Alerts

How an alert works

1. A rule names one or more channels and a condition on them: above or below a value, outside or inside a band, equal to a value, changing, or silent for a while.
2. It waits until a live stream or a loaded file has those channels, then checks every sample.
3. When the condition holds for For at least seconds, the alert is raised: the charts mark the span, a notice appears in the corner, and an optional sound plays.
4. When the condition has been false for Clear after seconds, it clears. The span on the charts ends there.
5. Hysteresis keeps a noisy signal from flickering: an alert above 120 with hysteresis 2 stays raised until the value drops to 118.

Create one from a chart’s alarm line

1. Open the chart’s settings and the alarm line of a series, a gauge, an axis, or the chart (the clock button).
2. Turn on Notify (“Turn this line into an alert”). The rule editor opens below the line, filled in from it: the channel, the value, a severity from the line’s colour.
3. Adjust the name, timing and conditions, then Accept. The line now shows a bell, follows the alert’s threshold, and is dashed while the alert is active.
4. The same alert is listed in the Alerts panel (the bell in the left rail), where you can edit or delete it. Editing it in either place changes the same alert.

Channels that don’t exist yet

You can name a channel nothing has yet. The editor says “Not seen yet: the rule waits until a stream or file has Oil_Temp”, and the rule is saved anyway. It shows Waiting for Oil_Temp until a stream starts sending that channel or you load a file with it; then it starts checking from that sample on.

Names are matched exactly, including upper and lower case: Oil_Temp and oil_temp are different channels. When a name differs only by case from one you have, the editor offers it.

Test on loaded data

In the Alerts panel, Rules, Test on loaded data runs your alerts over every loaded file against the worksheet’s X column, from its first row. It reports per file how many alerts it found, or what a rule still waits for, and marks the spans on the charts, so you can tune thresholds on yesterday’s run before going live.

Where alerts run

Alerts run in your browser while the workbook is open; closing the tab stops them. They are saved in your account (personal alerts) or in a project, so the next time you open the workbook they run again.

In end-to-end encrypted projects the rule’s conditions are encrypted in your browser before they are saved; see Data flow.

Limits