Granville-Phillips Series 330, Instruction Manual, Page: 23 / 76

2 Installation
23
Series 330 Vacuum Gauge Controller
Instruction Manual - 330004 - Rev. 02
When high voltages are used within the vacuum system and the gauge envelope is not reliably
grounded through its vacuum connection, either a separate ground wire must be added, or the
envelope must be shielded to positively prevent human contact. The gauge envelope may be
grounded by using a metal hose clamp on the gauge connected by a #12 awg copper wire to the
grounded vacuum chamber. See Figure 2-8.
1. Connect a heavy duty ground wire #12 AWG or larger from the ground lug on the back of the
Controller to your facility grounding electrode system. This will provide an earth ground for
the Controller in the event the interconnect cables are not in place. Do not connect the ground
lug to the vacuum system or other component. Connect it directly to the facility grounding
system such as a grounded outlet box or a grounded copper water supply pipe. Do not rely on
small metal water lines to ground a component. Later on someone may replace the metal
tubing with plastic tubing thus unwittingly causing a potentially dangerous situation.
2. Provide a connection to ground for other instruments with electrodes in the vacuum system
possibly exposed to high voltage electrical discharges.
3. Provide a connection to ground for each ungrounded metal component in, on or around the
vacuum system, including the gauge envelopes, which personnel may touch and which can
potentially be exposed to high voltage electrical discharges within the vacuum system. For
example, a metal bell jar resting on an organic O-ring must be connected to ground if a
Micro-Ion gauge is to be used or if other high voltage sources are present in the vacuum
system.
The placement of a second ground wire (dashed line in Figure 2−7) between the
vacuum chamber and the 330 Vacuum Gauge Controller chassis is NOT safe −
large currents could flow through it.
After each maintenance/service procedure and before operating the controller
and vacuum system, make sure that your vacuum system and controller are
grounded as shown in Figure 2−7.
FAILURE TO DO SO COULD BE FATAL.
Figure 2-8 Grounding a Convectron Gauge