the first electrode 706 and the first pin 714 may be referred to as a first branch, the second electrode 708 and the second pin 716 may be referred to as a second branch, the third electrode 710 and the third pin 718 may be referred to as a third branch, and the fourth electrode 712 and the fourth pin 720 may be referred to as a fourth branch.

[0099] Circuit 702 may include signal generator 722. Signal generator 722 may include signal generator 116 ( Figure 1) one or more characteristics. The signal generator 722 can be coupled to the first end of the bio-impedance 704 via the first pin 714 and the first electrode 706. The signal generator 722 can generate a signal and apply the signal to the bio-impedance 704. The signal applied to the bio-impedance 704 by the signal generator 722 can cause a current to flow through the bio-impedance 704 and generate a voltage drop on the bio-impedance 704. In some embodiments, the signal applied to the bio-impedance 704 can include a signal having a frequency between 0 Hz and 999 million Hz. In addition, in some embodiments, the signal applied to the bio-impedance 704 can include a sinusoidal signal.

[0100] The circuit 702 may also include a current measurement circuit 724. The current measurement circuit 724 may include a current measurement circuit 126 ( Figure 1 ) one or more characteristics. The current measurement circuit 724 can be coupled to the second end of the bio-impedance 704 through the fourth pin 720 and the fourth electrode 712, wherein the second end of the bio-impedance 704 is opposite to the first end of the bio-impedance 704. The current measurement circuit 724 can determine the amount of current entering through the fourth pin 720 and generate an indication of the amount of current (e.g., a voltage corresponding to the amount of current). Ideally, the current entering through the fourth pin 720 can be the entire current applied to the bio-impedance 704 by the signal generator 722. However, a portion of the current applied via the signal generator 722 can flow into other pins of the circuit 702, as described throughout the disclosure.

[0101] The circuit 702 may also include a voltage measurement circuit 726. The voltage measurement circuit 726 may include the voltage measurement circuit 118 ( Figure 1 ). For example, voltage measurement circuit 726 may include inAmp 728, DFT block 730, and summation block 732. Voltage measurement circuit 726 may determine an amount of voltage drop across bio-impedance 704. For example, voltage measurement circuit 726 may determine a voltage difference between a first end of bio-impedance 704 and a second end of bio-impedance 704.

[0102] The inAmp 728 of the voltage measurement circuit 726 can be coupled to the bio-impedance 704 via the second pin 716, the second electrode 708, the third pin 718, and the third electrode 710. In particular, the first input of the inAmp 728 can be coupled to the first end of the bio-impedance 704 via the second pin 716 and the second electrode 708. The second input of the inAmp 728 can be coupled to the second end of the bio-impedance 704 via the third pin 718 and the third electrode 710. In some embodiments, the first input of the inAmp 728 can include the positive input of the inAmp 728, and the second input of the inAmp 728 can include the negative input of the inAmp 728. The inAmp 728 can determine the voltage difference between the voltage at the first end of the bio-impedance 704 and the voltage at the second end of the bio-impedance 704 and can output an indication of the voltage difference. Ideally, the input of the inAmp 728 will not allow current to flow into the input of the inAmp 728. However, in practice, the input may present a high impedance, where current may flow into the input of the inAmp 728. The impedance presented to the input may include parasitic capacitance, where the parasitic capacitance may be caused by a grounded input impedance (such as grounded input impedance 202 ( Figure 2 ) and grounded input impedance 204 ( Figure 2 )) to express it.

[0103] The circuit 702 may further include a first impedance circuit 734 and a second impedance circuit 736. The first impedance circuit 734 may include the circuit 402 ( Figure 4 ), and the second impedance circuit 736 may include one or more features of circuit 404 ( Figure 4 ). The first impedance circuit 734 can be coupled between the first end of the bio-impedance 704 (through the second pin 716 and the second electrode 708) and the ground 738 of the circuit 702. The first impedance circuit 734 may include a first impedance 740 and a first switch 742. The first impedance 740 may be coupled to the ground 738 and the first switch 742 may be coupled between the first impedance 740 and the first end of the bio-impedance 704. The first switch 742 may selectively couple the first impedance 740 to the first end of the bio-impedance 704. In particular, the first switch 742 may couple the first impedance 740 to the first end of the bio-impedance 704 when closed and may decouple the first impedance 740 from the first end of the bio-impedance 704 when open. The first impedance 740 may include a first capacitor or a first resistor. The first switch 742 may include a mechanical switch or an electronic switch (e.g., a transistor configured in a switch arrangement).

[0104] The second impedance circuit 736 can be coupled between the second end of the bio-impedance 704 (through the third pin 718 and the third electrode 710) and the ground 738 of the circuit 702. The second impedance circuit 736 may include a second impedance 744 and a second switch 746. The second impedance 744 may be coupled to the ground 738, and the second switch 746 may be coupled between the second impedance 744 and the second end of the bio-impedance 704. The second switch 746 may selectively couple the second impedance 744 to the second end of the bio-impedance 704. In particular, the second switch 746 may couple the second impedance 744 to the second end of the bio-impedance 704 when closed and may decouple the second impedance 744 from the second end of the bio-impedance 704 when opened. The second impedance 744 may include a second capacitor or a second resistor. The second switch 746 may include a mechanical switch or an electronic switch (e.g., a transistor configured in a switch arrangement). In some embodiments, the second capacitor or the second resistor can be the same as the first capacitor or the first resistor, wherein the first switch 742 and the second switch 746 can both be coupled to the first capacitor or the first resistor and selectively couple the first capacitor or the first resistor to the corresponding side of the bio-impedance 704. In other embodiments, the first impedance circuit 734 and the second impedance circuit 736 can be omitted.

