The software for the procedure of definition of parameters of a cap of condenser structure with mobile facings on the basis of use of power action of an electrostatic field is considered. The offered technique allows on one operation of removal volt – capacitance characteristics to define the whole complex of the major parameters of a cap – size of a working air gap, a membrane deflection, electret surface potential and a membrane tension. The expressions for capacity of a cap as a function of specified parameters are obtained. The software is developed for the technique use, allowing to define required parameters of a cap and to estimate their error. The procedure considered in the present work is a not destroying monitoring.