Systems and methods for calibrating a tester that is used to calibrate conducted electrical weapons (“CEWs”). Providing a known magnitude of current for a calculated amount of time to a measurement capacitor stores a known amount of charge on the capacitor. The voltage corresponding to the known charge can be used to measure the amount of charge provided by a pulse of a stimulus signal while calibrating a CEW. A real-time clock may be used to ensure the accuracy of the time measurements over long time periods. Accurate measurement of resistors in a load circuit provides further tester accuracy.