3. Compass Record Selection — Radial Gauge

In this step you select the Compass record that the Radial Gauge widget will use. Your record must return a single row with a single numeric value; the gauge displays this value with its pointer.

Wizard route: /cartography/add/selectcompass

Prerequisite

Steps 1 (Gauge) and 2 (Radial Gauge) must be completed.

→ 02 — Chart Type Selection

1. Compass Record List

2. Suitable Record Structure for Radial Gauge

-- Instantaneous OEE
SELECT ROUND(oee_percent, 1) AS oee
FROM oee_calc
ORDER BY ts DESC
LIMIT 1;

-- Instantaneous kiln temperature (MQTT/TimescaleDB)
SELECT temperature
FROM sensor_log
WHERE machine_id = 1
ORDER BY ts DESC
LIMIT 1;

Column	Role in Step 4	Type
Single numeric column	Value Source	NUMERIC

Single Row Is Mandatory

If the query returns more than one row, the gauge uses only the first row. Guarantee this with ORDER BY ts DESC LIMIT 1.

MQTT for Gauge

An MQTT topic pushes a single value on every update, making it ideal for Radial Gauge. Select an MQTT record in Compass; the gauge flows live.

3. Compatible Data Sources for Radial Gauge

Data Source	Radial Gauge Compatibility	Notes
MQTT (live)	✅ Ideal	Single value per message; gauge is live
PostgreSQL / MSSQL / MySQL	✅ Suitable	Most recent value with `LIMIT 1`
REST API	✅ Suitable	API must return a single object / single value
Excel Offline	⚠️ Limited	Reads a single cell from the sheet; not live

4. Search and Tag Filter

Action	Effect
Search box	Instant filter
Tag filter	Only tags in use
Clear	Reset filters

Gauge Tags

Use gauge, kpi, live tags in Compass for gauge queries.

5. Confirm the Record

When you click a record the row is highlighted. Click the Next button at the top right to proceed.

Proceeding Without Selecting a Record

If no record is selected, Next gives a warning.

6. Excel Offline Sheet Selection

For Excel records, an additional Sheet dropdown appears.

7. Preview Execution

When you press Next, the record is executed and the result is held in memory.

8. Common Errors

Symptom	Likely Cause	Resolution
Gauge shows value 0	Record returns an empty row	Test the record in Compass
Multiple values	`LIMIT 1` missing	Add `LIMIT 1` to SQL
Value Source dropdown empty in Step 4	No numeric column	Return a numeric column with `ROUND` / `CAST(... AS NUMERIC)`

9. Next Step

→ 04 — Radial Gauge Axis Design