[0105] The circuit 702 may include a processor 748. The processor 748 may include one or more processors, one or more microprocessors, one or more microcomputers, or some combination thereof. The processor 748 may implement one or both of the techniques for determining the value of the correction or compensation bio-impedance 704 described throughout. For example, in some embodiments, the processor 748 may be coupled to a first switch 742 and a second switch 746, wherein the processor 748 may implement techniques for correction and / or compensation based on impedance sensitivity. The processor 748 may cause the first switch 742 to selectively couple the first impedance 740 to the first end of the bio-impedance 704 and cause the second switch 746 to selectively couple the second impedance 744 to the second end of the bio-impedance 704 to achieve correction and / or compensation based on impedance sensitivity. In particular, the processor 748 may cause the first switch 742 to couple the first impedance 740 to the first end of the bio-impedance 704 and cause the second switch 746 to decouple the second impedance 744 from the second end of the bio-impedance 704.

[0106] The processor 748 may be further coupled to the voltage measurement circuit 726 and cause the voltage measurement circuit 726 to determine a voltage difference between a voltage at a first end of the bio-impedance 704 and a voltage at a second end of the bio-impedance 704. A first voltage difference between a voltage at the first end of the bio-impedance 704 and a voltage at the second end of the bio-impedance 704 may be determined by the voltage measurement circuit 726, wherein the circuit 702 in a configuration having the first impedance 740 coupled to the first end of the bio-impedance 704 and the second impedance 744 decoupled from the second end of the bio-impedance 704. The first voltage difference determined by the voltage measurement circuit 726 may provide a voltage difference determined by Equation 4. The processor 748 may also cause the first switch 742 to decouple the first impedance 740 from the first end of the bio-impedance 704 and cause the second switch 746 to couple the second impedance 744 to the second end of the bio-impedance 704. A second voltage difference between a voltage at a first end of the bio-impedance 704 and a voltage at a second end of the bio-impedance 704 may be determined by the voltage measurement circuit 726, wherein the circuit 702 in a configuration has a first impedance 740 decoupled from the first end of the bio-impedance 704 and a second impedance 744 coupled to the second end of the bio-impedance 704. The second voltage difference determined by the voltage measurement circuit 118 may provide a voltage difference determined by Equation 5. The processor 748 may also cause the first switch 742 to decouple the first impedance 740 from the first end of the bio-impedance 704 and cause the second switch 746 to decouple the second impedance 744 from the second end of the bio-impedance 704. A third voltage difference between a voltage at a first end of the bio-impedance 704 and a voltage at a second end of the bio-impedance 704 may be determined by the voltage measurement circuit 726, wherein the circuit 702 in a configuration has the first impedance 740 decoupled from the first end of the bio-impedance 704 and the second impedance 744 decoupled from the second end of the bio-impedance 704. The correction voltage may be generated by correcting and / or compensating the third voltage difference with the first voltage difference and the second voltage difference according to Equation 8, where C1 of Equation 8 may be equal to the parasitic capacitance of the input terminal of inAmp 728 coupled to the first terminal of bioimpedance 704, and C of the second term of Equation 8 may be equal to the parasitic capacitance of the input terminal of inAmp 728 coupled to the first terminal of bioimpedance 704. P may be equal to the first impedance 740, C2 may be equal to the parasitic capacitance of the input terminal of inAmp 728 coupled to the second terminal of the bio-impedance 704, and C of the third term of Equation 8 may be equal to the first impedance 740, C2 may be equal to the parasitic capacitance of the input terminal of inAmp 728 coupled to the second terminal of the bio-impedance 704, and C P may be equal to the second impedance 744. Although an order of determining the voltage difference is described, it should be understood that the determination of the voltage difference (including the selective coupling of the first impedance 740 and the second impedance 744) may be performed in any order.

[0107] In some embodiments, the processor 748 can be coupled to the signal generator 722, wherein the processor 748 can implement techniques for correction and / or compensation based on frequency sensitivity. The processor 748 can cause the signal generator 722 to apply signals of different frequencies to the bio-impedance 704 to achieve correction and / or compensation based on frequency sensitivity. In particular, the processor 748 can cause the signal generator 722 to apply a signal of a first frequency to the bio-impedance 704. A first voltage difference between a voltage at a first end of the bio-impedance 704 and a voltage at a second end of the bio-impedance 704 can be determined by a voltage measurement circuit 726, wherein the configuration of the signal generator 722 applies the signal of the first frequency to the bio-impedance 704. The first voltage difference determined by the voltage measurement circuit 726 can provide the first term of equation 14. The processor 748 can further cause the signal generator 722 to apply a signal of a second frequency to the bio-impedance 704. A second voltage difference between a voltage at a first end of the bio-impedance 704 and a voltage at a second end of the bio-impedance 704 may be determined by a voltage measurement circuit 726, wherein the configuration of the signal generator 722 applies a signal of a second frequency to the bio-impedance 704. The second voltage difference determined by the voltage measurement circuit 726 may provide a portion of a first term of Equation 14, wherein ω may be a first frequency applied by the signal generator and Δω may be a difference between the first frequency applied by the signal generator 722 and the second frequency applied by the signal generator 722. The correction voltage may be generated by correcting and / or compensating the first voltage difference with the second voltage difference according to Equation 14.

