Components

The webapp’s components live in src/lib/components/. None talks to NATS: the pages load and save data, and the components display and edit it. That keeps the NATS code in one place per page and makes the components easy to reason about.

RealTimePlot

src/lib/components/RealTimePlot.svelte draws one channel as a line on a <canvas>. The plot page subscribes to the channel, applies the calibration, and passes the samples in.

The time axis puts 0 at the newest sample in continuous mode and at the trigger in frozen mode. Its ticks fall on round steps (1, 2 or 5 times a power of ten) counted from 0, in seconds or milliseconds, and the title says which: “Time (s)”, or “Time from trigger (s)” for a capture. Ticks are about 70 pixels apart; on a narrow plot they move closer, down to what the labels need, so at least a few show without overlapping. The value axis is titled “Value (unit)”, and the tick labels are kept clear of the title.

Continuous mode shows the last timeWindow seconds with the newest sample at the right. The right edge is the newest sample’s own time, not the browser clock, so a slow link does not leave a blank strip at the edge.

Frozen mode is used after a trigger fires. It shows the samples from frozenPreWindowSec before to frozenPostWindowSec after the trigger, with the trigger at 0 s, and holds still so the event can be inspected. A badge reads COLLECTING while the post-trigger samples are still arriving, then FROZEN.

Drawing is batched to one redraw per animation frame. Each frame keeps only the samples inside the window and reduces them to one minimum and one maximum per pixel column. At 2 kHz a ten-second window holds 20,000 samples for a plot a thousand pixels wide, so drawing every sample would be slow, and keeping the minimum and maximum (rather than averaging) means a one-sample spike is still visible. The line breaks wherever a sample is missing or the stream has a gap, so a gap is never drawn over. With autoscale on, the y axis snaps to round 1, 2 or 5 steps, and in continuous mode it only widens, so the scale does not jump with every frame.

Under the canvas the plot shows:

• Data Points: the samples inside the visible window, not everything held in memory.
• t=0 Src: the source clock of the sample at 0.
• Lag: how long that sample took to reach the browser. It is hidden while a trigger capture is held, since a held capture is not live.
• Latest: the latest value, in unit.
• Raw: when calibrated is set, the latest reading in volts before calibration.

The component emits no events. It exports one function, getDisplayedYRange(), which returns the y range of the last drawn frame; the channel card uses it to start Y Min and Y Max from what is on screen when Auto Y-Scale is turned off.

Plot page components

The plot page is split into four components. All of them only display and edit state the page owns.

• ChannelCard shows one plotted channel: the header with the data format, the unit tag, the trigger state and, for a channel with filters, the Filtered / Raw switch and a line naming the filters (and any that cannot run at the channel’s rate), the Mode & Axis panel, the Trigger Settings panel in the trigger modes, and its RealTimePlot. Props: view (the channel’s ChannelView), dataFormat, unitInfo and onchange, called after a change that alters what the plot shows.
• StatsPanel is the Data Statistics card. Props: config, assetNumber, channels (the plotted ones), views and connectionState.
• ExportDialog is the Export Historical Data form. Props: channels, selected, bindable start and end, error, warning, exporting, progress, total, filteredChannels (channels with filters; the “Include filtered values” box shows when there are any), bindable includeFiltered, and the callbacks ontoggle, onsubmit and onclose.
• ConnectionBanner is the yellow Reconnecting or red Disconnected banner. Props: state, reason and onreconnect.

LabJackConfigModal

src/lib/components/LabJackConfigModal.svelte is the form for adding or editing one LabJack configuration. It edits a copy of the document and hands the result to onSave; the LabJack list page writes it to the avenabox bucket. When adding, the page builds the key from site_id, box_id and source_id; when editing, it keeps the existing key. An empty source falls back to the LabJack name and then to asset<NNN>, the same order the live and export subjects use.

The form covers every field of the document: the identity fields, the subject root and stream, rotate_secs, and under sensor_settings the scan rate, scans per read, gain, on/off switch, enabled channels, and for each enabled channel its sensor type, calibration, unit and noise filters. Saving validates the whole form first; while adding, a name or asset number already used by another configuration is flagged as you type. Escape, the close button, Cancel or a click outside the form closes it without saving; if anything was changed, it asks first.

Channel calibration

Each channel has exactly one calibration, edited in place and saved with the rest of the form. There are no named presets and nothing to name.

• Sensor type (stored in data_formats): Voltage, Strain gauge, Pressure, Temperature, Current or Resistance. It decides which units are offered.
• Calibration: None (raw volts), Linear (a·x + b) or Polynomial (c0 + c1·x + c2·x² …), where x is the raw reading in volts.
• Unit: V for None. A linear or polynomial calibration must have a unit; switching to one picks the sensor type’s first unit (µε for a strain gauge, kPa for pressure). Strain gauges offer µε, mV/V and V; pressure kPa, Pa, bar and PSI.

The card header sums the channel up: sensor type, unit, the formula and what a raw reading of 1.000 V becomes, for example y = 481.26·x + 1058.722 · raw 1.000 V → 1539.98 µε.

For a strain gauge with a linear calibration you can type a and b or use the bridge helper. It takes the gauge’s calibration factor from its certificate (µε per mV/V, for example 481.26 for SG194 or 705.47 for SG159), the bridge excitation in volts, the amplifier gain (may be negative) and, optionally, the raw reading at rest, and computes

µε = factor × 1000 × (raw − zero) / (excitation × gain)
a  = factor × 1000 / (excitation × gain)
b  = −a × zero

It shows a, b and the 1 V preview before you apply them. What is stored is a plain linear calibration with unit µε; the helper’s inputs are not saved.

What the form saves for a channel, by sensor type:

{"type": "identity", "unit": "V"}
{"type": "linear", "a": 481.26, "b": 1058.722, "unit": "µε"}
{"type": "linear", "a": 250.0, "b": -125.0, "unit": "kPa"}
{"type": "polynomial", "coeffs": [0.5, 100.0, 0.2], "unit": "°C"}

On save the calibration’s unit is also written to the channel’s measurement_units entry, and a calibrated channel’s data_formats entry is set to a sensor type that offers the unit, so older readers see the same labels. An id from an older configuration is kept until the formula is changed; the form never asks for one.

Configurations saved before calibrations had units still open: a calibration without unit takes the channel’s measurement_units entry unless it is V. If it is V the unit box is empty and yellow, and the form will not save until a unit is chosen. The calibration.* preset keys that earlier versions wrote are no longer read.

Channel filters

Under each channel’s calibration is a Filters box: Remove spikes, Remove 10 Hz and Remove 11.9 Hz switches, and High-pass and Low-pass cutoffs in Hz (blank turns one off). They are saved in sensor_settings.filters (see LabJack configuration). The box names the filters that cannot run at the configured scan rate, and how far behind the live plot runs because of the despike window. A channel with every filter off has no entry, and a configuration with no filters has no filters field. Turning a channel off drops its filters.