225 Series User’s Manual
14
118120-001-Rev. A
7.5 FLOATING
OPTION
(“RF”):
The 225 Series can be purchased with a special option
which allows the user to float the output above or below
true earth (i.e., chassis) ground potential by as much as
2000V. All controls, programming and monitoring
functions work normally and remain “ground-based” so
there are no hazards with taking these measurements.
The high voltage output polarity, with respect to the
floating output terminal, is still reversible as in the
standard version of the 225 Series.
In supplies so equipped with the floating option, the high
voltage output current is no longer returned to the chassis
of the power supply via either the shield of the HV
output coaxial cable or the ground stud on the back of the
supply. Instead, the user would now connect the low end
of the application to a factory-installed MHV connector
(jack) which is located on the rear panel of the 225 series
HVPS. The shell of this connector is connected to
chassis ground (as the actual HV output connector’s shell
is) but the center conductor is the HV return.
To disable this feature on RF-equipped power supplies
the user must connect a “dead-end” MHV plug to the HV
return jack. A “dead end” connector would be one in
which the center conductor is hard-wired to the shell.
This reverts the 225 Series back to conventional ground-
based operation.
The floating option is useful in applications where the
low end cannot be connected directly to earth ground, or
for other reasons is not desirable to do so. A current
meter can also be inserted within this return path (with
appropriate protection across the meter) for the purpose
of measuring HV output current. We highly recommend
installing back-to-back diodes or a neon bulb across the
meter in the event that the meter connection is
inadvertently or accidentally opened during operation.
This will prevent the development of high voltage across
the meter leads.
*
