docs: add CLAUDE.md with S88 classification and superproject rule reference

References the flow-layout rule set in the EVOLV superproject
(.claude/rules/node-red-flow-layout.md) so Claude Code sessions working
in this repo know the S88 level, colour, and placement lane for this node.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,23 @@
+# diffuser — Claude Code context
+
+Aeration system control.
+Part of the [EVOLV](https://gitea.wbd-rd.nl/RnD/EVOLV) wastewater-automation platform.
+
+## S88 classification
+
+| Level | Colour | Placement lane |
+|---|---|---|
+| **Equipment Module** | `#86bbdd` | L3 |
+
+## Flow layout rules
+
+When wiring this node into a multi-node demo or production flow, follow the
+placement rule set in the **EVOLV superproject**:
+
+> `.claude/rules/node-red-flow-layout.md` (in the EVOLV repo root)
+
+Key points for this node:
+- Place on lane **L3** (x-position per the lane table in the rule).
+- Stack same-level siblings vertically.
+- Parent/children sit on adjacent lanes (children one lane left, parent one lane right).
+- Wrap in a Node-RED group box coloured `#86bbdd` (Equipment Module).

LICENSE

@@ -1,9 +1,9 @@
-MIT License
-
-Copyright (c) 2025 RnD
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+MIT License
+
+Copyright (c) 2025 RnD
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -1,3 +1,3 @@
-# convert
-
+# convert
+
 Makes unit conversions

diffuser.html

@@ -0,0 +1,92 @@
+<script type="text/javascript">
+RED.nodes.registerType('diffuser', {
+  category: 'wbd typical',
+  color: '#86bbdd',
+  defaults: {
+    name: { value: '', required: true },
+    number: { value: 1, required: true },
+    i_elements: { value: 1, required: true },
+    i_diff_density: { value: 2.4, required: true },
+    i_m_water: { value: 0, required: true },
+    alfaf: { value: 0.7, required: true },
+    i_zone_volume: { value: 0, required: false },
+    processOutputFormat: { value: 'process' },
+    dbaseOutputFormat: { value: 'influxdb' },
+    enableLog: { value: false },
+    logLevel: { value: 'error' },
+  },
+  inputs: 1,
+  outputs: 4,
+  inputLabels: ['control'],
+  outputLabels: ['process', 'dbase', 'reactor control', 'parent'],
+  icon: 'font-awesome/fa-tint',
+  label: function() {
+    return this.name ? `${this.name}_${this.number}` : 'diffuser';
+  },
+});
+</script>
+
+<script type="text/html" data-template-name="diffuser">
+  <div class="form-row">
+    <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
+    <input type="text" id="node-input-name" placeholder="Zone name">
+  </div>
+  <div class="form-row">
+    <label for="node-input-number"><i class="fa fa-list-ol"></i> Number</label>
+    <input type="number" id="node-input-number" min="1">
+  </div>
+  <div class="form-row">
+    <label for="node-input-i_elements"><i class="fa fa-th"></i> Elements</label>
+    <input type="number" id="node-input-i_elements" min="1">
+  </div>
+  <div class="form-row">
+    <label for="node-input-i_diff_density"><i class="fa fa-braille"></i> Density %</label>
+    <input type="number" id="node-input-i_diff_density" step="0.1" min="0">
+  </div>
+  <div class="form-row">
+    <label for="node-input-i_m_water"><i class="fa fa-arrows-v"></i> Water Height</label>
+    <input type="number" id="node-input-i_m_water" step="0.1" min="0">
+  </div>
+  <div class="form-row">
+    <label for="node-input-alfaf"><i class="fa fa-flask"></i> Alfa Factor</label>
+    <input type="number" id="node-input-alfaf" step="0.01" min="0">
+  </div>
+  <div class="form-row">
+    <label for="node-input-i_zone_volume"><i class="fa fa-cube"></i> Zone Volume</label>
+    <input type="number" id="node-input-i_zone_volume" step="0.1" min="0" placeholder="m3">
+  </div>
+  <h3>Output Formats</h3>
+  <div class="form-row">
+    <label for="node-input-processOutputFormat"><i class="fa fa-random"></i> Process Output</label>
+    <select id="node-input-processOutputFormat" style="width:60%;">
+      <option value="process">process</option>
+      <option value="json">json</option>
+      <option value="csv">csv</option>
+    </select>
+  </div>
+  <div class="form-row">
+    <label for="node-input-dbaseOutputFormat"><i class="fa fa-database"></i> Database Output</label>
+    <select id="node-input-dbaseOutputFormat" style="width:60%;">
+      <option value="influxdb">influxdb</option>
+      <option value="json">json</option>
+      <option value="csv">csv</option>
+    </select>
+  </div>
+  <div class="form-row">
+    <label for="node-input-enableLog"><i class="fa fa-book"></i> Enable Log</label>
+    <input type="checkbox" id="node-input-enableLog" style="width: auto;">
+  </div>
+  <div class="form-row">
+    <label for="node-input-logLevel"><i class="fa fa-signal"></i> Log Level</label>
+    <select id="node-input-logLevel">
+      <option value="debug">debug</option>
+      <option value="info">info</option>
+      <option value="warn">warn</option>
+      <option value="error">error</option>
+    </select>
+  </div>
+</script>
+
+<script type="text/html" data-help-name="diffuser">
+  <p>Diffused aeration device model.</p>
+</script>

