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Safety Interlock Feature
A safety interlock or secondary ground sense circuit is incorporated into each channel of the
Terranova® 752A to disable high voltage operation when open. The safety interlock circuit is
completed via an external lead available on most Duniway ion pump cables. The external lead
must properly connect the ion pump body to the respective GROUND SENSE stud of the control
unit (see
Figure 2
) to complete the safety interlock circuit and enable high voltage operation.
High voltage output will be disabled on the respective channel if an open circuit or ground fault
is detected. Both the HIGH VOLT INTERLOCK IS OPEN and selected pressure unit LED will
illuminate for the respective channel if the safety interlock circuit is open. To restart high
voltage operation, user must correct the grounding issue.
Table 1
lists various ground sense
connection conditions and effects on high voltage operation.
Case
Primary
(Cable Shielding)
Safety
Interlock
Redundant*
High Voltage
Operation
1
N
N
N
OFF
2
Y
N
N
OFF
3
N
Y
N
OFF
4
N
N
Y
OFF
5
Y
Y
N
ON
6
Y
N
Y
OFF
7
N
Y
Y
ON
8
Y
Y
Y
ON
Table 1
. Terranova® 752A Ground Sense Conditions
*
A redundant ground connection, either intentional or unintentional, between the control unit
and ion pump may circumvent the safety interlock feature. User should correct any grounding
issues to ensure safe operation. A potential (unintentional) redundant ground may occur
through chassis contact with the ion pump or vacuum system ground when both the ion
pump and Terranova® 752A are mounted on the same conducting rack or cart.
WARNING
Under no circumstances should the safety interlock lead be
connected directly to the Terranova® 752A case. This would
defeat the protection provided by this safety interlock feature and
may result in serious electrical shock.
