I have been chasing a noise problem on my lathe for some time now. I am
using a 7i29 2kw drive and am getting a lot of noise on the encoders,
even with filtering enabled at a pretty low frequency. I have tried just
about everything I can think of. I made a simple near-field probe and
did a bit of poking around. The 20kHz drive switching noise was strong
pretty much everywhere. After trying various things I found a common
mode choke on each motor output dropped the 20kHz noise down so it was
pretty much undetectable apart from right next to the chokes. However I
am still getting noise on the encoders. I have a spare encoder input on
a 7i33 so I moved one of the motor encoders to that input. I am getting
zero noise on that channel even though I extended the encoder cable to
reach the 7i33 with 6 individual wires instead of a screened cable. Even
with filtering disabled I see no noise. Unfortunately I don't have any
more spare encoder inputs for the other axis.
Has anyone else had noise issues with 7i29 drives?
Les
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