introduction to vibration from caption data limited
DESCRIPTION
Basic introduction to the measurement of vibration and vibration analysis in conjunction with the Zonicbook 618E.TRANSCRIPT
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Caption Data LimitedIntroduction to Vibration Analysis
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Schedule
Introduction to Vibration measurements Transducers
Acceleration Velocity Displacement Force
Sampling Aliasing Leakage Filtering
Caption Data LimitedIntroduction to Vibration Analysis
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Caption Data LimitedIntroduction to Vibration Analysis
Windows Averaging FFT Analysis
Spectrum Auto Spectrum PSD Cross Spectrum Transfer Function
Coherence Real/Imaginary Nyquist
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Caption Data LimitedIntroduction to Vibration Analysis
Rotating Machinery Analysis Order tracking Synchronous Signal Averaging
Basic Modal Analysis Data Acquisition Windowing Data quality Modeling
Resonant Frequency Non Destructive Testing (NDT)
Machine Health Monitoring (TOMAS)
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Caption Data Limited Introduction to Vibration Analysis
Accelerometers
The Model 353B03 is a quartz shear ICP® accelerometer designed for general purpose measurements. It has a sensitivity of 10 mV/g. The quartz shear-mode sensing elements reduce sensitivity to adverse environmental inputs, such as thermal transients, base strain, and transverse motion. The Model 353B03 features a side-exit, 10-32 coaxial connector. Its frequency range of 1 to 7 000 Hz (±5 %) makes this sensor an ideal candidate for general purpose vibration measurements such as vehicle studies, product qualification studies, structural response tests and vibration control
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Caption Data Limited Introduction to Vibration Analysis
Accelerometers
Miniature accelerometers are designed specifically to meet minimum size and weight requirements. Model 352C22 offers a 1 to 8 000 Hz (±5%) frequency range and a sensitivity of 10 mV/g. With a mass of only 0.017 oz (0,5 gm), this sensor excels in testing of lightweight, flexible structures, such as printed circuit boards, disk drives, and those requiring a low-profile unit.
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Caption Data Limited Introduction to Vibration Analysis
Accelerometers
The Model 356B11 is a miniature, four-gram, hermetically sealed titanium accelerometer. The hermetic titanium case provides a rugged, reliable sensor for minimal mass loading in triaxial vibration measurements. The 10 mV/g output from ceramic shear mode sensing elements provides a wide measurement range from 2 to 10 000 Hz (±5%) in the "Z" axis and 2 to 7 000 Hz (±5%) in the "X" and "Y" axes. The 5 ft integral shielded cable terminates in a four-pin connector.
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Caption Data Limited Introduction to Vibration Analysis
Velocity Transducers
Model Numbe
r
Output Sensitiv
ity
Frequency Range (Hz)
Temperature Range
Excitation Source
Mounting Base
Mating Connect
orIntegral Cable Product
Weight
4-102-0001 110 mV/ips 8 - 700+32 to +150°F
0 to +65°C
SELF- GENERATING
2-hole, #8 bolt
1.50" BC
11760 18 inches 14 oz
4-103-0001 110 mV/ips 8 - 700
+150 to +250°F +65 to
+121°C
SELF- GENERATING
2-hole, #8 bolt
1.50" BC
11760 18 inches 14 oz
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Caption Data Limited Introduction to Vibration Analysis
Displacement Transducers
Proximity ProbesThese transducers allow direct observation of shaft or target displacement for a variety of vibration, position, speed, and timing (i.e., phase) measurements. Various tip diameters and thread sizes/configurations are offered to allow measurement ranges as small as 200 micro inches to as large as 1 inch (typically used for differential expansion measurements on large steam turbines), and everything in between, including the popular 80 mil range used for the majority of machinery measurements.
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What are the Componentsof Vibration?
Amplitude Maximum value of vibration
Frequency Number of events or cycles per unit time
Phase Time relationship between vibrations of the
same frequency
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Vibration SourcesNatural Frequencies / Resonance
Machine Design Induced Machine Structure Mass and Stiffness Damping
Resonance When a forcing frequency excites a
natural frequency In rotating machinery, “Critical
Speed” www.captiondata.com
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Vibration SourcesForcing Frequencies
Machine Design
Universal Joints Asymmetrical
Shafts, Cams Gear Mesh Couplings Bearings Pumps & Fans Reciprocating
Machines Motors /
Generators
Machine Faults
Mass Unbalance Misalignment Bent Shaft Mechanical
Looseness Casing /
Foundation Distortion
Bearing Faults Motor Faults
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How is Vibration Measured?
Primitive, Qualitative Methods / Senses Can you actually SEE movement? Can you HEAR something different? What does it FEEL like? Does it SMELL funny? TASTE, not really recommended!
