67B Vibration Analyzer is a single module that requires two
Form C VXI spaces. It is designed to operate using the voltage supplied by
the VXI rack and to interface with the standard VXI Bus configuration with
a VXI memory base interface. The Analyzer System is designed to accom-
modate the vibration testing and balancing of the engines presently being
used in the military and commercial aircraft.
The salient features are nine data channels (acceleration or velocity input)
and three tachometer channels simultaneously. The system supplies simulta-
neous N1, N2, N3, wideband, and spectrum data in the Vibration Mode.
In the Balance Mode it also supplies the phase of the active channels
referenced to N1.
The mission of Trig-Tek, Inc. is to provide and meet the highest
quality standards for the products it supplies
for the VXI systems.
Trig-Tek, Inc.
VXI Bus Manufacturers ID No. 3716. Description & Spec - Model 667B
Since the Model 667B is a single-integrated instrument, it is the same as other instruments in the VXI
memory- based mode. This removes the requirement to use system resources to read and convert the
analog outputs of previous generation vibration monitors. This also eliminates the requirement to add
additional data buses, and associated overhead, required by stand-alone vibration systems.
Data Acquisition
The Model 667B Digital Analyzer is capable of reading and processing nine (9) vibration data channels
and three (3) tachometer inputs. The input data is acceleration pC/g or mV/g (CURR ON or OFF); or
velocity (ips). Each data channel has dedicated anti-alias filters and gain control circuits. Each tachom-
eter input is processed through a phase-locked divider/multiplier for speed measurement conditioning.
All twelve (12) inputs are Time Division Multiplexed (TDM) through a 16 bit Analog to Digital (A/D)
Converter. The TDM output of the A/D is passed into the on-board Digital Signal Processor (DSP).
The DSP continuously accepts the TDM data stream at 127931 samples per second. The data is
demultiplexed into blocks of data for each channel. The 16 bit fixed point data from the A/D converted
to 32 bit floating point data and the sample rate is converted to 10660 samples per second per channel
to provide compatibility with the 4 kHz per channel maximum frequency range 2 kHz, 1 kHz and 500
Hz are selectable. The data for the nine channels are provided to the VXI bus at approximately 10
updates per channel per second. This data is produced continuously, and is available upon demand by
system host computer. The tach speed information is updated nine (9) times faster or approximately 90
times per second.
1 - 2 Description & Spec - Model 667B
Digital Signal Processing
The demultiplexed, and filtered information is maintained in twelve (12) data buffers of 4096 words
each. The tachometer signals are processed simultaneously with each data channel to obtain the N1, N2
and N3 frequency, which corresponds to each channel. The data channels and tachometer channels are
then processed through a time domain window, which preconditions the time data, to provide optimum
frequency discrimination in the output. The windowed data is converted from time domain to frequency
domain using a Fast Fourier Transform (FFT). The FFT yields 1600, 800, or 400 equally spaced fre-
quency terms as selected that represent the vibration spectrum. The FFT data is weighted by frequency
domain scaling to allow integration from Acceleration (A) to Velocity (V), to Displacement (D), or no
integration. This allows the following output conversions: A-A, A-V, A-D, V-V, and V-D.
After integration weighting, the data is exponentially averaged, in time as magnitude squared vibration.
This provides smoothed output results. Each 1600, 800, or 400 element magnitude squared array is
summed to provide a wideband output for each data channel. The N1, N2 and N3 component of each
data channel is selected using the frequency location information for the N1, N2 and N3 component
derived from the tachometer input signal frequencies..
Balance Mode
When the BALANCE MODE is selected, the output of the DSP provides the magnitude of the N1, N2
and N3 components along with the relative phase shift between the selected channel inputs and the
tachometer input. To acquire valid phase measurements, the tachometer inputs must be once per
revolution with regards the N1 shaft speed. N1 can be selected to a once per rev tachometer input or the
normal N1 tachometer with selectable HI or LO blade operation.
Spectrum Outputs
Spectrum outputs are available from the 667B upon request from the data acquisition computer. Spec-
trum outputs from any two data channels may be retrieved for spectrum analysis. The data is available
regardless of the specific operating mode of the 667B.
1 - 3 Description & Spec - Model 667B
The data is generic, and does not require pre-formatting since the entire spectrum is captured, and
available at the VXI back plane. The data is transferred as a single block of data from the 667B to the
data acquisition computer. The block of data will be placed into an array for processing, storage or
display.
Data Processing and Storage
Data may be analyzed and/or displayed immediately upon retrieval, or saved for later analysis and or
display. Data may be saved temporarily in system memory, or permanently to disk. Data saved to disk
may be retrieved for off-line analysis. The 667B provides all data as an FFT processed output, but does
not require the data to be displayed or saved in a specific format. The TPS may be used to process and
display the data to meet the specific requirements of the Unit Under Test (UUT). Data may be stored to
disk as a database, spreadsheet, or other similar data file type. Data may be processed to the screen as
an appropriate numeric or graphical display. Graphs may include continuously updated vibration out-
puts or processed spectrum outputs. Resources required to perform each graphing function will vary in
accordance with the complexity of the required output, and the volume of the data being processed.