[0108] In some embodiments implementing these two techniques, the correction and / or compensation technique based on impedance sensitivity may be performed before the technique for correction and / or compensation based on frequency sensitivity. For example, when the signal generator 722 applies a signal of a first frequency, the processor 748 may selectively couple the first impedance and the second impedance to determine the voltage difference according to the technique for correction and / or compensation based on impedance sensitivity. The first correction voltage may be generated by a technique for correction and / or compensation based on impedance sensitivity using a determined voltage at the first frequency. When the signal generator 722 applies a signal of a second frequency, the processor 748 may selectively couple the first impedance and the second impedance to determine the voltage difference according to the technique for correction and / or compensation based on impedance sensitivity. The second correction voltage may be generated by a technique for correction and / or compensation based on impedance sensitivity using a determined voltage at the second frequency. The correction and / or compensation technique based on frequency sensitivity may then be applied to the first correction voltage and the second correction voltage to generate a third correction voltage.

[0109] The processor 748 may be coupled to the voltage measurement circuit 726 and the current measurement circuit 724. The processor 748 may receive the outputs of the voltage measurement circuit 726 and the current measurement circuit 724. For example, the processor 748 may receive an indication of a voltage difference determined by the voltage measurement circuit 726. In addition, the processor 748 may receive an indication of a current determined by the current measurement circuit 724. The processor 748 may also be coupled to the communication circuit 750 of the circuit 702. The communication circuit 750 may provide wired communication and / or wireless communication with other elements. For example, the communication circuit 750 may provide wireless communication with a remote device. The processor 748 may utilize the communication circuit 750 to provide an indication of a voltage difference and an indication of a current to the remote device. In some embodiments, the circuit 702 may include a storage device to store the indication of the voltage difference and the indication of the current before transmitting the indication to the remote device.

[0110] Figure 8 An example system arrangement 800 is illustrated that can implement the techniques described herein according to some embodiments of the present disclosure. In particular, the system arrangement 800 can implement one or both of techniques for correction and / or compensation based on impedance sensitivity and techniques for correction and / or compensation based on frequency sensitivity.

[0111] System arrangement 800 may include circuit 802. Circuit 802 may include circuit 150 ( Figure 1 ) and / or circuit 702 ( Figure 7 ). In addition, circuit 802 may perform one or more processes of circuit 150 and / or circuit 702. Circuit 802 may include processor 804, wherein processor 804 includes one or more features of processor 748 ( Figure 7 ). The circuit 802 may also include one or more computer readable media (CRM) 806. In some embodiments, the CRM 806 may include a non-transitory CRM. The CRM may store instructions that, when executed by the processor 804, cause the processor 804 to perform one or more processes.

[0112] The circuit 802 may be coupled to the subject's body 808 via one or more electrodes. For example, in the illustrated embodiment, the circuit 802 is coupled to the body via a first electrode 810, a second electrode 812, a third electrode 814, and a fourth electrode 816. Each electrode may include one or more features of electrodes described throughout the present disclosure. For example, the first electrode 810 may include the electrode 104 ( Figure 1 ) and / or the first electrode 706 ( Figure 7 ) one or more features. The second electrode 812 may include electrode 106 ( Figure 1 ) and / or the second electrode 708 ( Figure 7) one or more features. The third electrode 814 may include electrode 108 ( Figure 1 ) and / or the third electrode 710 ( Figure 7 ) one or more features. The fourth electrode 816 may include electrode 110 ( Figure 1 ) and / or the fourth electrode 712 ( Figure 7 )

[0113] The system arrangement 800 may also include a remote device 818. The remote device 818 may include a computer device, a server, or some combination thereof. The remote device 818 may be coupled (e.g., wired or wireless) to the circuit 802. The remote device 818 may receive an indication of a voltage difference and / or an indication of a current from the circuit 802. The indication of a voltage difference may indicate a voltage difference between two electrodes determined by the circuit 802 according to a procedure for determining a voltage difference described throughout the present disclosure, including selective coupling of impedances and / or multiple frequencies of a signal applied to the body 808. The remote device 818 may perform correction and / or compensation according to techniques related to impedance sensitivity and / or techniques related to frequency sensitivity.

[0114] The remote device 818 may include a processor 820. The processor 820 may generate a correction voltage using an indication of a voltage difference according to techniques related to impedance sensitivity and / or techniques related to frequency sensitivity. For example, the processor 820 may use the voltage difference to perform one or more calculations of the equations disclosed herein to generate a correction voltage. The remote device 818 may also include one or more CRMs 822. In some embodiments, the CRM 822 may include a non-transitory CRM. Instructions may be stored on the CRM 822, which, when executed by the processor 820, cause the processor 820 to perform one or more processes. In other embodiments, the remote device 818 may be implemented in the circuit 802 and / or the process performed by the remote device 818 may be performed by the circuit 802.

[0115] Circuit 802 and remote device 818 may perform method 500 ( Figure 5 ) and / or method 600( Figure 6). For example, where the circuit 802 and the remote device 818 perform method 500, the circuit 802 may perform a portion of the method 500 and the remote device 818 may perform another portion of the method. In some embodiments, the circuit 802 may perform 502, 504, and 506, and the remote device 818 may perform 508. Where the circuit 802 and the remote device 818 perform method 600, the circuit 802 may perform a portion of the method 600 and the remote device 818 may perform another portion of the method. In some embodiments, the circuit 802 may perform 602 and 604, and the remote device 818 may perform 606. In embodiments where the circuit 802 performs the described process performed by the remote device 818, the circuit 802 may perform the entire method 500 and / or the method 600.

[0116] Other technical advantages

[0117] Measuring bioimpedance is particularly useful for measuring body impedance to detect signs of congestive heart failure (e.g., by detecting fluid levels in the lungs). Measuring bioimpedance can also be used in electrical impedance tomography and spectroscopy to determine the composition of the body in a non-invasive manner (e.g., imaging of tissue and bone) by taking bioimpedance measurements at different frequencies. Users such as athletes and patients can greatly benefit from such applications.

