Signal Strength

Signal Strength

Device Sentinel watches the radio link quality of every device that reports one, learning each device's normal range and watching for a link that sits unusually low against its own normal. This screen tunes how that judgment works and who is excluded from it.

Judged Against Itself, Never a Chart

There is no universal number for a healthy signal. A sensor two rooms from the coordinator lives its whole life at a level that would mean trouble for one in the same room, and both can be perfectly reliable. So Device Sentinel never compares a device to a fixed threshold or to other devices: each is judged against its own history alone.

Two scales exist, LQI (higher is better) and RSSI in dB (closer to zero is better). Each device is judged on whatever it reports, and the two are never mixed.

Readings stuck at a rail value (255 LQI or -128 RSSI) are stale reports, not strong or weak links. They never feed the learning, and a device pinned there for three or more days is flagged as railed, which is its own finding.

The Learned Floor and the Danger Line

Each device's floor is the low edge of its own recent history: the lowest daily readings over the learning window, with the worst days trimmed off as anomalies so one terrible day does not define normal.

The danger line sits a margin above that floor. Time a device spends below its line is dwell, and dwell is what the chart and the anomaly table report. The comparison is strictly below, so a reading sitting exactly on the line does not count, and a device holding steady at its own floor reads zero.

The line is capped so it can never sit up among the readings a device makes every day: the cap is the device's recent average, less at least a small clearance (two LQI quantization steps, or 3 dB of RSSI). A device whose signal barely moves therefore reads healthy while it holds its normal value, however close to its floor that value sits.

The Four Sliders

They are listed here in the order they appear on the screen.

• Sensitivity (default 5, range 0 to 10): The margin above the floor, as a percentage of the distance between that floor and a perfect link (255 LQI, or -20 dBm). A device living near the dropout point gets the widest margin, and the margin narrows as a floor approaches perfect, dying to nothing there. A floor already below the dropout point (50 LQI, or -90 dBm) is given the same margin as one sitting on it, because everything down there is already trouble. Higher raises the line and flags dips sooner; at 0 only the lift below applies.
• Line lift (default 0, range 0 to 2 in quarter steps): A flat amount added to every device's line, in signal units rather than a percentage. It is the same amount at every floor, so it survives where the margin has narrowed to nothing and keeps a minimum watch on even the strongest links. Leave it at 0 unless you want that watch.
• Red Threshold (default 10, range 5 to 20): The dwell percentage that colors a day red on The Signal Dwell Chart and drives its Days Over Red column. This is a chart marking only; it does not alert.
• Anomaly Trim (default 0, range -2 to +2): The floor discards one lowest reading per full week of history on its own; this setting modifies that count. Positive discards more; negative discards fewer, and at least one reading always survives to be the floor.

What Alerts and What Does Not

A railed signal becomes a problem list item and follows the normal notification path, because a device reporting a false value is a real finding.

Low dwell is recorded and charted but never pushes. Signal alerting is deliberately held back while the recorded data matures; the state of that work is on The Signal Dwell Chart.

The Excludes

Excluding a device here stops signal judgment and reporting for that device only; its battery and freeze watching continue. For dropping a device entirely, use Global Exclusions.

The three lists run broad to narrow (integrations, labels, devices) and interact exactly like the global lists: a broader exclusion swallows the narrower entries it covers when you save.