Agilent Technologies N6705 User Manual page 43

NOTE
NOTE
Model N6705 User's Guide
Positive and Negative Voltages
Either positive or negative voltages with respect to ground can be
obtained from the output by grounding (or "commoning") one of the
output terminals. Always use two wires to connect the load to the
output regardless of where or how the system is grounded. The
instrument can be operated with any output terminal ± 240 VDC
including output voltage from ground.
Agilent Models N678xA SMU are optimized for grounding the negative output
terminal. Grounding the positive terminal may result in increased current
measurement noise and a reduction in current measurement accuracy.
Protecting Sensitive Loads from AC Power Switching Transients
If your load is connected directly to the output binding posts and is not
connected to chassis ground in any way, you do not need to worry about AC
power switching transients appearing at the output binding posts.
Operating the AC line switch can inject common mode current spikes
into the DC output leads, resulting in voltage spikes that may damage
loads that are highly sensitive to voltage or current transients. Note
that any electronic device meeting international standards for EMI
compliance is likely to generate similar current spikes. This situation
arises from the presence of EMI filters at both the AC input and the
DC output. These filters typically include common mode capacitors
connected to the chassis of the DC Power Analyzer. Since the AC
input has an earth ground, any load that is also earth-grounded
provides a possible return path for common mode currents.
The following steps will help mitigate common mode current spikes
appearing at the output binding posts when the DC Power Analyzer
is turned on or off by the AC line switch:
Install a separate "bonding" wire from the load's common point,

to the ground terminal of the DC Power Analyzer. This provides a
lower impedance path that helps direct injected currents away
from the DC output leads (and the sensitive load).
Disconnect the load from the output before turning the unit on or

off. This always protects the load from common mode currents.
Installation 2
43