I'm using multiple ADC channels on the Robovero expansion board to sample
neural signals captured from human muscles. Because the neural signals are
bipolar and the acceptable range of Robovero ADC is 0-3.3v. I built a
circuit which added 1.5 v to the raw neural signals so that the ADC input is
now between 0v and 3.3 v. However, I observed a lot of impulse noises in the
sampled data, which were random impulses that ranged from 0 to 3.3v.
I also tried to use a function generator to generate a sin wave as the
analog input. Same impulse noises were observed. As long as I connected some
wires to the ADC pins, there would be impulse noises. I cannot figure out
I tried to use some other commercial ADC systems (one from Motion Lab, one
from Measurement Computing, and one from Freescale MPC5566 evaluation board)
to collect data from my voltage adding circuit and the neural signals. The
results all looked perfect.
In my testing, I left the Vrefn and Vrefp floating. I believe these two pins
are already tied to VDD and VSS. I only connected the GND of Robovero to the
ground of my voltage adding circuit as well as the ground of the input
sensor. Is this configuration correct? Should I connect Vrefn and Vrefp to
some external voltages?
Any suggestion will be greatly appreciated!
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