Martino FerrariandClaude Opus 4.6
b505706d92
The SI prefix ladder in format_measure() was gated on a non-empty unit, so two decimals of a small unitless value printed `0.00` -- the reading gone, not merely coarse. That is a whole class of channels rather than a corner: a CONFIG need not declare a unit, and a math channel never has one. Below 1e-12 the same loss happened even with a unit, so that range falls back to three significant digits. With no unit the prefix goes tight against the number (`585.24m`), since the space exists to separate the number from its unit and a spaced `m` alone reads as metres. The mock declared `unit="V"` for every data signal, which is why no probe could see this; it now takes `--unit ''`. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
44 lines
2.7 KiB
Plaintext
44 lines
2.7 KiB
Plaintext
<b>Measurements</b>
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A measurement is a statistic of the <i>visible window</i> of one signal, recomputed as that
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window moves. The pane lists them with their values; each can also draw its result on the plot.
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<b>How to reach it</b>
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The measurements button in the toolbar, or <tt>m</tt>. The pane's <tt>+</tt> adds one; clicking
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a row opens the dialog where the signal, the type, the threshold share and the on-plot marks are
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set, with <b>Save</b> and <b>Delete</b>.
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<b>Worth knowing</b>
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• The types are average, top, bottom, min, max, peak to peak, amplitude, pulse duration, period
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and frequency. <i>top</i> and <i>bottom</i> are the means of the upper and lower halves, which
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is why a unit sine reads 0.637 (2/π) rather than 1.
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• The on-plot marks come in two kinds and the mix is the reading: a <i>level</i> mark is a ruler
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at a value, a <i>time</i> mark is a marker at a position. An average draws one level mark; a
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max draws a level mark <i>and</i> a time mark at the first sample that reached it.
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• Marks cannot be dragged. A measurement mark says what the measurement measured, so it is
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created unselectable — as is the trigger marker.
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• A pass is throttled to a cadence rather than run every frame, so a ruler over a live view is
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<i>stepped</i>. The number and the ruler come from the same pass, so they always agree.
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• An invalid pass keeps its <i>level</i> marks and drops its <i>time</i> marks. A level is a
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property of the signal and outlives the window; a position inside the window does not. That is
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what stops the rulers blinking off at a mode change.
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• A window with too few crossings reads <tt>invalid</tt> / <tt>--</tt> rather than a plausible
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invented number. Frequency over a window holding one edge is the usual case.
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• <tt>frequency</tt> is reported in Hz and <tt>period</tt>/<tt>pulse duration</tt> in seconds;
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every other type carries the channel's own unit. A value is written with a <i>metric prefix</i>
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so its digits sit in <tt>1..999</tt> — <tt>636.62 mV</tt>, not <tt>0.64 V</tt> — including when
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the stream declares no unit at all, which is always the case for a math channel: there the
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prefix goes tight against the number (<tt>636.62m</tt>), since two decimals of an unprefixed
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small value is <tt>0.00</tt>.
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• Cost is bounded by reading the summary pyramid the producer already maintains, not the raw
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window. The values are still exact: a bucket's sum is a sum.
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<b>Example</b>
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On a 1 Hz ±1 sine: <tt>average=0</tt>, <tt>top=0.636620</tt>, <tt>bottom=-0.636620</tt>,
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<tt>max=1</tt>, <tt>min=-1</tt>, <tt>peak to peak=2</tt>, <tt>amplitude=1</tt>,
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<tt>pulse duration=0.5 s</tt> (duty 0.5), <tt>period=1 s</tt>, <tt>frequency=1 Hz</tt>. Over a
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2 M-sample window those two passes read about 0.1% of the samples.
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