Abstract: Electrostimulator (2), comprising an interface for connecting a working electrode (2), as well as a pulse generator that is connected on the output side to the interface for transmitting electrical pulses to the working electrode (10), with a first measuring instrument (10) that is connected to the interface for measuring the electrical voltage present at the interface and/or the electrical current flowing over the interface, as well as an arithmetic unit, connected on the input side to the first measuring instrument, for computing an output signal reflecting the capacity of the working electrode in dependence on the current and/or voltage at the interface.