In accordance with the invention, {HEAD ~ this object} is achieved by exciting the active electrode with a HF current, measuring and combining {TAIL ~ values} of the partial currents entering the partial electrodes and generating an alarm signal which depends upon a comparison of this combination of the partial currents with a pre set limit value 
is achieved by measuring
In accordance with the invention , { HEAD ~ this object } is achieved by exciting the active electrode with a HF current , measuring and combining { TAIL ~ values } of the partial currents entering the partial electrodes and generating an alarm signal which depends upon a comparison of this combination of the partial currents with a pre set limit value
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH REL OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH