# measurement

> **Reflects code as of `125f964` · regenerated `2026-05-11` via `npm run wiki:all`**
> If this banner is stale, the page may be out of date. Treat as informative, not authoritative.

## 1. What this node is

**measurement** is an S88 Control Module that turns a raw sensor signal into a validated, scaled, smoothed reading and re-emits it for any parent. Two modes: **analog** (one channel built from the flat config) and **digital** (one Channel per `config.channels[]` entry). It is a leaf in the hierarchy — no children of its own.

## 2. Position in the platform

```mermaid
flowchart LR
    raw[Raw sensor / MQTT / inject<br/>analog scalar or digital object]
    m[measurement<br/>Control Module]:::ctrl
    p1[rotatingMachine<br/>Equipment]:::equip
    p2[machineGroupControl<br/>Unit]:::unit
    p3[pumpingStation<br/>Process Cell]:::pc

    raw -->|data.measurement| m
    m -->|child.register| p1
    m -->|child.register| p2
    m -->|child.register| p3
    m -.<type>.measured.<position>.-> p1
    m -.<type>.measured.<position>.-> p2
    m -.<type>.measured.<position>.-> p3
    classDef pc fill:#0c99d9,color:#fff
    classDef unit fill:#50a8d9,color:#000
    classDef equip fill:#86bbdd,color:#000
    classDef ctrl fill:#a9daee,color:#000
```

S88 colours: Control Module `#a9daee`, Equipment `#86bbdd`, Unit `#50a8d9`, Process Cell `#0c99d9`. Source of truth: `.claude/rules/node-red-flow-layout.md`.

## 3. Capability matrix

| Capability | Status | Notes |
|---|---|---|
| Analog mode — single channel from flat config | ✅ | Default. `data.measurement` payload is numeric. |
| Digital mode — many channels from `config.channels[]` | ✅ | Payload is an object keyed by `channel.key`. |
| Outlier detection | ✅ | Median ± window check. Toggleable via `set.outlier-detection`. |
| Scaling (input range → process range + offset) | ✅ | `config.scaling.{inputMin,inputMax,absMin,absMax,offset}`. |
| Smoothing (moving window) | ✅ | `config.smoothing.{smoothWindow,smoothMethod}`. |
| Min/max tracking | ✅ | `totalMinValue`, `totalMaxValue`, smoothed variants. |
| Calibration (capture current as zero/reference) | ✅ | `cmd.calibrate`. Mutates `config.scaling.offset`. |
| Built-in simulator | ✅ | Sinusoidal/noise driver — `set.simulator` toggles. |
| Repeatability / stability metrics | ✅ | `evaluateRepeatability()`, `isStable()`. |
| Accepts children of its own | ❌ | Leaf node. |

## 4. Code map

```mermaid
flowchart TB
    subgraph nodeRED["nodeClass.js — adapter (BaseNodeAdapter)"]
        nc["buildDomainConfig()<br/>static DomainClass, commands<br/>static tickInterval = 1000ms"]
    end
    subgraph domain["specificClass.js — orchestrator (BaseDomain)"]
        sc["Measurement.configure()<br/>mode = analog | digital<br/>builds Channel(s)"]
    end
    subgraph concerns["src/ concern modules"]
        channel["channel.js<br/>outlier → offset → scaling →<br/>smoothing → minMax pipeline"]
        simulation["simulation/<br/>built-in Simulator"]
        calibration["calibration/<br/>Calibrator + stability"]
        commands["commands/<br/>topic registry + handlers"]
    end
    nc --> sc
    sc --> channel
    sc --> simulation
    sc --> calibration
    nc --> commands
```

| Module | Owns | Read first if you're changing… |
|---|---|---|
| `channel.js` | Per-channel pipeline (outlier → offset → scaling → smoothing → emit) | Per-tick reading flow, unit semantics, emitted event name. |
| `simulation/` | Built-in signal generator for demos and offline tests | Sim behaviour, period / amplitude. |
| `calibration/` | Stability checks, repeatability, offset capture | `cmd.calibrate` behaviour, stable-window heuristic. |
| `commands/` | Input-topic registry and handlers | New input topics, payload validation. |

The analog/digital branch is decided once in `configure()` based on `config.mode.current`. There is no FSM — `tick()` only pumps the simulator when enabled.

```mermaid
flowchart LR
    cfg[config.mode.current]
    cfg -->|"=== 'digital'"| dig[Build N Channels<br/>from config.channels[]]
    cfg -->|"=== 'analog' (default)"| ana[Build 1 Channel<br/>from flat config]
    dig --> emit_d[handleDigitalPayload<br/>fan-out per channel]
    ana --> emit_a[inputValue setter<br/>single channel update]
```

## 5. Topic contract

> **Auto-generated** from `src/commands/index.js`. Do NOT hand-edit between the markers. Re-run `npm run wiki:contract`.

