Patent ID: 7340294

Claim:
Apparatus for assessing the electrical properties of an interface between a patient and electrodes applied to the patient, said apparatus comprising: a carrier signal source couplable to the electrodes, said carrier signal source receiving DC energization and AC energization and outputting two carrier signals comprising an AC signal with a DC offset, the two carrier signals being out of phase with each other by a pre-selected amount, one of said carrier signals being suppliable to a selected one of said electrodes, the other of said carrier signals being suppliable to others of said electrodes; amplifier means comprising at least one amplifier each having a pair of inputs, one of said inputs being couplable to the selected one of the electrodes, the other input being couplable to another of said electrodes, said amplifier producing an output lead signal in which AC and DC offset characteristics result from the electrical properties of the patient interfaces at the electrodes; and signal processing means coupled to said amplifier means and receiving said output lead signal of said amplifier, said signal processing means having means for obtaining and providing a first signal comprising the AC signal characteristics of the output lead signal and for providing a second signal comprising the DC characteristics in the output lead signal, said signal processing means having means employing said first signal to provide a first output indicative of the quality of an interface between the electrodes and the patient and said second signal to provide a second output indicative of the status of the connection between the electrodes and the patient.