diffuser.js

@@ -0,0 +1,9 @@
+const nameOfNode = 'diffuser';
+const nodeClass = require('./src/nodeClass.js');
+
+module.exports = function(RED) {
+  RED.nodes.registerType(nameOfNode, function(config) {
+    RED.nodes.createNode(this, config);
+    this.nodeClass = new nodeClass(config, RED, this, nameOfNode);
+  });
+};

diffuser_class.js

@@ -0,0 +1 @@
+module.exports = require('./src/specificClass');

graph.js

@@ -0,0 +1,152 @@
+/*
+Copyright: 
+Year : (c) 2023 
+Author/licensor : Rene De Ren
+Contact details : zn375ix3@gmail.com 
+Location : The Netherlands
+Licensee : Waterschap brabantse delta
+Address: Bouvignelaan 5, 4836 AA Breda
+
+Permission is hereby granted, to the licensee , to use this software only for the purposes of testing it in its R&D lab. 
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+The author shall be notified of any and all improvements or adaptations this software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
+INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+
+*/
+
+//A class to interact and manipulate machines with a parabolic curve
+class Graph {
+    /*-------------------               Construct and set vars               -------------------*/
+    constructor() {
+
+        // current x and y
+        this.x = 0;
+        this.y = 0;
+
+        //previous y and x
+        this.y_prev = 0;
+        this.x_prev = 0;
+
+        //slope of current value
+        this.slope = 0;
+
+
+    }
+
+    set slope(value){
+        this._slope = Math.round( value * 100 ) / 100;
+    }
+    get slope(){
+        return this._slope;
+    }
+
+    calc(x,y){
+
+        //store old values
+        this.x_prev = this.x;
+        this.y_prev = this.y;
+        
+        //store new values
+        this.x = x;
+        this.y = y;
+
+        //calc slope
+        this.slope = this.calc_slope(this.x,this.y,this.x_prev,this.y_prev);
+        
+
+    }
+
+    calc_slope(x,y,x_prev,y_prev){
+        
+        let slope = 0;
+        let incline = false;
+        let decline = false;
+
+        if( x_prev > x){
+            decline = true;
+            incline = false;
+        }
+        else if( x_prev < x ){
+            decline = false;
+            incline = true;
+        }
+        
+        //determine decline / incl
+        if( (!decline && !incline) ){
+            slope = 0;
+        }
+        else if(decline){    
+            slope = -( (y - y_prev) / ( x - x_prev) ) ;
+        }
+        else if(incline){
+            slope = ( (y - y_prev) / ( x - x_prev) ) ;
+        }
+
+        return slope;
+    }
+
+    // 1 a dimensional peak ( THIS WILL FIND ONLY 1 PEAK!! so assuming the array only has one !)
+    one_dim_peak_finder(array){
+
+        //define array length
+        let array_length = array.length;
+        //start position in array is middle
+        let recursive_pos = array_length/2;
+        //define end conditions
+        let max_iterations = 100;
+        let done = false;
+        let iteration = 0;
+        let peak_found = false;
+
+        while(!done){
+
+            //find peak going left
+            if( array[recursive_pos-1] > array[recursive_pos] ){
+                //calc new pos
+                recursive_pos = (recursive_pos-1) / 2;
+            }
+            //find peak going right
+            else if( array[recursive_pos+1] > array[recursive_pos] ){
+                //calc new pos
+                recursive_pos = (recursive_pos+1) / 2;
+            }
+            //found peak!
+            else{
+                done = true;
+                peak_found = true;
+                position_peak = recursive_pos;
+            }
+
+            //end prematurely
+            if(max_iterations >= iteration){
+                done = true;
+                peak_found = false;
+                position_peak = null;
+            }
+            iteration++;
+        }
+        //build response
+        let obj_peak = { found:peak_found , value_of_peak: array[position_peak] , position_peak:position_peak };
+        
+        return obj_peak;
+    }
+   
+
+} // end of class
+
+
+/*
+var graph = new Graph();
+
+
+//*/
+
+module.exports = Graph;

