Why are battery power-supply, fiber data transfer and small front-end
size so important ?
combination of a battery-powered front-end and optical fiber offers
minimal leakage currents in both normal operation an under fault
conditions. During normal operation this assures the best possible
rejection of all kinds of interference. Common mode as well as differential
mode interference voltages are therefore reduced far below the amplifier
noise level. Although high CMRR may solve the common mode problem
in mains powered systems, the differential mode interference remains
at least a factor of 10 worse than with our battery powered setup.
An additional advantage of the battery powered setup is the very
high protection for shock-hazard caused by the mains-supply. Because
of the fiber optic data transfer, the safety situation is completely
determined by the capacitance between the subject and the environment.
Because the dimensions of the front-end are very small compared
to the dimensions of the subject and because the front-end is located
very close to the subject, the capacitance between the subject and
the environment is not significantly increased by connecting the
front-end to the subject. Therefore the biopotential measurement
does not alter the situation in terms of protection against shock
hazards and leakage currents are well below the IEC 601-1 CF specifications.