Piezo-injector i.e. fuel injector, condition determining method for e.g. self-ignited internal combustion engine, involves changing actuating variable to obtain original characteristic of function variable of actuator and/or injector

摘要

The method involves providing a piezo-injector with an actuator (310) having original characteristic of a function variable. An electrical capacitance of the actuator is determined by electrical capacitance measurement, and an equivalent masses signal is measured from the determined electrical capacitance. An actuating variable of the actuator is changed in case of deviation of the equivalent masses signal from a masses signal that is to be estimated, so that the original characteristic of the function variable of the actuator and/or the piezo-injector is obtained.