Method and device for measurement of electrical bioimpedance

• US 7,706,872 B2
• Filed: 11/28/2003
• Issued: 04/27/2010
• Est. Priority Date: 12/06/2002
• Status: Expired due to Fees

• Current Assignee: Tallinn Technical University
• Original Assignee: Tallinn Technical University
• Inventors: Kink, Andres, Parve, Toomas, Min, Mart, Land, Raul
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): DANEGA, RENEE A
• Application Number:
  US10/537,643
• Publication Number:
  US 20060100539A1
• Time in Patent Office: 2,342 Days
• Field of Search: 600/547, 600/536, 378/70, 607/88, 324/525
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body

Abstract

A method of measuring of an electrical bio-impedance, the method being characterized in that a symmetrical bipolar pulse-form periodical excitation signal (electrical current or voltage) is applied to the input (11) of the bio-object (1), a corresponding reaction of the bio-object to the mentioned excitation signal is measured from the output (12), which is connected to the input (201) of the synchronous detector (200). A symmetrical bipolar pulse-form periodical signal is also applied to the reference input (202) of the synchronous detector (200), whereby both pulse-form signals are shortened by the predetermined time interval in each half period of the signal, said time intervals being different for the excitation and reference signals. The proposed method ensures an increased accuracy of the impedance analysis by decreasing the influence of the higher harmonics in the spectra of the excitation and reference signals of the synchronous detectors to the measurement result. The use of the rectangular signals ensures that the device for implementing of the proposed method has a simple design and low power consumption.

Claims

1. A device for measuring of an electrical impedance, of an object, comprising:

an in-phase and a quadrature measurement channels;

a generator of driving signals;

a circuit of an excitation signal, the output of which is connected to an input of the object, wherein first and second outputs of the generator of driving signals are connected to inputs and of reference circuits of synchronous detectors, wherein the generator of driving signals comprises a generator of quadrature signals and two formers of the bipolar rectangular signals;

the circuit of the excitation signal comprises a device for generating a shortened pulse, the control input of which is connected to the output of the auxiliary signal of the generator of quadrature signals, the input is connected to the output of the former of the bipolar rectangular signal, and the output is connected to the input of the bio-object;

the reference voltage circuit of the synchronous detector of the in-phase measurement channel comprises a device for generating of shortened pulse is introduced, the control input of which is connected to the output of the auxiliary signal of the generator of quadrature signals, the input is connected to the output of the former of the bipolar rectangular signal, and the output is connected to the reference input of the synchronous detector;

the reference circuit of the synchronous detector of the quadrature measurement channel comprises a device for generating of shortened pulse, the control input of which is connected to the output of the auxiliary signal of the generator of quadrature signals, the input is connected to the output of the former of the bipolar rectangular signal, and the output is connected to the reference input of the synchronous detector.

2. The device according to claim 1, wherein the generator of quadrature signals comprises a shift register of predetermined bit length and the quadrature triggers.

3. The device according to claim 2, wherein the switching multiplier in the synchronous detectors is implemented on the basis of digital techniques.

4. The device according to in claim 1, wherein the synchronous detectors are implemented on the basis of an analog multiplier.

5. The device according to claim 1, wherein the synchronous detectors are implemented on the basis of a switching multiplier.

6. The device according to claim 4, wherein the switching multiplier in the synchronous detectors is implemented on the basis of mixed signal analogue/digital techniques.