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).
defibrillator; delivered energy; internal capacitance; internal inductance; internal resistance; stored energy
Date of this Version
Babbs, Charles F. and Whistler, S J., "Evaluation of the operating internal resistance, inductance, and capacitance of intact damped sine wave defibrillators" (1978). Weldon School of Biomedical Engineering Faculty Publications. Paper 130.