CERTIFICATION EXAM REFERENCE MATERIAL
T = Time required to collect the waveform
Ts = Time between each sample
Fs = Sampling rate = Samples per second
N = Number of samples (1024, 2048, 4096, etc.)
Window factor = 1 (no window/uniform/rectangular) or 1.5 (Hanning window)
Separating frequency ≥ 2 x Bandwidth ≥ 2 x Resolution * Window Factor
Required spectral lines ≥ 2 x Window factor x Fmax / Separating frequency
Accuracy of frequency (at peak) = ± ½ x Resolution
Prime numbers: 1, 2, 3, 5, 7, 11, 13, 17, 19…
1 inch = 25.4 mm
1mm = 0.039 inches
Trial weight calculation:
F = 10% of rotor mass divided by the number of bearings in kg
K = 0.011
N = RPM/1000
R = Radius in cm
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Page 2 of 10 Certification Exam - Reference
Unit Conversions
𝐷 𝑉 𝐷 𝑉
𝐷 𝐴 𝐷 𝐴
𝑉 𝐴 𝑉 𝐴
D = Displacement: mils pk-pk D = Displacement: micron pk-pk
V = Velocity: in/sec pk V = Velocity: mm/sec rms
A = Acceleration: g rms A = Acceleration: g rms
F = Frequency: CPM F = Frequency: CPM
1g rms = 9.8m/sec2
ISO 10816-3 Vibration Severity Chart
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Certification Exam - Reference Page 3 of 10
ISO 10816-3 Vibration Severity Chart
Transducer Operating Regions
Frequency Range
100
Beyond amplifier voltage range
10
Volts out 1
Dynamic Range
0.5 g broadband response
of the (100 mV/g sensor)
.1
Sensor
.01
Operational Range
.001
.000 1
.000 01
.000 001
Below electronic noise floor
.000 000 1
.1 Hz 1 Hz 10 Hz 100 Hz 1000 Hz 10 kHz 40 kHz
6 cpm 60 cpm 600 cpm 6000 cpm 60 kcpm 600 kcpm 2.4 Mcpm
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Page 4 of 10 Certification Exam - Reference
Transducer Frequency Transducer Frequency
Response - Magnets on Curved Response - Magnets on Flat
Surfaces Surfaces
Transducer Frequency
Response - Stingers or Hand Transducer Frequency
Held Probes Response Curves
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Certification Exam - Reference Page 5 of 10
Transducer Effectiveness Regions
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Page 6 of 10 Certification Exam - Reference
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Certification Exam - Reference Page 7 of 10
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Page 8 of 10 Certification Exam - Reference
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Certification Exam - Reference Page 9 of 10
Stage One: Airborne Ultrasound, Shock Pulse, PeakVue, Stage Two: Envelope, Demodulation and Acceleration
Spike Energy, Envelope Spectrum
Stage Three: Outer race fault (inner race rotating) Stage Three: Outer race fault (outer race rotating)
Stage Three: Inner race fault (inner race rotating) Stage Three: Ball or roller fault (inner race rotating)
Stage Four
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
Page 10 of 10 Certification Exam - Reference
This page intentionally left blank
Copyright © 2016 Mobius Institute Board of Certification
Document ID: CRMVA-2-ENG