package.json

@@ -0,0 +1,24 @@
+{
+    "name": "diffuser",
+    "version": "0.0.1",
+    "description": "Control module diffuser",
+    "main": "diffuser",
+    "scripts": {
+      "test": "diffuser"
+    },
+    "repository": {
+      "type": "git",
+      "url": "diffuser"
+    },
+    "keywords": [
+      "diffuser"
+    ],
+    "author": "Rene De Ren",
+    "license": "MIT",
+    "node-red" : {
+        "nodes": {
+            "diffuser": "diffuser.js"
+          
+      }
+  }
+}

src/nodeClass.js

@@ -0,0 +1,141 @@
+const { outputUtils } = require('generalFunctions');
+const Specific = require('./specificClass');
+
+class nodeClass {
+  constructor(uiConfig, RED, nodeInstance, nameOfNode) {
+    this.node = nodeInstance;
+    this.RED = RED;
+    this.name = nameOfNode;
+
+    this._loadConfig(uiConfig);
+    this._setupSpecificClass();
+    this._registerChild();
+    this._startTickLoop();
+    this._attachInputHandler();
+    this._attachCloseHandler();
+  }
+
+  _loadConfig(uiConfig) {
+    const suffix = uiConfig.number !== undefined && uiConfig.number !== '' ? `_${uiConfig.number}` : '';
+    const resolvedName = uiConfig.name ? `${uiConfig.name}${suffix}` : this.name;
+
+    this.config = {
+      general: {
+        name: resolvedName,
+        id: this.node.id,
+        unit: uiConfig.unit || 'kg o2/h',
+        logging: {
+          enabled: uiConfig.enableLog,
+          logLevel: uiConfig.logLevel,
+        },
+      },
+      functionality: {
+        positionVsParent: uiConfig.positionVsParent || 'atEquipment',
+        softwareType: this.name,
+        role: 'aeration diffuser',
+      },
+      diffuser: {
+        number: Number(uiConfig.number) || 0,
+        elements: Number(uiConfig.i_elements) || 1,
+        density: Number(uiConfig.i_diff_density) || 2.4,
+        waterHeight: Number(uiConfig.i_m_water) || 0,
+        alfaFactor: Number(uiConfig.alfaf ?? 0.7) || 0.7,
+        headerPressure: Number(uiConfig.i_pressure) || 0,
+        localAtmPressure: Number(uiConfig.i_local_atm_pressure) || 1013.25,
+        waterDensity: Number(uiConfig.i_water_density) || 997,
+        zoneVolume: Number(uiConfig.i_zone_volume) || 0,
+      },
+    };
+
+    this._output = new outputUtils();
+  }
+
+  _setupSpecificClass() {
+    this.source = new Specific(this.config);
+    this.node.source = this.source;
+  }
+
+  _registerChild() {
+    setTimeout(() => {
+      this.node.send([
+        null,
+        null,
+        null,
+        {
+          topic: 'registerChild',
+          payload: this.node.id,
+          positionVsParent: this.config?.functionality?.positionVsParent || 'atEquipment',
+        },
+      ]);
+    }, 100);
+  }
+
+  _startTickLoop() {
+    setTimeout(() => {
+      this._tickInterval = setInterval(() => this._tick(), 1000);
+    }, 1000);
+  }
+
+  _tick() {
+    const raw = this.source.getOutput();
+    const processMsg = this._output.formatMsg(raw, this.config, 'process');
+    const influxMsg = this._output.formatMsg(raw, this.config, 'influxdb');
+    const reactorOtr = this.source.getReactorOtr(this.config.diffuser?.zoneVolume);
+    const controlMsg = {
+      topic: 'OTR',
+      payload: reactorOtr,
+      meta: {
+        source: 'diffuser',
+        diffuser: this.config.general?.name,
+        zoneVolume: this.config.diffuser?.zoneVolume,
+        oKgo2H: raw.oKgo2H,
+      },
+    };
+    this.node.status(this.source.getStatus());
+    this.node.send([processMsg, influxMsg, controlMsg, null]);
+  }
+
+  _attachInputHandler() {
+    this.node.on('input', (msg, send, done) => {
+      try {
+        switch (msg.topic) {
+          case 'density':
+            this.source.setDensity(msg.payload);
+            break;
+          case 'air_flow':
+            this.source.setFlow(msg.payload);
+            break;
+          case 'height_water':
+            this.source.setWaterHeight(msg.payload);
+            break;
+          case 'header_pressure':
+            this.source.setHeaderPressure(msg.payload);
+            break;
+          case 'elements':
+            this.source.setElementCount(msg.payload);
+            break;
+          case 'alfaFactor':
+            this.source.setAlfaFactor(msg.payload);
+            break;
+          default:
+            this.source.logger.warn(`Unknown topic: ${msg.topic}`);
+            break;
+        }
+        done();
+      } catch (error) {
+        this.node.status({ fill: 'red', shape: 'ring', text: 'Bad request data' });
+        this.node.error(`Bad request data: ${error.message}`, msg);
+        done(error);
+      }
+    });
+  }
+
+  _attachCloseHandler() {
+    this.node.on('close', (done) => {
+      clearInterval(this._tickInterval);
+      done();
+    });
+  }
+}
+
+module.exports = nodeClass;

