Method and apparatus for calibrating the energy output of a defibrillator

Abstract

A defibfillator has a self healing storage capacitor connected in parallel with a safety resistor, and a microcontroller. Upon receipt of a calibration request, the microcontroller charges the capacitor to a charging voltage greater than a starting voltage, then discharges the capacitor through the safety resistor. As the capacitor is discharging, the microcontroller continuously measures the voltage across the capacitor. When the microcontroller detects that the voltage across the capacitor is less than or equal to a starting voltage, a timer in the microcontroller is started. When the microcontroller detects that the voltage across the capacitor is less than or equal to an ending voltage, the timer in the microcontroller is stopped. The microcontroller then determines an elapsed time between the time the timer was started and stopped. The microcontroller then calculates a capacitance value of the capacitor based on the starting voltage, the ending voltage, and the elapsed time. This capacitance value is stored in memory, and used to calibrate the energy output of the defibrillator by assuring that the self healing storage capacitor has been charged to a voltage level sufficient to deliver the desired amount of energy to a patient.