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How is Vibration Measured?
Better, Quantifiable Methods / Amplitude Movement / Displacement Speed / Velocity Acceleration
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Sensors
Physical Movement / Displacement Proximity Probes
Velocity / Speed Velocity Transducers
Acceleration Accelerometers
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Vibration Units
‘English’ Units Pounds (lb) / Inch (in.) / Second (sec)
Displacement in mils, 1 mil = 1/1000th Inch
Peak-to-peak measure Velocity in Inches per second (in/sec or
ips) Peak or RMS measure
Acceleration in gs, 1 g = 386.1 in/sec 2
Peak or RMS measurewww.captiondata.com
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Frequency / Rotational Units
Vibration Frequencies are expressed as:
Cycles per Minute (CPM) or Cycles per Second (HZ)
Machine or Shaft Speed: Revolutions per Minute (RPM)
Phase is expressed as: Degrees, 360 degrees per revolution. May also be expressed as Leading or
Lagging www.captiondata.com
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Relationship of Amplitude, Velocity & Frequency
Any Quantity can be Calculated
If the remaining two Quantities are Known
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Oh man… MATH??
Mathematical Relationships / Displacement to Velocity
V = (2 π f) D
V = Velocity in Inches per second (ips)
π (pi) = 3.14159 (or, the button on your calculator)
f = Frequency in Hz
D = Displacement in mils peak
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Worse… Algebra!
Mathematical Relationships / Velocity to Displacement
If… V = (2 π f) D
Then… D = V / (2 π f)
Velocity to Acceleration
A = (2 π f) V / 386.1
Acceleration to Velocity
V = A * 386.1 / (2 π f)
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And Finally…
Mathematical Relationships / Acceleration to Displacement
A = D (2 π f)2 / 386.1
D= A * 386.1 / (2 π f)2
(we’re done now… you can all relax!)
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Machine Vibration Measures
MEASURE USEFUL FREQ. SPAN
PHYSICAL PARAMETER APPLICATION
Relative Displacement
(proximity probes)0-1000 Hz Stress / Motion Relative Motion in
bearings / casings
Absolute Displacement
(seismic)0-10 Hz Stress / Motion Machine Condition
Velocity(seismic)
10 – 1000 Hz Energy / Fatigue
General Machine Condition,
medium-high frequency vibrations
Acceleration(seismic)
> 1000 Hz Force
General Machine Condition,
medium-high frequency vibrationswww.captiondata.com
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Machine Design Vibration Sources
Eccentric Shafts / Cams Reciprocating Components Pumps & Fans Gears Bearings Couplings Universal Joints Motors & Generators
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Machine Design Vibration Frequencies
Eccentric Shafts / Cams Shaft Speed (1 X) and Multiples
(Orders)
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Machine Design Vibration Frequencies
Reciprocating Machines ½ and Full Multiples of Shaft Speed
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Machine Design Vibration Frequencies
Pumps & Fans Vane Pass & Blade Pass Frequencies
Shaft Speed X Number of Vanes Shaft Speed X Number of Blades Flow Noise / Cavitations
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Machine Design Vibration Frequencies
Gearboxes Gear Mesh Frequencies
Shaft Speed X Number of Teeth
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Machine Design Vibration Sources
Bearing Frequencies, Rolling Element Bearings BPFI – Ball Pass Freq. Inner Race BPFO -- Ball Pass Freq. Outer Race BSF – Ball Spin Frequency FTF -- Fundamental Train Frequency
Max Range Approximation: Shaft Speed X Number of Elements
X 0.6 www.captiondata.com
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Machine DesignVibration Sources
Bearings, Fluid Film / Sleeve Oil Whirl
0.40 – 0.48 X of Shaft Speed Oil Whip
Machinery Operating at > 2 X Critical Speed Oil Whirl Locks onto 2 X Critical
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Machine DesignVibration Sources
Couplings Shaft Speed X Number of Jaws
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Machine DesignVibration Sources
Universal Joints 2 X Shaft Speed
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Machine DesignVibration Sources
Motors & Generators Synchronous Motor Speed (SMS)
2 X Line Frequency / Number of Poles Slip Frequency
SMS – Actual Speed
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Minimum Acquisition Frequencies
COMPONENT / MACHINE SPAN
Shaft Vibration 10 X RPM
Gearbox 3 X Gear Mesh
Rolling Element Bearings 10 X Ball Pass Freq. Inner
Pumps 3 x Vane Pass
Motors / Generators 3 X Line Freq X 2
Fans 3 X Blade Pass
Sleeve Bearings 10 X RPM
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Applicable Sensors & Limits
Credit: John S. Mitchell, machinery Analysis and Monitoring 2 nd edition
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Sensor Mounting Conventions
Position Referenced from DRIVEN end of Shaft
Horizontal 90˚ CLOCKWISE from Vertical
Direction of Rotation Not Considered
Axial Transducers In the Load Zone
Credit: Ronald L. Eshleman, Basic Machinery Vibration
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Useable Frequency Spans ForAccelerometer Mounting Methods
METHOD FREQUENCY LIMIT
Hand Held (stinger) 500 Hz
Magnetic Mount 2,000 Hz
Adhesives2,500 – 4,000 Hz
(dependent on compound)
Bees Wax5,000 Hz
(watch surface temp!)
