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)
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-
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I/O Variable Name, VIBx
JPxA jumper is in the “P,A” position providing a +28 V weak pull-up for sensor failure detection and the JPxC jumper is in
the “PCOM” position to provide a closed circuit for the -28 V power applied to the sensor through the WNPS -28 V
daughterboard for TVBAH#A or TVBAS#A terminal boards only. JPxB is set in the 'PVA' position.
8.5.2.2 Seismic Sensors
The TVBA can input a maximum of eight seismic sensor inputs on channels 1 through 8. Seismic sensors are usually
moving-coil type probes that require no power. The heavy-duty gas turbines (HDGTs) use the Metrix 5235B, 5475C or 5485C
sensors on the bearing housings to measure the non-rotating vibration. The Metrix 5485C or similar sensor’s output is
connected directly to the PRxxH and PRxxL inputs. The seismic output is centered at 0 V dc. With a sensitivity range of 100
to 200 mV/in/sec. Tie the shield on the Mark VIeS end and leave the shield open on the sensor side.
Seismic
5485C
Transient
Suppression
Transient
Suppression
N
2
4
x
x
Transient
Suppression
PCOM OPEN
PRxxH
PRxxL
PCOM
3.6mA
V
S
P,A
+28V
-28V
YVIB /
PVIB
Vibration
Inputs
Vib: 1 – 8
Tracking
Filter: 1 - 3
Shield
Not Used
JPxA
JPxC
-28V to -24V Regulator
with current limit
-28V
JPxA jumper is in the ‘S’ position providing a -28 V weak pull-down for sensor failure detection and the JPxC jumper is in
the ‘PCOM’ position to allow the corresponding buffered output to be scaled the same as the signal input.
JPxB is set in the ‘S’ position.
YVIB Vibration Monitor Modules GEH-6855_Vol_II System Guide 277
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