From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2001-12-12 06:47:39
Michael,
The 6N139 opto couplers in Joerg's ModularEEG and RS232EEG
are around one dollar each. I have looked at dozens of bio
amplifiers and EEGs and all of them have opto isolation. I
can't find one anywhere that doesn't have it. Do you want
to be the only one without it? Isn't $2 worth it? What if
something goes wrong with the PC or a power surge happens?
I really don't think it makes sense to argue over a two
dollar part for extra protection.
Some patients are extraordinarily susceptible to electrical
shock hazards.A normally harmless 60 Hz current can cause
cardiac arrest under certain circumstances. As a result,
manufacturers of bioelectric amplifiers, especially EEG and
ECG equipment, use isolation amplifiers that provide as
much as 10^12 ohms of isolation between the patient and the
AC power line mains cord.
http://www.sensorsmag.com/articles/0199/iso0199/main.shtml
-- Doug
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