Vibration analysis vs Rotor

The application analyzes the data from the phone's accelerometer and builds a vibration spectrum. This allows the evaluation of not only the strength and frequency of the vibration, but also the speed of rotation of various mechanisms: fans, motors, various rotating components; since the vibration frequency often (but not always) coincides with the frequency of rotation. The application will be useful in determining the quality of fans and motors, in determining whether their actual parameters coincide with the ones declared by the manufacturer, it will find its uses in monitoring of malfunctions (e.g. in bearings) or while testing the quality of assembly and balancing of the homemade mechanisms with rotating parts. Do not expose your iPhone to an excessive vibration, as it may break. If the analyzed vibration is too strong, use a foam material pad, or put your iPhone at a distance where the force of the vibration is not dangerous to your device. In addition to decreasing vibration for the iPhone, a foam pad improves contact between the iPhone and the vibrating part, which makes the transmission of vibration more accurate and produces better results. BE SURE TO READ THE EXAMPLES OF THE VIBRATION SPECTRUM ANALYSIS AT THE APPLICATION WEB SITE (usefulmobileapps.com). Features of the full version of the application: • The choice of units of measurement. X-axis: Hz or RPM. Y-axis: g, m/s², ft/s², mm/s, in/s (ips), mm, mil, dB(A), dB(V). • FFT size (for built-in accelerometer): 64, 128, 256, 512, 1024, 2048, 4096 (data collection time from 0.64 sec. to 40 sec.). For an accelerometer connected to the headphone jack FFT size from 2048 to 131072. For Bluetooth-accelerometer FFT size from 512 to 32768. • Linear and logarithmic frequency scale. • Linear frequency scale with maximum details (there is a choice for the displayed frequency range). • Peak frequency detection. • Values of any point (for frequency scale and sound wave (at maximum detail)). • Selecting which axis of the accelerometer is to collect data. • Octave bands (1/1,1/3,1/6,1/12). • Window functions (Blackman, Hamming, Hann (Hanning), Blackman–Nuttall, Gaussian, Flat top). • Peak hold. • Exponential spectrum averaging. • Taking a screenshot by lightly touching the screen. • Root mean square (RMS, for vibration) or average value (AVG, for absolute values) for vibration wave. Values are calculated only for data displayed on the screen. • Calibration of the built-in accelerometer. Need EXCLUSIVELY for measuring absolute acceleration values (gravitational acceleration). To activate the settings, turn on the "Vibration wave" mode and turn off the "Only fluctuations" mode. The parameters of the accelerometer depend on the temperature and voltage of the battery, and may change over time. To obtain stable values, the accelerometer should work for several minutes. • Saving the measurement results in the application. Files with saved data (SavedData_[date]_[time].txt) can be copied to a desktop/laptop computer or transferred to another iPhone using iTunes. • Export data to a text ("Y=[y1 y2... yn]", "y1;y2;... yn", "x1;y1\nx2;y2;...") or WAV file. Number of points is adjusted via "FFT size". To export octaves, use "x1;y1\nx2;y2;...". • Accelerometer connects to the headphone jack (measurement range from 5 Hz to 24000 Hz). • A stroboscope for an external accelerometer (the feature was proposed by Todd French from Los Angeles, California). • Bluetooth accelerometer. When converting acceleration into speed or displacement, at 0-5 Hz frequencies noise starts prevailing over vibration peaks, which is why such frequencies are disregarded when doing the conversion. Should vibration frequency exceed 50 Hz, the peak will be recorded at an incorrect frequency, and hence speed or displacement will not be calculated correctly. Unrealistically high speed or large displacement may be a sign of this kind of false frequency.

Rotor turns your iPhone into a working vibration analyser. Hold it against a running motor, pump, fan or gearbox and read the overall velocity in mm/s RMS, graded A to D against ISO 20816, with the machine class cited. Then it tells you what is wrong, and shows you why it thinks so. THE NUMBER IS REAL Acceleration is integrated to velocity in the frequency domain, line by line, with a high-pass cutoff. It is never cumulative-summed in the time domain, which turns sensor bias into a wandering ramp. The graded overall is summed from a rectangular-windowed spectrum so it stays Parseval-exact instead of double-counting window leakage. If that means something to you, you already know why most phone vibration apps are wrong. VERIFY IT YOURSELF Rotor ships with a self-test. It runs a signal whose answer is known analytically through the same chain a real machine goes through, and shows you measured against expected, side by side. IT NAMES THE FAULT Unbalance, misalignment, looseness, blade and vane pass, gear mesh with sidebands, belt defects and electrical faults at twice line frequency. Every verdict quotes the lines it came from and gives you the specific next step. Check the coupling cold and hot. Inspect the impeller for build-up. Cut the power and watch whether the peak vanishes. IT KNOWS YOUR MACHINE Ten presets set the ISO class, the plausible speed range, where to hold the phone and which faults happen on that kind of kit. Enter the poles and supply frequency off the nameplate and Rotor computes running speed including slip. Count the blades or gear teeth, or measure the belt, and it draws those frequencies as labelled cursors. THREE AXES AT ONCE High axial vibration relative to radial is how misalignment is told apart from unbalance, so Rotor captures all three axes and shows which is worst. IT REFUSES TO GUESS If the sensor clipped, Rotor will not grade the capture, because a clipped waveform invents harmonics that look like severe looseness. If the signal is at the noise floor it asks whether the machine is running rather than awarding a confident Zone A to a desk. If a bearing's frequencies sit above what your phone can sample, it says so, because a missing cursor is not a healthy bearing. WATCH IT GET WORSE Log a reading and it keeps the full spectrum. Next month the trend line shows the overall crossing out of green, with the ISO zone bands drawn behind it. Rotor also compares against that machine's own baseline and lists the individual lines that grew, in dB. BEARINGS, THE HARD WAY Envelope demodulation, done properly. Band-pass the bearing's resonance, take the analytic signal by Hilbert transform, transform the envelope, and the defect rate falls out of the noise. Rotor matches it against the computed BPFO, BPFI, BSF and FTF to name which part is failing, computed from the bearing geometry. FIELD BALANCING Single and two plane by the influence coefficient method. Measure, bolt on a trial weight, measure again, and Rotor solves the correction weight and angle on a polar plot. READ THE SPECTRUM Orders axis, so 1x and 2x land on integers and a bearing line visibly does not. Peak table with frequency, order and likely cause. Linear, exponential and peak-hold averaging. Selectable resolution with the capture time shown. Hanning, flat-top and uniform windows. mm/s and microns or in/s and mils, with the ISO boundaries restated in both so the toggle never changes a verdict. PRIVATE BY DESIGN Everything runs on the device. No account, no cloud, no analytics, no network access at all. BE CLEAR ABOUT THE LIMITS The built-in accelerometer is usable to about 100 Hz. That covers unbalance, misalignment, looseness and ISO overall velocity on most slow and medium speed machines. It cannot see most bearing frequencies, and Rotor says so in the interface at the moment it matters rather than letting you believe a flat spectrum means a healthy bearing. That honesty is the reason to trust every other number in the app.