Impedance analyzer

• US 9,050,017 B2
• Filed: 07/23/2012
• Issued: 06/09/2015
• Est. Priority Date: 01/04/2012
• Status: Active Grant

• Current Assignee: National Chi Nan University
• Original Assignee: National Chi Nan University
• Inventors: Ching, Tak-Shing, Sun, Tai-Ping, Liu, Chia-Ming
• Primary Examiner(s): DOUGHERTY, SEAN PATRICK
• Application Number:
  US13/555,616
• Publication Number:
  US 20130169296A1
• Time in Patent Office: 1,051 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: G01R 27/26 Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
• CPC Class Codes: G01R 31/2882 Testing timing characteristics

Abstract

An impedance analyzer includes: a control voltage generating unit for generating a control voltage that has a predetermined amplitude value; a measuring unit operable to provide an output current, which has an amplitude value corresponding to that of the control voltage, for flowing through first and second body portions of a biological target, and to generate a measurement voltage that has an amplitude value corresponding to a difference between voltages at the first and second body portions attributed to flow of the output current therethrough; and a calculating module operable to determine an electrical impedance between the first and second body portions according to a predetermined adjustment value and the amplitude value of the measurement voltage.

Claims

1. An impedance analyzer suitable to be coupled electrically across first and second body portions of a biological target for determining electrical impedance therebetween, comprising:

a readout module including

a control voltage generating unit operable to generate a control voltage that has a predetermined amplitude value, and including

an oscillator circuit operable for generating an oscillation signal, and

an amplifying circuit that is connected electrically to said oscillator circuit for receiving the oscillation signal from said oscillator circuit, and that is operable to generate the control voltage based on the oscillation signal received by said amplifying circuit,

a measuring unit adapted to be coupled electrically across the first and second body portions, connected electrically to said control voltage generating unit for receiving the control voltage from said control voltage generating unit, and operable to provide an output current according to the control voltage received by said measuring unit for flowing through the first and second body portions, the output current having an amplitude value that corresponds to the amplitude value of the control voltage received by said measuring unit, said measuring unit being further operable to generate a measurement voltage that has an amplitude value corresponding to a difference between voltages at the first and second body portions attributed to flow of the output current through the first and second body portions; and

a calculating module having stored therein a predetermined adjustment value, connected electrically to said measuring unit for receiving the measurement voltage from said measuring unit, and operable to determine the electrical impedance between the first and second body portions according to the predetermined adjustment value and the amplitude value of the measurement voltage received by said calculating module;

wherein said amplifying circuit includes

first and second resistors, and

a first operational amplifier having a first input terminal that is connected electrically to said oscillator circuit via said first resistor for receiving the oscillation signal from said oscillator circuit, a grounded second input terminal, and an output terminal that is connected electrically to said first input terminal of said first operational amplifier via said second resistor, said first operational amplifier being operable to generate the control voltage for output via said output terminal thereof.

2. The impedance analyzer as claimed in claim 1, wherein said measuring unit includes:

a voltage-controlled current generator connected electrically to said control voltage generating unit for receiving the control voltage from said control voltage generating unit, operable to generate the output current according to the control voltage received by said voltage-controlled current generator, and adapted to be coupled electrically across the first and second body portions for providing the output current for flowing through the first and second body portions;

first and second buffers adapted to be coupled electrically to the first and second body portions for receiving the voltages at the first and second body portions, and operable to output first and second voltages according to the voltages received by said first and second buffers, respectively; and

a differential amplifier connected electrically to said first and second buffers for receiving the first and second voltages from said first and second buffers, respectively, and operable to output the measurement voltage according to the first and second voltages received by said differential amplifier, the amplitude value of the measurement voltage corresponding to a difference between the first and second voltages received by said differential amplifier.

3. The impedance analyzer as claimed in claim 2, wherein said voltage-controlled current generator includes:

a third resistor; and

a second operational amplifier having a first input terminal that is connected electrically to said control voltage generating unit via said third resistor for receiving the control voltage from said control voltage generating unit and that is adapted to be coupled electrically to the first body portion, a grounded second input terminal, and an output terminal that is adapted to be coupled electrically to the second body portion, a current flowing through said third resistor serving as the output current.

4. The impedance analyzer as claimed in claim 3, wherein:

said first buffer includes a third operational amplifier having a first input terminal, a second input terminal that is connected electrically to said first input terminal of said second operational amplifier, and an output terminal that is connected electrically to said first input terminal of said third operational amplifier, said third operational amplifier being operable to generate the first voltage corresponding to the voltage at the first body portion for output via said output terminal of said third operational amplifier, the first voltage having an amplitude value corresponding to the amplitude value of the voltage at the first body portion; and

said second buffer includes a fourth operational amplifier having a first input terminal, a second input terminal that is connected electrically to said output terminal of said second operational amplifier, and an output terminal that is connected electrically to said first input terminal of said fourth operational amplifier, said fourth operational amplifier being operable to generate the second voltage corresponding to the voltage at the second body portion for output via said output terminal of said fourth operational amplifier, the second voltage having an amplitude value corresponding to the amplitude value of the voltage at the second body portion.

