Vibration test rig

A Python script that simulates a small electric motor on a test bench: a single accelerometer channel sees rotational imbalance, misalignment, a non-integer bearing-defect harmonic, and broadband noise; a stereo microphone in the enclosure picks up the airborne sound. The script sweeps the motor's RPM up and down so the Waterfall widget renders an order-tracking spectrogram, and two Painter widgets draw an audio VU meter and a live system schematic, all from the same UDP stream.

Overview

This example exercises both new Pro widgets introduced in v3.3:

Waterfall (Campbell mode). The vibration channel feeds a 512-sample FFT at 1 kHz. The waterfall's Y axis is bound to the RPM dataset, so the spectrogram becomes a Campbell diagram (frequency on X, RPM on Y, amplitude as colour). Order lines (1×, 2×, 3×) appear as straight rays through the origin; the bearing harmonic at 5.43× shows up as a diagonal line at a different slope.
Painter (audio VU meter). Broadcast-style stereo VU with green/yellow/red zones, peak-hold markers that hold for 1.4 s before falling away, and dB-scale tick labels. All drawn in ~200 lines of JavaScript inside the project file.
Painter (system schematic). Live diagram of the rig: motor, bracket with accelerometer, and stereo microphones, each stage animated from its own dataset. The motor spins with RPM, the trace follows the vibration channel, and the mics pulse with level. ~380 lines of JavaScript.

Gauges for motor RPM and RMS vibration (computed by a rolling-RMS Lua transform on the vibration dataset) round out the dashboard so you can correlate spectrogram features with the sweep position.

Widgets exercised

Widget	Datasets	Purpose
Waterfall (Pro)	Vibration, with Motor RPM as Y axis	Order-tracking spectrogram (Campbell diagram)
Painter (Pro)	Mic L, Mic R	Stereo VU meter with peak hold
Painter (Pro)	Vibration, Motor RPM, Mic L, Mic R	Animated system schematic
Gauge	Vibration (RMS)	Rolling RMS level via a Lua transform
Gauge	Motor RPM	RPM sweep position
Plot	Vibration, Mic L, Mic R	Time-domain traces

Data format

The script emits one CSV frame per millisecond over UDP, terminated by a newline:

vibration,rpm,mic_left,mic_right\n

Column	Units	Range	Notes
vibration	g	-3.0 .. +3.0	Sum of 1×, 2×, 3× imbalance + 5.43× bearing + noise
rpm	RPM	900 .. 4800	Cosine sweep with the configured period
mic_left	dB FS	-60 .. +6	Tracks vibration envelope plus jitter
mic_right	dB FS	-60 .. +6	Independent jitter from `mic_left`

Usage

1. Start the simulator

The project includes a control loop that launches vibration_test_rig.py with its defaults automatically when you connect, so for a quick look you can skip this step and jump to 2. Configure Serial Studio. To explore the optional arguments below, run the simulator yourself before connecting (so the two don't run at once):

bash

python3 vibration_test_rig.py

Optional arguments:

--host HOST. UDP destination (default: 127.0.0.1).
--port PORT. UDP port (default: 9000).
--rate RATE. Sample/emission rate in Hz (default: 1000).
--rpm-min N. Minimum RPM (default: 900).
--rpm-max N. Maximum RPM (default: 4800).
--sweep-period SEC. Seconds for one full up + down sweep (default: 18).
--imbalance G. 1× rotational imbalance amplitude in g (default: 1.4).
--bearing-amp G. Bearing-defect harmonic amplitude in g (default: 0.45).
--noise G. Broadband noise amplitude in g (default: 0.08).

Examples:

bash

# Healthy motor (no bearing fault)
python3 vibration_test_rig.py --bearing-amp 0.0

# Loud bearing defect with a faster sweep so you can see the order line move
python3 vibration_test_rig.py --bearing-amp 1.2 --sweep-period 8

# Quiet rig (subtle harmonics, low noise)
python3 vibration_test_rig.py --imbalance 0.4 --noise 0.02

The script logs frame count and current RPM/vibration every two seconds.

2. Configure Serial Studio

Open Serial Studio (Pro build, since the Painter and Waterfall widgets are commercial features).
File → Open Project File, choose VibrationTestRig.ssproj.
The Network/UDP source is preconfigured for 127.0.0.1:9000. Hit Connect.

You should see:

The Vibration (Campbell) group rendering the Campbell diagram. Order lines from the imbalance harmonics will trace out as the RPM sweeps.
The VU Meter group with two horizontal bars rising and falling, with peak-hold markers that linger for ~1.4 s.
The System Schematic group animating the motor, bracket, and microphones in step with the live data.
The Vibration Gauge and RPM trend gauges tracking the rolling RMS level and the cosine sweep.

What to play with

Open the Project Editor and pick either Painter group — the JS source is right there in the editor. Tweak the colour zones, the peak-hold time, the motor animation. Hit Apply and the widget recompiles live.
Disable the bearing harmonic (--bearing-amp 0) and watch the diagonal line in the waterfall disappear, leaving only the rays from the integer harmonics.
Lower --rate to 250 Hz and notice how the waterfall still renders cleanly because the FFT sampling rate is fixed at 1 kHz inside the project — what changes is how often the Painter widgets' onFrame() ticks.

Files

vibration_test_rig.py — the UDP emitter.
VibrationTestRig.ssproj — Serial Studio project: 5 groups, two Painter scripts, Waterfall in Campbell mode, Lua CSV parser.