src/specificClass.js

@@ -0,0 +1,342 @@
+const { logger, interpolation, gravity, convert } = require('generalFunctions');
+
+class Diffuser {
+  constructor(config = {}) {
+    this.config = config;
+    this.logger = new logger(
+      this.config.general?.logging?.enabled,
+      this.config.general?.logging?.logLevel,
+      this.config.general?.name,
+    );
+
+    this.interpolation = new interpolation({ type: 'linear' });
+    this.convert = convert;
+    this.specs = this.loadSpecs();
+
+    this.idle = true;
+    this.warning = { state: false, text: [], flow: { min: { hyst: 2 }, max: { hyst: 2 } } };
+    this.alarm = { state: false, text: [], flow: { min: { hyst: 10 }, max: { hyst: 10 } } };
+
+    this.i_pressure = this.config.diffuser?.headerPressure || 0;
+    this.i_local_atm_pressure = this.config.diffuser?.localAtmPressure || 1013.25;
+    this.i_water_density = this.config.diffuser?.waterDensity || 997;
+    this.i_alfa_factor = this.config.diffuser?.alfaFactor || 0.7;
+    this.i_n_elements = this.normalizePositiveInteger(this.config.diffuser?.elements, 1);
+    this.i_diff_density = this.normalizeNumber(this.config.diffuser?.density, 2.4);
+    this.i_m_water = this.normalizeNumber(this.config.diffuser?.waterHeight, 0);
+    this.i_flow = 0;
+
+    this.n_kg = this.calcAirDensityMbar(1013.25, 0, 20);
+
+    this.n_flow = 0;
+    this.o_otr = 0;
+    this.o_p_flow = 0;
+    this.o_p_water = this.heightToPressureMbar(this.i_water_density, this.i_m_water);
+    this.o_p_total = this.o_p_water;
+    this.o_kg = 0;
+    this.o_kg_h = 0;
+    this.o_kgo2_h = 0;
+    this.o_kgo2 = 0;
+    this.o_kgo2_h_min = 0;
+    this.o_kgo2_h_max = 0;
+    this.o_flow_element = 0;
+    this.o_otr_min = 0;
+    this.o_otr_max = 0;
+    this.o_p_min = 0;
+    this.o_p_max = 0;
+    this.o_combined_eff = 0;
+    this.o_slope = 0;
+  }
+
+  normalizeNumber(value, fallback = 0) {
+    const parsed = Number(value);
+    return Number.isFinite(parsed) ? parsed : fallback;
+  }
+
+  normalizePositiveInteger(value, fallback = 1) {
+    const parsed = Math.round(Number(value));
+    return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback;
+  }
+
+  setDensity(value) {
+    this.i_diff_density = this.normalizeNumber(value, this.i_diff_density);
+    this.recalculate();
+  }
+
+  setFlow(value) {
+    this.i_flow = Math.max(0, this.normalizeNumber(value, 0));
+    this.recalculate();
+  }
+
+  setWaterHeight(value) {
+    this.i_m_water = Math.max(0, this.normalizeNumber(value, this.i_m_water));
+    this.o_p_water = this.heightToPressureMbar(this.i_water_density, this.i_m_water);
+    this.recalculate();
+  }
+
+  setHeaderPressure(value) {
+    this.i_pressure = this.normalizeNumber(value, this.i_pressure);
+    this.recalculate();
+  }
+
+  setElementCount(value) {
+    this.i_n_elements = this.normalizePositiveInteger(value, this.i_n_elements);
+    this.recalculate();
+  }
+