<!-- BEGIN AUTOGEN: topic-contract -->

| Canonical topic | Aliases | Payload | Unit | Effect |
|---|---|---|---|---|
| `set.simulator` | `simulator` | `any` | — | Toggle the built-in simulator on / off. |
| `set.outlier-detection` | `outlierDetection` | `any` | — | Toggle / configure outlier detection on the measurement pipeline. |
| `cmd.calibrate` | `calibrate` | `any` | — | Trigger a one-shot calibration of the measurement. |
| `data.measurement` | `measurement` | `any` | — | Push a raw measurement (analog: number; digital: per-channel object). |

<!-- END AUTOGEN: topic-contract -->

## 6. Child registration

`measurement` does **not accept children**. It only **registers itself** as a child on its upstream parent.

```mermaid
flowchart LR
    m[measurement]:::ctrl -->|"child.register<br/>(Port 2 at startup)"| parent[rotatingMachine /<br/>MGC / pumpingStation /<br/>reactor / monster]
    m -.->|"&lt;type&gt;.measured.&lt;position&gt;<br/>(measurements.emitter)"| parent
    classDef ctrl fill:#a9daee,color:#000
```

| What | softwareType payload | Side-effect on parent |
|---|---|---|
| Registration | `measurement` | Parent attaches listener for `<asset.type>.measured.<positionVsParent>`. |
| Subsequent updates | event on `child.measurements.emitter` | Parent mirrors value into its own `MeasurementContainer`. |

Position labels are normalised to **lowercase** in the event name (`upstream`, `downstream`, `atequipment`).

## 7. Lifecycle — what one event (or tick) does

```mermaid
sequenceDiagram
    participant ext as external sender
    participant m as measurement
    participant ch as Channel pipeline
    participant emitter as measurements.emitter
    participant parent as parent (e.g. rotatingMachine)

    ext->>m: data.measurement (12.4)
    m->>m: command dispatch (analog branch)
    m->>ch: update(12.4)
    ch->>ch: outlier check → offset → scale → smooth → minMax
    ch->>emitter: <type>.measured.<position> {value, ts, unit}
    emitter-->>parent: child event (subscribed at register-time)
    m->>m: notifyOutputChanged()
    m-->>ext: Port 0 + Port 1 (delta-compressed)
    Note over m: every 1000 ms: if simulation.enabled,<br/>simulator.step() → inputValue
```

## 8. Data model — `getOutput()`

Analog mode emits the legacy scalar shape. Digital mode emits a nested `{channels:{...}}` keyed by `channel.key`.

<!-- BEGIN AUTOGEN: data-model -->

| Key | Type | Unit | Sample |
|---|---|---|---|
| `mAbs` | number | — | `0` |
| `mPercent` | number | — | `0` |
| `totalMaxSmooth` | number | — | `0` |
| `totalMaxValue` | number | — | `0` |
| `totalMinSmooth` | number | — | `0` |
| `totalMinValue` | number | — | `0` |

<!-- END AUTOGEN: data-model -->

**Concrete digital sample** (when `mode='digital'`):

~~~json
{
  "channels": {
    "level-a": { "mAbs": 1.84, "mPercent": 73.6, "totalMinValue": 0.1, "totalMaxValue": 2.4 },
    "temp-a":  { "mAbs": 18.2, "mPercent": 36.4, "totalMinValue": 14.0, "totalMaxValue": 22.1 }
  }
}
~~~

In addition, the legacy `source.emitter` fires `'mAbs'` (analog only) — kept for the editor status badge during the refactor window.

