Bently Nevada 350500 Charge Amplifier; Pcb Piezotronics 682A02 Signal Conditioner - GE Mark VIeS System Manual

8.5.2.6 Bently Nevada 350500 Charge Amplifier

The TVBA vibration terminal board also supports the Bently Nevada 350500 charge amplifier used with dynamic-pressure
sensors examining the combustion dynamics of the LM2500 DLE gas turbines. The TVBA can input combustion dynamics
information on channels 1 through 8 where the I/O pack can provide band-passed, root-mean-squared (r.m.s.)
dynamic-pressure data for the LM2500 DLE combustion. The charge amplifier is powered with -24 V and the AC dynamics
output is riding on top of a negative DC bias signal that is used by the I/O module for signal health. 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. 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 charge amplifier. JPxB is set in the 'PVA' position.

8.5.2.7 PCB Piezotronics 682A02 Signal Conditioner

The PCB 682A02 signal conditioner can be connected to the TVBA terminal board for channels 1 through 8. The PCB system
is powered with +24 V instead of -24 V as applied to the Bently Nevada systems. The 682A02 signal conditioner is powered
externally by a +24 V source. The 682A02 converts the 24 V power to a 4mA constant-current source to power the PCB
682M57 charge amplifier. The 682A02 'Out' connects to the TVBA PRxxH/L terminal block screws. The AC dynamic
pressure signal is riding on top of a 10 – 13 V dc bias voltage used to determine the health of the combustion sensing system.
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 'S' position providing a -28 V weak pull-down. The JPxC jumper is in the 'OPEN' position to provide
a true differential input eliminating ground current loops with the external power supply. JPxB is set in the 'S' position.
280 GEH-6855_Vol_II GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
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