measurement/README.md

measurement

Node-RED custom node for sensor signal conditioning. Takes raw input — either a single scalar (analog mode) or an MQTT-style JSON object with many keys (digital mode) — and produces scaled, smoothed, outlier-filtered measurements. Part of the EVOLV wastewater-automation platform.

Registers itself on port 2 as a child of a parent equipment (rotatingMachine, pumpingStation, reactor, etc.). The parent consumes measurements via shared MeasurementContainer events.

Install

cd ~/.node-red
npm install github:gitea.wbd-rd.nl/RnD/measurement

Or pull the whole platform via the superproject. Restart Node-RED and the node appears in the palette under EVOLV.

Two input modes

Analog mode (default)

One scalar per message — the classic PLC / 4-20mA pattern.

{ "topic": "measurement", "payload": 42 }

The node runs one offset → scaling → smoothing → outlier pipeline and emits exactly one MeasurementContainer slot. Every existing flow built before digital mode keeps working unchanged.

Digital mode (MQTT / IoT)

One object per message, many keys:

{ "topic": "measurement",
  "payload": { "temperature": 22.5, "humidity": 45, "pressure": 1013 } }

Each key maps to its own channel with independently-configured scaling, smoothing, outlier detection, type, position, unit, and distance. A single inbound message therefore emits N MeasurementContainer slots — one per channel — so a downstream parent sees everything at once.

Pick the mode in the editor or via msg.mode. Analog is the default; digital requires populating channels (see Configuration).

Input topics

Topic	Payload	Effect
measurement	analog mode: number or numeric string — stored as inputValue and consumed on the next tick. digital mode: object keyed by channel names.	drives the pipeline
simulator	—	toggles the simulator flag
outlierDetection	—	toggles outlier detection
calibrate	—	adjust the scaling offset so current output matches inputMin (scaling on) or absMin (scaling off). Requires a stable window.

Output ports

Port	Label	Payload
0	process	analog: {mAbs, mPercent, totalMinValue, totalMaxValue, totalMinSmooth, totalMaxSmooth}. digital: {channels: {<key>: {mAbs, mPercent, ...}}}. Delta-compressed — only changed fields emit each tick.
1	dbase	InfluxDB line-protocol telemetry
2	parent	{topic:"registerChild", payload:<nodeId>, positionVsParent, distance} emitted once ~180ms after deploy

Configuration

Common (both modes)

• Asset (menu): supplier, category, assetType (measurement type in the container — pressure, flow, temperature, power, or any user-defined type like humidity), model, unit.
• Logger (menu): log level + enable flag.
• Position (menu): upstream / atEquipment / downstream relative to parent; optional distance offset.

Analog-mode fields

Field	Purpose
Scaling (checkbox)	enables linear source→process interpolation
Source Min / Max	input-side range (e.g. 4–20 mA)
Input Offset	additive bias applied before scaling
Process Min / Max	output-side range (e.g. 0–3000 mbar)
Simulator (checkbox)	internal random-walk source
Smoothing	one of: none, mean, min, max, sd, lowPass, highPass, weightedMovingAverage, bandPass, median, kalman, savitzkyGolay
Window	sample count for the smoothing window

Digital-mode fields

• Mode: set to digital.
• Channels: JSON array, one entry per channel. Each entry:

{
  "key": "temperature",
  "type": "temperature",
  "position": "atEquipment",
  "unit": "C",
  "scaling":  { "enabled": false, "inputMin": 0, "inputMax": 1, "absMin": -50, "absMax": 150, "offset": 0 },
  "smoothing": { "smoothWindow": 5, "smoothMethod": "mean" },
  "outlierDetection": { "enabled": true, "method": "zScore", "threshold": 3 }
}

scaling, smoothing, outlierDetection are optional — the node falls back to the top-level analog-mode equivalents when missing. key is the JSON field name inside msg.payload; type is the MeasurementContainer axis (can be any string — unknown types are accepted).

State and emit contract

Every channel runs the same pipeline: outlier → offset → scaling → smoothing → min/max tracking → constrain → emit. Output is rounded to two decimals. MeasurementContainer events follow the pattern <type>.<variant>.<position> all lowercase, e.g. temperature.measured.atequipment.

Unknown measurement types (anything not in the container's built-in measureMap — pressure, flow, power, temperature, volume, length, mass, energy) are accepted without unit compatibility checks. Known types still validate strictly.

Testing

cd nodes/measurement
npm test

71 tests cover every smoothing method, every outlier strategy, scaling, interpolation, constrain, calibration, stability, simulation, output-percent fallback, per-channel pipelines, digital payload dispatch, registration events, and example-flow shape.

Production status

Last reviewed 2026-04-13. See the project memory file node_measurement.md for the current verdict, benchmarks, and wishlist.

License

SEE LICENSE. Author: Rene De Ren, Waterschap Brabantse Delta R&D.