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3.1.4. Grounding considerations
Indiscriminate grounding of instruments can introduce ground loop interference. To pre-
vent this influencing the measuring and analyzing instruments with which the 1053 is
used, it is important that all the signal ground lines of the instruments are grounded at
only one point in the measurement system. To do this without prejudicing the operating
safety of the instruments, proceed as follows:
1.
Ensure that all instruments are switched off prior to checking their signal ground &
chassis connections and interconnecting the equipment.
2.
Connect the signal ground lines of all instruments together. This is done automati-
cally through the screens of the input- and output-cables used to interconnect the
instruments.
3.
If the same instruments are interconnected by more than one signal cable, or a
combination of signal and remote-control cables, each containing a signal ground
connection, keep the cables short and close together or disconnect the signal
ground connection of all but one of them.
4.
If non-IEC 348 Safety Class I or II instruments are used, disregard item 5 and check
that the signal ground line and chassis of these instruments are connected to mains
ground, either via their mains connector or via one of their ground terminals. In
addition, keep their power cables and ground lines short and close together and
check that the measurement transducer is electrically insulated from grounded mea-
surement sources.
5.
If instruments with mains connectors including a protective earth-chassis contact
are used, check that (a) one and only one of these instruments has its signal ground
line connected via chassis to mains ground and (b) the housing of the measurement
transducer is electrically insulated from grounded measurement sources.
6.
If the measurement arrangement is used free-standing without the instrument cabi-
nets touching, check that each of the other instruments in the measurement ar-
rangement has its chassis connected to (a) mains ground only or (b) signal ground
only. For instruments having a mains connector with protective earth-chassis con-
tact, (a) is preferred.
7.
If the measurement arrangement is mounted in an instrumentation rack, ensure that
one and only one of the instruments has its signal ground line connected to chassis
(and chassis connected to mains ground if equipped with a mains connector having
a protective earth-chassis contact). If more than one of the instruments has a per-
manent signal ground & chassis connection, then isolate the cabinets of these in-
struments from the rack using isolating flanges for mounting.
On the rear panel of the 1053, the signal ground may be disconnected from chassis
by removing the metal link which connects the Signal Ground
& Chassis. For stand
alone use of the instrument, the Signal Ground
& Chassis must always be kept
interconnected.
In addition to the above, the 1053 has a switch, adjacent to the Voltage and Charge
Input on its rear panel, for selection of either floating or grounded input modes with
respect to the vibration meter and compressor circuits of the instrument. Conse-
quently, a ground loop, completed by the compressor feedback loop, can be broken
by setting the switch to "Floating" mode. However, these inputs should be con-
nected to ground either via the switch or via the external equipment used by the
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