Abstract

A method is developed for determining actual values of circuit elements in a damped sine wave (Lown waveform) defibrillator, solely from measurements of the output, using two or more power resistors and a storage oscilloscope. If a defibrillator containing capacitance, C, inductance, L, and internal resistance, Ri, is discharged into increasing 5- to 100-ohm resistive loads, R, it is shown for underdamped output waveforms that aˆ = Ri/2L + R/2L and cˆ = CRi + CR, where aˆ = /[t2 tan(t1/t2)], cˆ = 2 aˆ /[ 2 aˆ + (/t2)2], t1 = time from onset to peak, and t2 = time from onset to first zero crossing of the output waveform on the oscilloscope trace. Linear plots of aˆ vs. R are constructed for seven defibrillators, and values of Ri and L computed as intercept/slope and 1/(2 slope) respectively. C is given by the slope of a linear plot of cˆ vs. R. Delivered energy is accurately predicted as stored energy  R/(Ri + R).

Comments

This is the author accepted manuscript of Babbs C.F., Whistler S.J., Evaluation of the operating internal resistance, inductance, and capacitance of intact damped sine wave defibrillators, Medical Instrumentation 12, 34-37, 1978. Copyright Elsevier, it is made available here CC-BY-NC-ND, and the version of record is available through the publisher http://www.sciencedirect.com/

Keywords

defibrillator; delivered energy; internal capacitance; internal inductance; internal resistance; stored energy

Date of this Version

1978

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