Sterlco A3 Blender Control and Data Acquisition Software - Manual (Page 119)

Page Number 119
You should see a response on the screen from the blender that looks
something like:
01T00BTest String 6C
If this works than communications is working. Try starting the blender and
then perform the same test. If when the blender is running this test fails
then the problem is noise from within the blender (consult service).
If this test fails and you see scrolling junk on the screen then the problem is
that you have noise on the com cable. The cable’s shield should only be
connected at the PC end and not at the blender end. When the cables are
unhooked there shouldn’t be continuity between the hoods on any of the
cables. If there is fix the problem.
If you’ve fixed the shields and are still seeing noise then start unhooking
blenders. If when you unhook a blender the noise goes away then check
the blender (consult service).
If the blenders aren’t causing the noise and you’ve ran the cables in
conduit (if not then you must), then some external device is creating the
noise. Begin shutting electrical devices off one at a time until you find the
problem. Sometimes this issue can be caused by weak ground circuits.
To resolve a weak grounding grid in the plant you have to drive a copper
spike through your floor into earth ground near the source of noise (no
other solution).