Specification (Analog Inputs)
Accel Inputs (9 ea, CH1 - CH9)
Impedance
Greater than 10 meg.
Amplitude Accuracy (20
°
-130
°
F)

±
2% of reading
±
1% FS
Maximum Input
22000 PC
Connector
3 Pins of D SUB 9P
1 - 4 System & Specifications - Model 667B
Velocity Input (9 ea. CH1-CH9)
Impedance
10k
±
1%.
Amplitude Accuracy (20
°
-130
°
F)

±
2% of reading
±
1% FS.
Maximum Input
20 Volts pk-pk
Connector
3 Pins of D SUB 9P
Tachometer Inputs (4 ea. ONCE/REV, N1, N2 and N3)
Impedance
Greater than 100k.
Waveform
Sine, Square, Triangle, or Pulse.
Level
50 mV to 100 Volts RMS.
N1 Tachometer Input
Normal Once/REV
Selects NORMAL or ONCE/REV when in the
Balance Mode.
Normal - Blade
Selects HIGH or LOW Blade when Blade Mode
is selected.
High - Low Blade
Selects HIGH or LOW Blade operation when
Blade Mode is selected.
Connector
2 Pins of D SUB 9 P
1 - 5 Trig-Tek, Inc.
Model 667B
VIBRATION ANALYZER
NOT INCLUDED
EQUIPMENT GENERAL
The vibration system is a Black Box which furnishes the
DESCRIPTION
host with frequency vibration and phase data. The Host
Computer controls the black box and all communication is
via VXI memory Base Interface.
VIBRATION INPUTS
Number of Vibration
Nine
Channels
Sensor Types
Accelerometer, Differential
Accelerometer, (Single Ended - Isolated)
Accelerometer with Integrated Circuits
Velocity Transducer, Differential, 10 k Impedance
Velocity with Integrated Circuit.
Accelerometer Input
>=10 M OHM or nominal 3-5 mA CURR for ICP Type
Impedance
Sensors
Velocity Pickup Input
10 K OHM or nominal 3-5 mA CURR for ICP Type Sensors.
Impedance
Accelerometer Sensitivity
0.10 to 1500 PC/G
Velocity Pickup Sensitivity
10 to 1500 mV/IPS
Accelerometer Level Ranges
30,000 PC Maximum
Accelerometer or Velocity
5-500 Hz, 5Hz-1kHz., 5Hz-2kHz or 5Hz-4kHz
Frequency Range (Selectable)
CALIBRATION
AUTO
TACHOMETER INPUTS
Tachometer Input
Once/Rev, N1, N2, and N3
Frequency
4 Hz to 25 kHz
Tachometer Input
200 K OHMS
Impedance
1 - 6 Model 667B
NOT INCLUDED
Tachometer Inputs...
Tachometer Input Levels
50 mV to 100 V RMS.
Tachometer Input Signal
AC coupled differential input, any recurring wave form,
Type
sine, triangle, square or pulse (40 us min)
ANALOG SIGNAL
CONDITIONING
Anti-Alias Filters
Fixed Low Pass Input Filters for Vibration and Tachometers
Integrators
Digital
Pre Integrator Filter
6-Pole High Pass Corner frequency 5Hz (-5% Point).
Also 15, 35, 40, 70 or 150 Hz are selectable.
Sensitivity Setting
Implemented by the DSP.
A/D Conversion Rate
10,666 Samples/second.
ANALOG SIGNAL
Broad Band vibration analog signal output for CH1-6 vibration
OUTPUTS
channel and N1 and N2 tachometers. Output current is limited
to 2MA. 10V pk-pk FS
DIGITAL SIGNAL
PROCESSING
Integration
Accel to Velocity, Velocity to Displacement
Units
English or Metric.
Tachometer Odd-Tooth
The reference pulse must be at least 25% greater than normal
Processing - Higher than
for Tach frequency <350Hz. The reference pulse must be
Normal
greater than 50% for Tach frequency >350Hz.
Tachometer Odd-Tooth
The reference pulse must be at least 50% smaller than
Processing - Lower than
Normal; 25% <Duty cycle of Tach pulse <75%.
Normal
Conversion from Tach
Speed to Rotor Speed
Tach ratios are entered as 100% Tach and 100% Rotor speeds.
1 - 7 Model 667B
NOT INCLUDED
Digital Signal Processing....
Tracking Filter Response
FIXED BW
1600 Lines
800 Lines
400 Lines
500Hz Range
1Hz
2Hz
4Hz
1000Hz Range
2Hz
4Hz
8Hz
2000Hz Range
4H