171589-0001 and 171589-0002). The reels are iden-
gain of the amplifier is adjusted by SENSITIVITY
t i c a l except for their width, and the cables are
controls, variable resistors R11, R13, R14 and R15.
identical except for their length. The cable assem-
E a c h variable resistor consists of two sections
b l i e s are used to connect the transducers to the
mounted on the same shaft. The A section of each
variable resistor adjusts the gain of the first stage
of the amplifier, and the B section adjusts the gain of
1-9. ADAPTERS. The vibration test kit contains eight
the second stage of the amplifier.
adapters for mounting the transducers to the engine,
and a grounding adapter for connecting to the ac plug.
1-14. For velocity measurements, the output of the
Adapters included are: Grounding Adapter Part No.
a d j u s t a b l e gain amplifier is connected through a
171581, Vibration Transducer Adapters Part Nos.
linear attenuator to the fixed gain amplifier tube V2A.
171580, 171574, and 171576, Inlet Housing Adapter
The linear attenuator consists of resistors R19, R21,
Part No. 171575, Power Turbine Adapters Part Nos.
R23 and R41. For displacement measurements, the
171578 and 171579, and Vibration Brackets Part Nos.
output of the adjustable gain amplifier is connected
362854 and 362855.
through an integrator to the fixed gain amplifier tube
1-10. FUNCTIONAL DESCRIPTION,
capacitors C6 and C7.
1-11. A simplified block diagram of the vibration
1-15. The fixed gain amplifier is a two-stage, fixed
gain amplifier utilizing the two sections of tube V2.
The output of the fixed gain amplifier is applied through
d e s i r e d transducer is selected by the CHANNEL
cathode follower tube V3B to the rectifier and filter
selector switch and applied to the input network. When
and meter circuitry serve to adjust a "calibrate
the INPUT NETWORK selector switch is set to the
signal" voltage to the proper value, which is then
OUT position, the input signal is applied without
filtering directly to the attenuator stage. When the
applied to the input of the instrument. When this is
done, t h e gain may be adjusted to permit direct
INPUT NETWORK selector switch is set to the 70
reading of velocity or displacement from the meter.
position, the signal from the transducers filtered by
Each channel has its individual SENSITIVITY (gain)
the 70 cps filter; when the switch is set to the 200
control, Both the high voltage dc (B+) and the dc
position, the signal is filtered by the 200 cps filter.
filament supplies are fully regulated.
The attenuated signal is increased by the adjustable
gain amplifier, tempered by the coupling network, and
again amplified by the fixed gain amplifler. The
amplified signal is full-waved rectified and filtered
The vibration meter is simultaneously "in
by the rectifier and filter circuit and applied to the
indicating meter M1 and the EXT. METER connector.
different sensitivities. Instrument calibration
may be accomplished by utilizing the internal
1-12. The ac voltage applied to the SCOPE output
connector and the ac current applied to the GALV.
output connector are both instantaneously propor-
tional to the transducer signal voltage. The output
a t the EXT. METER connector is a dc current
1-16. TECHNICAL CHARACTERISTICS.
proportional to the short term average value of the
transducer signal voltage. All outputs are integrated
1-17. The technical characteristics for the Vibration
when the OPERATION selector switch is set to the D
the technical characteristics for the Vibration Trans-
ducer Types 4-118-0107 and 4-128-0101 are listed in
Greater accuracy is obtained when the OPERA-
T I O N selector switch is set to Vx1.0 and
1-18. ASSOCIATED EQUIPMENT.
Dx1.0 positions, than when the switch is set
to the Vx0.1 and Dx0.1 positions.
through 1-23 is not required for normal operation of
the vibration test kit but may be used with the vibra-
1-13. The adjustable gain amplifier is a two-stage
tion meter to perform certain additional functions.
amplifier utilizing the two sections of tube V1. The