Apparatus for measuring the bioelectrical impedance of a living body

• US 20020079910A1
• Filed: 03/04/2002
• Published: 06/27/2002
• Est. Priority Date: 08/26/1999
• Status: Active Grant

• Current Assignee: Tanita Corporation (Tanita)
• Original Assignee: Tanita Corporation (Tanita)
• Inventors: Fukuda, Yoshinori
• Granted Patent: US 6,724,200 B2
• Time in Patent Office: Days
• US Class Current: 324/692
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body

Abstract

Disclosed is an improved bioelectrical impedance gauge which is so designed that the high-frequency current flowing between two selected points in a living body may be detected in the vicinity of either selected point, and that the voltage appearing between two points selected in the current passage in which the high-frequency current flows may be applied to a high-impedance buffer circuit proximate to the two points selected in the current passage.

Claims

2. An apparatus for measuring the bioelectrical impedance of a living body in which the impedance of the living body can be determined by making a weak electric current of high-frequency flow between two selected points on the living body and by determining the voltage between said two selected points or between another two points selected in the current passage in which the weak electric current flows characterized in that it comprises:

a measuring apparatus including a high-frequency current source, a high-frequency current determining section and a voltage determining section;

at least one high-frequency current supplying probe connected to said high-frequency current source via a shielded-conductor cable;

a pair of high-frequency current supplying electrodes to be applied to said two selected points;

two voltage measuring probes connected to said voltage determining section via shielded-conductor cables; and

a pair of voltage measuring electrodes to be applied to said two selected points or said another two points, each of said voltage measuring probes having a high input-impedance amplifier connected to and positioned in the vicinity of one or the other voltage measuring electrode.

1. An apparatus for measuring the bioelectrical impedance of a living body in which the impedance of the living body can be determined by making a weak electric current of high-frequency flow between two selected points on the living body and by determining the voltage between said two selected points or between another two points selected in the current passage in which the weak electric current flows characterized in that it comprises:

a measuring apparatus including a high-frequency current source, a high-frequency current determining section and a voltage determining section;

at least one high-frequency current supplying probe connected to said high-frequency current source via a shielded-conductor cable;

a pair of high-frequency current supplying electrodes to be applied to said two selected points;

two voltage measuring probes connected to said voltage determining section via shielded-conductor cables; and

a pair of voltage measuring electrodes to be applied to said two selected points or said another two points,

said high-frequency current supplying probe having a high-frequency current detector connected to and positioned in the vicinity of one of said pair of high-frequency current supplying electrodes.

3. An apparatus for measuring the bioelectrical impedance of a living body according to claim 1 or 2 wherein two high-frequency current supplying probes are connected to said high-frequency current source via shielded-conductor cables.

4. An apparatus for measuring the bioelectrical impedance of a living body according to claim 1 or 2 wherein one high-frequency current supplying probe is connected to said high-frequency current source via a shielded cable, said high-frequency current supplying probe having a high-frequency current detector connected to and positioned in the vicinity of one of the high-frequency current supplying electrodes, and the other high-frequency current supplying electrode being directly connected to said high-frequency current source.

5. An apparatus for measuring the bioelectrical impedance of a living body according to claim 1 wherein said high-frequency current detector comprises a protection circuit connected to one or the other high-frequency current supplying electrode, a reference resistor for detecting the high-frequency current, said reference resistor being connected to said protection circuit at one end, and to said high-frequency current source at the other end via the shielded-conductor cable, and a differential amplifier the input terminals of which are connected across said reference resistor, and the output terminal of which differential amplifier is connected to said high-frequency current determining section via the shielded-conductor cable and an associated impedance matching resistor.

6. An apparatus for measuring the bioelectrical impedance of a living body according to claim 1 wherein said high input-impedance amplifier comprises a protection circuit connected to one or the other voltage measuring electrode, a high-input impedance buffer circuit connected at its input terminal to said protection circuit and at its output terminal to said voltage determining section via the shielded-conductor cable and an associated impedance matching resistor.

6-1. An apparatus for measuring the bioelectrical impedance of a living body according to any of preceding claims wherein all shielded cables are of same length.