From: sleeper75se_at_yahoo.se
Date: 2001-12-04 10:05:23
Wow!
I'm gone for a few days and there were tons of messages waiting when
I got back. Sometimes, this group has been silent for weeks. What a
nice change!
Jim-M, you say your recordings are noisy. I'd like to make the
distinction between noise and interference. Ignoring the interference
(60Hz hum and muscle-signals) they look pretty good! :-)
Looking at the interference does clearly show the need for more bits
and a high CMRR. Of course, it's easier to get rid of the 50/60Hz hum
with today's more powerful computers.
Doug, I can see you are asking all the right questions.
The reason you are not getting many answers is that the specs you
want require solid understanding of analog design and not many people
has that kind of knowledge. It also take a couple of hours (if you do
the math by hand) to analyze someone elses design, and type up
something legible for others to read. Someone with the right knowlege
might not find it worth the trouble. How many, for instance, have
taken a good look at my active-electrodes schematics, trying to take
it apart, pointing out flaws? No one, is my guess, because it's too
time consuming.
By the way, my analysis of Joergs input stage is forthcoming. :-)
Joerg, or anybody, if you have the time and opportunity, could you
please do some noise measurements on the microcontroller? If you just
short the inputs to the instrumentation-amp together, how many bits
are toggling due to noise at the output? Although cheap, the ADC
inside a microcontroller is not the most noise-free solution.
As for the business model - my view is that all devices on the market
are too expensive to be used as a toy - this group tries to fill that
gap, hence the talk about cost. I agree that what has been produced
so far is not quite of commercial quality, primarily because it lacks
documentation, and is through-hole mounted. But who knows, the
brainmaster looks very much like a hobbyist-project too, so I'm
probably wrong about this.
Be well,
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:32 BST