System information

Troubleshooting
F-2 Vicon MX Hardware System Reference
Ground Loop and Equipment Power Supplies
Ground loop occurs if two pieces of equipment do not share a common
power supply ground or if there is a significant potential difference (or
resistance) between their respective grounds. Should a lower
resistance path be present, such as a common signal ground, then
this will become the preferred power supply ground return path.
Induced currents in the signal grounds will overlay the ADC data,
creating an unwanted sinusoidal-shaped noise, which may or may not
be at the same frequency as the mains power.
To avoid ground loop, ensure that the MX Control and associated
analog peripheral equipment power supplies are connected to a
common mains supply ground. Wherever possible and within the
bounds of safe electrical installation practice, ensure that there are
no alternative power return paths.
Ensure that all analog peripheral equipment share a common signal
ground by correctly installing the interface cables such that the
shields are connected to a SGND screw terminal on the Vicon patch
panel.
Troubleshooting Analog Data Capture
Try these suggestions for troubleshooting analog data capture:
• Ensure that all analog data generating and capture devices (e.g.
EMG equipment, force plates, MX Control) are connected to the
same, earthed electrical output to ensure a good ground.
• Eliminate other devices on the same electrical circuit that may
introduce noise or generate switching surges, such as electrical
fan coils, lighting, and heating systems.
• Ensure that force plates are mounted stably and in such a way as
to avoid vibrations from any source such as AC power equipment
in an adjoining room or movement of the surrounding floor.
• Ensure that no power cables lie near the electrode cables for EMG
equipment.
Try these suggestions for investigating noise problems that occur
during analog data capture:
• Check the earthing in the laboratory to eliminate a poor ground
as the source and also for reasons of safety.
MXhardware_Reference.book Page 2 Thursday, September 7, 2006 11:36 AM