Velomitor Sensors; Eddy-Current Or Proximitor Sensors For Position And Velocity - GE Mark VIeS System Manual

8.5.2.3 Velomitor Sensors

The TVBA accepts a maximum of eight Velomitor sensors on channels 1 through 8. The Bently Nevada 190501 and 3305xx
product line are a constant-current device requiring a -24 V power sourced from the WNPS power supply daughterboard(s)
for TVBAH#A and TVBAS#A terminal boards only to drive the current. The two-wire termination of this sensor uses the
N24xx and PRxxH screw points. The velocity or AC content of the Velomitor is riding on top of a negative DC bias in the -8
to -12 V dc range generated by the sensor. The shield is tied to chassis at the control end and left open on the sensor side to
prevent circulating ground currents. The sensor device usually has a sensitivity of 100 mV/in/sec.
JPxA jumper is in the 'V' position providing a 3.6 mA current diode driven by a -24 V source, N24xx. The JPxC jumper is in
the 'PCOM' position providing a return for the -24 V power source. JPxB is set in the 'PVA' position.

8.5.2.4 Eddy-current or Proximitor Sensors for Position and Velocity

The TVBA provides a maximum of 13 channels to connect an Eddy-current sensor to the terminal blocks. Channels 1 through
8 can condition both position and velocity information from the sensor and channels 9 through 13 can input only position
information between the terminal screws PRxxH and PRxxL. The Bently Nevada Proximitor 3300 family and Metrix Model
5533 are -24 V powered devices with the output signal proportional to the gap between the rotating shaft and the head of the
probe. Velocity information is extracted from the AC content riding on top of the DC gap signal. The shield is tied to chassis
at the control end and left open on the sensor end to prevent circulating ground currents.
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 return for the -24 V power supply sourced from the -28 V WNPS daughter-boards on the
TVBAH#A and TVBAS#A terminal boards only, and a low-side for the signal output of the sensor. JPxB is set in the 'PVA'
position.
The user can parallel the eddy-current signal to a second TVBA, but the N24xx power output would not be used from the
second TVBA and JPxC would be in the "OPEN" position.
278 GEH-6855_Vol_II GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
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