Stud Mount 6,000 – 10,000 Hz
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Caption Data Limited Introduction to Vibration Analysis
Digital Sampling Amplitude Resolution Effects of under sampling
Aliasing
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Caption Data Limited Introduction to Vibration Analysis
Over Sampling
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Caption Data LimitedIntroduction to Vibration Analysis
Minimum Sampling
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Caption Data Limited Introduction to Vibration Analysis
Leakage
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows No Window Hanning Blackman Harris Flat Top Exponential Decay Box Car/Rectangular
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows No Window
Transient events Fixed frequency
Cell centered
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows No Window
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Hanning
Continuous data Good frequency accuracy Most common window May not be suitable for transient data Good for separation of closely spaced
frequencies
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Hanning
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Blackman Harris
Similar characteristics to Hanning Continuous data Good frequency accuracy Most common window May not be suitable for transient data Good for separation of closely spaced
frequencies
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Blackman Harris
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Flat Top
Best amplitude Accuracy Frequency accuracy is sacrificed Continuous data Common window for order tracking
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Flat Top
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Exponential Decay
Used for Bump (impact) testing in Modal Analysis
Used for response channels only Decay is adjustable to eliminate leakage Adds artificial damping
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Exponential Decay
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Box Car/Rectangular
Used in Bump (impact) testing in Modal analysis
Used only on the reference channel Adjustable leading and trailing edge Zeros all data outside the window
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Caption Data Limited Introduction to Vibration Analysis
Weighting Windows Box Car/Rectangular
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Caption Data Limited Introduction to Vibration Analysis
Averaging Linear/Summation Exponential
Variable decay Peak Hold Time Synchronous
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Caption Data Limited Introduction to Vibration Analysis
Why do we average Improve statistical confidence Extract signals from noise Smooth random vibration
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Caption Data Limited Introduction to Vibration Analysis
Linear/Summation Reduces noise Improves statistical accuracy of repetitive or
stationary signals.
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Caption Data Limited Introduction to Vibration Analysis
Exponential Weights the average count New data carries the most weight Decays the old data Smoothes noise Slows rapidly changing signals
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Caption Data Limited Introduction to Vibration Analysis
Peak Hold Updates the spectral line value with a
new maximum Holds the maximum until updated
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Caption Data Limited Introduction to Vibration Analysis
Time Synchronous Averages in time domain based on a
Synchronous event Reduces effects of other operating equipment
in close proximity Very good for extracting signals from noise
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Caption Data Limited Introduction to Vibration Analysis
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ZonicBook/618E Hardware Features
8 Vibration Inputs Field expandable to 56 vibration inputs 4 tachometer inputs 8 digital I/O 10/100BaseT Ethernet connection Open ICP and over-range indicators on
front panel Signal conditioned output for each input
channel
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ZonicBook/618E Hardware Features
Software configurable ICP®, DC, or AC coupling
9 input voltage ranges 16 bit, 75 dB dynamic range New rugged package with built-in
handle TEDS support
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ZonicBook/618E Hardware Features
Expandable up to 56 analog inputs via WBK18 options
Other hardware options DBK34A battery/DC UPS
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Caption Data Limited Introduction to Vibration Analysis
eZ-AnalystReal Time Vibration Analysis
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eZ-Analyst
Real-Time Vibration Measurement and Analysis
Two Applications Impact
measurement and structure analysis
Continuous data recording and transient analysis
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eZ-Analyst – Impact Applications
Impact measurements 5 averaging methods Multiple reference
channels Interactive displays Cross-channel
analysis, FRF, transfer functions
Export data to Excel or modal analysis software
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eZ-Analyst – Impact Applications
Measurements for Modal Analysis Effect of mass, stiffness, and damping Operating deflection shapes
Automatically save after averaging Automatically increase
modal locations
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eZ-Analyst – Continuous Data Recording Applications
Record “gap-free” data to PC disk
Stripchart data analysis and reduction
Harmonic, SideBand, and FreeForm Cursors
Export data to Excel or eZ-Rotate
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Caption Data Limited Introduction to Vibration Analysis
Rotating Machinery Analysis Order Normalization Order tracking
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Caption Data Limited Introduction to Vibration Analysis
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Caption Data Limited Introduction to Vibration Analysis
eZ-NDTNon Destructive Testing for
Production
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Caption Data Limited Introduction to Vibration Analysis
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Caption Data Limited Introduction to Vibration Analysis
Assumptions If test articles are produced in the same
manner, and have like properties, then they will have the same natural or resonant frequencies.