[0118] Example Implementation

[0119] The following examples are provided by way of illustration.

[0120] Example 1 may include a circuit for determining a bio-impedance amount of a portion of a subject's body, the circuit comprising a first impedance circuit coupled to a first pin of the circuit, the first pin coupled to a first side of the body part, wherein the first impedance circuit selectively couples a first impedance to the first pin, a second impedance circuit coupled to a second pin of the circuit, the second pin coupled to a second side of the body part, wherein the second impedance circuit selectively couples a second impedance to the second pin, and a voltage measurement circuit coupled to the first pin and the second pin, the voltage measurement circuit being used to determine a first voltage difference between the first pin and the second pin when the first impedance is coupled to the first pin and the second impedance is decoupled from the second pin, and to determine a second voltage difference between the first pin and the second pin when the first impedance is decoupled from the first pin and the second impedance is coupled to the second pin, the first voltage difference and the second voltage difference being used to compensate to determine the bio-impedance amount.

[0121] Example 2 may include the circuit of Example 1, wherein the first impedance circuit includes a first impedance coupled to ground of the circuit, and a first switch coupled between the first impedance and the first pin, the first switch selectively coupling the first impedance to the first pin, and the second impedance circuit includes a second impedance coupled to ground of the circuit, and a second switch coupled between the second impedance and the second pin, the second switch selectively coupling the second impedance to the second pin.

[0122] Example 3 may include the circuit of Example 1, further comprising a signal generator coupled to the body via a third pin, the signal generator applying a signal to the body to determine the first voltage difference and the second voltage difference.

[0123] Example 4 may include the circuit of Example 3, wherein the signal applied to the body via the signal generator comprises a sinusoidal signal.

[0124] Example 5 may include the circuit of Example 1, wherein the circuit further includes a processor coupled to the first impedance circuit, the second impedance circuit, and the voltage measurement circuit, the processor configured to cause the first impedance circuit to couple the first impedance to the first pin, cause the voltage measurement circuit to determine the first voltage difference when the first impedance circuit has a first impedance coupled to the first pin, cause the second impedance circuit to couple the second impedance to the second pin, and cause the voltage measurement circuit to determine the second voltage difference when the second impedance circuit has a second impedance coupled to the second pin.

[0125] Example 6 may include the circuit of Example 5, wherein the processor is further configured to cause the first impedance circuit to decouple the first impedance from the first pin, cause the second impedance circuit to decouple the second impedance from the second pin, and cause the voltage measurement circuit to determine a third voltage difference when the first impedance circuit has the first impedance decoupled from the first pin and the second impedance decoupled from the second pin, wherein the third voltage difference is compensated by the first voltage difference and the second voltage difference to determine the bio-impedance amount.

[0126] Example 7 may include the circuit of Example 1, wherein the first impedance includes a first capacitor and wherein the second impedance includes a second capacitor.

[0127] Example 8 may include the circuit of Example 1, wherein the first pin is coupled to a first electrode, the first electrode is positioned at a first end of a portion of the subject's body, wherein the second pin is coupled to a second electrode, the second electrode is positioned at a second end of the portion of the subject's body, and wherein the portion of the subject's body generates bioimpedance.

[0128] Example 9 may include a system for determining a bioimpedance value of a portion of a subject's body, comprising a first electrode positioned at a first end of the portion of the body, a second electrode positioned at a second end of the portion of the body, and a circuit coupled to the first electrode and the second electrode, the circuit determining a voltage difference between the first electrode and the second electrode, the circuit comprising a first impedance circuit coupled to the first electrode, the first impedance circuit selectively coupling a first impedance between the first electrode and a ground for the circuit, a second impedance circuit coupled to the second electrode, the second impedance circuit selectively coupling a second impedance between the second electrode and the ground for the circuit, and a voltage measurement circuit coupled to the first electrode and the second electrode, the voltage measurement circuit being used to determine the voltage difference between the first electrode and the second electrode when the first impedance is selectively coupled between the first electrode and the ground for the circuit and the second impedance is selectively coupled between the second electrode and the ground for the circuit.

[0129] Example 10 may include the system of Example 9, wherein determining a voltage difference between the first electrode and the second electrode while the first impedance is selectively coupled and the second impedance is selectively coupled includes determining a first voltage difference between the first electrode and the second electrode while the first impedance is selectively coupled between the first electrode and a ground of the circuit and the second impedance is decoupled between the second electrode and the ground of the circuit, and determining a second voltage difference between the first electrode and the second electrode while the first impedance is decoupled between the first electrode and the ground of the circuit and the second impedance is selectively coupled between the second electrode and the ground of the circuit, the first voltage difference and the second voltage difference being used to compensate for a third voltage difference to determine a bio-impedance value.

[0130] Example 11 may include the system of Example 10, wherein the third voltage difference is determined with the first impedance being decoupled between the first electrode and a ground for the circuit and the second impedance being decoupled between the second electrode and a ground for the circuit.

[0131] Example 12 may include the system of Example 9, wherein the first impedance circuit includes a first impedance coupled to ground of the circuit, and a first switch coupled between the first impedance and the first electrode, the first switch selectively coupling the first impedance to the first electrode, and the second impedance circuit includes a second impedance coupled to ground of the circuit, and a second switch coupled between the second impedance and the second electrode, the second switch selectively coupling the second impedance to the second electrode.

