feat: add dewpoint

.dockerignore

@@ -0,0 +1,4 @@
+node_modules
+.vscode
+grafana
+.editorconfig

Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18 as build
+FROM node:18-alpine as build
 
 WORKDIR /app
 COPY package*.json ./
@@ -8,11 +8,11 @@ RUN npm ci
 COPY . .
 RUN npm run build
 
-FROM node:18 as release
+FROM node:18-alpine as release
 
 WORKDIR /app
 COPY --from=build /app/dist ./dist
-COPY package.json package-lock.json ./
+COPY package*.json ./
 RUN npm ci --only=production
 
 EXPOSE 3000

src/dewPoint.ts

@@ -0,0 +1,21 @@
+/**
+ * Function to calculate the dew point.
+ * @param temperature Current temperature (°C)
+ * @param relativeHumidity Relative humidity (%)
+ * @returns Dew point (°C)
+ */
+export function calculateDewPoint(
+  temperature: number,
+  relativeHumidity: number,
+): number {
+  // Magnus formula constants
+  const a = 17.27;
+  const b = 237.7;
+
+  // Calculation of dew point using Magnus formula
+  const alpha =
+    (a * temperature) / (b + temperature) + Math.log(relativeHumidity / 100);
+  const dewPoint = (b * alpha) / (a - alpha);
+
+  return parseFloat(dewPoint.toFixed(1));
+}

src/index.ts

@@ -23,6 +23,7 @@ import {
   noxIndexGauge,
 } from './metrics';
 import { isUndefined } from 'lodash';
+import { calculateDewPoint } from './dewPoint';
 
 const app = express();
 
@@ -73,15 +74,20 @@ async function getStatus() {
   const available = (await client.readDiscreteInputs(0x0040, 20)).data;
   await new Promise<void>((resolve) => client.close(resolve));
 
+  const temperature = result.readInt16BE(12) / 100;
+  const humidity = result.readUInt16BE(14) / 100;
+  const dewPoint = calculateDewPoint(temperature, humidity);
+
   return {
     ...(available[0] ? { tvoc: result.readUInt16BE(0) / 1000 } : {}),
     pm1: result.readUInt16BE(2) / 10,
     pm25: result.readUInt16BE(4) / 10,
     pm4: result.readUInt16BE(6) / 10,
     pm10: result.readUInt16BE(8) / 10,
     co2: result.readUInt16BE(10),
-    temperature: result.readInt16BE(12) / 100,
-    humidity: result.readUInt16BE(14) / 100,
+    temperature,
+    humidity,
+    dewPoint,
     abs_humidity: result.readUInt16BE(16),
     pressure: result.readUInt16BE(18) / 10,
     noise: result.readUInt16BE(20),