GE Bently Nevada 86517 Operation Manual page 21

Notes for Figure 2.5
1 The accelerometer case is connected to the machine earth and the
differential signal output is isolated. The installer must ensure that the
accelerometer mounting structure has the same ground potential as barrier
ground. Total earth loop impedance should be less than 1 ohm. The
accelerometer case connects to the extension cable shield through the cable
connector for the hardline cable and to the inner shield for the softline connector.
3 The interface module case must be isolated. The interface module must be
installed in a housing which meets approval agency requirements for the
installation site.
Wiring Recommendations:
2 Accelerometer to interface: Use extension cable, Bently Nevada part
numbers 45358-07 and -09, or 83387-xxx, or equivalent.
4 Interface module to monitor Power, Common, and Velocity signal wiring
recommendation: 18 to 22 AWG stranded, three conductor wire with insulating
sheath and 100% shield coverage. The -Velocity output at the interface module is
not connected. The maximum cable length between the monitor and the
interface module is 1000 feet (305 metres) and the maximum length between the
interface module and the barrier is 800 feet (244 metres). 18 AWG Belden 83336
or 22 AWG Belden 83334 can be used.
Shielding:
5 Barrier ground is the single point earth ground. The shields should be
earthed only at this point.
7 Shield floats at the monitor and is earthed at barrier ground.
Safety Barriers:
6 MTL 796(-) barrier recommended for power and velocity signal. Power:
V = -26 V, R = 300 ohms. Velocity: V
max min
8 3300 series monitors other than the 3300/95 must be modified before
connection to the interface module. Contact your Bently Nevada representative.
Other connections are possible. For example the acceleration signal could be
connected to a monitor for some special applications.
NOTE: When you use external barriers, remove the jumper between signal
common and rack chassis on the 3300 Power Input Module at the rear of the
3300 rack. See the 3300 System Installation Instructions, (document number
80172-01).
Section 3 - INSTALLATION
= -20 V, R = 390 ohms.
max min
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