초록 ▼

A protection circuit for a defibrillator that prevents a defibrillator pulse from being generated if the impedance between the defibrillator\s electrode leads is not characteristic of the impedance between a pair of defibrillator electrodes properly connected to the defibrillator. The impedance meas

A protection circuit for a defibrillator that prevents a defibrillator pulse from being generated if the impedance between the defibrillator\s electrode leads is not characteristic of the impedance between a pair of defibrillator electrodes properly connected to the defibrillator. The impedance measuring circuit applies a current to the electrode leads and the resulting voltage is measured to provide an indication of the electrode\s impedance. The current is applied between the electrodes at about 33 kHz to approximate the impedance between a pair of defibrillator electrodes during a defibrillation pulse. The output of the measurement circuit is converted to an 8 bit word by an analog-to-digital converter and read by a microprocessor which compares the measured impedance to various impedance values in order to either generate an enable signal for the defibrillator or display messages indicative of open or short circuited electrode leads or a patient monitoring electrode connected to the electrode leads. The impedance measurement circuit operates in either of two ranges which are selected by the microprocessor on the basis of the measured impedance values.

대표청구항 ▼

An impedance measurement circuit for measuring an impedance in a device under test, comprising: a pair of measurement leads which are adapted to be connected to said device under test; an AC current source connected between said measurement leads so that the voltage between said leads is proportiona

An impedance measurement circuit for measuring an impedance in a device under test, comprising: a pair of measurement leads which are adapted to be connected to said device under test; an AC current source connected between said measurement leads so that the voltage between said leads is proportional to the impedance of said device under test; and an amplifier having a pair of differential inputs connected between said leads, said differential inputs having an input impedance therebetween that is substantially greater than the impedance of said device under test; range adjustment means for causing an output signal at the output of said amplifier to have a voltage that is proportional to a relatively large multiple of said impedance in a low impedance range and to a relatively small multiple of said impedance in a high impedance range, thereby increasing the range of said impedance measurement circuit for a predetermined sensitivity and range of output signal voltages; and range control means controlling the operation of said range adjusting means, said range control means causing said impedance measurement circuit to initially measure the impedance between said electrodes in said low range and switching said impedance measuring circuit to said high range when the voltage of said output signal is a value indicative of an impedance larger than a first predetermined value.