A circuit for measuring body impedance comprising a voltage source having a predetermined frequency and a current source; a first pair of electrodes adapted to receive one portion of the body for applying said current source to said body; a second pair of electrodes adapted to receive another portion of the body for sensing a voltage therebetween; a comparator having first and second inputs and an output for producing an output signal based on signals applied to said first and second inputs; an instrumentation amplifier arrangement coupled to one of said comparator inputs and responsive to the voltage across the second pair of electrodes for providing an input signal to said first comparator input; a variable resistor coupled to the second input of said comparator and responsive to said voltage source for developing a first voltage signal applied to said second comparator input; and a processor responsive to the output signal of the comparator for controlling the resistance of the variable resistor to cause a corresponding change in said first voltage, whereby when said voltage at said first input corresponds to the voltage at said second input of said comparator; said comparator output signal transitions from a first state to a second state to cause the processor to terminate resistor adjustment, whereby the body impedance value corresponds to the resistance value of the variable resistor.

Apparatus and method for measuring bioelectric impedance

A body fat measuring apparatus for measuring body fat in a patient's body comprises apparatus for simultaneously measuring an impedance between the patient's feet, and for measuring the patient's height and the patient's weight, and a calculator for calculating body fat from the measured impedance value, height and weight. The calculator estimates body density using a formula having a correction term either for increasing the body density upon increase of the impedance compared to the original impedance or a correction term for decreasing the body density upon increase of the weight with respect to the original weight.

Apparatus for measuring body fat

A method and an apparatus for measuring quantities relating to a person's cardiac activity, such as for example quantities proportional to heart rate, cardiac stroke volume and cardiac output. A person is positioned on a measuring support (S), so that a blood flow pulse caused by a stroke of heart is matched by a change in a person's weight (G). Said change of weight is recorded and the recorded changes of weight are used for deriving information about a person's cardiac activity, such as for example about stroke volume and cardiac output as well as heart rate.

Method and apparatus for measuring quantities relating to a person's cardiac activity

Method and apparatus for measuring body fat

A method and apparatus is provided for measuring the volume and density of an object, including a living being, which avoids the necessity of immersing the subject in a liquid medium. Where the subject is a living being, the percentage of body fat may readily be determined from the density value. The density of the subject is measured by recording the weight of the subject for several different temperatures of a fluid, preferably air, surrounding the subject. The apparent weight change of the subject at the different measured temperatures of surrounding air represents changes in the buoyant forces exerted by the air on the subject at different air densities. The buoyant force acting on the subject is calculated from these measurements, and the volume of the subject is determined from its relationship with the buoyant force. The density of the subject can then be calculated from the volume and weight parameters. Where the subject is a human being or animal, its density is monotonically related to its fat content.

Method and apparatus for measuring the density of an object including a living being

The fat-to-lean ratio of tissue on a human subject is measured by the subject standing on a platform (100), raising his or her heels, then allowing his or her weight to fall onto the board near a transducer to produce a force. A sensor transmits a voltage signal to an analog-to-digital (A/D) converter. The subject's stomach (300), buttocks (310), and other flesh will continue moving in a downward direction (335) (below their rest position) after the skeleton has stopped moving. This results in a downward force on the board which is registered as a data peak (580) in a computer through the action of the sensor and the A/D converter. Tissue elasticity will cause the stomach and buttocks to then move upward (350), above their normal resting position. This will result in a lessening of the force and a corresponding minimum (590) in the output wave. The wave thus is a damped sinusoid which can be analyzed using various means to result in an "excess pendulous fatty tissue index" which is indicated by humanly sensible readout display.

Lloyd D. Clark

Papers

Dynamic measuring system for determining the amount of excess body fat