+  setAlfaFactor(value) {
+    this.i_alfa_factor = this.normalizeNumber(value, this.i_alfa_factor);
+    this.recalculate();
+  }
+
+  recalculate() {
+    if (this.i_flow <= 0) {
+      this.idle = true;
+      this.n_flow = 0;
+      this.o_otr = 0;
+      this.o_p_flow = 0;
+      this.o_flow_element = 0;
+      this.o_p_total = this.o_p_water;
+      this.o_kg = 0;
+      this.o_kg_h = 0;
+      this.o_kgo2_h = 0;
+      this.o_kgo2 = 0;
+      this.o_combined_eff = 0;
+      this.o_slope = 0;
+      this.warning.text = [];
+      this.warning.state = false;
+      this.alarm.text = [];
+      this.alarm.state = false;
+      return;
+    }
+
+    this.idle = false;
+    this.calcOtrPressure(this.i_flow);
+  }
+
+  getCurveKeys(curve) {
+    return Object.keys(curve)
+      .map(Number)
+      .sort((a, b) => a - b);
+  }
+
+  interpolateSeries(points, x) {
+    this.interpolation.load_spline(points.x, points.y, 'linear');
+    return this.interpolation.interpolate(x);
+  }
+
+  interpolateCurveByDensity(curve, density, x) {
+    const keys = this.getCurveKeys(curve);
+    if (keys.length === 1) {
+      const only = curve[keys[0]];
+      return {
+        value: this.interpolateSeries(only, x),
+        minY: Math.min(...only.y),
+        maxY: Math.max(...only.y),
+        minX: Math.min(...only.x),
+        maxX: Math.max(...only.x),
+        slope: this.getSegmentSlope(only, x),
+      };
+    }
+
+    const lowerKey = keys.reduce((acc, key) => (key <= density ? key : acc), keys[0]);
+    const upperKey = keys.find((key) => key >= density) ?? keys[keys.length - 1];
+    const lowerCurve = curve[lowerKey];
+    const upperCurve = curve[upperKey];
+
+    if (lowerKey === upperKey) {
+      return {
+        value: this.interpolateSeries(lowerCurve, x),
+        minY: Math.min(...lowerCurve.y),
+        maxY: Math.max(...lowerCurve.y),
+        minX: Math.min(...lowerCurve.x),
+        maxX: Math.max(...lowerCurve.x),
+        slope: this.getSegmentSlope(lowerCurve, x),
+      };
+    }
+
+    const lowerValue = this.interpolateSeries(lowerCurve, x);
+    const upperValue = this.interpolateSeries(upperCurve, x);
+    const ratio = (density - lowerKey) / (upperKey - lowerKey);
+
+    return {
+      value: lowerValue + (upperValue - lowerValue) * ratio,
+      minY: Math.min(...lowerCurve.y) + (Math.min(...upperCurve.y) - Math.min(...lowerCurve.y)) * ratio,
+      maxY: Math.max(...lowerCurve.y) + (Math.max(...upperCurve.y) - Math.max(...lowerCurve.y)) * ratio,
+      minX: Math.min(...lowerCurve.x),
+      maxX: Math.max(...lowerCurve.x),
+      slope: this.getSegmentSlope(lowerCurve, x),
+    };
+  }
+
+  getSegmentSlope(curvePoints, x) {
+    const xs = curvePoints.x;
+    const ys = curvePoints.y;
+    for (let i = 0; i < xs.length - 1; i += 1) {
+      if (x <= xs[i + 1]) {
+        return (ys[i + 1] - ys[i]) / (xs[i + 1] - xs[i]);
+      }
+    }
+    const last = xs.length - 1;
