Three machines are failing.
Can you read them?
A bearing breaking down. A machine flexing itself out of shape. A phase survey that settles an argument the spectrum cannot. Three simulators, already running, showing the time waveforms and spectra of the real faults behind them — and the analysis that catches each one. This is the work TCAT certifies you to do. Hover any plot for a cursor readout.
Nothing to set up
Every simulator starts on its own and cycles through its states, so the difference between a healthy machine and a failing one plays out in front of you. It runs slowly by default; set it to analyst speed below if you would rather. Take manual control any time — the cycling stops and waits.
Simulators, not videos
You are driving an analyser, not watching a clip. Pick a state and the machine, the waveform, the spectra and the verdict are all worked out on the spot from the fault you selected — bearing geometry, running speed, severity and all.
Analyser-grade maths
Band-pass, Hilbert transform, envelope, FFT, single-bin phase — the same chain a real instrument runs, executed here on the samples in front of you. Change a state and the numbers move because the transform re-ran, not because a caption changed.
Words this page uses, in plain English
- Time waveform
- The raw movement, plotted against time. What the sensor actually felt, in order.
- Spectrum · FFT
- The same movement sorted by frequency instead of time. Tall line = a lot of movement repeating at that rate.
- 1× (one times)
- Once per shaft revolution. At 1500 rpm that is 25 times a second.
- BPFO
- Ball Pass Frequency, Outer race — how often a rolling element passes one spot on the outer ring. A defect there gets hit at that rate.
- Envelope
- A way of listening for the rhythm of small repeated knocks instead of the loud ringing they cause. It is how a bearing fault is found before it is loud.
- Phase
- Whether two places on the machine move at the same moment or at opposite moments. Same time, or opposite, is the whole diagnosis in many cases.
- ODS
- Operating Deflection Shape — the picture of how the whole machine is flexing while it runs, not just how much.
- Orbit
- The path the shaft centre traces as it turns, drawn from two sensors at right angles.
Watch a bearing fail — and watch the raw spectrum miss it.
An outer-race defect on a 6205-type bearing at 1500 rpm, in three states. The overall level barely moves between healthy and early. The raw spectrum has no line at BPFO. The envelope spectrum has one, with harmonics. That gap is why enveloping exists, and it is the single most useful thing a Category II analyst knows.
Bearing fault · outer race · envelope analysis
The picture below is the machine this signal comes from. The flash at the bearing is a rolling element hitting the damaged spot — that is the event everything else is about.
Bottom-left is the ordinary spectrum. Bottom-right is the envelope spectrum. Same signal, same moment — watch which one shows a clear line when the fault is still early.
The verdict box under the plots is written from the numbers, not from a script. Switch between Healthy, Early and Advanced and watch it change with them.
The machine behind the signal. The flash at the housing is an impact as the rolling elements pass the defect.
A shaft spinning in two bearings. One bearing has a small damaged patch on its outer ring. Every time a ball rolls over it, the housing gets a tiny knock — far too small to hear or feel, but the sensor catches it.
The signal itself. Green ticks mark the nominal BPFO spacing — the impacts jitter about them, which is exactly why a bearing line smears while a shaft order stays sharp.
The raw movement, as it happened, left to right in time. The green ticks are where the knocks should land. They arrive near the ticks but never exactly on them — a bearing slips slightly, so the rhythm is close but not perfect.
Raw spectrum from 200 Hz up, so the shaft orders do not set the scale. The impact energy is not missing — it is parked up at the housing ring-down, thousands of hertz above the defect rate that caused it.
The same raw spectrum, zoomed to where BPFO, BPFI, BSF and FTF would appear. In the early state there is nothing there to find.
This is the obvious place to look for a bearing problem — and while the fault is early, there is nothing here. This is how a real bearing fault gets missed.
Band-pass the ring-down, take the Hilbert envelope, transform again. BPFO and its harmonics, from the same samples.
The same signal, listened to differently: the loud ringing is thrown away and only its rhythm is kept. The knock rate that was invisible next door is now the tallest line on the plot.
Two details worth naming, because they are what separates a competent analysis from a lucky one. First, the demodulation band is found, not chosen: the page scans candidate bands and keeps the one whose band-passed envelope has the highest kurtosis — the most impulsive one, which is not always the one with the most energy. Second, every defect frequency on the plots is computed from the bearing's geometry at the running speed, not typed in. Change the speed and they all move, in the ratios the kinematics fix.