[0132] Example 13 may include the system of Example 12, wherein the circuit further includes a controller coupled to the first switch and the second switch, wherein the controller causes the first switch and the second switch to switch states to selectively couple the first impedance to the first electrode and selectively couple the second impedance to the second electrode.

[0133] Example 14 may include the system of Example 9, wherein the circuit includes an instrumentation amplifier (inAmp), the positive input of the inAmp being coupled to the first electrode and the negative input of the inAmp being coupled to the second electrode, the inAmp being used to determine a voltage difference between the first electrode and the second electrode.

[0134] Example 15 may include the system of Example 9, wherein the circuit further comprises a signal generator coupled to a third electrode located on the body, wherein the signal generator applies a signal to the body to generate a voltage difference.

[0135] Example 16 may include the system of Example 9, wherein the first impedance comprises a first capacitor and wherein the second impedance comprises a second capacitor.

[0136] Example 17 may include a method for determining a bio-impedance value of a portion of a subject's body, comprising determining, by a circuit, a first voltage difference between a first electrode located on a first side of the body portion and a second electrode located on a second side of the body portion, wherein the circuit has a first configuration, and after determining the first voltage difference, the circuit changes from the first configuration to the second configuration, and determining, by the circuit, a second voltage difference between the first electrode and the second electrode, wherein the circuit has a second configuration, and the first voltage difference and the second voltage difference are used to compensate to determine the bio-impedance value.

[0137] Example 18 may include the method of Example 17, wherein the first configuration has a first impedance of a circuit coupled to the first electrode and a second impedance of the circuit decoupled from the second electrode, wherein the second configuration has a first impedance decoupled from the first electrode and a second impedance coupled to the second electrode, and wherein changing from the first configuration to the second configuration includes decoupling the first impedance from the first electrode through the circuit and coupling the second impedance to the second electrode through the circuit.

[0138] Example 19 may include the method of Example 17, wherein determining a first voltage difference between the first electrode and the second electrode includes comparing a first voltage of the first electrode with a first voltage of the second electrode through a voltage measurement circuit of the circuit, wherein the circuit has a first configuration, and outputting the first voltage difference based on the comparison of the first voltage of the first electrode with the first voltage of the second electrode through the voltage measurement circuit, and determining a second voltage difference between the first electrode and the second electrode includes comparing a second voltage of the first electrode with a second voltage of the second electrode through the voltage measurement circuit, wherein the circuit has a second configuration, and outputting the second voltage difference based on the comparison of the second voltage of the first electrode with the second voltage of the second electrode through the voltage measurement circuit.

[0139] Example 20 may include the method of Example 17, further comprising applying a signal to the body via a signal generator of the circuit to generate the first voltage difference and the second voltage difference.

[0140] Example 21 may include a circuit for determining a bio-impedance amount of a portion of a subject's body, the circuit comprising: a signal generator to apply a signal to the portion of the body, the signal generator applying a first signal having a first frequency to the portion of the body and applying a second signal having a second frequency to the portion of the body; and a voltage measurement circuit coupled to a first pin coupled to a first side of the body portion and a second pin coupled to a second side of the body portion, the voltage measurement circuit determining a first voltage difference between the first pin and the second pin, wherein the first signal having the first frequency is applied to the portion of the body; and determining a second voltage difference between the first pin and the second pin using the second signal having a second frequency applied to the body portion, the first voltage difference and the second voltage difference being used to compensate to determine the bio-impedance amount.

[0141] Example 22 may include a circuit for determining a bio-impedance amount of a portion of a body, the circuit comprising a signal generator to apply a first signal having a first frequency to the portion of the body and a second signal having a second frequency to the portion of the body, a first impedance circuit coupled to a first pin of the circuit, the first pin coupled to a first side of the body portion, wherein the first impedance circuit selectively couples a first impedance to the first pin, a second impedance circuit coupled to a second pin of the circuit, the second pin coupled to a second side of the body portion, wherein the second impedance circuit selectively couples a second impedance to the second pin, and a voltage measurement circuit coupled to the first pin and the second pin, the voltage measurement circuit for determining a first set of voltage differences using the first signal having the first frequency applied to the body portion, the first impedance circuit selectively couples the first impedance to the first pin, and the second impedance circuit selectively couples the second impedance to the second pin, and a voltage measurement circuit for determining a second set of voltage differences using the second signal having the second frequency applied to the portion of the body, the first impedance circuit selectively couples the first impedance to the first pin, and the second impedance circuit selectively couples the second impedance to the second pin, the first set of voltage differences and the second set of voltage differences being used to determine the bio-impedance amount.

[0142] The foregoing summarizes the features of one or more embodiments of the subject matter disclosed herein. These embodiments are provided to enable a person of ordinary skill in the art (PHOSITA) to better understand the various aspects of the present disclosure. Certain well-understood terms and underlying technologies and / or standards may be referenced without detailed description. It is expected that PHOSITA will have or have access to background knowledge or information in those technologies and standards sufficient to practice the teachings of the present disclosure.

[0143] PHOSITA will understand that they can easily use this disclosure as a basis for designing or modifying other processes, structures or variations to achieve the same purpose and / or achieve the same advantages of the embodiments introduced herein. PHOSITA will also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions and modifications herein without departing from the spirit and scope of the present disclosure.