+    return (ys[last] - ys[last - 1]) / (xs[last] - xs[last - 1]);
+  }
+
+  combineEff(oOtr, oOtrMin, oOtrMax, oPFlow, oPMin, oPMax) {
+    const otrSpan = oOtrMax - oOtrMin;
+    const pSpan = oPMax - oPMin;
+    const eff1 = otrSpan > 0 ? (oOtr - oOtrMin) / otrSpan : 0;
+    const eff2 = pSpan > 0 ? 1 - ((oPFlow - oPMin) / pSpan) : 0;
+    return Math.max(0, eff1 * eff2 * 100);
+  }
+
+  calcAirDensityMbar(pressureMbar, RH, tempC) {
+    const Rd = 287.05;
+    const Rv = 461.495;
+    const T = tempC + 273.15;
+    const A = 8.07131;
+    const B = 1730.63;
+    const C = 233.426;
+    const e_s = Math.pow(10, (A - (B / (C + tempC))));
+    const e = RH * e_s / 100;
+    const pressurePa = this.convert(pressureMbar).from('mbar').to('Pa');
+    const p_d = pressurePa - (e * 100);
+    return (p_d / (Rd * T)) + ((e * 100) / (Rv * T));
+  }
+
+  heightToPressureMbar(density, height) {
+    const pressurePa = gravity.getStandardGravity() * density * height;
+    return this.convert(pressurePa).from('Pa').to('mbar');
+  }
+
+  calcOtrPressure(flow) {
+    const totalInputPressureMbar = this.i_local_atm_pressure + this.i_pressure;
+    this.o_kg = this.calcAirDensityMbar(totalInputPressureMbar, 0, 20);
+    this.o_kg_h = this.o_kg * flow;
+    this.n_flow = (this.o_kg / this.n_kg) * flow;
+    this.o_flow_element = Math.round((this.n_flow / this.i_n_elements) * 100) / 100;
+
+    const otr = this.interpolateCurveByDensity(this.specs.otr_curve, this.i_diff_density, this.o_flow_element);
+    const pressure = this.interpolateCurveByDensity(this.specs.p_curve, 0, this.o_flow_element);
+
+    this.o_otr_min = otr.minY;
+    this.o_otr_max = otr.maxY;
+    this.o_p_min = pressure.minY;
+    this.o_p_max = pressure.maxY;
+    this.o_otr = Math.round(otr.value * 100) / 100;
+    this.o_p_flow = Math.round(pressure.value * 100) / 100;
+    this.o_p_total = Math.round((this.o_p_water + this.o_p_flow) * 100) / 100;
+    this.o_kgo2_h = Math.round(this.convert(this.o_otr * this.n_flow * this.i_m_water * this.i_alfa_factor).from('g').to('kg') * 100) / 100;
+    this.o_kgo2_h_min = Math.round(this.convert(this.o_otr_min * this.n_flow * this.i_m_water * this.i_alfa_factor).from('g').to('kg') * 100) / 100;
+    this.o_kgo2_h_max = Math.round(this.convert(this.o_otr_max * this.n_flow * this.i_m_water * this.i_alfa_factor).from('g').to('kg') * 100) / 100;
+    this.o_kgo2 = this.o_kgo2_h / 3600;
+    this.o_combined_eff = Math.round(this.combineEff(
+      this.o_otr,
+      this.o_otr_min,
+      this.o_otr_max,
+      this.o_p_flow,
+      this.o_p_min,
+      this.o_p_max,
+    ) * 100) / 100;
+    this.o_slope = Math.round(otr.slope * 1000) / 1000;
+
+    this.warningCheck(pressure.minX, pressure.maxX);
+    this.alarmCheck(pressure.minX, pressure.maxX);
+  }
+
+  warningCheck(minFlow, maxFlow) {
+    this.warning.text = [];
+    this.warning.state = false;
+    const minHyst = minFlow * (this.warning.flow.min.hyst / 100);
