Patent ID: 7218961

Claim:
A percent body fat measuring apparatus comprising: first and second electrodes with which a living body is brought into contact; a detection resistor of which one terminal is connected to the second electrode; a signal generator which produces a measurement signal and applies a produced measurement signal between the first electrode and the other terminal of the detection resistor; a level detector for detecting the level of a signal which develops between the terminals of the detection resistor and is an object of detection; and a percent body fat computer for determining percent body fat on the basis of a result of detection operation performed by the level detector, wherein a measurement signal produced by the signal generator is analogous to a half-wave waveform; wherein the level detector detects the level of a waveform analogous to a half-wave of the signal to be detected; wherein the signal generator includes; a pulse generator for generating a pulse signal indicating the cycle of the measurement signal, a first resistor of which one terminal is connected to an output terminal of the pulse generator, a second resistor of which one terminal is connected to the other terminal of the first resistor, a first p-n-p transistor of which base is connected to the other terminal of the second resistor, of which collector is grounded, and of which emitter is connected to a positive power supply via a third resistor, a first capacitor of which one terminal is connected to a node between the first and the second resistors and of which other terminal is connected to the emitter of the first p-n-p transistor, and a second capacitor connected between a base of the first p-n-p transistor and a ground level; wherein the level detector includes: a third capacitor of which one terminal is connected to the second electrode, a second p-n-p transistor of which base is connected to the other terminal of the third capacitor, of which collector is grounded via a fourth resistor, and of which emitter is connected to the positive power supply via a fifth resistor, a bias circuit for supplying a bias current to the base of the second p-n-p transistor, and a rectifier circuit for rectifying an output from the collector of the second p-n-p transistor; wherein the pulse generator includes: an original pulse generator which is formed from a microcomputer and produces the original pulse signal indicating the cycle of the measurement signal, a sixth resistor of which one terminal is connected to the positive power supply, and a switching element of which one terminal is connected to the other terminal of the sixth resistor, of which other terminal is grounded, and of which connection is controlled by an original pulse signal; wherein a node between the sixth resistor and the switching element is a terminal for outputting the pulse signal.