Tube Display
Show a fill level as a vertical sight-glass cylinder with the Tube display — tanks, silos, reservoirs.
The Tube display is a vertical cylinder that fills from the bottom as the reading rises between a minimum and a maximum, with tick marks down the side and the value shown on the tube. It reads like a physical sight glass — the fill height is the reading.
Tube is the natural choice for anything you already picture as a level. Because the conditions decide the colors, it works equally for "how full" and "how empty" — a tank filling up, or a reserve draining down.
Watch a drop, or watch a rise
The Tube has no built-in "good" or "bad" end. You decide which direction is the problem and paint the conditions to match — the same widget covers two opposite jobs:
Monitor a decrease — when the danger is running low. A diesel or heating-oil tank, a chemical reserve, a water cistern: the level falls as it's consumed, so put the warning colors at the bottom. The column reads green while well stocked and turns yellow then red as it drains toward empty, so a refill is never a surprise.
Monitor an increase — when the danger is rising too high. A sump or drainage pit kept low by a pump: if the pump malfunctions the water has nowhere to go and the level climbs, so put the warning colors at the top. The column sits short and green in normal service and rises into a red band near the overflow point, flagging the fault before it floods.
The mechanism is identical — only where you place the red condition changes. Both setups are shown in full below.
When to choose it
A genuine physical level — a storage tank, a silo, a cistern, a reservoir, a sump pit.
A reserve or consumable where the question is "how much is left," and the fill falling toward the bottom is the signal.
A contained level that must not climb past a safe point, where the fill rising toward the top is the signal.
Any reading where an operator's instinct is to picture a column rising and falling.
Wherever a value has a meaningful floor and ceiling and "level" is the mental model, the Tube fits — the conditions then decide which end is the one to watch.
Configure a Tube display
Here is a complete setup for one real case — monitoring the level in a storage tank so you know when to refill it. The tank stands 100 cm tall, and a level sensor reports the current fill in centimeters — so the reading is 0 when the tank is empty and 100 when it is full to the top. Those two numbers, 0 and 100, become the scale for the whole widget, and every condition is a slice of that 0–100 cm height. This is only an example: the same steps fit salt, grain, feed, water, fuel, or any material on a scale — only the device and the numbers change.
Open the dashboard in edit mode and click Last data in the widget picker. The settings panel opens on the Datasource tab, with no data sources yet.
Click Add datasource. A Datasource 1 block appears.
In the block, click Choose device and select the tank's level sensor.
Click Add metric. A metric row appears.
In the row, set Data type to Telemetry, choose the fill-level reading under Device metric, and pick an Icon.
This display needs a number. The Device metric list offers every metric type, but a gauge fills against a scale — pick a numeric reading here; a non-numeric text value reads as 0. (To show text or an on/off value as-is, use the Value display.) To change how a metric is stored, open Devices → Metrics — see Metrics.
Click Conditions: N to open the Conditions modal. Set a Default color — the color the reading falls back to whenever none of your conditions match the current value — then for each band click Add condition and fill the row — enter a Condition name, set Data type to Number (the condition's own Data type, not the metric row's), Because for this example our tank is 100cm in Height enter From 0cm (Bottom of the tank) and To 100cm , and pick a Color. Then you can enter the color levels. For example:
Working up from the bottom:
"Critical" — From 0, To 10 — burgundy (a deep red, darker than the next band)
"Refill now" — From 10, To 30 — red
"Refill soon" — From 30, To 60 — yellow
"Healthy" — From 60, To 100 — green
Click Save to close the modal. 7. Click Next to open the Appearance tab. 8. Enter a Widget name — for example "Tank level" — and an optional Description. 9. Under Widget type, choose Tube. A Value range section appears for the metric. 10. Set Min value to 0 (an empty tank) and Max value to 100 (full to the top) — the same 0–100 the conditions are built on — and set Tick marks to 10 so the tube is divided every 10 cm (each tick takes the color of the band it falls in). 11. Switch on Display data legend if you want the metric labeled, then click Save.
The result: a cylinder that stands tall and green while the tank is well stocked, drops through yellow and red as the contents run down, and shows a burgundy sliver when it is nearly empty — so a glance tells you when to act. Swap in a different sensor and different band edges and the very same setup watches a salt tank, a grain store, a feed bin, or a chemical drum.
Worked examples
Sump or groundwater pump — a rising level A sump or drainage pit relies on a pump to keep the water low; if the pump fails, the level climbs and the basement floods. Put a level sensor in the pit and show it on a Tube. The pit is about 100 cm deep, so 0 is a dry floor and 100 is water at the overflow point — set Min value 0 and Max value 100, then add three conditions: "Normal" — From 0, To 30 — green; "Level rising" — From 30, To 60 — yellow; "Critical — check the pump" — From 60, To 100 — red. In normal service the column is short and green; if the pump quits, the water has nowhere to go and the column climbs into the red band. The sensor matters here: a level sensor reads higher as the water rises, while a top-mounted distance sensor reads lower — set the red condition on whichever value represents high water for the sensor you installed. The Tube makes the rising level visible on the dashboard; for an actual notification, use an Alarm.
Heating-oil or rainwater tank Any stored liquid works the same way — a level sensor in a heating-oil tank or a rainwater cistern, with Min value 0 for an empty tank and Max value set to that tank's own full level. The tube rises as the tank fills and falls as it is drawn down, with conditions coloring the low end so a refill is never a surprise.
See also
Last Data Widget — Full setup reference and the other display types
Conditions — Numeric From/To color rules for the fill
Other display types: Value · Doughnut · Pie · Gauge · Radial gauge
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