+    const maxHyst = maxFlow * (this.warning.flow.max.hyst / 100);
+
+    if (this.o_flow_element < minFlow - minHyst) {
+      this.warning.state = true;
+      this.warning.text.push(`Warning: flow per element ${this.o_flow_element} is below ${Math.round((minFlow - minHyst) * 100) / 100}`);
+    }
+
+    if (this.o_flow_element > maxFlow + maxHyst) {
+      this.warning.state = true;
+      this.warning.text.push(`Warning: flow per element ${this.o_flow_element} exceeds ${Math.round((maxFlow + maxHyst) * 100) / 100}`);
+    }
+  }
+
+  alarmCheck(minFlow, maxFlow) {
+    this.alarm.text = [];
+    this.alarm.state = false;
+    const minHyst = minFlow * (this.alarm.flow.min.hyst / 100);
+    const maxHyst = maxFlow * (this.alarm.flow.max.hyst / 100);
+
+    if (this.o_flow_element < minFlow - minHyst) {
+      this.alarm.state = true;
+      this.alarm.text.push(`Alarm: flow per element ${this.o_flow_element} is below ${Math.round((minFlow - minHyst) * 100) / 100}`);
+    }
+
+    if (this.o_flow_element > maxFlow + maxHyst) {
+      this.alarm.state = true;
+      this.alarm.text.push(`Alarm: flow per element ${this.o_flow_element} exceeds ${Math.round((maxFlow + maxHyst) * 100) / 100}`);
+    }
+  }
+
+  getStatus() {
+    if (this.alarm.state) {
+      return { fill: 'red', shape: 'dot', text: this.alarm.text[0] };
+    }
+    if (this.warning.state) {
+      return { fill: 'yellow', shape: 'dot', text: this.warning.text[0] };
+    }
+    if (this.idle) {
+      return { fill: 'grey', shape: 'dot', text: `${this.o_kgo2_h} kg o2 / h` };
+    }
+    return { fill: 'green', shape: 'dot', text: `${this.o_kgo2_h} kg o2 / h` };
+  }
+
+  getOutput() {
+    return {
+      iPressure: this.i_pressure,
+      iMWater: this.i_m_water,
+      iFlow: this.i_flow,
+      nFlow: Math.round(this.n_flow * 100) / 100,
+      oOtr: this.o_otr,
+      oPLoss: this.o_p_total,
+      oKgo2H: this.o_kgo2_h,
+      oFlowElement: this.o_flow_element,
+      efficiency: this.o_combined_eff,
+      slope: this.o_slope,
+      idle: this.idle,
+      warning: [...this.warning.text],
+      alarm: [...this.alarm.text],
+    };
+  }
+
+  getReactorOtr(zoneVolumeM3) {
+    const volume = Number(zoneVolumeM3);
+    if (!Number.isFinite(volume) || volume <= 0) {
+      return 0;
+    }
+    return this.o_kgo2_h * 1000 * 24 / volume;
+  }
+
+  loadSpecs() {
+    return {
+      supplier: 'GVA',
+      type: 'ELASTOX-R',
+      units: {
+        Nm3: { temp: 20, pressure: 1.01325, RH: 0 },
+      },
+      otr_curve: {
+        2.4: {
+          x: [2, 3, 4, 5, 6, 7, 8, 9, 10],
+          y: [26, 25, 24, 23.5, 23, 22.75, 22.5, 22.25, 22],
+        },
+      },
+      p_curve: {
+        0: {
+          x: [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
+          y: [40, 42.5, 45, 47.5, 50, 51.5, 53, 54.5, 56, 57.5, 59],
+        },
+      },
+    };
+  }
+}
+
+module.exports = Diffuser;

