order opsignal → tableimport fullseye as fs; fs.ledger.order_spectrum(x, rate, rpm, samples_per_rev=64, revolutions=None, max_order=None, n_peaks=5) (実装を直接呼ぶなら import acoustics; acoustics.order_spectrum(x, rate, rpm, samples_per_rev=64, revolutions=None, max_order=None, n_peaks=5)、台帳から引くなら opsacoustics.get("order_spectrum"))Amplitude against shaft order — the spectrum a run-up should be read in.
:func:angular_resample followed by an rFFT over a whole number of
revolutions (the record is cropped to that). Bin spacing is
1 / whole_revolutions in orders.
revolutions overrides how many whole revolutions to keep, and it matters
more than it looks. An order o lands exactly on a bin only when
o * revolutions is an integer; otherwise it straddles two and both read
low. Measured on the run-up below, which happens to cover 79.994
revolutions:
============== ========== ============= ============= revolutions resolution amp at o=1.0 amp at o=3.5 ============== ========== ============= ============= 79 (default) 0.012658 0.999967 0.636961 78 (even) 0.012821 1.000009 0.999371 ============== ========== ============= =============
That 0.637 is the classic two-bin scallop loss, and nothing raises: the peak
is at the right order and 36 % too small, with a second peak of almost equal
height one bin away (measured 0.6370 at order 3.4937 and 0.6353 at 3.5063).
Cropping to an even number of revolutions puts every half-integer order
on a bin. The default is the largest whole number available; pass
revolutions when the order you care about is fractional.
Returns a dict: orders, magnitude (single-sided, 2/N),
peak_order, peak_amplitude, peak_orders / peak_amplitudes,
resolution_order, whole_revolutions, samples_per_rev,
mean_rpm, max_order.
Measured, and this is the whole argument for the operator. A 4 s run-up from
600 to 1800 rpm at 5 kHz carrying exactly two shaft-locked components
(orders 1.0 and 3.5, unit amplitude) plus one fixed 400 Hz resonance, read
with revolutions=78:
========================== ===================== ==================== quantity ordinary spectrum order spectrum ========================== ===================== ==================== order-3.5 peak amplitude 0.070203 (of true 1) 0.999371 (of true 1) its -3 dB width 66.50 Hz (= 3.33 ord) 0.00000 order 400 Hz resonance amplitude 1.0000, one bin 0.0517, over 26.7 ord ========================== ===================== ====================
The ordinary spectrum recovers 7 % of the shaft-locked component’s amplitude, because the energy is spread over 3.3 orders’ worth of bins; the order spectrum recovers 99.94 % of it in a single bin whose -3 dB width is one bin. The 400 Hz resonance goes the other way — sharp in hertz, smeared across 26.7 orders after resampling. That reversal is the diagnostic, and it is why both spectra are worth computing: what stays sharp under angular resampling turns with the shaft, and what stays sharp under ordinary transformation does not.
Raises ValueError: everything :func:angular_resample refuses (in
particular the aliasing refusal), a revolutions larger than the record
actually contains, and a max_order above the angular Nyquist
samples_per_rev/2.
py -3.11 examples/acoustic_condition_monitoring.pytable を入力に取れる)order)Provenance: acoustics.py — ACOUSTICS operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.