5. The impedance analyzer as claimed in claim 4, wherein said differential amplifier includes:

fourth, fifth, sixth, and seventh resistors; and

a fifth operational amplifier having

a first input terminal connected electrically to said output terminal of one of said third and fourth operational amplifiers via said fifth resistor for receiving a corresponding one of the first and second voltages from said one of said third and fourth operational amplifiers,

a second input terminal connected electrically to said output terminal of the other of said third and fourth operational amplifiers via said fourth resistor for receiving a corresponding one of the first and second voltages from the other of said third and fourth operational amplifiers, and connected electrically to ground via said sixth resistor, and

an output terminal connected electrically to said first input terminal of said fifth operational amplifier via said seventh resistor, said fifth operational amplifier being operable to generate the measurement voltage for output via said output terminal thereof according to the first and second voltages received thereby.

6. The impedance analyzer as claimed in claim 1, wherein the predetermined adjustment value corresponds to the amplitude value of the output current generated by said measuring unit.

7. A readout module suitable to be coupled electrically across first and second body portions of a biological target so as to generate a measurement voltage according to a difference between voltages at the first and second body portions attributed to flow of an output current through the first and second body portions, said readout module comprising:

a control voltage generating unit operable to generate a control voltage that has a predetermined amplitude value; and

including

an oscillator circuit operable for generating an oscillation signal, and

an amplifying circuit that is connected electrically to said oscillator circuit for receiving the oscillation signal from said oscillator circuit, and that is operable to generate the control voltage based on the oscillation signal received by said amplifying circuit; and

a measuring unit adapted to be coupled electrically across the first and second body portions, connected electrically to said control voltage generating unit for receiving the control voltage from said control voltage generating unit, and operable to provide the output current according to the control voltage received by said measuring unit for flowing through the first and second body portions, the output current having an amplitude value that corresponds to the amplitude value of the control voltage received by said measuring unit, said measuring unit being further operable to generate the measurement voltage that has an amplitude value corresponding to the difference between the voltages at the first and second body portions;

wherein said amplifying circuit includes

first and second resistors, and

a first operational amplifier having a first input terminal that is connected electrically to said oscillator circuit via said first resistor for receiving the oscillation signal from said oscillator circuit, a grounded second input terminal, and an output terminal that is connected electrically to said first input terminal of said first operational amplifier via said second resistor, said first operational amplifier being operable to generate the control voltage for output via said output terminal thereof.

8. The readout module as claimed in claim 7, wherein said measuring unit includes:

a voltage-controlled current generator connected electrically to said control voltage generating unit for receiving the control voltage from said control voltage generating unit, operable to generate the output current according to the control voltage received by said voltage-controlled current generator, and adapted to be coupled electrically across the first and second body portions for providing the output current for flowing through the first and second body portions;

first and second buffers adapted to be coupled electrically to the first and second body portions for receiving the voltages at the first and second body portions, and operable to output first and second voltages according to the voltages received by said first and second buffers, respectively; and

a differential amplifier connected electrically to said first and second buffers for receiving the first and second voltages from said first and second buffers, respectively, and operable to output the measurement voltage according to the first and second voltages received by said differential amplifier, the amplitude value of the measurement voltage corresponding to a difference between the first and second voltages received by said differential amplifier.

9. The readout module as claimed in claim 8, wherein said voltage-controlled current generator includes:

a third resistor; and

a second operational amplifier having a first input terminal that is connected electrically to said control voltage generating unit via said third resistor for receiving the control voltage from said control voltage generating unit and that is adapted to be coupled electrically to the first body portion, a grounded second input terminal, and an output terminal that is adapted to be coupled electrically to the second body portion, a current flowing through said third resistor serving as the output current.

10. The readout module as claimed in claim 9, wherein:

said first buffer includes a third operational amplifier having a first input terminal, a second input terminal that is connected electrically to said first input terminal of said second operational amplifier, and an output terminal that is connected electrically to said first input terminal of said third operational amplifier, said third operational amplifier being operable to generate the first voltage corresponding to the voltage at the first body portion for output via said output terminal of said third operational amplifier, the first voltage having an amplitude value corresponding to the amplitude value of the voltage at the first body portion; and

said second buffer includes a fourth operational amplifier having a first input terminal, a second input terminal that is connected electrically to said output terminal of said second operational amplifier, and an output terminal that is connected electrically to said first input terminal of said fourth operational amplifier, said fourth operational amplifier being operable to generate the second voltage corresponding to the voltage at the second body portion for output via said output terminal of said fourth operational amplifier, the second voltage having an amplitude value corresponding to the amplitude value of the voltage at the second body portion.

11. The readout module as claimed in claim 10, wherein said differential amplifier includes:

fourth, fifth, sixth, and seventh resistors; and

a fifth operational amplifier having

a first input terminal connected electrically to said output terminal of one of said third and fourth operational amplifiers via said fifth resistor for receiving a corresponding one of the first and second voltages from said one of said third and fourth operational amplifiers,

a second input terminal connected electrically to said output terminal of the other of said third and fourth operational amplifiers via said fourth resistor for receiving a corresponding one of the first and second voltages from the other of said third and fourth operational amplifiers, and connected electrically to ground via said sixth resistor, and

an output terminal connected electrically to said first input terminal of said fifth operational amplifier via said seventh resistor, said fifth operational amplifier being operable to generate the measurement voltage for output via said output terminal thereof according to the first and second voltages received thereby.