[0144] Note that the activities discussed above with reference to the accompanying drawings are applicable to any integrated circuit involving signal processing (e.g., gesture signal processing, video signal processing, audio signal processing, analog-to-digital conversion, digital-to-analog conversion), particularly those that can execute specialized software programs or algorithms, some of which may be associated with processing digitized real-time data. Certain embodiments may involve multi-DSP, multi-ASIC or multi-SoC signal processing, floating point processing, signal / control processing, fixed function processing, microcontroller applications, etc. In certain contexts, the features discussed herein may be applicable to medical systems, scientific instruments, wireless and wired communications, radar, industrial process control, audio and video equipment, current sensing, instruments (which may be high-precision), and other digital processing-based systems. Moreover, certain embodiments discussed above may be provided in digital signal processing technology for medical imaging, patient monitoring, medical instruments, and home healthcare. This may include, for example, lung monitors, accelerometers, heart rate monitors, or pacemakers, and their peripherals. Other applications may involve automotive technology for safety systems (e.g., stability control systems, driver assistance systems, braking systems, infotainment, and any type of interior applications). In addition, powertrain systems (e.g., in hybrid and electric vehicles) can use high-precision data conversion, rendering, and display products in battery monitoring, control systems, reporting controls, maintenance activities, and the like. In other example scenarios, the teachings of the present disclosure can be applied to industrial markets including process control systems that help improve productivity, energy efficiency, and reliability. In consumer applications, the teachings of the above-described signal processing circuits can be used for image processing, autofocus, and image stabilization (e.g., for digital cameras, camcorders, etc.). Other consumer applications may include audio and video processors for home theater systems, DVD recorders, and high-definition televisions. However, other consumer applications may involve advanced touch screen controllers (e.g., for any type of portable media device). Therefore, these technologies can easily become part of smartphones, tablets, security systems, PCs, gaming technology, virtual reality, simulation training, and the like.

[0145] The foregoing summarizes the features of several embodiments so that those skilled in the art can better understand aspects of the present disclosure. Those skilled in the art will appreciate that they can easily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also appreciate that such equivalent constructions do not depart from the spirit and scope of the present invention, and that various changes, substitutions, and modifications may be made to this document without departing from the spirit and scope of the present invention.

[0146] Certain embodiments of the present disclosure may readily include a system-on-chip (SoC) central processing unit (CPU) package. SoC stands for an integrated circuit (IC) that integrates the components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and radio frequency functions: all of which can be provided on a single chip substrate. Other embodiments may include a multi-chip module (MCM), in which multiple chips are located within a single electronic package and are configured to interact closely with each other through the electronic package. Any module, function, or block element of an ASIC or SoC may be provided, where appropriate, in a reusable "black box" intellectual property (IP) block that can be distributed separately without disclosing the logical details of the IP block. In various other embodiments, digital signal processing functions may be implemented in one or more silicon cores in application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and other semiconductor chips.

[0147] In some cases, the teachings of the present disclosure may be encoded into one or more tangible, non-transitory computer-readable media having executable instructions stored thereon, which when executed instruct a programmable device (e.g., a processor or DSP) to perform the methods or functions disclosed herein. Where the teachings herein are at least partially embodied in a hardware device (e.g., an ASIC, an IP block, or a SoC), the non-transitory medium may include a hardware device whose hardware is programmed with logic to perform the methods or functions disclosed herein. The teachings may also be practiced in the form of register transfer level (RTL) or other hardware description languages ​​such as VHDL or Verilog, which may be used to program a manufacturing process to produce the disclosed hardware elements.

[0148] In example implementations, at least some parts of the processing activities outlined here may also be implemented in software. In certain embodiments, one or more of these features may be implemented in hardware provided outside the elements of the disclosed drawings, or may be merged in any appropriate manner to achieve the desired function. Various components may include software (or reciprocating software) that can be coordinated to achieve the operation outlined herein. In other embodiments, these elements may include any suitable algorithm, hardware, software, component, module, interface or object that facilitates its operation.

[0149] In addition, some components associated with the described microprocessors may be removed or otherwise combined. In general, the arrangements depicted in the figures may be more logical in their representation, while the physical architecture may include various arrangements, combinations, and / or hybrids of these elements. It must be noted that countless possible design configurations can be used to achieve the operational goals outlined herein. Therefore, there are countless alternative arrangements, design choices, equipment possibilities, hardware configurations, software implementations, equipment options, etc. for the associated infrastructure.

[0150] Any appropriately configured processor component can execute any type of instruction associated with data to implement the operations detailed here. Any processor disclosed herein can convert an element or article (e.g., data) from one state or thing to another state or thing. In another example, some of the activities outlined here can be implemented with fixed logic or programmable logic (e.g., software and / or computer instructions executed by a processor), and the elements identified here can be a certain type of programmable processor, programmable digital logic (e.g., FPGA, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), including digital logic, software, code, electronic instructions, flash memory, optical disk, CD-ROM, DVD ROM, magnetic card or optical card ASIC, other types of machine-readable media suitable for storing electronic instructions, or any suitable combination thereof. In operation, the processor can store information in any suitable type of non-temporary storage medium (e.g., random access memory (RAM), read-only memory (ROM), FPGA, EPROM, electrically erasable programmable ROM (EEPROM), etc.), software, hardware, or in any other suitable component, device, element or object in a suitable case and based on specific needs. In addition, based on specific needs and implementations, information tracked, sent, received, or stored in the processor may be provided in any database, register, table, cache, queue, control list, or storage structure, all of which may be referenced in any suitable time frame. Any memory item discussed herein should be interpreted as being included within the broad term "memory." Similarly, any potential processing element, module, and machine described herein should be interpreted as being included within the broad term "microprocessor" or "processor." In addition, in various embodiments, the processor, memory, network card, bus, storage device, related peripheral devices, and other hardware elements described herein can be implemented by a processor, memory, and other related devices configured by software or firmware to simulate or virtualize the functionality of these hardware elements.