test/specificClass.test.js

@@ -0,0 +1,80 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const Diffuser = require('../src/specificClass');
+
+function makeConfig(overrides = {}) {
+  return {
+    general: {
+      name: 'Zone_1',
+      logging: {
+        enabled: false,
+        logLevel: 'error',
+      },
+    },
+    functionality: {
+      softwareType: 'diffuser',
+      role: 'aeration diffuser',
+    },
+    diffuser: {
+      number: 1,
+      elements: 4,
+      density: 2.4,
+      waterHeight: 4.5,
+      alfaFactor: 0.7,
+      headerPressure: 0,
+      localAtmPressure: 1013.25,
+      waterDensity: 997,
+      ...overrides,
+    },
+  };
+}
+
+test('diffuser starts idle with zero production', () => {
+  const diffuser = new Diffuser(makeConfig());
+  const output = diffuser.getOutput();
+
+  assert.equal(diffuser.idle, true);
+  assert.equal(output.oKgo2H, 0);
+  assert.equal(typeof output.oPLoss, 'number');
+});
+
+test('diffuser calculates oxygen transfer and pressure once airflow is applied', () => {
+  const diffuser = new Diffuser(makeConfig());
+  diffuser.setFlow(24);
+
+  const output = diffuser.getOutput();
+  assert.equal(diffuser.idle, false);
+  assert.ok(output.oFlowElement > 0);
+  assert.ok(output.oOtr > 0);
+  assert.ok(output.oPLoss > diffuser.o_p_water);
+  assert.ok(output.oKgo2H > 0);
+});
+
+test('diffuser increases total pressure when water height rises', () => {
+  const diffuser = new Diffuser(makeConfig());
+  diffuser.setFlow(24);
+  const lowHeadLoss = diffuser.getOutput().oPLoss;
+
+  diffuser.setWaterHeight(6);
+  const highHeadLoss = diffuser.getOutput().oPLoss;
+
+  assert.ok(highHeadLoss > lowHeadLoss);
+});
+
+test('diffuser raises warnings and alarms when flow per element is too low', () => {
+  const diffuser = new Diffuser(makeConfig({ elements: 1, waterHeight: 3 }));
+  diffuser.setFlow(0.5);
+
+  assert.equal(diffuser.warning.state, true);
+  assert.equal(diffuser.alarm.state, true);
+  assert.equal(diffuser.getStatus().fill, 'red');
+});
+
+test('diffuser converts oxygen output to reactor OTR per zone volume', () => {
+  const diffuser = new Diffuser(makeConfig({ waterHeight: 4.5 }));
+  diffuser.setFlow(24);
+
+  const expected = diffuser.getOutput().oKgo2H * 1000 * 24 / 500;
+  assert.ok(Math.abs(diffuser.getReactorOtr(500) - expected) < 1e-8);
+});