## 9. Configuration — editor form ↔ config keys

```mermaid
flowchart TB
    subgraph editor["Node-RED editor form"]
        f1[Mode: analog / digital]
        f2[Asset type + unit]
        f3[Position vs parent]
        f4[Scaling: inputMin/Max, absMin/Max, offset]
        f5[Smoothing: window + method]
        f6[Outlier detection: enabled + window]
        f7[Simulation: enabled + amplitude/period]
        f8[Digital channels list]
    end
    subgraph cfg["Domain config slice"]
        c1[mode.current]
        c2[asset.type / asset.unit]
        c3[functionality.positionVsParent]
        c4[scaling.*]
        c5[smoothing.*]
        c6[outlierDetection.*]
        c7[simulation.*]
        c8[channels []]
    end
    f1 --> c1
    f2 --> c2
    f3 --> c3
    f4 --> c4
    f5 --> c5
    f6 --> c6
    f7 --> c7
    f8 --> c8
```

| Form field | Config key | Default | Range | Where used |
|---|---|---|---|---|
| Mode | `mode.current` | `analog` | enum (`analog`, `digital`) | `Measurement.configure` |
| Asset type | `asset.type` | `pressure` | enum | event name + unit policy |
| Position vs parent | `functionality.positionVsParent` | `atEquipment` | enum | event name suffix |
| Scaling enabled | `scaling.enabled` | `false` | bool | `Channel._applyScaling` |
| Input min/max | `scaling.inputMin/Max` | `0` / `1` | numeric | linear map foot/top |
| Output min/max | `scaling.absMin/absMax` | `50` / `100` | numeric | linear map foot/top |
| Offset | `scaling.offset` | `0` | numeric | calibration target |
| Smoothing window | `smoothing.smoothWindow` | `10` | ≥ 1 (samples) | moving window |
| Outlier detection | `outlierDetection.enabled` | varies | bool | `Channel._isOutlier` |
| Simulation enabled | `simulation.enabled` | `false` | bool | `tick()` step |

## 10. Examples

| Tier | File | What it shows | Status |
|---|---|---|---|
| Basic | `examples/basic.flow.json` | Inject + dashboard, no parent | ⚠️ legacy shape, pre-refactor |
| Integration | `examples/integration.flow.json` | measurement registered as child of a parent | ⚠️ legacy shape, pre-refactor |
| Edge | `examples/edge.flow.json` | Outlier / scaling / simulator edge cases | ⚠️ legacy shape, pre-refactor |

Tier 1/2/3 visual-first example flows are still TODO (see `MEMORY.md` "TODO: Example Flows"). Screenshots will land under `wiki/_partial-screenshots/measurement/` when the new flows ship.

## 11. Debug recipes

| Symptom | First thing to check | Where to look |
|---|---|---|
| Parent never receives `<type>.measured.<position>` | `assetType` must match parent's filter exactly (e.g. `flow` — not `flow-electromagnetic`). | `config.asset.type` + `MEMORY.md` integration gotcha. |
| Position labels look uppercase to parent | Event name lowercases — but `functionality.positionVsParent` is sent as-is on `child.register`. | `_buildAnalogChannel` event-name composition. |
| Outliers seem to pass through | `outlierDetection.enabled` may be off (default varies by config). Toggle with `set.outlier-detection`. | `Channel._isOutlier`. |
| `cmd.calibrate` does nothing | Calibrator requires ≥ 2 stable samples — check `isStable()` first. | `calibration/calibrator.js`. |
| Digital payload silently dropped | Unknown channel keys land in the `unknown` log line only at debug level. | enable `logging.logLevel=debug` momentarily. |
| Simulator still running after toggle off | `tick()` reads `config.simulation.enabled` each tick — confirm the toggle actually mutated the config. | `toggleSimulation`. |

> Never ship `enableLog: 'debug'` in a demo — fills the container log within seconds and obscures real errors.

## 12. When you would NOT use this node

- Don't use measurement to **fuse** signals from multiple sensors — it's per-channel only. Aggregate at the parent.
- Don't use measurement for **control output** — it's read-only signal conditioning. Use `rotatingMachine` / `valve` for actuation.
- Don't use measurement for **alarm logic** — there is no threshold-trip output. Build that on top of the emitted reading at the parent or in a dashboard rule.

## 13. Known limitations / current issues

| # | Issue | Tracked in |
|---|---|---|
| 1 | Legacy `source.emitter` 'mAbs' event still fired alongside `measurements.emitter` — slated for removal in Phase 7. | `OPEN_QUESTIONS.md` (2026-05-10) |
| 2 | Digital mode's per-channel scaling/smoothing falls back to the analog block's defaults when not specified per channel. | `_buildDigitalChannels`. |
| 3 | Tier 1/2/3 visual-first example flows not yet written; current `examples/` only contains pre-refactor flows. | P9 / P2.14 follow-up. |
| 4 | No automatic recalibration — `cmd.calibrate` is operator-triggered. | `calibration/calibrator.js`. |