[0151] The computer program logic that implements all or part of the functions described herein is embodied in various forms, including but not limited to source code form, computer executable form, hardware description form, and various intermediate forms (e.g., mask works, or forms generated by an assembler, compiler, linker, or locator). In one example, the source code includes a series of computer program instructions implemented in various programming languages, such as object code, assembly language, or high-level languages ​​such as OpenCL, RTL, Verilog, VHDL, Fortran, C, C++, JAVA, or HTML, for various operating systems or operating environments. The source code can define and use various data structures and communication messages. The source code can be in a computer executable form (e.g., by an interpreter), or the source code can be converted (e.g., by a translator, assembler, or compiler) to a computer executable form.

[0152] In the discussion of the above embodiments, capacitors, buffers, graphic elements, interconnect boards, clocks, DDR, camera sensors, converters, inductors, resistors, amplifiers, switches, digital cores, transistors and / or other components can be easily replaced, substituted or otherwise modified to suit specific circuit requirements. In addition, it should be noted that the use of complementary electronic devices, hardware, non-transitory software, etc. provides equally viable options for implementing the teachings of the present disclosure.

[0153] In one example embodiment, any number of circuits of the accompanying drawings can be implemented on a board of an associated electronic device. The board can be a general circuit board that can accommodate various components of the electronic system inside the electronic device and further provide connectors for other peripheral devices. More specifically, the board can provide an electrical connection through which other components of the system can communicate electrically. Any suitable processor (including a digital signal processor, a microprocessor, a supporting chipset, etc.), a storage element, etc. can be appropriately coupled to the board according to specific configuration requirements, processing requirements, computer design, etc. Other components, such as external memory, additional sensors, audio / video display controllers, and peripherals, can be connected to the board as a plug-in card, via a cable, or integrated into the board itself. In another example embodiment, the circuits of the accompanying drawings can be implemented as independent modules (e.g., devices with related components and circuits configured to perform specific applications or functions) or as plug-in modules inserted into dedicated hardware of an electronic device.

[0154] Note that, through the numerous examples provided here, interactions can be described based on two, three, four or more electrical components. However, this is done only for clarity and example. It should be understood that the system can be combined in any suitable manner. Along similar design alternatives, any components, modules and elements shown in the figures can be combined in various possible configurations, all of which are obviously within the broad scope of the present disclosure. In some cases, it may be easier to describe one or more functions of a given set of processes by referring only to a limited number of electrical components. It should be understood that the circuits taught by the drawings and the circuits taught therein are easily expandable and can accommodate a large number of components and more complex / precise arrangements and configurations. Therefore, the examples provided should not limit the scope or inhibit the broad teachings of circuits that may be applied to countless other architectures.

[0155] Numerous other variations, substitutions, changes, alterations, and modifications may be ascertained by those skilled in the art, and the present disclosure is intended to include all such variations, substitutions, changes, alterations, and modifications that fall within the scope of the appended claims. To assist the United States Patent and Trademark Office (USPTO) and any reader of any patent granted by this application in interpreting the appended claims, applicants wish to note that applicants: (a) do not intend any of the appended claims to invoke 35 U.S.C. §112(f) as it existed on the date of filing this application unless the words "means" or "step" are specifically used in a particular claim; and (b) do not intend any statement in this disclosure to limit the present disclosure in any manner not otherwise reflected in the appended claims.

Claims

1. A circuit for determining a bioimpedance quantity, comprising: a first impedance circuit coupled to a first pin of the circuit, the first pin configured to couple with a first end of a portion of a body of a subject, wherein the first impedance circuit is configured to selectively couple a first impedance to the first pin; a second impedance circuit coupled to a second pin of the circuit, the second pin configured to couple with a second end of the portion of the body, wherein the second impedance circuit is configured to selectively couple a second impedance to the second pin; and A voltage measurement circuit coupled to the first pin and the second pin, the voltage measurement circuit being configured to: determining a first voltage difference between the first pin and the second pin with the first impedance coupled to the first pin and the second impedance decoupled from the second pin; and With the first impedance decoupled from the first pin and the second impedance coupled to the second pin, a second voltage difference between the first pin and the second pin is determined, wherein the first voltage difference and the second voltage difference are used to compensate for an error due to electrode contact impedance in determining the bio-impedance amount of the part of the body of the subject.

2. The circuit of claim 1 , wherein: The first impedance circuit comprises: a first impedance coupled to ground of the circuit; and a first switch coupled between the first impedance and the first pin, the first switch selectively coupling the first impedance to the first pin; as well as The second impedance circuit comprises: a second impedance coupled to ground of the circuit; and A second switch is coupled between the second impedance and the second pin, the second switch selectively coupling the second impedance to the second pin.

3. The circuit of claim 1, further comprising a signal generator configured to be coupled to the body through a third pin, the signal generator applying a signal to the body for the determination of the first voltage difference and the determination of the second voltage difference.

4. The circuit of claim 3, wherein the signal applied to the body via the signal generator comprises a sinusoidal signal.

5. The circuit of claim 1 , wherein the circuit further comprises a processor coupled to the first impedance circuit, the second impedance circuit, and the voltage measurement circuit, the processor being configured to: causing the first impedance circuit to couple the first impedance to the first pin; causing the voltage measurement circuit to determine the first voltage difference when the first impedance circuit has a first impedance coupled to the first pin; causing the second impedance circuit to couple the second impedance to the second pin; and The voltage measurement circuit is caused to determine the second voltage difference when the second impedance circuit has a second impedance coupled to the second pin.