Fig. 1 — where BPFO, BPFI, BSF and FTF come from. Four contact geometries, four rates, one set of formulae.
Fig. 2 — the envelope chain the panel above actually executes: band-pass, demodulate, low-pass, transform.
An operating deflection shape is a machine caught in the act.
Amplitude alone tells you something is wrong. An ODS tells you what is moving against what. Each station on this train moves at its own measured amplitude and its own measured phase, so the animation is not an impression of shaking — it is the deflection shape, and it changes character completely between the three states.
Operating deflection shape · motor–pump train
The drawing below moves the way the real machine moves. Do not look at how big the movement is — look at which parts move together and which move opposite each other.
Each row is one measurement point. The last column says whether that point is moving with the reference point or against it. A row that turns is a point moving the other way.
Unbalance, soft foot and resonance make the same machine flex in completely different shapes. One foot moving alone means something different from half the machine moving together.
Reference: a beam's second bending mode. When an ODS looks like a mode shape — antinodes, a dead node, a 180° flip across it — the rotor is not the problem. The structure is.
The phase column is measured, not asserted: each station's amplitude and phase are read back out of its own samples by a single-bin transform. The table's last column is the one that decides — a station 180° from the reference is moving the other way, and the row turns. In the soft-foot state exactly one foot and the plate under it do that. In the resonance state half the machine does.
Phase is the reading that settles the argument.
Unbalance, misalignment and looseness all raise 1×. The spectrum narrows it; the phase relationships close it. The needles below all turn at running speed, each trailing by its own measured lag against the tacho reference — so the 90°, the 180° and the refusal to repeat are things you watch, not things you are told. The survey is re-taken every couple of seconds, live.
Phase survey · unbalance vs misalignment vs looseness
Each dial is one sensor position. The needle points to when in each turn that spot reaches its highest point. All four turn at the same speed — what matters is where they point relative to each other.
A quarter turn apart, or dead opposite, are the two relationships that decide the answer. The chips below name the rule each pair is being tested against, and whether it fired.
The survey is re-taken every few seconds. Steady numbers mean one thing; numbers that will not settle are not a bad measurement — they are the finding.
The spectrum at 2V. It narrows the field — it does not close it. Two of these three states can look like this.
Shaft centreline orbit for the same state: a circle for a rotating force, a figure-of-eight when it reacts twice a turn, truncated when something is loose.
The last chip is the one people underuse. A phase reading that will not repeat is not a bad reading — it is the finding. Looseness does not re-seat identically every revolution, so the number moves between acquisitions, and that instability is diagnostic in a way no single number on a spectrum is. Watch the row of successive 2V readings above: steady for unbalance, wandering for looseness.
This is the job, not a brochure.
Three panels, three faults, three different pieces of reasoning — and every one of them is something a condition-monitoring analyst is paid to get right on an ordinary Tuesday.
Most training sites show you a screenshot of a spectrum. This one hands you the instrument. The signal generator, the FFT, the band-pass, the Hilbert transform and the bearing kinematics all ship with the page and run in your browser — nothing is fetched, nothing is pre-rendered, and nothing is a picture. Change a state and the numbers change because the transform ran again.
That matters commercially, not just technically. A plant does not pay for someone who can recognise a labelled diagram; it pays for someone who can look at an unlabelled machine and say what is wrong, how sure they are, and what to do about it this week. That is what TCAT certifies, and these three panels are written at exactly that level.
This lab is the demonstration, not the exam. The credential is decided by graded diagnostic tasks — see how assessment works.
TCAT is a TIERA-issued credential aligned with the ISO 18436-2 body of knowledge. It is not an accredited ISO certification, TIERA is not an ISO certification body, and TCAT training hours do not count towards the formal training an accredited ISO 18436 certification requires.
If what you just watched felt unfamiliar rather than obvious, you are not TCAT's audience yet — and that is a fine place to be. TCAT assesses people who already work with vibration data; it does not teach the subject from zero. The honest starting point is the free TIERA 101 primers: self-paced, beginner-first, no cost, and they issue a completion badge when you finish. Go there first if that is where you actually are — nothing about TCAT is a reason to skip them, and nothing you do there is required before you come back.
This is the level the assessment is written at.
If reading these three panels felt like your job, TCAT is aimed at you. If it felt like a foreign language, start with the free primers first.