If the test articles have a change in mass, stiffness or damping, then the resonant or natural frequencies will change.
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Caption Data Limited Introduction to Vibration Analysis
What causes the changes? Changes in mass may be caused by void or
missing operation in the test article Changes in stiffness may be caused by a
material or process variation. Changes in damping can be caused by a
material or process variation or a crack in the test article.
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Caption Data Limited Introduction to Vibration Analysis
The measurement process The test data is converted into the frequency
domain by the analysis software. Key resonant peaks are identified and their frequencies are noted
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Caption Data Limited Introduction to Vibration Analysis
The measurement process Known good and defective test articles are
tested and compared for shifts in fundamental resonant frequencies.
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Caption Data Limited Introduction to Vibration Analysis
The measurement process Each resonant frequency of a known good part is examined
and bands are placed around the peak. If the frequency of a tested part is outside of these bands, then the test article fails.
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Caption Data Limited eZ-TOMAS – Applications and Machinery
eZ-TOMAS On line condition monitoring and
analysis
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Caption Data Limited eZ-TOMAS – Applications and Machinery
Petrochemical, Power Utility, Paper and Steel Mill, Pharmaceutical, etc…
Turbines, Compressors, Gearboxes, Pumps, Motors, Generators, etc…
Typically, 1 to 3 machines per system.
10 to 100,000 RPM range
Temporary or Continuous Monitoring
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Vibration Analysis & Monitoring eZ-TOMAS – Gauge Window
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Vibration Analysis & MonitoringeZ-TOMAS – Gauge Window
Current Values & Status
Vertical Amplitude
Circular Phase Limit Checking /
Log Events FIFO Storage High Water
Marks Relay Outputs
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Vibration Analysis & MonitoringeZ-TOMAS - Configuration Setup
Acquisition Fmax: up to 20 KHz Lines: up to 25,600 Hanning / Flat Top FFT Scale Pref: RMS, PK, P-
P Input Channels
D: DC Cplg, +/- 25V A: ICP, AC Cplg, +/- 5V Gap & Runout Ref. Orbit / Tach Pairs
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Vibration Analysis & MonitoringeZ-TOMAS - Configuration Setup
FIFO Storage Up to
200,000 Records/Channel/File
RPM Range Change in
RPM, Time, Vibration
Alarm Condition
User Snapshot
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Vibration Analysis & Monitoring eZ-TOMAS - Configuration Setup
Spectral Bands OAll, Vdc, 1xA &
1xP 6 User Defined Overall, Peak,
Phase Fault Toolkit
Spectral Limits 2 High / 2 Low Delay Text Message www.captiondata.com
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Vibration Analysis & Monitoring Rotating Machinery Analysis
Orbit, Time Waveform w/ or w/o
Filtered N Revolutions
Bode w/ or w/o
Runout OAll, 1x, nX
Waterfall Order Tracks RPM Annotation
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Vibration Analysis & Monitoring Rotating Machinery Analysis
Polar Runout, Limits Annotation
Spectrum Harmonic,
Sideband Peak Cursors
Shaft Center Line Trend
OAll, 1x, nX Cursor to History
Location www.captiondata.com
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Vibration Analysis & Monitoring Rotating Machinery Analysis
Automatic Tach Analog
Inputs Dynamically
adjust trigger levels
Trigger Direction
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Vibration Analysis & Monitoring Learning Limits
Statistical Report Steady State
Condition Min, Avg, Max,
Dev Calculate
Limits based on Normal Operation
Before / After Shutdown comparisons
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Vibration Analysis & Monitoring Configuration Setup – Storage
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Vibration Analysis & Monitoring Edit - Spectral Bands
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Vibration Analysis & Monitoring Edit – Spectral Limits
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Vibration Analysis & Monitoring Gauge Window – Monitor Vibration Levels
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Vibration Analysis & MonitoringGauge Window – Monitor Vibration Levels
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Vibration Analysis & Monitoring Plot Windows – Data Source
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Vibration Analysis & Monitoring Plot Windows – Time Waveform
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Vibration Analysis & Monitoring Plot Windows – Spectrum
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Vibration Analysis & Monitoring Plot Windows – Orbit
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Vibration Analysis & Monitoring Plot Windows – Waterfall
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Vibration Analysis & Monitoring Plot Windows – Bode
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Vibration Analysis & Monitoring Plot Windows – Polar
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