6. The circuit of claim 5, wherein the processor is further configured to: enabling the first impedance circuit to decouple the first impedance from the first pin; causing the second impedance circuit to decouple the second impedance from the second pin; and When the first impedance circuit has a first impedance decoupled from the first pin and a second impedance decoupled from the second pin, the voltage measurement circuit is enabled to determine a third voltage difference, wherein the third voltage difference is compensated by the first voltage difference and the second voltage difference to determine the bio-impedance amount.

7. The circuit of claim 1, wherein the first impedance comprises a first capacitor, and wherein the second impedance comprises a second capacitor.

8. The circuit of claim 1 , wherein the first pin is configured to couple to a first electrode configured to be positioned on a first end of the portion of the body of the subject, wherein the second pin is configured to couple to a second electrode configured to be positioned on a second end of the portion of the body of the subject, and wherein the portion of the body of the subject generates bioimpedance.

9. A system for determining a bioimpedance value, comprising: a first electrode configured to be positioned on a first end of a portion of a subject's body; a second electrode configured to be positioned on a second end of the portion of the body; and a circuit coupled to the first electrode and the second electrode, the circuit being configured to determine a voltage difference between the first electrode and the second electrode, the circuit comprising: a first impedance circuit coupled to the first electrode, the first impedance circuit configured to selectively couple a first impedance between the first electrode and a circuit ground; a second impedance circuit coupled to the second electrode, the second impedance circuit configured to selectively couple a second impedance between the second electrode and a circuit ground; and A voltage measurement circuit is coupled to the first electrode and the second electrode, the voltage measurement circuit being configured to determine a voltage difference between the first electrode and the second electrode when the first impedance is selectively coupled between the first electrode and a ground of the circuit and the second impedance is selectively coupled between the second electrode and the ground of the circuit.

10. The system of claim 9, wherein to determine a voltage difference between the first electrode and the second electrode when the first impedance is selectively coupled and the second impedance is selectively coupled, the circuit is further configured to: determining a first voltage difference between the first electrode and the second electrode with the first impedance coupled between the first electrode and a ground of the circuit and the second impedance decoupled between the second electrode and the ground of the circuit; and A second voltage difference between the first electrode and the second electrode is determined when the first impedance is decoupled between the first electrode and the ground of the circuit and the second impedance is coupled between the second electrode and the ground of the circuit, and the first voltage difference and the second voltage difference are used to compensate for an error in a third voltage difference caused by electrode contact impedance in determining the bio-impedance value of the part of the body of the subject.

11. The system of claim 10, wherein the circuit determines the third voltage difference in a configuration having the first impedance decoupled from between the first electrode and ground of the circuit and the second impedance decoupled from between the second electrode and ground of the circuit.

12. The system of claim 9, wherein: The first impedance circuit comprises: a first impedance coupled to ground of the circuit; and a first switch coupled between the first impedance and the first electrode, the first switch configured to selectively couple the first impedance to the first electrode; as well as The second impedance circuit comprises: a second impedance coupled to ground of the circuit; and A second switch is coupled between the second impedance and the second electrode, the second switch being configured to selectively couple the second impedance to the second electrode.

13. The system of claim 12, wherein the circuit further comprises a controller coupled to the first switch and the second switch, wherein the controller causes the first switch and the second switch to switch states to selectively couple the first impedance to the first electrode and selectively couple the second impedance to the second electrode.

14. The system of claim 9, wherein the circuit comprises an instrumentation amplifier inAmp having a positive input coupled to the first electrode and a negative input coupled to the second electrode, the inAmp being used to determine a voltage difference between the first electrode and the second electrode.

15. The system of claim 9, wherein the circuit further comprises a signal generator coupled to a third electrode configured to be located on a body, wherein the signal generator is configured to apply a signal to the body to generate a voltage difference.

16. The system of claim 9, wherein the first impedance comprises a first capacitor, and wherein the second impedance comprises a second capacitor.

17. A method for determining a bioimpedance value, comprising: determining, by the circuit with the circuit having a first configuration, a first voltage difference between a first electrode located at a first end of a portion of a body of a subject and a second electrode located at a second end of the portion of the body; After determining the first voltage difference, changing from the first configuration to a second configuration through the circuit; and in a case where the circuit has a second configuration, determining a second voltage difference between the first electrode and the second electrode by the circuit, wherein the first voltage difference and the second voltage difference are used to compensate for an error due to electrode contact impedance to determine a bioimpedance value of the portion of the body of the subject, wherein the first configuration has a first impedance of a circuit coupled to the first electrode and a second impedance of the circuit decoupled from the second electrode, wherein the second configuration has a first impedance decoupled from the first electrode and a second impedance coupled to the second electrode, and wherein changing from the first configuration to the second configuration includes decoupling the first impedance from the first electrode through the circuit and coupling the second impedance to the second electrode through the circuit.

18. The method according to claim 17, wherein: Determining a first voltage difference between the first electrode and the second electrode includes: When the circuit has a first configuration, a first voltage of the first electrode and a first voltage of the second electrode are compared by a voltage measurement circuit of the circuit; and outputting the first voltage difference based on a comparison between the first voltage of the first electrode and the first voltage of the second electrode by the voltage measurement circuit; and Determining a second voltage difference between the first electrode and the second electrode includes: When the circuit has the second configuration, the second voltage of the first electrode and the second voltage of the second electrode are compared by the voltage measurement circuit; and The second voltage difference is output by the voltage measurement circuit based on comparison between the second voltage of the first electrode and the second voltage of the second electrode.

19. The method of claim 17, further comprising applying a signal to the body via a signal generator of the circuit to generate the first voltage difference and the second voltage difference.

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