Method for measuring capacitance and equivalent parallel resistance

摘要

C_X is measured in the presence of R_P by charging C_X with a constant current I_C for a period time and taking four (time, voltage) pairs: (t_A,V_A), (t_B,V_B), (t_C,V_C) and (t_D,V_D). The first pair are sufficiently close together that the short straight line segment connecting (t_A, V_A) and (t_B, V_B) is not significantly different from the corresponding segment of a true graph of the capacitor's actual charging. A similar requirement is imposed on the time interval between t_C and t_D. The time interval t_At_B need not be the same as t_Ct_D. The interval t_Bt_C should be long enough that if there is significant R_P present then there is at least a discernable difference between the true graph and a straight line between the first pair and the second. C_X and R_P are computed as a function of the four pairs and I_C, and C_X may then be diminished by a previously measured value for a stray capacitance present in the absence of C_X.